TW434059B - Cast strip and steel material with excellent workability, and method for processing molten steel therefor and method for manufacturing the strip and material - Google Patents

Abstract

A cast strip with excellent workability, characterized in that not less than 60% of the total cross section thereof is occupied by equiaxed crystals, the diameter (mm) of which satisfy the following formula: D < 1.2X<SP>1/3</SP> + 0.75, wherein D designates the diameter (mm) of the equiaxed crystals in terms of internal structure in which the crystal orientations are identical, and X the distance (mm) from the surface of the cast strip. The cast strip and the steel material obtained by forming the cast strip have few surface flaws and internal defects.

Description

I Λ3Α0 5 9 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the Invention (1) Technical Field The present invention relates to a solidified structure with a uniform particle size, with less occurrence of surface defects and internal defects, and its processing. A slab having good properties and good quality characteristics, and a steel material produced by processing the slab. In addition, the present invention relates to the use of a molten steel after decarburization refining to make ingots and casts using the agglomeration method and continuous casting method to promote the formation of solidified nuclei, and to refine the solidified structure and improve its quality. Treatment method of molten steel with characteristics and processing characteristics. Furthermore, the present invention relates to a method for manufacturing a chromium-containing molten steel having a fine solidified structure with few surface defects and internal defects, and a seamless steel pipe manufactured using the same. BACKGROUND ART In the past, molten steel was fixed by using Block making method of casting mold and continuous casting method using vibrating casting mold, belt caster, steel belt caster, etc., thick blocks, preliminary rolled slabs, steel plates, thin cast slabs, etc., which are casted, and these are according to the predetermined size Cut and make. After the monthly ingot slab 'is subjected to a heat treatment such as a heating furnace, it is further subjected to processing such as rough rolling and finish rolling to produce steel materials such as steel plates and shaped steels. In the same way, the "strips for seamless steel tubes" are manufactured by casting molten steel into a preliminary rolled slab and a steel plate by using a block making method and a continuous casting method. This slab is subjected to a heat treatment in a heating furnace or the like, and then subjected to rough rolling, and is then transferred to a pipe-making step as a steel material for pipe-making. Then, the steel was reheated to form a rectangle and a circle, and then perforated with a mandrel to manufacture a seamless steel pipe. This paper size applies to the Zhongguanjia standard (CN &amp; 4 specifications⑵ο X 297 mm) ---- -4---------— {装 ------—— —Order ---- ---- This (Please read the notes on the back before filling this page) A7 printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs ------______ B7_; ___ V. Description of the invention (2) The material and quality of the steel, In addition to processing conditions such as calendaring, the solidification structure of the slab before processing has a huge impact. As shown in Figure 7, the structure of a common slab is solidified from the surface layer by rapid cooling and solidification into a relatively small cold-quenched crystal, a large columnar crystal formed on the inner side, and a central portion. Composition of Bai Jing: Depending on the situation, some of the columnar crystals reach the center. Therefore, 'when coarse columnar crystals exist in the surface layer of the slab, the grain boundaries of large columnar crystals' free elements such as Cu and their compounds form grain boundary segregation, making their parts brittle.' Surface defects such as sags and the like caused by unevenness such as cracks and cooling are generated, and thus productivity such as increased preparation for grinding and reduction of slabs is reduced. When such castings are used for processing such as calendaring, the deformation anisotropy caused by the non-uniformity of the crystal grain size increases, and the deformation behavior in the width direction and the length direction is different, causing peeling defects and cracks easily. Defects such as' r value (extrusion index), or surface defects such as corrugation flaws i (especially bulges and ropes on steel plates). In particular, the appearance of non-mineral steel materials where surface defects such as side seam flaws and rope-like defects occur, resulting in poor appearance. The amount of edge trimming has increased. In addition, when a good steel pipe is manufactured by using this type of iron, there are surface defects such as spalling flaws and cracks caused by slabs in the steel pipe; or internal defects such as internal cracks, voids, and center segregation, etc. In addition, the above-mentioned defects are increased in the 'pipe-making b' by forming and perforating, and defects such as cracks and peeling defects are generated on the inner surface of the steel pipe. Therefore, the entire paper size caused by grinding, etc., conforms to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) ---- I ---- Order! !! --- (Please read the notes on the back before filling this page) 5 A7

4 3 4-059 V. The increase in the description of the invention (3) or the decrease in productivity due to frequent occurrence of fragmentation, etc. This tendency is particularly noticeable in seamless steel pipes containing chromium-containing pure grain iron-based stainless steel. In addition, when there are coarse columnar crystals and large equiaxed crystals in the slab, the slab is produced: internal cracks caused by deformation caused by swelling and rolling correction, and due to dissolution of steel. Internal defects such as loose cores in the solidification contraction (sag in the middle), and central segregation caused by unsolidified molten steel flow at the end of solidification. For this reason, the "surface defects occurring in the wafers" have decreased productivity due to increased preparations such as grinding and frequent occurrence of fragmentation. Therefore, when using such as-is-type ballasts for rough rolling and finishing, etc., the surface defects occurred in the video recording plus the internal defects such as internal cracks, central depression and center segregation of the steel, Causes problems such as UST failure, reduced strength, or deterioration of appearance, and problems such as increased steel preparation and frequent fragmentation. Β The surface defects and internal defects of such blades are improved by the solidification structure of the blades. Can suppress its occurrence. The occurrence of surface defects such as cracks on the surface and sags caused by uneven cooling and uneven shrinkage caused by the cast piece can be suppressed by forming the solidified structure of the prayer piece into a uniform and fine structure. And 'the occurrence of internal cracks and internal defects such as center porosity (center depression) and center segregation caused by the solidification shrinkage and the flow of unsolidified molten steel in the slab can be improved by increasing the equiaxed crystal ratio inside the slab. inhibition. This paper size applies to China National Standard (CNS) A4 (210 x 297 mm) I —---- II--X-^ i I I ^ '— — 1 —--! This (please Read the notes on the back before filling this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 6 A7 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs The suppression of the occurrence of surface defects and internal defects and the improvement of the quality characteristics such as the processing characteristics and toughness of the slab in the manufacture of steel are to suppress the coarsening of the columnar crystals in the surface layer of the slab and to increase the equiaxed crystal ratio in the slab. It is important for the entire body to form a uniform and fine solidified structure. As a countermeasure *, or to find a way to deal with the shape of inclusions in molten steel, or control the solidification process to form a fine equiaxed crystal structure, various methods have been tried to prevent the casting And the occurrence of surface defects and internal defects in the steel obtained by processing the slab. Also known in the past are methods to increase the equiaxed crystallinity in the solidification structure of the slab; 1) Low temperature casting methods to reduce the temperature of the molten steel 2) a method of electromagnetic stirring the molten steel during the solidification process; 3) a method of adding solidified nucleus oxides and inclusions to the molten steel when the molten steel is solidified; A method of combining these 1} to 3). A specific example of the above-mentioned method of low temperature casting, for example, in Japanese Patent Publication No. 7-84617, when the molten steel is continuously cast, the superheat degree (the actual molten steel temperature minus the liquidus temperature of the molten steel) Method for controlling the temperature below 40 ° C and pulling out while cooling in the mold to form a solidified slab with an equiaxed crystal ratio of more than 70% 'and a method for preventing the pure grain iron-based stainless steel plate from bulging. . However, in the method described in Japanese Patent Publication No. 7-84617, because the overheating temperature is too low, the molten steel solidifies during casting or the nozzle is blocked, which causes the casting of the base metal to form casting difficulties; and the viscosity of the molten steel increases to prevent inclusions. Caused by floating, or inclusions remaining in molten steel ---- installation -------- order ---- I ---- line (please read the precautions on the back before filling this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 434059 A7 ---- B7 V. Invention Description (5) Defects, etc. Therefore, in the above method, it is difficult to reduce the thermal temperature in the process of obtaining a slab having a sufficient equiaxed crystal ratio. In addition, how to prevent surface defects and internal defects, and use it to produce cast pieces with excellent processing characteristics; what particle size will be formed from the surface layer to the internal equiaxed crystals, and how to uniformly treat the solidification curse of the cast piece, so far Unknown yet. Also, in Japanese Patent Application Laid-Open No. 57-62804, it was mentioned that, in order to eliminate internal defects such as center porosity in prayer tablets, in the state where the interior is not solidified, it is used to press down the cast piece. Approaching the center. However, in the method described in the above-mentioned Japanese Patent Application Laid-Open No. 57-62804, when the non-solidified portion is large due to the vicinity of the center of the slab after pressing, when the fragile solidified layer is subjected to a large downward pressure. This is the cause of internal cracks and center segregation. On the other hand, when undercutting occurs, internal defects such as loose cores remain. For this reason, internal defects such as cracks and peeling defects occurred during the perforation process in the pipe-making process, resulting in a reduction in the quality of the steel pipe. And other issues. Therefore, in the past methods, 'slabs of chromium-containing steel having a fine solidified structure and pressed surface defects and internal defects were produced: Furthermore, the slabs after continuous casting were Tube processing is extremely difficult. In addition, 'the stable production of chrome-containing steel (pure-grain-type stainless steel) steel pipes without defects in the industry' is still unclear as to how to perform ideal casting and slab processing. Also, the method of electromagnetically stirring the molten steel in 2) is described in, for example, Japanese Patent Application Laid-Open No. 49-52725 and Japanese Patent Application Laid-Open No. 2-151354. ---- I ---- I) 'pack- --Order--III I --- line (Please read the precautions on the back before filling this page)

Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Invention Description (6) The electromagnetic stirring is performed on the molten steel in the solidification process in the mold or on the lower side of the mold to promote the floating of inclusions and suppress columnar crystals. Grow, a method used to improve the coagulated texture of a ball. However, the method described in Japanese Patent Application Laid-Open No. 49-52725 and Japanese Patent Application Laid-Open No. 2-151354 uses electromagnetic search and mixing to dissolve the molten steel in the vicinity of the mold. Although the surface layer of the ball can be finely formed, The solidification structure of the film is not sufficient. D On the other hand, when the molten steel stirring flow is applied to the downstream side of the mold, the solidification structure inside the film can be refined, but The surface layer portion of the steel sheet is formed with coarse columnar crystals, and the surface layer portion of the slab and the internal solidified structure cannot be simultaneously refined. However, 'It is difficult to produce a prayer sheet with a predetermined particle size and a fine solidified structure through electromagnetic stirring and stirring flow only in the molten steel during the solidification process.' In itself, there are limits. The method of electromagnetically dissolving and dissolving molten steel is described in Japanese Patent Application Laid-Open No. 5-6016616: electromagnetically mixing molten steel in the solidification process to cut off the apex of growing columnar crystals. The cut-off piece is used as a method of preventing the bulge when the equiaxed crystal ratio in the solidified structure of the cast slab forming the slab is more than 600/0. However, in the method described in Japanese Patent Application Laid-Open No. 50-16616, the slab flowing out of the mold is subjected to electromagnetic disturbance mixing, and there are formed columnar crystals on the surface portion of the slab. Surface defects such as cracks and sags occur in the slab; or surface defects such as spalling and cracking and bulging occur in steel materials processed by rolling or the like. This paper size applies to China National Standard (CNS) A4 specification (210 κ 297 mm) I — — — — — —-- ^ -----! ^ --------- {Please read the back first Please fill in this page again) 9 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 4 3 4 0 5 9 A7 V. Description of the invention (7) Also 'as described in JP 52-47522: Department A method for manufacturing an ingot having a fine solidified structure by stirring the electromagnetic stirring device at a position of 1.5 to 300 m from the molten surface in the continuous casting mold with a thrust of 60 mmHg: or As described in Japanese Patent Application Laid-Open No. 52_6〇231, the superheat degree of the molten steel is set to 0-50. 〇 Casting is performed; and the electromagnetic stirring of the unsolidified layer of the slab during casting is carried out to form a fine structure composed of equiaxed crystals in the solidified structure of the ball, and it is used to produce a center segregation and a loose center. Internal defects in steel. However, in the method described in Japanese Patent Application Laid-Open No. 52-47522, electromagnetic stirring of molten steel that has been continuously solidified in a rotary mold suppresses columnar crystals (growth of pine forest structure). The solidification structure has a certain degree of fineness. However, to form the fine solidification structure of the entire slab, a multi-stage electromagnetic stirring device is necessary, and there is a problem that the equipment cost is increased. According to the viewpoint of installation space, the multi-stage electromagnetic stirring device is installed. It is also extremely difficult, so the method described in Japanese Patent Application Laid-Open No. 52-47522 has its limits for producing a cast piece obtained by miniaturizing the entire solidified structure. Furthermore, the method described in Japanese Patent Application Laid-Open No. 52-6023 1 In the low temperature casting process, 'inclusions are stuck on the inner surface of the immersion nozzle and nozzle clogging occurs' or the temperature of the molten steel in the rotary mold is lowered, which results in melt surface crusting. Depending on the situation, casting may have to be interrupted. Therefore, in the case of low-temperature front forming, the casting temperature is interrupted, and the blocking of the immersion nozzle of the casting mold is interrupted, or the casting is interrupted. Decreasing the amount of casting results in a reduction in casting speed, etc. The casting temperature is lowered to a temperature at which the solidification structure of a stable slab can be stabilized and refined. The paper size is suitable for the national standard (CNS) A4 (21G X 297). (Chu) (Please read the precautions on the back before filling out this page) -------- Order ------------ ^ 10 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 5 The invention description (8) is extremely difficult. In the case of using an electromagnetic stirring device, even when local electromagnetic stirring is performed during the solidification of molten steel, columnar crystals and coarse equiaxed crystals are formed on the surface or inside of the slab. 'This is the cause of the formation of surface defects or internal defects, resulting in a decrease in productivity due to the increase in equipment and frequent occurrence of fragmentation' or damage to the steel due to internal defects such as internal cracks, center porosity, and center segregation. Disadvantages of quality. On the other hand, 'we have also considered to refine the solidification structure of the entire cross section of the cast slab according to the electromagnetic stirring device installed on the downstream side including the meniscus'. The degree of transformation is different, and stable and fine solidified structure cannot be obtained throughout the entire slab. However, to obtain a stable and fine solidified structure, the number of electromagnetic stirrer installations is increased. The number of electromagnetic stirrer installations is determined by equipment costs and continuous From the viewpoint of the structure of the ballasting device, it is difficult to install the necessary number due to restrictions. However, even if many electromagnetic stirring devices are installed, it is not possible to achieve sufficient miniaturization of the solidified structure. Also, the addition of the above 3) The oxides and inclusions forming the solidified nuclei themselves are included in the molten steel 'a specific example of a method for generating the molten steel in the molten steel through the addition of ingredients', for example, in Japanese Patent Application Laid-Open No. 5 3-90129, it is mentioned that iron powder and Iron wire composed of oxides such as c0, 8, W, and Mo is added to the molten steel, and a stirring flow is imparted to the molten steel by electromagnetic stirring at the dissolving position of the iron wire, and the entire slab is processed into solidification composed of equiaxed crystals. The method of organization ^ However, in this method, there is a case where a dissolved residue is generated due to unstable dissolution of an additive in the wire. When dissolving residues occur, the dissolving residues cause the size of this paper to comply with Chinese National Standard (CNS) A4 specifications (210 X 297 mm) ----------- 'packing ------ --Order --------- line (please read the notes on the back before filling in this page) 11 434059 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 _____B7 ______ V. Description of Invention (9)

Causes of product defects. Even if the additives in the iron wire are completely dissolved, it is very difficult to uniformly disperse the additives from the surface layer to the entire interior of the cast slab. 1 As a result, the size of the solidified structure is not uniform, which is not desirable. Furthermore, the effect of the isometric crystallization is affected by the electromagnetic stirring position and the stirring thrust, so it has the disadvantage of being limited under the conditions of the equipment. Further, in Japanese Patent Application Laid-Open No. 63-140061, a method of adding fine particles such as TiN during casting has been mentioned. However, when this method was implemented, it was found to have the same disadvantages as Japanese Patent Application No. 90129. The effect of forming inclusions that form solidified nuclei through the addition of required components to molten steel. For example, it is generally known that TiN is generated in molten steel of pure grain iron-based stainless steel and the solidified structure is axially crystallized. (For example, iron and steel, 4_S79, 1973) «However, for the purpose of knowing the full equiaxed crystallization effect by the formation of the above-mentioned TiN, it has been mentioned in the above" iron and steel ": it is necessary to dissolve the steel The Ti concentration in the solution was increased to more than 0.015% by weight. Therefore, in order to obtain a sufficient equiaxed crystallization effect by the above-mentioned generation of TiN, the amount of high-priced Ti alloy is increased. As a result, not only the manufacturing cost is increased, but also the nozzle clogging or Problems such as peeling and crazing on the product board occur. In addition, due to the relationship with the amount of addition, the composition of the steel is limited, so the applicable steel types are also limited. Therefore, a method of adding a trace amount of a certain component to obtain a slab having a fine equiaxed crystal structure at an effective rate has been sought. Therefore, a method of adding Mg to molten steel has been mentioned. However, the boiling point of 'Mg is about 1107. (： The temperature is lower than the molten steel, due to the Chinese standard of the paper lion Chinese standard &lt; CNS) A4 size ⑵G x 297 public love) (Please read the precautions on the back before filling this page) -------- Order --------- 12 Printed by A7 B7, Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (10) The solubility in the molten steel is almost non-existent. The metal Mg is put into the molten steel, and even if most of it is added, it also forms steam. And escape. Therefore, even if it is added by a general method, since the Mg residual rate is very low, a method for adding Mg is necessary. Furthermore, the present inventor has found that, in the research conducted on the addition of Mg, the residual ratio of Mg and the composition of the oxides formed after the addition of Mg have an effect not only on the dissolved steel component but also on the slag component. In other words, it was found that it was difficult to generate only inclusions with a functioning composition as solidified nuclei in the molten steel by adding only Mg to the molten steel. For example, in Japanese Unexamined Patent Publication No. 7-48616, it was mentioned that the slag covered on the surface of the molten steel in a container such as a molten iron can be processed into Mg 0 ~ 15% by weight. FeO, Fe203, and MnO are below 5% by weight. CaO · Si02. A12〇i-based slag 'through this slag and adding Mg alloy to increase the content of Mg in molten steel, and generate fine Mg〇 and MgO. A1203 oxide to improve the quality of steel method. In the method described in Japanese Patent Application Laid-Open No. 7-486 16, ca. Si〇2 · A! 203-based slag covers the surface of the molten steel, which has the advantages of suppressing the evaporation of Mg and improving the content rate. . However, in the method described in Japanese Patent Application Laid-Open No. 7-48616, only the total amount of Fe0, &gt; Fe2O3 and MnO in the slag covering the molten steel is specified to be 5% by weight or less, and the amount of 8o2 is not specified. . Therefore, when the content of Si02 in the slag is excessive, when Mg and Mg alloys are added, Mg reacts with Si02 contained in the slag, and the Mg content in the molten steel decreases. When the Mg content rate is too low, it is not possible to modify Al2O3 in the molten steel or MgO-containing oxides. As a result, the ai2O3 series rough paper size is in accordance with Chinese National Standard (CNS) A4 (210 X 297) 1) 1 ---------- II — I--III »^ ------- I (Please read the notes on the back before filling out this page) 13 Consumption by the Intellectual Property Bureau of the Ministry of Economic Affairs Printed by the cooperative 434059 A7 _B7__ V. Description of the invention (11) Large oxide residues in the dissolved steel 'This is the cause of the turning and steel defects. Because the degree of its role as a solidifying core is small, the solidified structure of the scales is coarsened, which causes defects such as cracks, center segregation, and looseness in the surface or inside of the slab; and To the reduction of slab productivity. In addition, the "steel processed by this slab" also has surface defects and internal defects caused by coarse solidified structures, and has problems such as productivity and quality degradation. Furthermore, the CaO concentration in the slag or the dissolved steel The Ca concentration is not set to any limit, so it replaces the generation of high melting point Mg0, etc., and generates a low melting point composite compound (CaO-Al2O3-MgO-based oxides) that does not generate a solidifying nucleus. )situation. It was also mentioned in Japanese Patent Application Laid-Open No. 10-102131 and Japanese Patent Application Laid-Open No. 10-296409 that Mg 〇〇〇〇 丨 ～ 0.015% by weight is contained in the molten steel and a fine and well-dispersed oxide is formed. A method for improving the solidification structure of the cast moon by distributing the oxide throughout the town A. However, in the method described in Japanese Unexamined Patent Application Publication No. 10-10213 and the method described in Japanese Unexamined Patent Application Publication No. 10-296409, oxides are uniformly distributed at a rate of 50 / mm2 or more from the surface layer portion to the inside of the slab. The high-density dense distribution 'so defects such as cracks and peeling defects due to oxides occur in slabs, slabs during processing, or steel obtained after processing slabs'. In this case, it is necessary to carry out surface grinding and the like, and the productivity of the product is lowered due to the occurrence of the reduction of the steel material or fragmentation. This paper ~ secondary steel standard (CNS) A4 size iT2W x Tear the public) ----- -----! &Lt; illm ^ --------- line- (Please read first Note on the back, please fill out this page again) 14-Consumer Cooperation of Intellectual Property Bureau of the Ministry of Economic Affairs Du printed A7 ------- B7 ---------- V. Description of Invention (I2) When the oxide is exposed on the surface of the steel or the oxide is near the surface, when it comes into contact with acid, salt water, etc., the oxide (oxide containing MgO) will dissolve, and the corrosion resistance of the steel bar will be reduced. . In addition, the inventors have re-discovered that in order to find the optimal conditions for adding equiaxed crystallization by adding Mg to molten steel, various experimental results were performed, such as even the same molten steel composition and / or With the same slag composition, the order of deoxidizing elements such as A1 and the addition of Mg all have a large effect on the equiaxed crystallization effect. In other words, "when Mg is added to the molten steel" and "a 丨" is added, since the surface of the MgO generated after the addition of Mg is covered with eight [203], it is found that the generated MgO cannot effectively function as a solidifying nucleus. As a result, the micronization effect of the solidified structure cannot be obtained by MgO; the solidified structure is coarsened, cracked surface defects, center segregation, and center internal defects occur. This result causes an increase in the preparation of the ball and steel, or causes fragmentation of the steel and steel, thereby reducing the productivity and quality of the product. Therefore, 'in the past, the method of adding oxides and inclusions as solidified nuclei in molten steel * by adding required components to generate solidified nuclei in molten steel' is used to obtain a defect-free turntable with a uniform solidified structure. Difficult; for this reason, there is a problem that it is impossible to obtain a cast piece with high processing characteristics such as rolling, and it is impossible to obtain a good quality steel with few defects. Moreover, at the present point in time, there is no industrially stable manufacturing of slabs with good defect-free workability, and it is not clear how the solidified structure is processed ideally. This paper size applies to China National Standard (CNS) A4 specification (210 * 297 mm) --------------------- Order · ----] — — { Please read the precautions on the back before filling this page) 15 4 3 4-059 A7 B7 V. Description of the invention (13) Therefore, 'low temperature casting and electromagnetic stirring, or the addition of oxides that form solidified nuclei to achieve the slab etc. In the past method of axial crystallization, although one side can suppress the occurrence of surface defects and internal defects such as cracks and sags, center segregation, center looseness (central depression) and the like that occur in the slab: and obtain a uniform particle size The solidified structure produces a defect-free cast piece; however, the current situation cannot improve the processing characteristics of the blade, and it is an industrially stable high-quality steel with few manufacturing defects. DISCLOSURE OF THE INVENTION In view of the above-mentioned circumstances, the present invention provides a processing feature that forms a solidified structure with a fine and uniform structure, and suppresses the occurrence of surface defects and internal defects such as cracks, center porosity, and center segregation. And / or cast slabs with good quality characteristics. The present invention also aims to provide a steel material having no surface defects and internal defects, and having good processing characteristics and / or quality characteristics, by processing the cast slab. In addition, the present invention provides a method for processing molten steel that promotes the formation of a high melting point containing MgO oxide in molten steel and acts as a solidification core, and can refine the solidified structure of the ball. The invention also provides a continuous casting method, which can form the solidified structure of the ball chip into a fine solidified structure to suppress the occurrence of surface defects and internal defects such as cracking and segregation; when the scales are processed into steel, the The number of defects is small. In addition, it is possible to cast a chipper with good quality characteristics such as corrosion resistance. Also, the present invention provides a method for forming the solidified structure of a cast piece into a fine paper size which is applicable to the Chinese National Standard (CNS) A4 (210 X 297 mm) &lt; Please read the precautions on the back before filling this page). -------- Order --------- Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 16 • Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 ________B7____ V. Description of the Invention (I4) Solidified structure to suppress the occurrence of surface defects and internal defects such as cracking and segregation; when casting a slab into a seamless steel pipe, the steel pipe has fewer defects and can improve product productivity. The purpose of the casting method of a slab and a steel pipe manufactured from the slab is to be used. The slab (hereinafter referred to as "slab A") of the present invention based on the foregoing object is characterized in that 60% or more of the total cross-section of the film after casting is an equiaxed crystal satisfying the following formula. . D &lt; 1.2X1 / 9 + 0.75. Among them, D is the diameter (mm) of equiaxed crystals with the same structure of crystal orientation, and X is the distance (mm) from the surface of the slab. For slabs, the solidification structure obtained by satisfying the above formula reduces the amplitude of the columnar crystals remaining on the surface layer of the slabs, suppresses the microsegregation caused by the solid-liquid distribution of the dissolved steel components during solidification, and enhances the resistance to cracking , And can control the occurrence of cracking defects caused by the deformation during the solidification process and the slab bulging and rollback correction stress; in addition, it can prevent the solidification shrinkage of the molten steel at the center of the thickness and the caused by the molten steel flow. Occurrence of internal defects such as center porosity and center segregation. Also, "cast XA having a solidified structure that satisfies the above formula, when processed by rolling or the like" has high processing characteristics due to deformation uniformity, so the processed steel can suppress the occurrence of surface defects and internal defects. Furthermore, the aforementioned equiaxed crystals in the 'slab A' can form a full section filled with the slab. When the entire section of the cast piece is formed into a uniform and fine solidified structure without columnar crystals, the microsegregation in the surface layer and the interior of the cast piece is changed, and the Chinese national standard (CNS) A4 specification can be applied to this paper scale ( 210 X 297) Chu ill ---- I--I ^ *-I ---- ^ --- III I-- &lt; Please read the notes on the back before filling this page) 17 Ministry of Economic Affairs Printed by the Consumer Cooperative of the Property Bureau 'Λ 3 4. Ο 5 9 Α7 ------ Β7 ____ 5. Description of the invention (M) The resistance to cracking caused by deformation and stress in the solidification process is further enhanced. As a result, it is possible to prevent the occurrence of surface defects and internal defects in the slab; and to increase the uniformity of the deformation of the moon from the surface layer to the interior during processing and improve the processing characteristics. The other slabs (hereinafter referred to as "slabs B") having excellent processing characteristics of the present invention based on the foregoing purpose are characterized in that the maximum crystal grain size at the same depth from the surface of the cast slabs after the casting, and the position Within three times the depth of the average crystal grain size. By obtaining a solidified structure in which the crystal grain size satisfies the above-mentioned relationship, it is possible to uniformly treat the crystal grain size existing at a predetermined depth from the surface layer of the cast slab. As a result, local grain boundary segregation of free elements such as Ca can be suppressed ', and grain boundary cracks in the surface layer portion can be suppressed. In addition, uniform deformation of crystal grains can be obtained during processing. 'Because the deformation of specific crystal grains can be suppressed, the so-called r value of the extrusion process characteristic index can be increased; and the surface of ripple defects, bulges, ropes, etc. can be prevented. defect. In addition, in the slab B, a slab thickness of 60 ° / 0 or more in the cross-section can be equiaxed to the surface. The solidification structure of the slab can be formed into a solidified structure in which the growth of columnar crystals is suppressed by equiaxed crystallization of a cross section of 60% or more in the thickness direction of the slab. As a result, the grain boundary segregation in the surface layer and the interior of the slab is further suppressed, and the crack resistance caused by deformation and stress in the solidification process is increased. Not only the occurrence of surface defects and internal defects in the slab can be suppressed, but also implemented at the same time. Improve the isotropy of its deformation behavior during processing (by extending its width and length) and improve its processing characteristics. In other words, it can prevent the Chinese paper standard in steel from applying the Chinese National Standard (CNS) A4 specification (210 X 297 mm) ----------- ▲ 『装 ----- I 丨 丨 Order --------- End ί (Please read the precautions on the back before filling in this page ) 18 A7 B7 'Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, 5th, 5. Description of the invention (10 cracks and peeling flaws, ripple defects caused by uneven processing deformation and other surface defects. And, The full section of the thickness direction of the sequel in the town piece B can be equiaxed. Crystallization of similar solid-state structures such as 'microsegregation' is further suppressed. Due to the formation of a more uniform solidified structure, the tortoise in the cast piece The restraint of cracks and the like is more shaped and strengthened. Prevent surface defects and internal defects from occurring; and increase uniformity of deformation from the surface layer to internal processing, and further improve the processing characteristics, r value, and tensile properties. Based on the foregoing purpose, the scales with good quality characteristics and processing characteristics of the present invention (hereinafter It is called "Town Piece C".) 'It is characterized by inclusions containing 100 or more per cm2 or less of 6% or less of the lattice mismatch between the 5 pure grains of iron formed during the solidification of the molten steel. Inflammables with a small lattice mismatch between 5 pure grains of iron can effectively generate a large number of solidified nuclei and act as seeding nuclei. The more solidified nuclei formed, the finer the solidified structure, and as a result, the cast The microsegregation in the surface layer and the interior of the moon is suppressed, and the crack resistance to uneven cooling and shrinkage and deformation is improved. Moreover, the blocking effect of the solidified nuclei formed after solidification (inhibits the growth of crystal grains immediately after solidification) ), While suppressing the coarsening of the solidified structure, it is possible to achieve a more stable and fine solidified structure. Therefore, when a slab having such a solidified structure is subjected to processing such as rolling, it is easy to press down In other words, the slab has extremely high processing characteristics. In addition, when the number of inclusions in the slab is less than 100 / cm2, this paper size applies the Chinese National Standard (CNS) A4 specification ( 210 X 297 public love)! ----------- ^ -------- ^ ------- 11 (Please read the precautions on the back before filling this page) 19 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 434-0 5 9 A7 __I_R7 __ V. Description of the invention (I7) Because the number of solidified nuclei formed is reduced and the blocking effect after solidification is insufficient, the cast solidified structure is coarse As a result, surface defects and internal defects occur in the cast slab. In addition, the cast slab C may contain at least 100 inclusions per cm 2 or less in size. The finer the inclusions, the more efficiently many solidified nuclei can be generated: Moreover, the blocking effect can be increased, so that a finer and more uniform solidified structure can be produced. Castings having such a solidified structure have high workability when processed by rolling, and the steel does not have surface defects such as spalling defects, surface cracks, and wrinkles, and internal defects. When the size of the inclusions is larger than 10 μm, problems such as spalling defects and cracks easily occur due to its role as a solidification nucleus when the molten steel is solidified. It is also possible to use a steel of 5 pure grain iron in the solidified primary crystal of the slab C. A phase transformation occurs during the cooling of the cast slab, even if a steel species with a structure other than pure grain iron is formed after solidification or cooling. The inclusions in the chip C act as a seed nucleus, which promotes <5 pure grain iron. Due to the formation of solidified nuclei, a fine and uniform solidified structure can be obtained. As a result, the crystal structure of the cooled binding piece can be made finer. The scales with good quality characteristics of the present invention (hereinafter referred to as "casting piece D") based on the foregoing objects are casting pieces which are cast by adding a metal or a metal compound added to the molten steel to form a solidified core when the molten steel is solidified. It is characterized in that the number of metal compounds with a size of 10 or less relative to the surface layer portion of the slab is less than 10 wm contained in the surface layer portion. — — — — — ^ —— — — — — II · 11111111, 1 (Please read the precautions on the back before filling this page)

20 A7

Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of Invention (18) The number of metal compounds with a size greater than 1.3 times. Therefore, in the slab D, a metal compound produced by adding a metal to the molten steel or a metal compound directly added to the molten steel, wherein the inside of the slab contains more metal compounds of the following sizes than the surface layer portion of the slab. This metal compound acts as a solidified nucleus during solidification 'and reduces the equiaxed crystal diameter of the solidified structure. As a result, grain boundary segregation is suppressed. In addition, this metal compound has a blocking effect to suppress the coarsening of equiaxed crystals after solidification. As a result, as for the sheet C, it is possible to prevent the occurrence of cracks and sags caused by the deformation and stress during the solidification process, surface defects caused by inclusions, and the like, and increase the slab bulging and rollback correction. The added deformation causes resistance to internal cracks; and it can suppress the occurrence of internal defects such as center porosity (center depression) and center segregation caused by the solidification shrinkage and flow of the molten steel at the end of solidification. Also, as for the slab D, since the number of metal compounds in the surface layer portion is less than the internal metal compound estimate, when the slab is subjected to processing such as rolling, surface defects caused by inclusions are reduced. Improve the quality characteristics and workability of surname. In addition, the surface layer portion 'in the blade D means that the surface layer portion is more than 0 from the surface layer. / 〇 in the range up to 25% from the surface layer. When deviating from this range, the surface layer part is too thin, and the inner part of the metal compound is close to the surface layer. The number of internal metal compounds increases. The surface layer part cannot form a fine solidified structure. defect. Therefore, the metal compounds contained in the molten steel and the standard of this paper when the molten steel is solidified are in accordance with the Chinese National Standard (CNS) A4 (210 X 297 mm) III I--installation i — I 订 order --- II! I _Line (Please read the precautions on the back before filling this page) 21 4 3 4 0 5 9 A7

V. Description of the invention (19) It is also acceptable to set the degree of lattice unconformity between the pure grain iron formed by the consumer cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs to be less than 6%. With this treatment, the formation energy of the solidified nuclei is increased during the solidification of the molten steel, and a finer solidified structure can be obtained, and the microsegregation in the surface layer portion and the interior can be minimized. In addition, it is easier to deform in the depression direction, and stable slabs with good processing characteristics and quality characteristics can be produced. Further, the cast piece D can be made into a cast piece of pure-grain iron-based stainless steel. In the slab D of the pure-grain iron-based stainless steel, a solidified structure that is easily coarsened can be formed into a fine equiaxed crystallization treatment. In the above-mentioned slab of the present invention, 'Mg or Mg alloy is added to the molten steel so that it can be filled with the generated MgO-containing oxide. By containing MgO-containing oxides, it is used to suppress the aggregation of oxides in molten steel and improve the dispersibility of oxides, and to increase the number of gaseous substances that act as solidified nuclei. As a result, the solidified structure of the slab forms a more stable and fine solidified structure. After the above-mentioned slab of the present invention is subjected to a heat treatment, for example, a steel material produced by processing such as rolling at 丨 丨 00 ～ 丨 35 ° C is subjected to heat treatment, because it has the above-mentioned characteristics, it is rolled. The resistance to cracking during processing is high. When processing is performed, specific crystal grains can be prevented from being concentratedly deformed, and uniform deformation of the crystal grains (isotropic behavior of deformation) can be obtained. Therefore, 'the above-mentioned slab of the present invention has uniform deformation in the width and length directions when pressed', so the steel of the present invention produced by processing the slab rarely has surface defects such as peeling flaws and cracks of the steel. And internal defects such as center porosity and center segregation. In addition, the steel of the present invention is also less suitable for the paper size applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) i- ^ -------- ^ --------- line ( Please read the precautions on the back before filling out this page) 22 B7 B7 Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs, consumer cooperation Du printed 5. Description of the invention (20) There are surface defects and internal defects caused by inclusions, and there are also good Quality characteristics such as money resistance. (4) A method for dissolving steel (hereinafter referred to as "processing method of the present invention") necessary for producing the above-mentioned blade of the present invention will be described. One of the treatment methods of the present invention (hereinafter referred to as "treatment method j") is characterized in that the total Ca content in the molten steel after the refining treatment is set to 0.0010% by mass in a refining furnace, and then the predetermined amount of Mg is set. It is added to the molten steel. According to the processing method I ', the generation of dance salt in the molten steel. Shao acid salts (^ 2 CaO · 7Α12〇3 and other low melting point inclusions) can be suppressed. As a result, good Ming salt In addition, the formation of CaO-Al2O3-Mg〇 ternary complex oxides in the form of MgO (MgO) is prevented, and high melting points such as MgO and MgO. Al2O3 as solidified nuclei can be formed. Oxide, where the total Ca amount refers to the total amount of Ca components in caustic compounds such as ca and ca0 present in the dissolved steel; the content specified in the treatment method j is that the dissolved steel does not contain Ca at all; or 'It contains 〇〇〇 丨 〇0 / ◦ content in the following cases. In addition, in the processing method I of the present invention, it is not a problem to treat the molten steel into a composite oxide containing no calcium and aluminate. After this treatment, when the oxide (Mg〇) is usually present in the molten steel, To prevent the formation of Ca. Al2O3-MgO ternary composite oxides formed by calcium, aluminates and oxides (Mg〇); as a result, MgO and MgO. Al in molten steel can be more reliably formed; 〇3 and other high melting point oxides (hereinafter referred to as "MgO-containing oxides"), the solidification structure of the slab can be micro-sized. The paper size is applicable to the Chinese National Standard (CNS) A4 specification (2) 0 X 297 mm. ) ------------- Installation ----- I--Order ------ I--line &lt; Please read the notes on the back before filling this page) 23 Economy Printed by the Consumer Cooperatives of the Ministry of Intellectual Property Bureau Λ 3 4 Ο 5 9 Α7 ____ Β7__. _ V. Description of the invention (21) Refinement can prevent the surface defects and inner surface defects of the casting. The amount of Mg added to the molten steel is preferably 0.0010 to 0.10% by mass. When the amount of Mg added is less than 0.0010%, the number of solidified nuclei formed by the MgO-containing oxide in the molten steel decreases, and the solidified structure cannot be made finer. On the other hand, when the amount of Mg added exceeds 0.10 / 0 mass, the micronization effect of the solidified structure is saturated, and the added Mg and Mg alloys are wasted; and, due to the oxidation containing MgO and MgO, Defects caused by the increase of gaseous matter. The molten steel processed by the processing method I of the present invention is poured into a casting mold and cooled, and the cast slab of the present invention is manufactured by finely solidifying MgO and / or an oxide containing MgO to form a solidified structure. Produced by suppressing the occurrence of surface defects such as cracks and sags on the slab surface, internal cracks, and internal defects such as center porosity (center sag) and center segregation. Therefore, when processing such as post slab rolling is performed to manufacture steel, surface defects and internal defects occurring on the steel can be prevented; and the productivity and material quality of the product can be improved by arranging and shredding. Another treatment method of the present invention (hereinafter referred to as a "treatment method Π") 'is characterized in that before adding a predetermined amount of Mg to the molten steel, adding a predetermined amount of an alloy containing A1 to the molten steel for deoxidizing treatment. In this treatment method, an alloy containing Al · is firstly added, and the alloy containing A1 reacts with oxygen, Mn0, SiO2, FeO, etc. in the dissolved steel to form eight 丨 203, and then red / ¾ • is added with a predetermined amount of Mg. On the surface of M2O3, Mg is oxidized to form MgO; or, Mg0 is formed, and MgO is present on the surface of a from M2; or, Mg0 · A12O3, because of the solid particles with solidified primary crystals ----- 丨 _ 丨 — 丨 丄 -------- Order ------- | * Edge (Please read the notes on the back before filling this page)

24-Printed A7 by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs ---------- ---- ____B7 _ V. Description of the invention (η) The degree of lattice mismatch between irons is below 6%, so when molten steel During solidification, it acts as a solidified core. As a result, the solidified structure is made finer, which can suppress the occurrence of surface defects such as cracks and internal defects such as center segregation and center porosity. Also, it can suppress the decrease in workability and corrosion resistance. A1 alloys are those that contain A1, such as metal A1 and Fe-Al alloys; and Mg added means that metals that contain Mg, Fe-Si-Mg alloy, ^ Ni-Mg alloy, etc. alloy. In addition, in the treatment method Π of the present invention, before adding Mg to the molten steel, a predetermined amount may be added in addition to the A1 alloy, or a predetermined amount may be added to perform a deoxidation treatment. After the addition of the Ti-containing alloy described above, Ti forms a solid solution in the molten steel, and a part of it generates TiN, which acts as a solidified core; and 'on the surface of Al203 formed by deoxidation, it forms MgO Or MgO · Α1: 03 'together can act as a solidifying nucleus. In addition, the Ti-containing alloy means a Ti-containing substance such as metal Ti and Fe-Ti alloy.

Ik.-In the processing method Π of the present invention, it is preferable to set the amount of Mg to be 0.0005 to 0.010% by mass. When Mg is added in this range, sufficient MgO or MgO · A1203 can be formed on the surface of A1203 produced by deoxidation. This MgO or MgO. Al203 can sufficiently act as a solidification core when the molten steel is solidified, and refine the solidified structure. When the amount of Mg added is less than 0.0005% by mass, the number of surface oxides having a lattice mismatch between 5% pure grain iron and 6% or less is insufficient, and the solidified structure cannot be refined. On the other hand, When the amount of M g exceeds the standard of this paper, the Chinese National Standard (CNS) A4 specification (210 X 297 mm) is applicable ------------- installation ------- Order II ------- line (please read the notes on the back before filling this page) 25 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 434059 A7 —_______ B7_______ V. Invention Description (23) When 0.010% quality is exceeded ' Not only is the micronizing effect of the solidified structure of the oxide saturated, but also the cost required for the addition of Mg is increased. Also, in the processing method of the present invention, the molten steel can be processed into a molten steel of pure iron-based stainless steel. Treatment according to the present invention Method Π can refine the solidification structure of pure-grain iron-based stainless steel where the solidification structure is easily coarsened; as a result, it can be used to suppress cracks and sags on the surface of the slab, such as internal cracks, loose cores, and central segregation. The processing method I and the processing method of the present invention In the method π, the ore contained in the molten steel; the oxides produced by the desulfurization products and the oxides generated when Mg is added to the molten steel are added to satisfy the following formulae (1) and (2) Correction phase 17.4 (kAl2O3) + 3.9 (kMgO) +0.3 (kMgAl2O3) + 18.7 (kCaO) ^ 500… (1) (kAl203) + (kMg0) + (kMgAl203) + (kCa0) ^ 95… (2) Among them, k is the mole% of the oxide. By adding this Mg, the degree of lattice mismatch between 5 pure grain iron and 6% is less than or equal to 6 ', which can generate oxides that function effectively as solidified nuclei (: & amp 〇 · Al2〇3 · MgO, MgO · A1203, MgO and other composite oxides. When the molten steel solidifies, 'these composite oxides act as solidification nuclei, so that equiaxed crystals are formed and the solidification structure of the cast piece is fine The addition of Mg can also be applied to molten steel of pure-grain iron-based stainless steel. In other words, the solidified structure can be easily roughened through the addition of Mg. The paper size can be adapted to the Chinese National Standard (CNS) A4 specification (210 X 297 mm). ------- I 1 ^ 'install --------order-! I-line (please read the notes on the back before filling this page) 26 Member of Intellectual Property Bureau, Ministry of Economic Affairs Printed by the Industrial and Consumer Cooperatives A7 B7 V. Description of the invention (24) Dahua's pure grain iron system does not record the solidified structure of steel, forming a finer solidified structure, which can be used to suppress internal cracks and center segregation in the sepals, Looseness of the center, etc., and 'The steel material processed by the binding piece can be used to prevent the occurrence of rope-like and side seam defects caused by coarse solidified tissue. Another processing method of the present invention (hereinafter referred to as "processing method plate j" is characterized in that it is above the liquidus temperature of the molten steel, and a predetermined amount of M g is added to satisfy the T i of the solubility product of T i N crystals. Concentration and N concentration. According to this treatment method, at the high temperature where TiN is not crystallized, MgO and MgO with good dispersibility are generated. The Mg0-containing oxide of 203 is reduced as the temperature of the molten steel decreases. TiN is crystallized on MgO-containing oxides and does not disperse in the molten steel. This 4 acts as a solidification nucleus to refine the solidification structure of the slab. In addition, the addition of Mg is made by adding the metal M0Fe_Si_Mg alloy, Ni- Mg alloys and other Mg-containing alloys are used. Among them, the Ti concentration [% Ti] and N concentration [% N] are preferably those that satisfy the following formula. [% Ti] X [% N] ^ ( (% Cr) 2 · 5 + 150) × 1〇-6 However, '[% Ti] is the mass of Ti% in molten steel, and [〇 / 〇ν] is the mass of N% in molten steel. [% Cr] is molten steel Mass of Cr% in the treatment method III of the present invention, 'the Ti and n contained in the molten steel; the degree is maintained at a predetermined range', and then added With a given amount of Mg, the generated TiN can be stably dispersed in molten steel accompanied by a highly dispersive MgO-containing oxide. This TiN acts as a solidification nucleus when the molten steel solidifies, and solidifies the slab. The organization is more fine-grained. This paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) — — — — — 1 — — — ·· 1 --- Order ------- I &lt; Please read the precautions on the back before filling this page) 27 A7 B7 Printed by the Consumers' Cooperative of Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (25) The treatment method of the present invention is Cr-containing even if the solidified structure is easily coarsened The pure-grain iron-based stainless steel can also exert the effect of miniaturizing the solidified structure, and can prevent surface defects and internal defects occurring in Zhenyue steel. The processing method of the present invention is for pure grain iron containing 10 to 23% by mass of Cr. The stainless steel is particularly suitable for casting. When the content of Cr is less than 10% by mass, not only does the steel's survivability decrease, but the desired miniaturization effect cannot be achieved. On the other hand, when the content of cr exceeds 23% Quality, ie The addition of Cr alloyed iron does not improve the financial properties of the steel. 'At the same time, the increase in the amount of alloyed iron increases the manufacturing cost. Another processing method of the present invention (hereinafter referred to as "processing method W")' is characterized by . It is formed by covering the molten steel with 1 to 30% by mass of the oxide recovered by Mg. According to this treatment method IV, the total amount of oxides contained in the slag is maintained at a predetermined level. The amount of Mg added to the molten steel can increase the production ratio (productivity) of Mg0 and MgO-containing oxides. As a result, fine MgO or MgO-containing oxides (hereinafter referred to as "MgO-containing oxidation") can be increased. Thing. " ) Dispersed in molten steel. In ytterbium, ytterbium MgO or MgO-containing oxides act as solidification nuclei, and the solidification structure of the slab is refined. As a result, it is possible to suppress cracks and sags that occur on the surface of the slab, cracks and segregation that occur inside the center, and loosening of the center. The processing of the cast slab can also improve the quality of its steel. (Please read the precautions on the back before filling out this page)-Install ---- Order --------- Printed by A7 B7, Consumer Cooperative of Intellectual Property Bureau of the Ministry of Economic Affairs V. Invention Description (26) 'The oxide in the aforementioned slag means one or more of FeO, Fe203, MnC>, and Si02. By properly selecting the oxides in the slag, the consumption of Mg due to the oxides in the mine and fishing can be suppressed and the productivity of Mg can be improved, and Mg can be effectively added to the molten steel. In addition, in the treatment method IV of the present invention, it is preferable to set Al2O3 contained in the molten steel to a mass of 0.005 to 0100 / 〇. Therefore, Al2O3 with a high melting point can be processed into a composite oxide of MgO. Al, Ch and the like; and the dispersibility of MgO can be used to uniformly and completely disperse the composite oxide in molten steel, which can improve the The ratio of MgO-containing oxides acting as solidified nuclei. Another treatment method of the present invention (hereinafter referred to as "treatment method V") is characterized in that the CaO activity in the slag covering the molten steel is controlled before the addition of the force σ g without a fixed amount of M g to the molten steel. Below 0.3. According to this processing method V, by adding Mg added to the steel, MgO having a good lattice integration with δ pure grain iron and high-melting point MgO-containing gas can be finely formed, and can be made to dissolve in the steel. Medium dispersion. Then, when the molten steel is solidified, the MgO and the MgO-containing oxide function as a solidification nucleus, so that the solidification structure of the slab is refined. When the activity of CaO in the slag exceeds 0.3, low-melting-point oxides containing CaO that do not act as solidified nuclei or oxides with a lattice unconformity of &lt; 5 pure grain iron exceeding 6% increase. In the treatment method V of the present invention, it is preferable to set the alkalinity of the slag to 10 or less. This paper size applies to China National Standard (CNS) A4 (210x297 mm) ---------- I! Packing -------Order --------- Line { (Please read the notes on the back before filling out this page) 29 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, 4 3 4059 Α7 ______ Β7__ V. Description of the invention (27) If the alkalinity of the mine is adjusted below 10 It can stably inhibit the activity of CaO in the slag; and containing Mg〇 oxide can prevent low melting point oxides or oxides with a lattice mismatch between 6 pure grain iron and more than 60/0 Formation. The treatment method V of the present invention can be suitably applied to molten steel of pure grain iron-based non-mineral steel. If the treatment method V of the present invention is applied to the dissolving steel of pure-grain iron-based stainless steel, 'when the dissolving steel is solidified', the solidified structure that can be easily coarsened can be made finer, and it can be used to prevent slabs and processed steel. Surface and internal defects that have occurred. The above-mentioned casting slab according to the present invention can be manufactured by continuous casting. The continuous casting method is characterized in that a molten steel containing MgO or Mgo oxide is poured into a mold, and the molten steel is stirred while using an electromagnetic stirring device. Caster on one side. According to this continuous casting method, the molten steel is filled with the formed high-dispersion MgO and / or MgO-containing oxides, and the promotion and blocking effects of solidification nuclei generated by the oxides (for inhibiting the structure immediately after solidification) Growth) 'and the solidification structure of the slab can be made finer. And 'the oxides present on the surface layer of the cast slab can be reduced through the stirring process of the electromagnetic stirring device' to prevent defects such as peeling defects and cracks caused by the oxide on the rotor and the steel: and can improve the Finance touch. Moreover, in the continuous casting method of the present invention, the electromagnetic search and mixing device is installed in a range from the meniscus liquid level to the downstream side within 25 meters of the mold. The paper size is applicable to the Chinese National Standard (CNS) A4 standard (210 ^ 297 mm) ------------ Gray -------- ^ ------- .1 (Please read the notes on the back before filling this page) 30 A7 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the invention (28) is appropriate. ”When the electromagnetic stirring device is set in the above range, the oxides captured after the initial surface layer is solidified are flow washed to form the surface layer. A fine solidified structure at the end; and a large amount of ^^ 〇 and / or MgO-containing oxides are contained inside the slab, and the solidified structure can be formed into a finer solidified structure. As a result, it is possible to prevent defects such as spalling flaws and cracks caused by slabs and steel materials due to oxides, and to improve the corrosion resistance. The stirring position using the electromagnetic stirring device cannot provide an effective stirring flow for molten steel when it is located on the upper part of the meniscus (melt level); on the other hand, if it is located on the downstream side exceeding 2.5m, a solidified shell is formed If it is too thick, there is a problem that the oxide in the solidified shell forming the surface layer portion increases and the corrosion resistance decreases. Further, in the continuous casting method of the present invention, it is preferable to use an electromagnetic stirring device to impart a flow rate of the molten steel stirring flow to 10 cm / sec or more. Therefore, the oxide captured by the solidified shell of the cast slab can be removed by continuously washing the molten steel. When the flow velocity of the search-mixing stream is less than 10em / sec, the halide near the solidified shell cannot be continuously washed and removed. In addition, the flow velocity of the agitating stream is too strong. 4 Because the powder covering the surface of the molten steel is entangled, and the meniscus in the mold produces a turbulent flow ', the upper limit of the flow rate of the agitating stream is set to 50 £; 111 / sec is preferable. It is also preferable that the "electromagnetic stirring device" is provided to the molten surface in the mold so as to impart a stirring flow rotating in the horizontal direction. With the horizontally swirling stirring flow, the paper size captured by the surface layer of the slab is applied to the Zhongguanjia Standard (CNS) A4 size ⑵Q x 297 public love) -------------- installation --I (Please read the precautions on the back before filling out this page) Magic--Line-31 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 434059 A7 _____B7__ V. Description of the Invention (29) The oxide is continuously and effectively washed And it can be removed, and the inside of a slab can be filled with a fine amount of fine oxides. The continuous casting method of the present invention can also be suitably applied to the case where a molten steel of pure grain iron-based stainless steel is used to make ballast. In particular, the above-mentioned molten steel contains chromium 10 to 23 /. Mass, 0.0005 ~ 0.010% mass of molten steel. Based on this method, highly dispersive Mg0 and / or MgO-containing oxides are formed in the molten steel, and the promotion and blocking effects (for inhibiting the growth of the structure immediately after solidification) are generated through the formation of solidified nuclei. The solidified structure of the sheet forms a fine solidified structure. Therefore, 'can be used to suppress defects such as surface defects occurring in the surface layer portion of the slab, cracks occurring in the interior portion, and looseness in the center. In addition, when the slab is perforated after processing, the occurrence of cracks and peeling defects in the inner surface of the ceremony is suppressed, and the quality of the steel pipe is improved. When the content of Mg is less than 0.0005% by mass, MgC) in the molten steel is reduced, and the formation of solidified nuclei is insufficient, and the blocking effect is weakened, so that the solidified structure cannot be refined. On the other hand, when the content of Mg exceeds 0.001 0/0 / mass, 'the micronizing effect of the solidified structure is saturated and no significant effect is found'. At the same time, the amount of Mg's containing Mg alloys and the like increases, and the manufacturing cost increases . When the content of chromium is less than 10% by mass, the corrosion resistance of the steel pipe is reduced, or the effect of miniaturizing the solidified structure is reduced. When the content of the network exceeds 23% by mass, the amount of the chromium alloy added increases the manufacturing cost. In addition, when the continuous ballasting method of the present invention is applicable to the continuous casting of molten steel of pure grain iron-based stainless steel, an electromagnetic stirring device is used to apply the paper size to the national standard &lt; CNS) A4 specification (210 X 297 public t) — — — — — — — — — — — — 11111111 (Please read the notes on the back before filling out this page) 32 • Intellectual Property Bureau, Ministry of Economic Affairs, Consumer Cooperative, printed A7 &quot; --- 1 -—-— _ B7 __— V. Description of the invention (3〇) Dissolving the steel and stirring it while casting is not a problem. Through the above-mentioned stirring, the tip of the columnar crystals generated during solidification is broken, and by suppressing the growth of the columnar crystals and the interaction of the solidified nuclei of the broken pieces, the solidified structure of the rotating piece can be made more fine. In addition, in the above-mentioned applicable cases, it is preferable to start the light pressing process of the slab from the range of the solid phase ratio 0.2 to 1 of the casting &gt; 1. After the pressing process, the center looseness caused by the solidification shrinkage of the unsolidified part remaining inside the slab can be pressed, and the center segregation caused by the flow of the unsolidified molten steel can be prevented. When the solid phase rate is lower than 0.2, and the pressing is performed, the unsolidified range is too large, and the pressing effect cannot be obtained even if the pressing is performed; and the fragile solidification may crack or crack. When the solid phase ratio is larger than 0.7 and the pressing is performed, there may be cases where the heart is loosened and not pressed. In addition, as for the crimping treatment for the center shrinkage, a large downforce must be formed, and the size of the downpressure device is increased. The seamless steel pipe according to the present invention based on the foregoing object is a molten steel containing chroman ~ 230 / ° weight and 0.0005 ~ 0010% by weight of Mg is poured into a casting mold, and the cooling of the casting mold and the use of a support section The scattered water of the cooling water nozzle installed on the section is used for cooling-while making it solidify, the cast piece after continuous conversion processing is made by perforating in the pipe-making step. This steel pipe uses a fine cast piece with a solidified structure. Therefore, the occurrence of cracks and sags on the surface and the inner surface of the pipe during perforation in the pipe-making step is suppressed, and it is a good quality steel pipe that does not require grinding or the like. . Brief description of the drawing This paper size is applicable to China National Standard (CNS) A4 (210x297 mm) ^--------- --------- ^ (Please read the note on the back first Please fill in this page for further information) 33 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs * 4 3 4 0 5 9 A7 _____B7______ V. Description of the Invention (Μ) Figure 1 is a sectional view of the continuous casting device for casting the slab of the present invention . Fig. 2 is a sectional view of a mold near the continuous casting apparatus shown in Fig. 1; Fig. 3 is a BB cross-sectional view of the mold shown in Fig. 2. Fig. 4 is an A-A cross-sectional view of the continuous casting apparatus shown in Fig. 1; Fig. 5 is a sectional view of a processing apparatus used in the molten steel processing method of the present invention. Fig. 6 is a cross-sectional view of another treatment device used in the molten steel treatment method of the present invention = Fig. 7 is a schematic view of a solidification structure in the thickness direction in a conventional slab. Fig. 8 is a graph showing the relationship between the distance from the slab position to the surface layer, the equiaxed crystal diameter, and the width of the columnar crystal of the present invention. Fig. 9 is a schematic view showing the solidified structure in the thickness direction of the slab of the present invention. Fig. 10 is a graph showing another relationship between the distance between the slab position and the surface layer and the equiaxed crystal diameter of the present invention. Fig. 11 is a graph showing other relationships between the distance between the slab position and the surface layer, the equiaxed crystal diameter, and the columnar crystal width of the present invention. Fig. 12 is a diagram showing another relationship between the distance from the slab position of the present invention to the surface layer and the equiaxed crystal diameter. Fig. 13 is a sectional view of the slab position of the present invention in the thickness direction. Fig. 14 is a graph showing the relationship between the distance between the slab position of the present invention and the surface layer and the maximum particle diameter / average particle diameter of the crystal grain size. This paper size applies to China National Standard (CNS) A4 (2J0 X 297 public love) (Please read the precautions on the back before filling this page)

Mil -------------- ^ ί, 34 A7

V. Explanation of the invention (32) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. Figure 15 is a graph showing the relationship between the distance between the surface of the conventional cast slab and the surface and the maximum particle size / average particle size of the crystal size. Fig. 16 is a graph showing the relationship between the number of inclusions (10 Å or less) in the cast slab (each plus 2) and the equiaxed crystal ratio (%). Fig. 17 is a state diagram of the Ca0_A12〇3_Mg0 system, and is a diagram showing the composition range of the present invention. FIG. 18 is a graph showing the relationship between the solubility product between Ti concentration and N concentration in the molten steel treatment method card of the present invention: [% men] X [% N], and Cr concentration. Fig. 19 is a graph showing the relationship between the total mass of FeO, Fe203, MnO, and SiO2 in the slag before the Mg addition and the Mg content of the molten steel t after the Mg treatment in the molten steel treatment method of the present invention. Fig. 20 is a graph showing the relationship between the alkalinity of slag and the activity of CaO in the molten steel treatment method of the present invention. Best Mode for Carrying Out the Invention 1) Next, referring to the attached drawings, the embodiment of the present invention will be described for the understanding of the present invention. As shown in Figs. 1 and 2, the "continuous casting device 10 used for the manufacture of the slab of the present invention" is provided with a gate tray 12 for storing molten steel u melt, and a spout 14 provided to dissolve the molten steel 11 from Gate plate 12 impregnation nozzle 15 poured into mold 13, electromagnetic stirring device 16 for stirring molten steel in antimony mold 丨 shown in the figure, using molten water from cooling water nozzle to support molten steel 丨 丨 solidification support Segment 17, the segments 9 and 9 are pressed down by the central part of the following pressing piece 18, and the pinch rolls 20 and 21 for taking out the cast pieces after the pressing treatment. This paper size is applicable to China National Standard (CNS) A4 specification (21〇χ 297 public love) — II!-Installed --- ordered-I-line (Please read the precautions on the back before filling this page) 35 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs * '4340 5 9 A7 ---- -_B7 ___—__ V. Description of the Invention (33) The electromagnetic stirring device 16, as shown in Figure 3, is set in the mold 13 On the outside of the long pieces 13a and 13b, electromagnetic coils 16a '16b are arranged on the long piece Ua side; and on the long pieces 13b side, electromagnetic coils 16c'i6d are arranged. The electromagnetic stirring device 16 is used as necessary. As shown in Fig. 4, the pressing section 19 'is formed by a supporting roller 22 holding the lower surface of the cast sheet 18 and a lower pressing roller 24 having a convex portion 23 in close contact with the upper side of the cast sheet 18. The pressing roller 24 is pressed by an oil pressure device not shown in the figure, and the convex portion 23 is pressed to a predetermined depth position so that the unsolidified portion 18b of the slab 18 is pressed down. The symbol 8a in the second figure is a solidified shell of the cast piece 18. The cast slab 18 'is cut to a predetermined size and then transported to the next step. The steel sheet is placed in a heating furnace, soaking furnace, etc. not shown in the figure, and is processed by electric heating or rolling to produce steel. The processing device used in the processing method of the present invention is shown in Figs. 5 and 6, and the processing device 25 shown in Fig. 5 is provided with a molten iron tank 2 6 after the molten steel 11 is loaded; A hopper 27 is arranged above the tank 26 for storing A1 alloy; and it is used for storing sponge Ti, Fe-Ti alloy Teranoi alloy, Fe-N alloy, N-Mn alloy, N-Cr alloy, etc. N alloy hopper 28; the above-mentioned alloy is added to the molten steel tank 11 of the molten steel 11 in the molten iron tank 26 from such storage hoppers 27 and 28 as needed. Further, the processing device 25 is provided with a linear iron wire 30 that is processed by covering an iron pipe with metal Mg and guided by a guide pipe 32, and the iron wire 30 passes through the slag 33 and is supplied to the molten steel 11 Inside supply device 3 ^. In addition, reference numeral 34 in FIG. 5 denotes a porous pipe plug for supplying inert gas to the molten steel 11 in the molten iron tank 26. This paper size applies to China National Standard (CNS) A4 specifications (210 X 297 mm) ί Please read the precautions on the back before filling this page) 丄-装 ----— 订 --------- Line Γ 36 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 ·· _ 11,1 Printed 5. Description of the Invention (34) In addition, the processing shown in Figure 6 is set to 35, which is equipped with a molten iron tank ^ and Plutonium into which powder of Mg or Mg alloy is blown. The spray gun is immersed in the molten steel n contained in the molten iron tank 26 and the ore crash 33 is formed on the surface; and the spray gun 36 uses an inert gas according to "§ amount will be equivalent to 0.0005 ~ 0_010 % Mass of Mg or Mg alloy powder is blown in. The solidification structure of general slabs is shown in Figure 7. It is a cold quenched crystal that is rapidly cooled and solidified in the surface layer (surface layer part) due to the mold to form a fine crystal structure. And formed by columnar crystals with a large crystal structure formed inside the cold-quenched crystals. In addition, in the slab, equiaxed crystals may be formed, and columnar crystals may reach the center. Columnar When a coarse solidified structure of a crystal system is subjected to processing such as rolling, the deformation anisotropy is large, and the deformation behavior in the width direction and the length direction is different. Therefore, the casting is made of a solidified structure having a large proportion of columnar crystals. The steel material produced by the sheet is inferior to the steel material produced by the cast sheet with fine equiaxed crystals, and is prone to surface defects such as ripple defects. Also, there are cases of coarse columnar crystals on the surface layer of the meal sheet. In large columnar crystals Grain boundary formation has micro-segregation with fragile properties, and its existing parts become brittle. 'Surface defects such as cracks and depressions occur on the surface of the slab.' Also, there are columnar crystals in the interior of the slab, or there are The case of large-diameter isomorphic crystals' occurs in micro-segregation and solidification shrinkage of solidified structures, etc. This paper size is applicable to Chinese National Standard (CNS) A4 specification (⑵〇 X 297 mm)

-------------- Installed! (Read the precautions on the back before you fill in this page.) Magic ·-Line · 37 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 4 3 4 U 5 9 A7 _____B7___ V. Internal Tortoise Caused by Invention Description (35) Internal cracks (cracks) and loose cores (center sinking) 'Internal defects such as center segregation caused by the flow of molten steel just before solidification, which damage the quality of the slab and the quality of the steel => 2), (1) above The occurrence of surface defects and internal defects can be prevented by treating more than 60% of the entire cross section of the cast piece with a solidified structure having an equiaxed crystal satisfying the following formula. D &lt; 1.2Xt / 3 + 0.75 In addition, D refers to the equiaxed crystal aperture (mm) 'X of the structure with the same crystal orientation, and it is the distance from the surface of the slab. In other words, a slab composed of a solidified structure having equiaxed crystals satisfying the above formula is the slab A of the present invention. The diameter of these axial crystals is a complete process of etching the molten steel in the thickness direction of the slab after solidification, and when light is irradiated on its surface, the brightness of the reflected light reflected by the crystal orientation of the macrostructure is a specific treatment. The size of the solidified tissue. The detection of the diameter of the axial crystal is based on the thickness section of the slab cut and exposed, and the section is polished, for example, with the hydrochloric acid, nitric acid and ethanol corrosion solution (mixed solution of nitric acid and ethanol), etc. A reaction is generated to perform an etching process. The average equiaxed crystal diameter &gt; is obtained by taking an enlarged photograph of 1 to 100 times the macrostructure, and then subjecting the enlarged photograph to image processing to obtain the isometric crystal diameter (mm) obtained. The largest of the equiaxed crystal diameters is the largest equiaxed crystal diameter. The eighth circle indicates the relationship between the distance from the surface layer and the equiaxed crystal diameter of the slab A 'of the present invention. Because the full section of the cast piece is processed at more than 60% of the processing cost, the paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) 1! &Lt; * I ------ ^ «— — — — — — 1— Γ f Please read the precautions on the back before filling out this page) 38 A7 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs V. Description of the invention (36) Solidified structure with equiaxed crystals that satisfy the aforementioned formula, Not only can the formation of columnar crystals in the surface layer be prevented, but a fine equiaxed crystal diameter is also formed inside. In this slab A, as shown in Fig. 9, since the growth of columnar crystals in the surface layer portion is suppressed, there is little brittle microsegregation existing at the grain boundary; and even if there is, it is extremely small. Therefore, in this blade A, surface defects such as cracks and sags that occur at the microsegregation region as a starting point are suppressed because the shrinkage and unevenness of stress occur during cooling of the die and during solidification. . Also, as shown in FIG. 9, due to the shrinkage of the internal equiaxed crystal diameter, the microsegregation generated at the same grain boundary as the surface layer portion becomes smaller, and the resistance to cracks increases, accompanied by the swell of the slab and The occurrence of internal cracks caused by the correction of the rollback correction is suppressed. Therefore, since the slab A has good processing characteristics and materials, when a steel material is produced using the slab A, a steel material without surface defects such as corrugation flaws can be produced. For the equiaxed crystals satisfying the foregoing formula, when the full cross-section of the cast surface is less than 60%, the range of columnar crystals increases, and at the same time, the internal equiaxed crystal diameter increases, and cracks and sag defects occur on the cast slab. As a result, it is necessary to prepare the slabs, cause fragmentation, and the like; and 'the surface defects and internal defects of the steel materials occur when the slab processing is performed' causes a reduction in the quality of the steel materials. In the solidified structure of the slab A of the present invention, as shown in FIG. 10, equiaxed crystals satisfying the foregoing formula are formed through the entire cross section of the slab, and the solidified structure can be formed throughout the entire slab to form a uniform solidified structure. , Can also reduce the brittle microsegregation existing in the grain boundary throughout the slab. As a result, the resistance of the slab to cracks is improved, even if shrinkage due to cooling and solidification of the mold occurs, and the Chinese paper standard (CNS) A4 (210x297 mm) is applied to this paper size ------ ------.-- Install --- (Please read the precautions on the back before filling this page) .- Line 39 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 43405g A7 _____B7____ V. Description of the Invention (37) The non-uniformity of the cracks and surface defects such as cracks and sags that start from the microsegregation, the swelling of the slabs, and the internal cracks caused by the deformation caused by the rollback are also surely achieved. inhibition. In addition, when the solidification core is used as a starting point for solidification, the equiaxed crystal diameter can be reduced. As a result, the flowability of the molten steel immediately before the completion of the solidification is improved, and the looseness of the center and the central segregation due to the shrinkage of the molten steel are caused Defects such as these are prevented, and defect-free ballasts can be cast. Furthermore, 'the slab A' of the present invention sets the maximum equiaxed crystal diameter to within 3 times the average equiaxed crystal diameter, and further forms a solidified structure into a fine solidified structure to obtain a desired result.

As a result, the non-uniformity of the equiaxed crystal diameter in the solidified structure is reduced, and a slab having a solidified structure with high uniformity is formed. The microsegregation formed in the equiaxed crystal boundary is suppressed to be smaller, and can be prevented. The occurrence of surface defects and internal defects D is also 'due to the small equiaxed crystal diameter'. When processing such as rolling, the uniformity of deformation behavior is further improved. When the maximum equiaxed crystal diameter exceeds 3 times the average isocratic crystal diameter, the local part of the processing deformation becomes uneven, and stripe-like ripple defects may occur. Also, "the cast piece A of the present invention focuses on the oral control of the equal sleeve crystal edges obtained through the image processing, as shown in Fig. Π." 60% or more of the full-cut piece of the cast piece can satisfy the following formula Equiaxed crystals can obtain ideal solidified structure. D &lt; 0, 〇8X ° 78 + 0.5 This paper size is applicable to China National Standard (CNS) A4 (210 X 297 mm) ------- I --- &lt; β--I ---- -^ &lt; Please read the notes on the back before filling out this page) 40 A7

Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, where X is the distance from the surface of the slab (mm), and D is the diameter of the equiaxed crystal (mm) from the surface of the slab to X. In addition, as shown in Fig. 12, the slab A of the present invention can form an equiaxed crystal satisfying the above formula, and a more ideal solidified structure can be obtained. When the slab A of the present invention is continuously cast in the continuous casting apparatus shown in FIGS. 1 and 2, Mg or Mg alloy is added to the molten steel 11 in the gate plate 12 to form molten steel 丨 丨MgO monomer or MgO-containing composite oxide (hereinafter referred to as "MgO-containing oxide" ^).

MgO has good dispersibility and forms fine particles uniformly dispersed in molten steel u to act as a solidification nucleus; at the same time, the above oxides themselves block (inhibit the coarsening of the solidified structure immediately after solidification) and suppress the coarsening of the solidified structure To form an equiaxed crystal; at the same time, the equiaxed crystal itself is refined to form a homogeneous slab. The added Mg or Mg alloy is a sufficient amount of Mg 0.0005 ~ 0.10% by mass added to the molten steel; the Mg added to the molten steel, the oxygen in the molten steel, and FeO 'Si02, Oxygen supplied by a hafnium compound such as MnO reacts to form MgO or MgO-containing oxide. In addition, the method of adding Mg or MgO alloy is to directly add the alloy to the molten steel; or, the Mg or Mg alloy is coated with thin steel and processed into linear wire to continuously supply. When the added amount of Mg is less than 0.0005% by mass, the number of solidified nuclei is insufficient ', and it is difficult to obtain a fine solidified structure due to insufficient generated nuclei. Also, when the added amount of Mg exceeds 0-10% by mass, the standard paper size of its equiaxed crystals conforms to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) IIII --- • Package --- I --- 1 Order ----- Line {Please read the notes on the back before filling out this page) 41 t '4340 b 9 A7 B7 The effect is saturated, at the same time, the total oxide content inside the slab increases and the corrosion resistance decreases. And the alloy cost increases. The slab cast through this process has a uniform and fine solidification structure, very few surface defects and internal defects, and has good In addition, the slab A of the present invention can be cast in addition to continuous casting, using other block making methods, and casting methods with small wheels, twin rolls, and the like. Next, the slab A of the present invention is manufactured The steel material of the present invention is a slab A having 60% or more of the entire cross-section of the solidified structure and having an equiaxed crystal solidified structure satisfying the following formula, using a heating furnace and a soaking furnace (not shown). And so on, after heat treatment at 115 to 250 ° C, It is further processed by special processing (for example, steel plate, shaped steel). D &lt; 1.2Xi / 3 + 〇.75 and D is the equiaxed crystal diameter (mm) of the structure with the same crystal orientation, and X is from Jing Sheet surface distance (mm) »Since this steel is manufactured from cast piece A with the above-mentioned solidified structure, the brittle microsegregation existing in the grain boundary is small, and the crack resistance of the microsegregated portion is increased. It becomes a steel village with few surface defects such as cracks and spalling. Also, in the slab, the center looseness (center depression) caused by cracks and solidification shrinkage of unsolidified steel, and the center segregation caused by the flow of molten steel. It can be suppressed, so in the steel, there are very few internal defects caused by the internal defects existing in the slab. In addition, the 'bond sheet A of the present invention' has high uniformity of deformation during processing such as rolling, due to its processing. The characteristics are good, so for steel, it is' toughness, etc. (Please read the precautions on the back before filling this page) -Installation !! I ---- Order ·! ------ Line 42. Ministry of Economic Affairs Intellectual Property Bureau's Consumer Cooperation Du printed A7 B7 Five 'Invention Description (40) Good surface defects such as corrugated flaws and cracks. In particular, the use of slabs with a full cross-section that satisfies the aforementioned equiaxed crystals, followed by heating? "• Steel produced by processing such as calendering, because of its uniformity The solidified structure has fewer surface defects and internal defects, and the deformation uniformity during processing is better, so the processing characteristics and material are good. Also, by setting the maximum equiaxed crystal diameter of the cast piece. Within 3 times the average equiaxed crystal diameter, 'the size of the microsegregation formed in the boundary of the equiaxed crystal diameter can be suppressed', and a steel material having a more homogeneous material property can be obtained. (2) The casting of the present invention The sheet B 'is characterized in that the maximum value of the crystal grain size at an equal depth from the surface of the cast sheet is set to within 3 times the average crystal grain size at the depth. As shown in FIG. 13, the slab B is the same as the maximum value of the crystal grain size at a position of 2 mm from the surface of the slab is 2 mm, for example, the maximum value of the crystal grain size at the position of 2 to 10 mm. When the crystal grain size is set within 3 times, coarse columnar crystals formed in the surface layer are suppressed, and grain boundary segregation of free elements such as Ca is reduced. As a result, sag flaws and cracks caused by uneven cooling and solidification shrinkage of the wafer can be prevented, and a structure having high resistance to cracking of the cast structure can be formed. As a result, since cracks and the like occurring on the surface and inside of the ball pieces are reduced, the preparation of the ball pieces by grinding and the shredding of the blades are reduced, and the productivity of the cast pieces is improved. In addition, the processability of the sheet when it is processed by calendering has been greatly improved. 0 This paper size applies the national standard (CNS) A4 specification (210 X 297 mm)----------- -* Equipment -------- Order II-II! -Line (please read the precautions on the back before filling this page) 43 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 _____B7____ V. Description of the Invention (41) The value of the crystal grain size of this crystal at a depth of 2 mm from the surface of the cast piece is, for example, the value of the crystal grain size of the exposed surface measured by grinding from the surface of the ball piece to a position of 2 to 10 mm. The grinding may be performed as close to the center of the slab. The maximum value of the crystal grain size located at the same depth from the surface of the slab. When the average crystal grain size exceeds 3 times, the unevenness of the crystal grain size increases. As a result, the deformation stress during processing is concentrated on the specific crystal grain. The formation of surface defects, such as unevenness in the formation of waves, causes a reduction in productivity. In addition, it is easy to form a high portion of the grain boundary segregation, and surface cracks and internal cracks may occur from this portion. As a result, the occurrence of surface defects and internal defects causes an increase in slab preparation, slab fragmentation, and the like, thereby reducing productivity, and reducing the material quality of the steel. Also, as shown in FIG. 14, the slab B of the present invention sets the maximum value of the crystal grain size within 3 times the average crystal grain size value aligned at the same depth; and At least 60% of the entire section of the sheet forms an equiaxed crystal 'as shown in Figure 9, the formation of coarse columnar crystals at the surface layer is suppressed', and a uniform structure can be formed throughout the whole. Fig. 15 shows the relationship between the distance from the surface of the conventional cast slab and the maximum particle diameter / average particle diameter of the crystal grain diameter. When the slab B of the present invention is processed, it is possible to suppress the deformation stress from being concentrated on specific crystal grains, so that the isotropic behavior of the deformation behavior (the extension in the width direction and the length direction after the pressing process) can be ensured. The slab B of the present invention has higher workability. For this reason, when processing the slabs to manufacture steel, not only the cracked paper but also the timely family standard (CNS) A4 specification C 297 public love 1 ----- -44. ------ ----- 'I I ----- ^ -------- Γ (Please read the notes on the back before filling out this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs ----- ----- B7 —_; ___ 5. Description of the invention (42) and #sags such as peeling defects, 1 and can prevent the occurrence of corrugated defects (especially the bulge and rope shape on stainless steel plates). Furthermore, it is possible to reduce grain boundary segregation such as CU and other free elements formed at the grain boundary, and further improve the resistance to cracking during processing such as stupidity caused by the reduction of rolling and the like, and prevent slabs. And defects such as cracks in steel. &gt; However, when the equiaxed crystal is less than 60% of the full cross section of the front, the range of columnar crystals increases, causing cracks and sinking defects, or increasing the number of rounds of slab preparation and fragmentation. ; Surface defects and internal defects of the steel material after processing occur, and productivity may decrease, and quality may be reduced. For the same reason, by forming the equiaxed crystal of the entire cross-section of the cast surface and forming a structure with fine and uniform crystal grains throughout the whole, the grain boundary segregation is reduced. 'The crack resistance of the surface layer and the interior is increased, and the depression Defects and cracks are suppressed; the isotropy of deformation after processing is improved, and the quality and materials such as r value (extrusion processing characteristics) and toughness of steel are improved. "Crystal particle size" refers to the particle size (mm) of the structure with the same crystal orientation. The surface of the slab is etched, and the solidification structure specified by the crystal orientation of the macrostructure and the brightness of the reflected light is used. size. The detection of the crystal grain size is 'the cross section of the slab thickness direction after solidification is cut and exposed according to the existing length', and is ground from the outer periphery to a predetermined depth, and the exposed surface is polished, and for example Hydrochloric acid, nitric acid, and ethanol corrosive solution (mixed solution of nitric acid and ethanol), etc., are reacted to advance the paper size (National Standards (CNS) A4 specification (2) 0x 297) -I ----- ------- • Equipment -------- Order -------- line f, please read the precautions on the back before filling this page) 45 system

Iv 43 ^ A 3 4 Ο 5 9 a7 ------ B7___ V. Description of the invention (43) Processing. Next, a magnified photograph of 1 to 100 times of macroscopic tissue was taken, and image processing was performed to measure the crystal grain size, and the maximum diameter and average value were obtained. In the continuous casting of the slab B of the present invention, Mg or an Mg alloy is added to the molten steel 11 in the gate pan 12 (see Figs. 1 and 2) to form a monomer of MgO in the molten copper 11 Or containing MgO oxide.

The addition amount, effect and method of adding Mg are the same as those of the slab A of the present invention. Also, the slab B 'of the present invention is continuously cast except for the same continuous casting as the slab a of the present invention. Casting may be performed by a casting method such as a pulley or a double roll. The slab B of the present invention is heated at a temperature of 1150 to 1250 ° C through a heating furnace and a soaking furnace (not shown), and then processed by rolling or the like to produce steel materials such as steel plates and shaped steels. This steel material is a steel material with good processing characteristics because it has few surface defects such as cracks and peeling, and internal defects such as internal cracks. In particular, when a ball having a cross section in the thickness direction of at least 60% is equiaxed or a full cross section is equiaxed, the number of defects formed is small, and the processing characteristics such as extrusion processing characteristics can be obtained. Steel. (3) The ball chip C of the present invention is characterized in that 100% / cm2 or more of inclusions having a degree of lattice mismatch between &lt; 5 pure grain iron formed during solidification of molten steel and less than 6% are included. Solidified primary crystal (the initial crystalline phase of molten steel 11 during solidification) is a molten steel of the pure steel type of iron (a pure grain iron stainless steel containing 13% chromium). Bu tc ;, M aft fft I two certificates: 丨------------- A ------ Order ------- (Please read the notes on the back before filling (This page) 46

(Ministry of Intellectual Property Bureau, Ministry of Economic Affairs, Employees' Cooperative, printed steel) 11, washing solution to the mold 13 through the immersion nozzle 15 provided in the gate tray 12 (refer to Figures 1 and 2), and the solidified shell 18a is continuously formed after cooling. The cast piece 18 is obtained, and then is input below the support segment π, and the cooling water is used to perform heat removal 'sequentially' while increasing the thickness of the solidified shell 183, while passing through the pressing process of the pressing section 19 on the way (See Figure 4) Completely solidified. As shown in Fig. 7, the solidified structure of the conventional slab thickness section is attached to the surface layer (surface layer portion) of the slab. The mold is rapidly cooled to form a cold crystalline crystal with a fine structure after quenching. A large columnar crystal is formed inside the cold-headed crystal. As far as the surface layer part is located in the boundary of columnar crystals, there is microsegregation. Because the segregated part has crisp characteristics, surface defects such as cracks on the surface of the cast slab and depression due to uneven cooling and shrinkage of the mold are formed. s reason. Also, the inside of the slab * is slower in cooling than the surface layer portion, and columnar crystals or large equiaxed crystals are generated. The microsegregation existing in the surface layer portion is the same as that in the surface layer portion. This micro-segregation has the same crisp characteristics as the surface layer portion, and the internal cracks are formed by mechanical stress such as heat shrinkage, swelling of the slab, and roll-back correction during internal solidification. On the other hand, if the equiaxed crystal grains located inside the slab are large, as the solidification progresses, the center caused by the insufficient supply of molten steel inside the slab and the center caused by the flow of molten steel immediately before the end of solidification are formed. Internal defects, such as segregation, impair the quality of the slab. Therefore, 'to prevent the above-mentioned surface defects and internal defects, when the molten steel is solidified, this paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) -II I -------- in ----- — — — — F Please read the notes on the back before filling out this page) 47 434059 A7 B7 V. Description of the invention (45) It is necessary to make the dissolution degree of the lattice between the δ pure grain iron and the δ pure grain iron 6 exist in the molten steel. The number of central impurities below / 0 is 100 pieces / cm2 or more. This inclusion 'is a metal added to react with oxides such as 0, C, N, S, and SiO2 contained in the molten steel 12 to form inclusions; or, the inclusions are added to the molten steel through the inclusions themselves, and are present throughout Dissolved in steel. Inclusions formed by the reaction of the above metals with 0, C, N, S, SiO2, etc. in the molten steel; or, inclusions added to the molten steel to form inclusions below 10 / zm in the molten steel Thing. The moxibustion debris acts as a coagulation nucleus when the steel is solidified, and forms the starting point of the beginning of solidification β. Furthermore, the blocking effect of the above-mentioned impurities can inhibit the growth of the solidified weave, and a cast piece having a fine solidified structure can be produced. . In particular, when inclusions with good dispersibility are used, the solidification of the molten steel η in the casting mold 3 and the stirring with an electromagnetic stirring device are used to form 100 or more inclusions with a size of 10 or less, and the solidification is more prominently found. The nucleus and its blocking effect, as shown in Fig. 16, can be obtained with an equiaxed crystal ratio of 60. The solidified structure of the slab a with a solidified structure of more than / 0 is shown in Fig. 9 as a solidified structure in a section of the slab thickness direction. A fine equiaxed crystal structure is formed in the slab, and the surface layer The growth of columnar crystals is suppressed. Therefore, as the inclusions below 10 &quot; m increase, the solidified structure from the surface layer portion of the slab to the entire internal section can form finer and more uniform equiaxed crystals. The slab C of the present invention with fine equiaxed crystals is not prone to cracks and sags that occur on the surface of the slab due to crack resistance. Rtf Read this first ¾ Note on the back before filling this Page), Chu ----- Order I --- I! --- Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 48 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the Invention (46 In addition, the inside of the slab C of the present invention has few micro-segregated parts, and even if heat shrinkage and any kind of stress occur, internal cracks and the like are less likely to occur: and the supply of molten steel immediately before the end of solidification is insufficient. The occurrence of internal defects such as center porosity and center segregation can also be prevented. Also, when processing such as slab rolling, the fine equiaxed crystals in the slab C of the present invention are easily deformed in the pressing direction. t Therefore, the slab C of the present invention belongs to the one with higher processing characteristics. Moreover, due to good processability, no surface defects such as corrugation (rope-like, raised, edge seam) occurred after processing such as rolling; Also, calendering, etc. During processing, the occurrence of internal defects such as cracks caused by internal defects existing in the slab can also be eliminated. Formation of inclusions used in pure-grain iron-based steel grades (the inclusion-based metal compounds) are based on the use of Mg , Mg alloy, Ti, Ce, Ca, Zf and other metals and metal compounds, and react with the oxides of 0, c, N, § and &amp; 0, etc. in the molten steel. Miscellaneous materials, which use Mg〇, MgAl204, ΤΝΝ, CeS, Ce203, CaS, Zr〇2, TiC, VN, etc., and the degree of lattice inconsistency between 5 pure grain iron and less than 6%. In terms of the later dispersibility and stability of solidified nuclei, Mg0, MgA ^ 〇3, and TiN are particularly desirable. Moreover, the degree of lattice mismatch between the pure iron and the pure iron is a pure steel produced by solidification. The difference between the lattice number of the grain iron and the lattice number of the metal compound is divided by the value of the solidified core lattice number of the molten steel. The smaller the value, the larger the paper size_China National Standards⑵ X 297 Public love)

49 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 434059 A7 ____B7 V. Description of Invention (47) The better the formation of the solid core. The measurement of the number of inclusions in the slab is calculated by using a scanning electron microscope SEM, a slime method, and the like to calculate the number of inclusions per unit area of 10 m or less. The size of the metal compound is determined by observing inclusions on the entire cross section using an electron microscope such as SEM. The average diameters of the largest and smallest diameters of the inclusions are taken as the size of the inclusions. On the other hand, in the case of the slime method, the entire section of the cast piece is cut out, and then the cut piece is dissolved, and then the inclusions are classified and taken out, and the maximum diameter of the inclusions is separately And the minimum diameter is averaged to determine its size to find the number of each size. Also, when continuous casting of a slab containing such impurities, metal is added to the molten steel 11 (see Figs. 1 and 3) in the gate pan 12 to dissolve oxygen or FeO, Si02, and MnO in the molten steel. , N, C, etc. react to form inclusions such as MgO, MgAl204, TiN, TiC; or 'add such inclusions directly. In particular, when Mg or Mg alloy is added to the molten steel, when the molten steel forms inclusions composed of MgO monomers or MgO-containing oxides, the dispersibility of the impurities in the dissolved steel can be improved, so it can be obtained. More ideal results. For example, the Mg or Mg alloy added to the molten steel may be added to Mg of 0.0005 to 0-10% by mass. Adding method 'refers to adding Mg or Mg alloy directly to molten steel, or' continuous wire processing with Mg or Mg alloy coating thin steel to form linear iron wires. This paper applies the National Solid State Standard (CNS) A4 specification ⑵〇χ 297 Gongchu) ---------------------------------------------------------------------------------------------------------------------—————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————— Therefore, T. 50. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7-~ ___ B7 _ V. The supply of invention description (48) was supplied to Ronggang (see Figures 5 and 6). When the added amount of Mg is less than 0.0005% by mass, it is difficult to obtain a fine solidified structure due to insufficient solidification nuclei. In addition, since the blocking effect of the inclusion itself is weakened, the effect of suppressing the growth of the solidified structure is reduced, and a fine solidified structure cannot be obtained. On the other hand, when the added amount of Mg exceeds 0.10% by mass, not only the solidification nuclei are formed and saturated, but also the total amount of oxides in the cast slab increases and its survivability decreases. In addition, the cost of alloys increases. In addition, the solidified primary crystal system is a molten steel of a steel type of <5 pure grain iron, for example, SUS stainless steel containing 11 to 17% by weight of chromium. Therefore, 'the slab C' of the present invention has a uniform and fine solidification structure, and the occurrence of surface defects and internal defects is suppressed ', so that it has good processing characteristics. In addition, in addition to continuous casting, the slab C of the present invention may be cast using a block making method, a casting method such as a pulley, a double roll, etc.a The slab C of the present invention is obtained by using pinch rollers 20, 21 ( (Refer to Fig. 1) Extraction 'is then cut to a predetermined size by a cutting machine not shown in the figure, and is then transferred to the post-rolling step β. The cast slab C of the present invention after the above transfer uses the unshown figure Heating furnaces and soaking furnaces are heated at 1150 ~ 1250 ° c, and then processed by rolling and other processes to 'steel, plate, and shaped steel. This type of steel has a strong resistance to cracking in the structure. It is a steel with few surface defects such as cracks and spalling during and after processing. &Lt; This type of steel has a center segregation located inside the slab, etc. The Zhongguanjia Standard (CNS &gt; A4 Specification (2) G 297 Gongchu) is applied to this paper standard II— ί 111 — -----—-- Order · 1 — 111 — II · 5 ^ · (Please read first Note on the back, please fill out this page again) 51 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 4 3 4 Ο 5 9 Α7 ----------- V. Description of Invention (49) The internal defects caused by the internal defects of the cast slab are few. Furthermore, the cast slab C of the present invention having a fine and uniform solidified structure can easily perform the processing of the cast slab due to its good processing characteristics such as r value; and 'The toughness of the welded part after processing is also very good. In particular, the steel sheet produced by processing such as rolling with a large amount of inclusions having a size of 10 μm or less is good in dispersibility. And cracks are surely prevented, and (4) The slab D of the present invention is characterized by the fact that the molten steel is added to the molten steel to form a solidified core when the molten steel is solidified. In the slab, in which the number of metal compounds in the surface layer portion of the slab is smaller than the number of metal compounds in the surface layer portion and the number of metal compounds in the surface layer portion is 13 times or more. In order to prevent surface defects and internal defects, the casting slab D 'of the present invention is a metal compound or a metal compound itself formed by adding a metal compound that reacts with 0, C, N, and oxides in the molten steel to the molten steel. When the molten steel solidifies, it forms the formation of solidified nuclei. However, the formation of metal compounds of various sizes in the molten steel, when the size of the metal compound exceeds the size of the solidified nuclei, the formation of solidified nuclei is difficult; The effect of suppressing the coarsening of the axial crystal is not sufficiently exhibited, and the solidification structure cannot be made fine. Therefore, the metal or gold added to the molten steel Compounds are those with good dispersibility and a large amount of metallized human paper below the size. Applicable to China National Standard (CNS) A4 (210 X 297 mm) -------! I Λ I ---------- II I--Γ f Please read the notes on the back before filling out this page) 52 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 ----- --- E7_____ 5 2. The description of the invention (50) The owner is extremely important. Moreover, it is necessary to set the number of these metal compounds below 10 / zm to 13 times or more with respect to the number 'existing in the surface layer portion of the baffle. The reason is because the surface layer of the prayer sheet is cooled rapidly, so even if there are relatively few metal compounds forming a solidified core, a fine equiaxed solidified structure can be obtained. Also, the "position inside the slab" is to set the number of metal compounds below 金属 to 倍 to 1.3 times the number in the surface layer portion. By acting as a solidifying nucleus and blocking, the equiaxed crystals are fine. The transformation is promoted and the coarsening of the equiaxed crystals is suppressed, and a uniform and fine solidified structure can be obtained. As shown in Fig. 9, more than 60% of the solidified structure in the thickness section of the slab is a fine equiaxed crystal, and a slab having a solidified structure in which the columnar crystals of the surface layer portion are reduced and suppressed can be obtained. Further, a slab having a solidified structure composed of fine and uniform equiaxed crystals from the surface layer portion to the entire internal cross section of the slab can also be obtained. As a result, in the slab D of the present invention, the occurrence of cracks and depressions caused by deformation and stress in the solidification process and the occurrence of surface defects caused by inclusions are suppressed; and the slab swell and correction of the slab are strengthened Resistance to internal cracks due to the deformation: In addition, due to the molten steel fluidity is ensured, the occurrence of internal defects such as center porosity and center segregation is suppressed. -------------- installation ---- I --- order ------- line (please read the precautions on the back before filling this page)

53 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs • 4340 5 9 A7 _______B7_; ____ V. Description of the invention (51) In particular, the slab D of the present invention has a small number of metal compounds forming a solidified core in the surface layer, but There are many internal parts. Therefore, when casting slabs are processed into steel such as sheet steel and shaped steel, the occurrence of surface defects such as surface peeling defects and cracks caused by inclusions can be suppressed. In addition, metal compounds are exposed on thin plates and shaped steel. Reduction of corrosion resistance caused by the surface or the presence of the surface layer can also be prevented. When the number of the inside of the slab is less than 1.3 times the number of the surface layer portion of the slab, the solidification nuclei for miniaturizing the solidified structure are insufficient; and because the blocking effect is reduced, the solidified structure is coarsened, and uniformity cannot be obtained. The solidification structure 'has surface defects such as cracks and depressions caused by internal stress such as cooling during the casting and uneven solidification during cooling, and internal shrinkage, and internal defects such as loose cores and center segregation, which hinders the rolling process. Machinability during processing. The metal compounds contained in the molten steel use Mg0,

MgAl204, TiN, CeS, Ce203, CaS, Zr02, TiC, VN, etc. The degree of lattice mismatch between 5 pure grain iron and less than 6%. Among them, MgO, MgAl204, and TiN are preferred from the viewpoints of dispersibility and solidification nucleation when added to molten steel. The metal to be added to the molten steel is a metal such as Mg, Mg alloy, butadiene, Ce, Ca, Zr or the like. The metal compounds are formed by reacting with halides such as 0 and c, N, and SiO2 in the molten steel, and metal compounds containing these metals may also be used. In particular, the metal used to form a metal compound with a degree of lattice mismatch between 5 pure grains of iron and 6% or less, or a metal compound added to the molten steel. The paper size is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 public love) (please read the precautions on the back before filling this page), install --III I--order --------- line 54 printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs-- _____B7 V. The situation after (52) of the invention can effectively promote the formation of solidified nuclei; and because of the prominent manifestation of the blocking effect, a cast piece with a solidified structure composed of finer equiaxed crystals can be obtained The slab is easy to deform in the downward direction, and the processing characteristics such as elongation are particularly good. For continuous casting of slabs containing such metal compounds, Mg, Mg alloy, Ti, Ce, Ca 'Zn, etc. are added to In the molten steel 11 in the gate plate π (refer to i and 2), it reacts with the gas or core 0, Si02, MnO'N, C, etc. in the molten steel 1 to form MgO, MgAl204, TiN. And TiC, especially Mg or Mg When dissolving gold in molten steel to form MgO monomers or MgO-containing oxides in molten steel, more favorable results can be obtained due to the improved dispersibility of metal compounds in falling steel. For example, 'addition of Mg or Mg alloy' is a solution to molten steel. Addition is made of 0.005 to 0.010% by mass of Mg. The addition method is to directly add Mg or Mg alloy to molten steel, or Mg or Mg alloy is coated with thin steel and processed into linear iron wires to be continuously supplied. In molten steel (see Figures 5 and 6). When the amount of Mg added is less than 0.0005% by mass, the absolute amount of solidified nuclei is insufficient, the solidified nuclei and blocking effects are reduced, and it is difficult to obtain a fine solidified structure. 'When the amount of Mg added exceeds 0.01% by mass, the effect of forming solidified nuclei is saturated' while the total amount of oxides in the slab increases' and the corrosion resistance and the like decrease. Moreover, the cost of the alloy increases. The slab D of the present invention has a uniform solidified structure, and the occurrence of surface defects and internal defects has been suppressed. It has a good paper size and is applicable to the national standard (CNS) A4 specification (210 X 2). 97 issued) ------------- 1 ---- II Order ---- ---- • Line (Please read the precautions on the back before filling this page) 55 434059 Economy Printed by the Consumers ’Cooperative of the Ministry of Intellectual Property Bureau A7 B7 V. Description of the invention (53) Processing characteristics. In addition to continuous casting, the slab D of the present invention can also use agglomeration methods, casting methods such as pulleys, double rollers, etc. Casting; when the thickness is more than 100inm, the adjustment of the distribution of inclusions (metal compounds) is easy to perform. Since the equiaxed crystals in the solidified structure from the surface layer to the interior can be easily adjusted, ideal results can be obtained. " Even in the method of casting, for example, a method in which a mold having both ends penetrating is cast by continuous or vertical continuous casting, the effect of miniaturization is greatly increased, and ideal results can be obtained. The slab D 'of the present invention is 1150 to 1250 using a heating furnace, a soaking furnace, etc., which are not shown in the figure. (: After heat treatment, a steel sheet such as a sheet or a shaped steel is processed by rolling or the like.

This steel has an increased resistance to cracks in the microsegregation section of the slab, and is a steel with few surface defects such as cracks and peeling. In addition, as for the inside of the steel, internal defects and rolling caused by internal defects in the slab The occurrence of internal defects such as internal cracks caused by such processing. In addition, "the town sheet D of the present invention has good processing characteristics and financial properties", so the steel produced by processing the cast sheet D also has good processing characteristics and financial properties. 3) When producing the slab of the present invention, it is necessary to perform any kind of treatment on the molten steel. The processing method of the molten steel of the present invention (processing methods I to V of the present invention) is described below. (1) The processing method I of the present invention is characterized in that the total Ca of the molten steel is set to 0'0010% by mass or less, and then Mg is added to the molten steel. Figures 5 and 6 show that the inversion of the molten steel paper in the 'system hot metal tank%' of the processing device is in accordance with the Chinese National Standard (CNS) A4 specification (210 X 297 cm) --------- II ^ ~ Install -------- Order. —_ | _1 --- line, 1 (Please read the precautions on the back before filling out this page) 56 -Printed by A7 of the Intellectual Property Bureau Staff Consumer Cooperatives of the Ministry of Economy ~- ___B7_____ V. Description of the invention (54) 11 'The total Ca content after the combination of Ca or CaO contained in the molten steel is adjusted to 0.0010% mass or less (there is also a case of 0). In addition, it does not generate Al; a low melting point compound (complex oxide) of 203 and CaO, aluminate (12CaO * 7A1203). When the total Ca content in the molten steel exceeds 0.0010% by mass, Ca, which is a strong deoxidizing agent, forms CaO, which is added with CaO previously contained to combine with Al203 to form a low melting point compound. In addition, MgO produced by the addition of Mg or Mg alloy is combined with a composite oxide of CaO. Al203 to form a low melting point CaO · Ai; 〇3-MgO ternary composite oxide. Since this composite oxide dissolves in the temperature range of molten steel, its function as a solidified core disappears, and as a result, a fine solidified structure cannot be obtained. Alternatively, even if the above-mentioned complex hafnium-based inclusions are relatively high-precision inclusions, since CaO 'is contained, the lattice mismatch between the inclusions and the 5 pure grain iron is low, and they cannot function as solidified molten steel. Regarding the adjustment of the total Ca content and the formation of calcium aluminate, when the molten steel η is deoxidized in a refining furnace, a molten iron tank 26, etc., deoxidation is performed by ca and Ca alloys; or, alloy iron containing no Ca is used Deoxidation treatment of alloy iron with low Ca content.

The addition amount of Mg or Mg alloy is set to 0.0005 to 0.10% by mass corresponding to Mg. When the added amount of Mg is less than 0.0005% by mass, the solidified nuclei formed are insufficient, and it is difficult to obtain a fine structure; and when the amount of Mg is exceeded, the effect of the% • axis crystal formation is saturated, and The total oxide inside the slab increases and the corrosion resistance and the like decrease. And alloy costs increase. So 'for the processing method I of the present invention, since the paper size contained in the molten steel is in accordance with the Chinese National Standard (CNS) A4 specification (210 X 297 mm) ------------- pack- ------- Order --------- line (please read the notes on the back before filling out this page) 57 Printed by the Intellectual Property Bureau Employee Consumer Cooperative of the Ministry of Economic Affairs 434059 A7--B7 V. Description of the invention (55) The total Ca content is relatively low, and through the oxygen contained in the molten steel and the oxygen supplied by oxides such as FeO, SiO2, MnO, etc., a composite oxide of MgO monomer and MgO 'Al2 03' is formed. Such oxides are finely divided and uniformly dispersed in molten steel. During the solidification of this molten steel, a large number of solidification nuclei are formed. In addition, the oxide itself suppresses the coarsening of the solidification structure of the cast slab due to the effect of blocking (inhibiting the coarsening of the structure immediately after solidification). Crystals and equiaxed crystals themselves are refined and homogenized. &Gt;

The amount of Mg added and the total amount of Ca contained in the molten steel are adjusted in the processing devices 25 and 35 (see Figures 5 and 6) to suppress the low melting of calcium and aluminates (12CaO, 7 Al2O3, etc.). It is advisable to adjust the generation of dot compounds). Then, through the oxygen contained in the molten steel and the oxygen supplied from the oxides of FeO, SiO2, MnO, etc., the monomers of MgO and MgO-containing oxides such as MgO. A1203 are formed, and the finely-granulated oxides are formed. Evenly dispersed in molten steel. As shown in FIG. 9, the solidified structure of the ball which is continuously cast by the molten steel processed by the processing method I of the present invention is a solidified structure formed of homogeneous and fine equiaxed crystals. The slabs cast by this process are cut to a predetermined size, and then transported to the next step, and then processed by a heating process such as a heating furnace or a soaking furnace, which is not shown in the figure, and then processed by rolling to produce steel. As for this slab, since the workability has been greatly improved, the steel produced from the slab has good extrusion processability and toughness. (Please read the precautions on the back before filling out this page) Install -------- Order .--------

-58-A7 B7 'Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs * 1 ^ V. Description of the Invention (S6) In addition to continuous casting, other methods of block making, town making with pulleys and double rollers are used. Can also be made. For example, when continuous casting is used to cast slabs with a thickness of 100 mm or more, the equiaxed crystal diameter in the internal structure can be easily adjusted from the surface layer to achieve the desired effect due to the effect of miniaturization. (2) The treatment method η of the present invention is characterized by adding a predetermined amount of an Ai-containing alloy to the molten steel before adding a predetermined amount of Mg to the molten steel for deoxidizing treatment. The processing device 25 shown in FIG. 5 stores the molten steel 11 (150 tons) after the decarburization refining treatment in a molten iron tank and adjusts the composition, and then sends 75 kg of A1 from the storage hopper 27 and adds it through the chute 29 * At the same time, argon is supplied from the porous pipe plug 34 installed at the bottom of the molten iron tank 26, and the molten steel 11 is fully deoxidized by adding A1 while stirring the molten steel 11. After deoxygenation by A1, the argon gas is supplied by the porous pipe plug 34, and the supply device 31 is started. The rotary drum (not shown in the figure) introduces the iron wire 30 through the guide pipe 32 and sends it out, while passing the slag 33 through. , And a metal Mg (0.0005 to 0.10% by mass) of 0.75 to 15 kg is supplied in the molten steel η. Therefore, before adding the given amount of Mg, add the given amount of A] to react with oxygen, Mn0'Si02, Fe0, etc. in the dissolved steel to produce 丨 2203, and then add Mg, which is pure with &lt; 5 The degree of lattice mismatch between the iron particles is greater than 6%. When the molten steel solidifies, it is on the surface of the nucleus, which is an ineffective solidifying core. It causes MgO, MgO, AI2O3, and other MgO-containing oxides to form. . Therefore, the reduction of the lattice mismatch between the inclusions in the molten steel and the 6 pure grain iron is reduced to the paper size of China National Standard (CNS) A4 (210 X 297 public love) --- ------- -Install ----- I--Order -------- • Line (Please read the precautions on the back before filling this page) 59 434059 A7

Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the invention (57) is small but less than 6%, so that the inclusion acts as a solidification nucleus when the molten steel solidifies. As a result, the molten steel contains most dispersed MgO and / or When MgO-containing oxides are solidified, such oxides start to solidify at various places as a starting point to form a slab solidified structure. According to the treatment method 羾 of the present invention, it is possible to eliminate cracks and sinking defects on the surface of the cast slab, and to suppress center segregation and loosening of the center, etc., and at the same time to suppress the slab and the preparation and shredding of the processed steel. Dedicated 'while improving quality. Also, 'Mg is added before the molten steel 11, in other words, after A! Deoxidation, 50 kg of Fe-Ti alloy is sent out from the storage hopper 28 and passed through; the writing groove 29 can also be added to the molten steel 11 in the molten iron tank 26. . Previously, A1 was added to the dissolved steel, and after deoxidation reaction, A1〇3 was formed. Therefore, even if Fe-Ti alloy was added, Ti did not form Ti02, and the price in the dissolved steel formed a solid solution state; or, it was combined with N in the dissolved steel to form TiN. . After that, the rotary drum of the supply device 31 is started in the molten steel, and the iron wire 30 is loaded while being guided by the guide pipe 32 to supply 0.75 to 15 kg of Mg in the molten steel 11 'on the surface of A1] 03. Generates MgO and MgO oxides (MgO · A1203) 〇 Mg and / or MgO · A1203 covering the surface of Al2O3, because the degree of lattice mismatch with ¢ 5 pure grain iron is less than 6%, so when the molten steel solidifies It acts as a solidified nucleus. In addition, the aforementioned TiN also functions as a solidification nucleus, and by multiplying the effect with MgO and / or MgO., The solidification structure can be adapted to the Chinese National Standard (CNS) A4 specification at the paper size. (210 X 297 mm) — — — — —! — — — — — ^ IIII --- tli—— — — — — Γ (Please read the notes on the back before filling this page) 60 A7 B7 Ministry of Economic Affairs Wisdom Printed by the Consumer Cooperatives of the Property Bureau V. Invention Description (58) Miniaturization. In particular, in the order of addition of A1 and Ti, in addition to the foregoing order of addition, other Ti is first added to generate Ti0 2, and then, after adding A1, Ti 0 2 is returned to the original Ti and solidified Ti is produced in the molten steel. Soluble anyway. In addition, even in any case, Ti on MgO-containing oxide or forming a separate TiN can further enhance its role as a solidified core. Therefore, since Ti can be added in a small amount, a reduction in alloy cost can be achieved; and 'can prevent defects caused by TiN. A sample of the molten steel treated by the treatment method Π of the present invention was sampled 'and its composition containing MgO oxide was investigated by an electron microscope using EPMA (electron probe microanalysis). As a result, when Mg is added after adding A1, it is confirmed that the internal system is Al2O3, and the outer system is composed of MgO or MgO. A 丨 2O3 as an impurity that solidifies as a nucleus. Covered with MgO oxide. In the case of "adding A 丨 then adding Ti" and then adding Mg, "the surface of Al203 is covered with MgO-containing oxide; and further, inclusions having a structure that partially covers TiN on the outer periphery are observed, The inclusion has a degree of lattice mismatch with δ pure grain iron of less than 6. /. Therefore, it is effectively produced as the role of solidifying nuclei. The order of adding Ti is in the order of Ti and A1 (or the order of ΑTi), and then adding Mg; or, adding A1 and then Mg, and then adding Ti, any one of the cases The coating structure of inclusions is a structure in which the surface of A1203 is coated with MgO or MgO · Al2O3, and its partial or whole system is coated with TiN, which is very effective as a solidified core. Therefore, the paper size cast from the molten steel that implements the processing method Π of the present invention applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) -----! _ 装 ------- -Xu --------- (Please read the notes on the back before filling out this page) 61 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs • ί 4340 5 9 Α7 — Β7 V. Description of Invention (59) As shown in FIG. 9, in the cast piece, the surface layer portion and the solidified structure in the cast piece are sufficiently fined in any case. (3) Regarding the processing method I and the processing method ε of the present invention, the oxides such as ore crushing and deoxidation products contained in the steel and the oxides generated when Mg is added to the steel are dissolved to satisfy the following (1 ) And (2), it is suitable to add a predetermined amount of Mg to the molten steel. 17.4 (kAl2〇3) +3.9 (kMg〇) +0.3 (kMgAl203) + 1 8.7 (kCaO) g 500 ... (kAl203) + (kMg0) + (kMgAl203) + (kCa0) = 95… (2) Where k 'is an oxide. 〇mole e Mg is added to dissolve the steel to form a hafnium compound. When the solidification structure of the cast slab is refined, and then the composition of other added elements and slag, etc., Mg0. . CaO-based plutonium compounds, or south melting point oxides that form MgO 'CaO 糸. However, 'MgO · A 丨 203. CaO-based oxides have a low melting point', so that they do not act as solidified nuclei when the molten steel is solidified. On the other hand, 'Mg〇.CaO-based oxide exists in a solid phase state due to a high melting point' and has poor lattice integration with &lt; 5 pure grain iron of the solidified primary crystal and does not generate a solidified core. Therefore, the inventors of the MgO · Al203 · CaO-based oxides and MgO 'CaO 糸 oxides 1 after intensive research and found that: The ear fraction is set in an appropriate range. 'Not only the low melting point of the halogenated compound can be suppressed; but also the paper size can be improved by applying the Chinese National Standard (CNS) A4 specification (210 x 297 mm) ------ -— 1-4 Pack -------- Order · --I--IIV (Please read the notes on the back before filling out this page) 62 Printed by A7 of the Intellectual Property Bureau Employee Consumer Cooperative of the Ministry of Economic Affairs _ B7 V. Description of the invention (60) The degree of lattice mismatch between the solidified primary crystal &lt; 5 pure grain iron. The processing device shown in Fig. 5 is "using a refining furnace" to dissolve steel 11 after decarburization and removal of impurities such as phosphorus and sulfur. 50 tons are poured into a molten iron tank 26 = afterwards. The argon gas was blown in, while adding 50 to 100 kg of A1 from the hopper 27, the molten steel was uniformly mixed while being stirred to perform deoxidation. Then, the molten steel 11 was sampled, and the structure of the oxide was analyzed using an epma (electron probe microanalyzer), and the lattice mismatch between the oxide and 6 pure grain iron was calculated using the following formula (3). The index α value of degree. When the value is 500 or less', the amount of Mg added is determined in consideration of productivity, and the Mg wire corresponding to the value is added to the molten steel 11 by the guide pipe 32 while guiding the supply device 31 on one side. a = 17.4 (kAl2O3) +3.9 (kMgO) +0.3 (kMgA! 2O4) + 18.7 (kCaO) ^ 500… (3) and k is an oxide. /. Mor. Fig. 17 is a ternary state diagram of CaO-Al203-Mg0; if it is the CaO-Al2O3 that satisfies the above formula (3) and exists in the area of the figure (the range surrounded by the oblique line marked with 0) MgO-based composite oxides effectively function as solidified nuclei. When the α value exceeds 500, even if the composite oxide has a low melting point or a high melting point ', the MgO-containing oxide on the surface of the coated oxide decreases, and the role as a solidified core disappears. In addition, the call value is obtained by the following formula (4). When the cold value is less than 95, SiO, 'This paper size applies to China National Standard (CNS) A4 (210 X 297 mm)

ί — ί t lliit --------- line f Jing first read the viit items on the back before filling in this page; I 63

ϊ '4 3 4 Ο 5 Q Α7 ______ Β7 ______ V. Description of the invention (61)

Other oxides, such as FeO, increase resistance to the formation of complex oxides that form a solidified core.

(Please read the notes on the back before filling in this page W β = (kAl203) + (kMg0) + (kMgAl203) + (kCa0) S 95 ... (4) In addition, k is the mole of the oxide (% Therefore, the value is set to less than 500, the / 3 value is set to 95 or more, and the added amount of Mg is obtained in consideration of the productivity. Therefore, the Mg iron wire 30 corresponding to the obtained Mg value is used to guide the official road. The 32-side guide starts the supply device 31 and adds it to the molten steel η. As a result, in addition to CaO and CaO plus MgO, in addition to forming a large number of CaO. AljCV MgO ternary oxides, the other also produces 8 Mg〇 · MgO; disperse the composite oxide in the molten steel, and as the temperature decreases, at the same time, the molten steel U starting from the solidified nuclei starts to solidify, and the equiaxed crystals are formed to produce a fine solidified structure. After this process, the solidified structure of the slab after the solidification of the molten steel 11 forms a fine solidified structure as shown in Fig. 9. The consumer cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs prints the microstructure of the solidified structure by miniaturizing it ' Can prevent internal defects such as internal cracks, center segregation, and center looseness of the town In addition, the workability of steels processed by slabs with a fine solidified structure, such as calendering, is good, and stable formation of edge flaws, rope-like surface defects, and the like can be formed. The amount of Mg added 'It is adjusted to be within a range corresponding to the mass concentration of 0.0005 ~ 〇〇 丨 〇0 /.'

When Mg concentration is less than 0.005% by mass, 'cannot be produced with s pure grain iron paper size applicable Chinese National Standard (CNS) A4 specification (210 X 297 public love) 64 • Intellectual Property Bureau of the Ministry of Economic Affairs employee consumption Cooperative prints A7 ------- _B7____ V. Description of Invention (62) The degree of lattice mismatch between 5. The composite oxide is not more than / 0, and it is not possible to refine the solidified structure of the slab. On the other hand, when the Mg concentration is increased by more than 0.0010% by mass, the effect of miniaturizing the solidified structure is saturated, and the cost of adding Mg also increases. (4) The treatment method m of the present invention is characterized in that a predetermined amount of Mg is added to a molten steel that satisfies the Ti concentration and the N concentration of the solubility product of ΉN crystals above the liquidus temperature of the molten steel. Therefore, according to the treatment method m of the present invention, in the case of dissolving steel of pure steel-based pure steel stainless steel, it is preferable that the aforementioned Ti concentration [% Ti] and N concentration [% N] satisfy the following formula. [% Ti] X [0 / oN] ^ ([% Cr] 2 · 5 + 150) χΐ〇-6 However, [% Ti] is the mass of Ti% in the molten steel, and [% ν] is the N% of the molten steel Mass, [% cr] is the mass percentage of cr% in molten steel. In the treatment method II of the present invention, the Al2O3 contained in the molten steel is set to 0.005 to 0.10% by mass. The degree of lattice inconsistency between TiN and pure grain iron (the difference between the lattice number of 与 N and the lattice number between &lt; 5 pure grain iron divided by the lattice number of pure grain iron) is Although 4% is said to be good, the TiN is easily aggregated. For this reason, coarse TiN may cause clogging of the impregnation nozzle, or cause defects such as cracks in the steel. In the treatment method II of the present invention, in addition to TiN acting as a solidifying nucleus during the solidification of molten steel, it is a feature of other points: the addition of MgQ-containing oxides produced by molten steel has extremely good dispersibility; and, TiN in Preferred crystals on MgO-containing oxides. This paper size is applicable to Ling Gu National Standard (CNS) A4 specification (210 X 297 cm) ------------- Installation -------- Order --------- --- line (please read the notes on the back before filling this page) 65 434059 A7 B7 V. Description of the invention (") The inventor focused on this point. In the processing method of the present invention, the use of MgO-containing oxides To improve the dispersibility of TiN crystallized on MgO-containing oxides as solidification nuclei, and to make the solidification nuclei effective for miniaturizing the solidified structure are mostly dispersed in the molten steel. When Ti and N are added to the molten steel, the product of Ti concentration and N concentration, the so-called solubility product [% Ti] X [% N], determines the crystallization temperature of TiN. For example, Ti and N added to molten steel, depending on the amount added, are at a liquidus temperature above about 500 ° C; and 'at a crystallization temperature of 1506 ° C above the TiN, a solid solution state is formed. It exists in molten steel as it is, but when cooled to a crystallization temperature of about 1505 ° C or less, crystallization of TiN can begin. The inventors focused on the relationship between the solubility product of the Ti concentration and the N concentration and the Cr concentration in order to refine the solidification structure of a pure grain iron-based non-recording steel containing a predetermined amount of Cr, and performed experiments to obtain the results shown in Results in Figure 18. The above formula 'is obtained from the results shown in FIG. Note that the X-series solidified structure in Figure 18 is not an example of miniaturization; 〇 is an example of the solidified structure that has been fully refined; and the △ -series solidified structure has been refined, but it occurs during prayer Example of a blocked nozzle. The processing apparatus shown in FIG. 5 uses a refining furnace to wash and dissolve the molten steel 11 150 in the molten iron tank 26 after decarburization and removal of impurities such as dishes and sulfur. The molten steel 11 is a pure-grained iron-based non-mineralized steel and contains Cr in an amount of 10 to ay0. After that, 150 kg of Fe-rhenium alloy was added from the hopper 27 and 30 kg of N-Mn alloy was added from the hopper 28, and the molten steel 11 was mixed uniformly. Also 'As far as the addition of the above-mentioned Fe-Ti alloy and N-Mn alloy is concerned, the size of the paper is compatible with the Chinese National Standard (CNS) A4 specification &lt; 210 X 297 issued) &lt; Please read the notes on the back Refill this page) -1111

^ OJ * in I Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 66 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the invention (64) The concentration of Ti and N contained in steel 11 meets the above formula ; In the case of 0% mass Cr, Ti concentration is added: 0.020% mass, N concentration: 0.024% mass.

The degree of lattice mismatch of TiN and (5 pure grain iron is as low as 4%, it is easy to form a solidified core of 5 pure grain iron. Therefore, the molten steel is easy to generate equiaxed crystals during solidification, and the micronization effect of the solidified structure is good. To make TiN act as a solidification nucleus, it is necessary to be above the liquidus temperature at which the molten steel starts to solidify, for example, TiN begins to crystallize above 1500 ° C, but even at a lower temperature than the liquidus temperature, solidification cannot be achieved. Therefore, to determine the liquidus temperature, its solubility product is in a range that satisfies the above formula, and it is necessary to add Ti and N. Since this TiN can further improve the effect of miniaturization, it is conceivable that Ti and The increase in the amount of N increases the amount of TiN crystals at the same temperature. However, depending on the steel type, the amount of Ti and N is limited. For example, when the amount of Ti and N is increased, as the crystallization time elapses, TiN aggregates and It can be seen that the number of solidified nuclei does not necessarily increase due to the coarsening, but the disadvantages such as nozzle clogging due to the coarse TiN and the occurrence of peeling defects of the steel can be seen. Therefore, even if the amount of Ti and the amount of N are the same The supply device 31 is started in the molten steel 11. The Mg iron wire 30 is guided by the guide pipe 32 (refer to FIG. 5), while supplying 75 kg of Mg in the molten steel, forming Mg of 0.0005 to 0.010% by mass. The formation of MgO-containing oxides can make the crystallized TiN fully dispersed in the molten steel in a fine state. In other words, before Ti and N are added; or after Ti is added, the Chinese national standard applies to this paper scale ( CNS) A4 specification (210 X 297 mm) ------------- install -------- II order · ------ · cord (Please read the precautions on the back first (Fill in this page again) 67 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 4340 5 9 A7 _____ B7 V. Description of the Invention (65) Mg is added at a temperature higher than the crystallization temperature of TiN to form MgO-containing oxides. As the temperature of the molten steel decreases, TiN crystals form, and due to the close lattice mismatch between the MgO-containing oxide and TiN, TiN preferentially crystallizes over the finely dispersed MgO-containing oxide, compared to when Mg is not added It disperses in molten steel more efficiently and forms most crystals. The content of Mg added to the molten steel is maintained, and Mg is added after Ti is added. When the time until casting is shortened, ideal results can be achieved. As a result, the addition of Ti and N (without Mg) can be prevented. Due to the unstable operation of nozzle blockage caused by coarse TiN, and the small amount of Ti added, the solidified structure of the slab after the solidification of the molten steel can be refined as shown in Figure 9. By the solidified structure The micronization can prevent internal defects such as internal cracks, center segregation, and center looseness caused by shrinkage during solidification and coarse structures. As a result, steels processed from slabs with a fine solidified structure have a fine solidified structure, and therefore the occurrence of surface defects such as flaking defects, edge seam defects, and rope-like products is also stably suppressed. (5) The treatment method IV of the present invention is characterized in that it is carried out in a slag covering molten steel and contains an oxide 1 to 300 / reduced by Mg. Quality person. Therefore, the oxide reduced by Mg in the treatment method IV of the present invention is one or more of FeO ′ Fe203, MnO, and SiO2. This paper size applies to China National Standard (CNS) A4 specification (210 X 297 mm) ------------- ^ Installation -------- Order --------- --4Γ (Please read the notes on the back before filling out this page) 68 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the invention (66) In the processing method rv of the present invention, it will be dissolved in steel The contained Al203 is set to 0.005 to 0.10% by mass. In the processing apparatus shown in FIG. 5, after decarburization refining, the molten steel 11 subjected to vacuum secondary refining (secondary refining) is washed and poured into a molten iron tank 26. A deoxidizer of aluminum and aluminum alloy is added to molten steel 11 so that it contains 0.005 to 0.10% by mass of A1203. Therefore, 'promote the formation of composite oxides such as MgO and Al2O3, and form a high melting point MgO-containing oxide, and then combine with ΑΙΑ3, which is easily aggregated due to poor dispersibility, and MgO to improve micronization and dispersibility' It also improves the role as a solidification nucleus, and refines the structure of slabs and steels. When the Al2O3 contained in the molten steel is less than 0.005% by mass, the generated MgO is combined with FeA3, SiC ^, etc. Low melting point oxides, which reduce their role as solidified nuclei. On the other hand, when the amount of 丨: 〇3 contained in the molten steel is more than ο’ι% by mass, AI2O3, which is easy to agglomerate, is formed excessively, resulting in defects caused by slabs and steel due to oxides. When the molten steel 11 is washed and cast in the molten iron tank 26, the molten steel 11 is mixed in the converter, or flows into the molten iron tank after secondary refining and the addition of a flux and the like, and the slag 33 is formed to cover the surface of the molten steel 11 in the molten iron tank 26. Next, the supply device 31 is started to guide the wire 3G of the Mg * Mg alloy through the guide line 32 at a speed of 2 to 5 Gm / min through the mine fishery 33 to penetrate the molten steel 11 to add Mg in the molten steel 11. In the past, the slag covering the surface of the molten steel was mainly composed of Ca0, Si〇2, Ai2O3, FeO Fe2O3, MnO, etc., and the size of the paper covered by the ore collapse _ 巾 关 # 鲜 （cns) A4 Rule 297 mm) ------------ — 1111--Order · ------ II (Please read the notes on the back before filling this page) 69 434059 A7 B7 Ministry of Economic Affairs Printed by the Intellectual Property Bureau's Consumer Cooperatives V. Invention Description (When Mg is added to 67 steel, the oxide in the slag at the interface between the molten steel and the slag and Mg and the Mg alloy produced by the reaction are miscible in the slag. It As a result, the concentration of Mg in the molten steel cannot be increased, but the content of! ^^ in the molten steel is reduced. As a result of repeated research on the phenomenon, the present inventors have found that the free energy of oxide formation is greater than the free energy of MgO formation; in other words, There is an important relationship between the total weight of thermodynamically unstable oxides and the Mg content in molten steel. In other words, 'as shown in Figure 19, there is no son-in-law on the thermoton in the slag before Mg is added. · The% thermal weight i of FeO, Fe203, MnO, and 8 is set to a range of 1 to 30% by mass. When the iron wire through slag of jyjg and Mg alloy is supplied to the molten steel, the Mg content rate of more than 10% can be achieved. In addition, the content of 5 Mg is based on the Mg contained in the molten steel and all MgO-containing oxides. The content rate when the amount is Mg. Actually, the form existing in the molten steel is' It is almost a monomer of MgO; or it is a composite oxide of Mg. AI, 〇3, etc. When Mg is added to> Gu Gang At this time, the oxides in the aforementioned slag can be conceived to be returned according to the chemical reactions shown in the following formulas (丨) to (4) through 1 ^ §. FeO + Mg—MgO + Fe… (1)

Fe203 + 3Mg- &gt; 3MgO + 2Fe… (2)

MnO + Mg—MgO + Mn ... (3)

Si02 + 2Mg- &gt; 2Mg0 + Si ... (4) Then, the chemical reaction shown in the above formulas (1) to (4) of Mg added to the molten steel is consumed, and the generated MgO is transferred to the mine. This paper size applies to China National Standard (CNS) A4 (210x 297 mm) (Please read the precautions on the back before filling this page)

Installation i 丨 -11 Order ------ II 70 • Printed by A7 of Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs ^^ '— --------- V. Description of the invention (from) In this case, slag When the total mass of FeO'Fe203, Mn0, and s02 in% is less than 1% by mass, although the reaction between Mg and slag in the added alloy can be suppressed, the molten steel determined by the thermodynamic equilibrium of the slag and molten steel is also reduced. The amount of dissolved oxygen in. As a result, once the %% added to the molten steel itself cannot be formed

MgO or MgO. Compounds such as A 丨 203 are evaporated over time. Their Mg content is reduced. Also, when the total weight of the oxides in the slag exceeds 30% by weight, the reaction between Mg in the Mg and Mg alloy added to the molten steel and the slag is intensified, because most of the added Mg are according to the above formulas (1) to (4) The chemical reaction produces Mg0 and transfers it to the slag. Therefore, the amount of fine MgO-containing oxides that form a solidified nucleus function in the molten steel decreases, and the content of added MgO oxides is reduced, and it is not possible to achieve miniaturization of each piece of tissue. In addition, the treatment of the necessary Mg concentration for miniaturization requires an increase in the amount of addition, which results in an increase in manufacturing costs and a decrease in temperature due to the addition of Mg and Mg alloys. Furthermore, operations due to changes in slag properties, etc. Difficulties. Therefore, the content of Mg added to the molten steel is increased to form complex oxides such as MgO and MgO · 80 丨 203, which are used to generate more stable and fine solidified nuclei, and to remove the radon in the slag. It is preferable to set the compound to the range shown by the following formula; and when it is set to the range of 2 to 20% by weight, a more desirable result can be obtained. Mass S FoO + Fe203 + MnO + Si02S 30% mass Adjust the oxide concentration in the slag covering the molten steel to the national standard (CNS) A4 specification (210 x 297 public love) of the paper size applicable to the above formula (210 x297) —-I --- 11 I Order ·· ------ I Line (Please read the notes on the back before filling out this page) 71 Printed by the Employees' Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 434059 A7 ____B7___ V. Description of Invention (69) In the range shown, take out the slag before adding Mg to reduce the amount of slag, and use the reduction component in the dissolving steel to make the reduction easy; or, you can also add a reduction agent to the slag and treat it. usage instructions. The Mg alloy added to the molten steel may be an alloy such as a Si-Mg alloy, a Fe-Si-Mg alloy, an Al-Mg alloy, or a Fe-Si-Mn-Mg alloy. (6) The treatment method V of the present invention is characterized in that a predetermined amount of Mg is added to the molten steel, and the CaO activity in the slag covering the dissolved copper is set to 0.3 or less. Therefore, in the treatment method V of the present invention, the alkalinity of the slag is set to 10 or less. The processing device shown in FIG. 5 contains carbon after decarburization refining and vacuum secondary refining (secondary refining). The carbon content is 0.001 to 0.05% by mass, 0.10 to 0.50% by mass, and chromium 1 0 to 20% by mass of molten steel 11 of pure grain iron-based stainless steel is cast into a molten iron tank 26. When the molten steel 11 is washed and cast in the molten iron tank 26, the surface of the molten steel 11 is covered by the slag 33 generated by mixing into the converter or flowing into the secondary refining by adding a flux or the like. The slag 33 has a thickness of 50 to 100 mm: the CaO activity in the slag 33 is adjusted to 0.3 or less by adding a flux or the like; and the basicity (Ca0 / Si02) is set to 1 °. the following. Next, the start-up supply device 31 uses the guide pipe 32 to guide the Mg and Mg alloy wire 30, and penetrates the slag 33 at a speed of 2 to 50 m / min to enter the molten steel 11 ', and adds Mg and Mg alloy to the molten steel. in. In the past, the slag covering the surface of the molten steel contained CaO and SiO2. This paper size is in accordance with the Chinese National Standard (CNS) A4 specification (21〇χ: 297mmt &gt; Ϊ I --------- 5 ^ ·- --- --- Order -------- II r (Please read the notes on the back before writing this page in Yunnan) 72 Printed by the Consumer Cooperative of the Intellectual Property Office of the Ministry of Economic Affairs A7 B7 V. Description of the invention (7 〇)

The oxides' such as Al2O3, FeO, etc. are good treatments for desulfurization and dephosphorization in the converter and the secondary refining process, while increasing the concentration of CaO in the slag. In this case, as shown in the following formula, the Ca concentration in the molten steel is also increased based on the equilibrium reaction between the slag and the molten steel.

CaO—Ca + O When Mg or Mg alloy is added to the molten steel, low melting point composite oxides such as ca〇_Al2〇r Mg◦ are formed, or the degree of lattice unconformity with ancient pure grain iron is generated. Big oxide. Such oxides do not act as solidified nuclei during solidification of the molten steel; they also do not produce blocking effects (inhibit the growth of equiaxed grains immediately after solidification), so the solidified structure is coarsened. Therefore, in order to improve the role of the solidified nucleus and the blocking effect, as shown in FIG. 20, the degree of field search by the mine is set and the Cao activity (aCaO) in the obtained slag is set to '3 or less, and it is necessary to add j ^ g or

Mg alloy. aCaO = 0.027 (CaO + SiO2) ° 8 + 〇, 13 By setting the CaO activity (aCaO) in the slag to 0.3 or less, Mg 'contained in Mg and Mg alloys, etc., forms MgO or MgO-Al2〇3 High MgO-containing oxides with a high melting point and a low lattice mismatch with 5 pure grains of iron, 'sufficiently produce a role as a solidification nucleus during the solidification of molten steel. In addition, since the MgO-containing oxide also sufficiently exhibits the blocking effect, the solidification structure of the slab is formed to be finer, and the occurrence of surface defects and internal defects in the slab can be suppressed. When the CaO activity is set below 0.2, the size of the paper produced can be increased to comply with the Chinese National Standard (CNS) A4 specification (210 X 297 mm) ---- I-- !! equipment --- -Order-I!-Line (please read the precautions on the back before filling this page) 73 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 4340 5 9 A7 __B7 _ V. MgO oxide containing invention description (71) Melting point, and can further enhance the effectiveness as a solidified core. Further, instead of the CaO activity of the slag, the basicity of the slag is set to 10 or less to generate MgO or MgO-containing high melting point-containing oxides such as MgO or MgO-Al203. The CaO activity and alkalinity can be adjusted by adjusting the thickness of the slag covering the molten steel or by adding a flux containing A1203 and MgO to the slag. When the alkalinity exceeds 10, the added Mg and Mg contained in the Mg alloy form a low-melting point composite oxide such as Ca0-Al203-Mg0, which not only has no effect as a solidifying nucleus, but also causes the origin of defects. Impede the quality of slabs or steel. In addition, when the CaO activity is set to 0.2 or less or the alkalinity is set to 6 or less, "the production of MgO-containing oxides (producing a role as a solidifying nucleus) is promoted" and the blocking effect is further improved, so that The solidified structure of the slab is finely refined. The Mg alloy added to the molten steel is an alloy such as Si-Mg alloy, Fe-Si-Mg alloy, Al-Mg alloy, Fe-Si-Mn-Mg alloy, Ni-Mg alloy, and the like. Then, the molten steel after adding Mg 0.0005 to 0.00% by mass was washed into a mold 'to produce a gradually solidified slab. 4) Next, a method for manufacturing the slabs A to D of the present invention will be described. The slabs A to D of the present invention are manufactured by casting a molten steel containing MgO oxide into a mold, and continuously casting the molten steel while stirring the molten steel using an electromagnetic stirring device. This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) ----------- ^ -------- IIII I-- * 5 ^ · {Please first Read the precautions on the back and fill in this page) 74 A7 _B7 V. Description of the invention (72) When the slab of the present invention is continuously cast, the electromagnetic search and mixing device is placed on the meniscus surface to the downstream side of the mold. 2 to 5m. In addition, when the slab of the present invention is subjected to continuous ballasting, the flow rate of the electromagnetic drop-out device and the drop-out flow is set to 1 Ocm / sec or more. In the continuous performance town-making device shown in FIGS. 1 to 4, the molten steel 11 ′ containing 16.5% by mass of chromium is poured into the binding mold 13 through the discharge port 14 of the impregnation nozzle 15, and the cooling generated by the casting mold 13 and It supports the cooling by the scattered water of the cooling water nozzle provided in the section 17, and continuously forms a solidified shell 18a ', and then uses the pinch rollers 20 and 21 to pull out the cast piece a while solidifying. The molten steel 11 contains 0.0005 to 0.000% by mass, and the Mg reacts with oxygen in the dissolved steel 11 and oxides such as si02, MnO, and the like to form MgO, MgO, and other oxides. . When the Mg content is less than 0.0005% by mass, Mg0 in the molten steel is reduced, the amount of solidified nuclei generated and the degree of blocking effect are reduced, and the solidified structure cannot be refined. On the other hand, when the Mg content exceeds 0.01 〇 At% mass, the effect of miniaturizing the solidified structure is saturated, and no significant effect can be found, and the addition cost of Mg and the like increases. The electromagnetic stirring device 16 is disposed at a position 500 mm from the downstream side of the solution surface (meniscus) in the mold 13. The stirring mode is to use the electromagnetic coils 16a and 16b to apply the stirring flow along the inner side of the long piece 13a of the mold B from the short film 13d to the short film 13c, and use the electromagnetic coils 16c and 16d to provide the short film 13c along the inner side of the long film 13b to 13d. Applicable to China Paper Standard (CNS) A4 specifications (2) 0 X 297 mm with this paper size. ----------- Install i I (Please read the precautions on the back before filling this page) Order-. Line-• Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 75 Λ 3 4 Ο 5 9 Α7

5. Description of the invention (? 3) Stir flow. As a whole, as shown by the arrow in Fig. 3, a stirring flow swirling in the flat direction of the molten steel is applied. In addition, the molten steel u cast from the discharge port 14 is cooled by the mold 13 and flow-washed the oxides existing near the solidified shell 18a to prevent the oxides from being captured by the solidified shell 18a, thereby forming a surface layer portion with little oxide. . This surface layer portion is cooled at a rapid cooling rate by the cooling of the mold 13 and the scattered water passing through the cooling water nozzle provided in the support section 17, so that a fine solidified structure is easily formed. In addition, the apex of columnar crystals is cut off by agitated flow, or the so-called composition undercooling (the local melting point is lowered as the solute component thickens due to the solid-liquid distribution at the solidification interface) is eased and promoted. Equiaxed crystallization, even if the oxide is reduced, a fine solidified structure can be obtained. In addition, part of the oxide that has flowed and washed near the solidified shell 18a floats on the surface of the meniscus and is captured by the powder not shown in the figure. Since the inside of the slab almost remains as a solidified core, At the same time, a blocking effect is formed, so the inside of the slab can form a fine solidified structure. The stirring flow of the molten steel 11 is communicated through three phases with different phases of the electromagnetic coils 16a to 16d. According to the well-known Fleming rule, the moving magnetic field acts on the molten steel 11 by applying the generated thrust (5 ~ 90mmFe) to the To. The strength of the thrust is adjusted by changing the current value passing through the electromagnetic coils 16a to 16d, and adjusted to a flow rate of 10 to 40 cm / 粆. As a result, the surface layer portion of the cast piece 18 and the inside can reduce 60%. The above solidified structure forms a fine solidified structure, which suppresses surface defects such as cracks and sunken flaws, and internal cracks caused by correction of bulges and rollbacks. This paper size applies Chinese National Standard (CNS) A4 specifications (210 X 297 mm) (Please read the precautions on the back before filling out this page) -------- Order --------- Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs Consumer Cooperatives 76 • Intellectual Property of the Ministry of Economic Affairs A7 __B7___ printed by the Bureau ’s Consumer Cooperatives. 5. Description of the Invention (74) At the same time, it guarantees the fluidity of unsolidified molten steel, and can manufacture high-quality cast slabs 18 that suppress the occurrence of center porosity (center depression) and center segregation. The rolled steel of the town sheet 18 has been suppressed due to cracks and peeling defects, surface looseness (center depression) and center segregation, and other surface defects and internal defects. Those who have sound processing characteristics and material characteristics. When the fine solidified structure of the cast slab 18 is less than 60%, the crystal grains thereof become large, and surface defects and internal defects are formed, and materials such as press processing characteristics are deteriorated. In addition, for the reasons described above, by forming a fine solidified structure through the entire cross-section of the thickness direction of the slab 18, the solidified structure can be formed to have a higher uniformity, and the surface and internal defects of the ball and steel can be prevented more reliably. The material can also be improved more stably. In particular, since the slab manufactured by this process contains less oxide in the surface layer portion, it is possible to reduce the oxides on the surface of the sheet, the profiled steel, etc., which are subjected to processing such as rolling, and the nearby oxides. Therefore, when the oxide on the surface or near the surface is reduced, the contact with acid, brine, etc. can suppress the dissolved oxides (including MgO oxides), so the corrosion of the steel from which it starts can be prevented . Therefore, the steel produced by processing the slab manufactured by the continuous casting method of the present invention has good corrosion resistance. (8) 'The continuous casting method of the present invention can be applied to the continuous casting of pure grain iron-based stainless steel molten steel. Especially suitable for containing chromium 10 ~ 23% by mass, Mg 0.0005 ~ This paper is sized according to the Chinese National Standard (CNS) A4 specification ⑵G X 297 mm> -------- installation ------ order- -I--ί Thread &lt; Please read the notes on the back before filling out this page) 77 434059 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the invention (75) Pure grain iron of 0.010% quality Continuous casting of stainless steel molten steel. In the continuous casting apparatus shown in Figs. 1 to 4, the molten steel 11 containing 10 to 23% by weight of chromium is poured into the mold 13 through the discharge port 14 of the impregnation nozzle 5 and is stirred using an electromagnetic stirring device 16-side. While being cooled by the mold 13 and by the scattered water of the cooling water nozzle provided by the support section 17, a solidified shell 18a 'can be formed. Then, while being solidified, the cast piece 18 is pulled out by the pinch rollers 20 and 21. . In the molten steel Π ', so that it contains 0.0005 ~ 00100 / mass, the Mg reacts with the oxides such as 〇, Si〇2, Mn〇 and the like contained in the molten steel 11: MgO or High melting point oxides such as MgO. A1203. The oxides such as MgO or MgO. Al203 are used as solidification nuclei to promote the equiaxed crystallization of solidified tissues. Moreover, the growth of tissues is inhibited immediately after solidification, that is, gastric obstruction is exerted. In addition, the promotion of the formation of equiaxed crystals can form more than 60% of the entire cross section into a fine solidified structure (equiaxed crystals). When the fine solidification structure (equiaxed crystal) of the cast slab is less than 60%, the crystal grain size of the entire cross section becomes large, and the formation surface and internal defects are liable to occur. When the content of Mg is less than 0.0005% by mass, Mg0 and / or MgO-containing oxides in the molten steel are reduced, and the formation of solidified shells and the reduction in blocking effect cannot be reduced to refine the solidified structure. On the other hand, when the content of Mg exceeds 0.010% by mass, the micronization effect of the coagulation structure is saturated and a significant effect cannot be achieved, and the addition cost of Mg and the like increases. The electromagnetic stirring device 16 is arranged at a distance of 500 mm from the molten surface (meniscus) on the downstream side of the mold 13 and the molten steel 11 in the town mold 13 is swirled along the inner wall of the mold 13. This paper size is in accordance with Chinese National Standard (CNS) A4 (210 X 297 mm) — HHIIHIIL Pack · ------- Order --- -----. &Gt; (Please read the precautions on the back first (Fill in this page again.) 78 V. Inventor (76) A7 B7 The effect of the flow velocity of the agitated stream is as described in the previous paragraph 10 of the Ministry of Economic Affairs ’Intellectual Property Bureau employee consumer cooperatives. As shown in Fig. 9, the surface layer part formed by the flow-off effect forms extremely fine equiaxed crystals, and the crotch part has a fine isocratic solidified structure. In addition, the fine equiaxed solidified structure has good fluidity of the molten steel in the unsolidified portion 18b located inside the slab, so the occurrence of center porosity (center depression) and center segregation can be suppressed. The occurrence of surface defects and internal defects such as cracks and peeling defects in steel pipes made from cast steel can also be eliminated. In addition, in order to suppress the occurrence of center porosity, the slab may be subjected to a light pressing treatment. In other words, by using the pressing section 19, the lower surface of the cast piece i 8 is kept fixed by the support roller 22, and the protrusion 23 of the pressing roller 24 is used to perform a light pressing process to form an upper center of about 3 to 10 mm. Stake amount. By this light pressing process', the unsolidified portion 18b and the generated center inside the slab 18 can be loosely pressed. The light pressing process is started at a solid phase ratio (solidified thickness / slab thickness) of the slab 18 in the range of 0.2 to 0.7. The "solid phase ratio" is obtained by driving a wedge into a slab, determining the state of dissolution of the tip, and measuring the solidified (solid phase) range and the unsolidified range of the slab. This cast 18 does not need to be pressed with a reduction ratio exceeding 0.90 (&gt; reduction). Cut manufacturing costs. begging

X ----------!-Install ------ order --------- · line (please read the precautions on the back before filling this page) This paper size is suitable for 囷National Standard (CNS) A4 Specification &lt; 210 X 297 mm) 79 434059 Employees 'Co-operation of Intellectual Property Bureau of the Ministry of Economy Du Yin *' ^ A7 B7 V. Description of Invention (77) Next, the castings made by this process will be The sheet is cut to a predetermined length, and after being subjected to a re-heating process after the tube-making step, a core rod is used for perforation processing to manufacture a seamless steel pipe. The cast piece used in the manufacture of the steel pipe has a fine solidified structure and is then lightly pressed to reliably press the center to loosen it. Therefore, when the core rod is used for internal expansion and perforation processing, it is easy to deform and deform. It is possible to reliably prevent internal cracking and flaking from occurring and to obtain a good quality steel pipe. In addition, it is not necessary to carry out preparations such as grinding after pipe production, and the fragmentation caused by defects can be prevented, which can improve product productivity and productivity. In particular, in the case of processing the ballast tube made by electromagnetic mixing near the front die, the surface layer of the slab contains less oxide, and the surface of the steel tube that has been perforated by the trachea step and its vicinity are present. The amount of halide can also be reduced, so the amount of oxides (including MgO oxides) eluted when the surface is contacted with acid, brine, etc. can be suppressed, and the corrosion of the steel pipe starting from this can be suppressed and its corrosion resistance can be improved. 5) Examples of the present invention will be described below. The present invention is not limited to the examples, and changes in conditions and changes in implementation forms within the scope of not departing from the purpose of the present invention are within the scope of the present invention. Example 1 -1 This example relates to eight cast pieces of the present invention. It is made by adding Mg 0.005% mass to the molten steel in the pan, and then — I win — — — — — — — ^^-— — — 11 — I ---— — — — — — «. ( Please read the precautions on the back before filling this page) A7 B7 V. Description of the invention (78) Cast in a mold with a width of 1200mm and a thickness of 250mm. The mold is cooled by the cooling of the mold and the water from the supporting section to cool the mold. And solidify, and then use the pressing section to perform a pressing process of 3 to 7 mm and pull out by a pinch roller. Next, the slab is cut, and the solidified structure (state of equiaxed crystals) in the thickness direction and the surface defects and internal defects of the slab are investigated. The slab is heated to 1250 ° C and then rolled. The surface and internal defects and processing characteristics of the steel are investigated. The results are shown in Table 1. Table 1 -----— — — — — — — — — — II (Please read the precautions on the back before filling out this page) Line_ Item @ 实施 例 1 实施 例 2 实施 例 3 Macrostructure of the slab · Inside of columnar crystals: equiaxed crystals (60%) full-section equiaxed crystals full-section equiaxed crystals, whose maximum equiaxed crystal diameter is within 3 times of the average equiaxed crystal diameter. Surface quality of steel scales. 00 Surface defects of steel ○ ◎ □ Internal defects of U shell 〇 ◎ ◎ Workability of steel # 〇 ◎ Table 2 Item § Comparative Example I Comparative Example 2 Macrostructure of cast slab Surface layer: columnar grains (50%) Although the cross section is equiaxed grains * But inside the surface layer: The equiaxed crystal (50%) does not satisfy the quality of the casting slab of the present invention X Δ Quality of the steel surface defect X Δ Internal defect X △ Workability of the steel X △ Example 1 in Table 1 printed by the consumer cooperative is formed by the 60% solidified structure of the entire cross section located in the thickness direction of the cast slab which satisfies the following formula (equal crystal diameter of 1 to 5.2mm) As for the caster, as far as the caster is concerned, it is found that the surface of the paper is cylindrical National Standard (CNS) A4 Specification (210 X 297 mm) 81 Employees' Cooperatives of Intellectual Property Bureau of the Ministry of Economic Affairs 裂 4 3 4 0 5 9 Α7 -___—— —_Β7 ___ V. Description of the Invention (79) Several scopes of crystals The occurrence of internal defects such as “cracks that are internal defects”, such as center depression and center segregation, can be suppressed, and good results (indicated by 0) can be obtained. D &lt; 1.2Xl / 3 + 〇_75 Also, the orientation of the D series crystal is the diameter (mm) of equiaxed crystals of the same structure, and the X series is the distance (mm) from the surface of the slab. Also, the occurrence of peeling flaws and cracks in the surface layer of the "rolled steel after rolling using this cast piece" is reduced, and internal defects such as cracks, center depression and center segregation are also reduced (indicated by 0), which is good and due to solidification The fine structure has a small segregation, so it is easy to deform in the down pressure direction, and the toughness after processing is also good (indicated by 0). Example 2 is a slab composed of a full section of the thickness direction of the prayer slab which is formed by an equiaxed crystal (equivalent crystal diameter of 1.0 mm to 4.5 mm) satisfying the above formula; the slab, / The surface layer forms columnar crystals, and the surface layer and internal defects are of good quality (indicated by 0). Also, the "steel rolled steel using this slab" has very few occurrences of spalling flaws and cracks on the surface layer, and has very few internal defects such as cracks, center depression, and center segregation (shown by ◎). In addition, this steel has a fine solidified structure and a small amount of segregation, so it is easy to be deformed in the pressing direction, and has good toughness after processing (indicated by 0). Example 3 relates to the solidified structure of the entire cross-section located in the thickness direction of the slab, which is composed of the equiaxed crystals (equal crystal control of 0.9 to 2.6mm) satisfying the aforementioned formula. At the same time, the maximum equiaxed crystal diameter is set at Those who are within 3 times the average equiaxed crystal diameter. The micro-segregation formed in the surface layer of the cast sheet is small; and the paper size is applicable to the Chinese National Standard (CNS) A4 specification (2IQ X 297 metric t) &quot; -------- --Ill —- ---— 1 pack I i —---— order ---------- I one (please read the precautions on the back before filling out this page)丨 ————-— B7 V. Explanation of the invention (so) and the unevenness is suppressed, so the occurrence of spalling flaws and cracks is less. Even inside, there are no internal defects such as center depression and center segregation. (Indicated by 0). In addition, the steel material after rolling using this cast piece is extremely excellent (indicated by ◎) for internal defects such as peeling flaws and cracks on the surface layer, and internal defects such as center depression and center segregation. Deformation easily occurs, and the toughness after processing is also very good (indicated by ◎). In contrast, as shown in Table 2 of Comparative Example 1, 50% of the cross-sections in the thickness direction of the slab are equiaxed crystals, and 50% of the stellate crystals are present in the surface layer. In this slab, cracks occurred in the surface columnar crystals, and internal defects caused poor evaluation (indicated by X.). In addition, the rolled steel using this cast slab has surface defects such as spalling and cracking, internal defects such as cracks, center depression, and center segregation (indicated by X), workability, and toughness after processing. The evaluation is also poor (indicated by X). &gt; Comparative Example 2 is a slab in which the entire cross section in the thickness direction of the slab is an equiaxed crystal, and the surface layer (the entire 40 ° / °) of the equiaxed crystal does not satisfy the aforementioned formula. In the case of the binding sheet, the surface defects such as peeling flaws and cracks in the surface layer, and internal defects such as center porosity and center segregation were slightly inferior evaluations (indicated by △). As for the calendering process using the scales, In the later steel, only a small amount of peeling flaws and cracks occurred on the surface layer, and internal defects such as center depression and center segregation were only slightly less and slightly inferior (indicated by △), and their workability and toughness after processing were also slightly Those who are not good (indicated by △). Example 1 -2 The paper size applies the Chinese National Standard (CNS) A4 specification (21〇χ 297mm) I— II ii — ll Order----- (please first Read the notes on the back and fill in this page again.) 83 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs? '4 3 4 0 5 9 A7 ______B7________ V. Description of the Invention (SI) This Example' , The caliber (mm) of its equiaxed crystals satisfies 0 &lt; 0.08? (£ | .76 + 0.5 (: 5 {: distance from the surface of the slab (111111),] :): 1% 质。 The case of X-distance isometric (mm)). The molten steel added to the gate plate is cast into a casting mold with a width of 1200mm and a thickness of 250mm. The cooling of the casting slab and the solidified water produced by the support section cool the slab and solidify it. The pressing section is pressed down by 3 to 7 mm and pulled out by the pinch roll. Next, the blade is cut, and the solidified structure (state of equiaxed crystal diameter) of the thickness section and the position of the cast piece are investigated. Defects in the surface layer and the interior. In addition, the cast slab was heated to 1250 ° C before calendering, and the defects and processing characteristics in the surface layer and the interior of the steel were investigated. The results are shown in Table 3. Table 3

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Surface defects of the slab △ 〇 × Δ σσ internal defects 〇〇 ◎ XX surface defects of steel Δ 〇 × Δ σ iW internal defects 〇〇 ◎ XX processing characteristics ○ XX In Table 3, ◎ represents excellent, 〇 represents good, △ represents slightly better, and X represents poor quality. Example 1 in Table 3 is about 60% of the solidified structure of the entire cross section of the cast slab to satisfy the above formula of equiaxed crystals (15 ~ 32mm equiaxed crystal diameter) (please read the note on the back first Please fill in this page for matters) -11 -----Order --- 11 ---- * 5 ^

84. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the invention (82) The sharpened sheet and the steel using the cast sheet. As for the quality of slabs, cracks are relatively rare, and internal defects such as cracks, center sags, and center segregation are not good. In addition, the quality of the steel material after calendering using the cast sheet is relatively small, and the occurrence of surface peeling and cracking is relatively small, and internal defects such as cracking, center sag and center segregation are also good. Toughness after processing, etc. Good results were also formed. Example 2 relates to a slab composed of an equiaxed crystal (equal-axis crystal diameter of 0.3 to 2.9 mm) whose entire cross section satisfies the above formula, and a steel material using the same. In terms of the occurrence of cracks in the slab, internal defects such as cracks, center depression, and center segregation did not form good quality. It also uses the quality of the steel after calendering using this cast sheet, and the occurrence of surface peeling defects and cracks is small, and internal defects such as cracks, center depression and center segregation are not good, and the toughness after processing is also good. Is good. Example 3 is a ball-shaped piece composed of cast iron with a cross section occupying an entire diameter of 0.5 to 4 mm, and the largest equiaxed crystal diameter is formed within 3 times the average equiaxed crystal diameter, and the use thereof The cast steel. In this town, cracks occur less often, and internal defects such as internal cracks, center depression, and center segregation do not have extremely good quality. In addition, the use of the steel material after calendering of this cast piece has greatly suppressed the occurrence of surface defects such as peeling flaws and cracks on the surface, and internal defects such as cracks, center depression, and center segregation, and the toughness after processing was also good. In contrast, Comparative Example 1 has columnar crystals in the section from the surface of the solidified structure to more than 40% of the section located in the thickness direction of the slab. This paper applies the Chinese National Standard (CNS) A4 specificationAG x 297 Public Love) — It — — — --- I --- Order -------- 1 ^. &Lt; Please read the notes on the back before filling out this page) 85 Employee Consumer Cooperatives, Intellectual Property Bureau, Ministry of Economic Affairs Printed ′ 4 3 4 0 5 9 Α7 _____ Β7 ___ V. Description of the invention (83) A cast piece composed of an equiaxed crystal diameter of a solidified structure of 20 ~ 3 · lmm, and a steel made of the cast piece. . For this slab and steel, the microsegregation on the surface layer is large, cracks caused by the cooling process during casting and the mold, etc., and internal defects such as cracks, center depression and center segregation also occur. In addition, the steel material obtained by calendering using the cast slab had surface defects such as spalling flaws and cracks, internal flaws such as cracks, center sags, and center segregation, and the processability and toughness after processing were also poor. Comparative Example 2 is a slab in which the solidified structure of the section 400/0 in the thickness direction of the slab satisfies the equiaxed crystals (equivalent crystal diameter of 2.8 to 5.7 mm) described above, and the slab using the slab. Steeler. For the slab and the steel, cracks and the like at the surface layer can be suppressed to a certain extent, but internal defects such as internal cracks, center depression and center segregation still occur. In addition, as for the rolled steel using this town chip, peeling flaws and cracks also occurred on the surface layer, internal defects such as cracks, center depression, and center segregation also occurred, and workability and toughness after processing also occurred. Not good. Example 2 This example relates to the slab B of the present invention. After adding 0,005% by mass of Mg to the molten steel in the dishwasher, continuous casting is performed in a casting mold with a width of 1200 mm and a thickness of 250 mm. The cooling of the casting moon and the solidification of the casting moon by the cooling of the casting mold and the scattered water from the support section, Then, the pressing section is used to perform a pressing process of 3 to 7 mm and pulled out by a pinch roller. Next, the cast piece was cut to measure the equiaxed crystal of the cross-section structure in the thickness direction, and the surface of the cast piece was ground every 2 mm, and the paper was measured at the same thickness position. A4 specification (210 X 297 public love) ------- I1JI-4 --- I! 1-^ ---- -1 11 · r (Please read the precautions on the back before filling this page) 86 Printed by A7 _____B7, Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the invention (84) Determine the crystal grain size on the surface; at the same time, investigate the defects located on the surface and inside of the casting. In addition, investigations were made on the surface flaws and corrugations of the steel material after rolling the slab to 1250 ° C, and its processing characteristics. The results are shown in Table 4. Table 4

Project slab steel surface cracks internal crack surface cracks corrugation flaw processing characteristics Example 1 0000 Example 2 ◎ ◎ ◎ ◎ ◎ Comparative Example XXXXX Example 4 in Table 4 is related to the blade thickness 300 / 〇 of the entire cross-section of the direction is formed by equiaxed crystals; and on the surface of the same thickness position, the maximum crystal grain size / average crystal grain size is 2 to 2.7. Regarding this slab, there were no surface cracks or internal cracks (indicated by 0), and the occurrence of surface flaws and corrugation defects in steel produced by rolling the slab was also slight (indicated by 〇). The characteristics are also called good (indicated by 0). Example 2 relates to a cast piece shown by a solid line in Fig. 14 and 60 ° / is formed on the inside. The surface of the above equiaxed crystals' at the same thickness position takes a slab having a large crystal grain size / average crystal grain size of [7 to 25]. As for this slab, there are no surface cracks or internal cracks (indicated by ◎); the steel produced by performing the extension processing on the slab has no surface defects and ripple defects (indicated by ◎) 'its processing characteristics Very good (indicated by ◎). In contrast, Comparative Example 1 is about the "sheet" indicated by the solid line in Figure 15 and the equiaxed crystal ratio inside the scale is as low as 20%, and the central part is thick 1 ----- II — 丨 i — · 111 — 111 Order — 1 — 111 — I (Please read the notes on the back before filling out this page) -87 434059 A7 B7 V. Description of the invention (85) Large equiaxed crystal; Among the crystal grains, some of them have slabs with a maximum crystal grain size / average crystal grain size of more than 3 times (2.5 to 4.7). For this slab, surface cracks and internal cracks (indicated by χ) ), The steel produced by subjecting the slab to the mechanical processing has surface defects such as surface cracks and corrugation defects (indicated by X), and its processing characteristics are also poor (indicated by X). Example 3 This implementation Example relates to the casting slab C of the present invention »0.005% by mass of Mg is added to the molten steel of the gate plate, and continuous casting is performed in a casting mold having a width of 1200 mm and a thickness of 250 mm. , The mold is cooled and solidified, and the pressing section is used for 3 to 7 mm Next, it is pulled down by a feed roller. Next, the equiaxed crystal ratio, average equiaxed crystal diameter (mm), and defects in the surface layer and the interior of the solidified structure in the thickness direction of the slab cut are investigated. 'The cast piece was heated to 1250. (: Then calendering was performed, and the defects and processing characteristics located on the surface and inside of the steel were investigated. The results are shown in Table 5. Table 5 (Please read the precautions on the back before filling in (This page)

• B—K ---- Order --------- line Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs

Number of items including inclusions, isometric average slabs, steel slabs, and steel materials of steel (the size of the crystallographic axis and the diameter of the material on the surface of the diameter of the inner surface of the material Γ welds / cm2) (_ (% ) (mm) Defect Defect Toughness Example I 104 10 or more 62 1.8 0.0000 Example 2 141 10 or less 81 1.3 ◎ ◎ ◎ 6 Comparative Example 1 70 10 or less 27 2.5 XXXX ___ — ^ Comparative Example 2 45 10 or less 15 4.7 XXXX Example 5 in Table 5 is related to the standard of the paper contained in the slabs of pure grain iron steel. The Chinese National Standard (CNS) A4 specification (210 X 297 mm) is used. 88 Intellectual Property Bureau, Ministry of Economic Affairs, Employee Consumption Cooperative printed A7 B7 V. Description of the invention (86) <5 The lattice mismatch of pure grain iron is less than 6%. The number of central_debris is set to 104 / cm2, and the size of the inclusion is set. On the top, a cast piece with an 62% equiaxed crystal ratio and an average equiaxed crystal diameter of 1.8mm is formed. As for this cast piece, the occurrence of surface defects such as cracks and sags is small (indicated by 0). Internal defects such as cracks, central depression and central segregation Good (indicated by 0). Also, the rolled steel using this slab has fewer surface bulges and side seam defects (indicated by 0), and internal defects such as cracks, center depression and center segregation are also It is good (indicated by 0), and the r value, which is a formability index, is also good (indicated by 0). Example 2 is related to the δ pure grain iron crystal lattice contained in the cast steel of pure grain iron steel. The number of inclusions with a degree of integration of 6% or less is set to 14 1 per cm 2 ′, and the size of the inclusions is 10 μm or less, and a cast having an equiaxed crystal ratio of 81% and an average equiaxed crystal diameter of 1.3 mm is formed. For this cast, the occurrence of surface defects such as cracks and sags is small (indicated by ◎), and internal defects such as cracks, center sags, and center segregation, which are internal defects, are also good (with ◎ The steel products that have been subjected to post-processing by this casting have fewer surface bulges and side seam defects (indicated by ◎), and internal defects such as cracks, center sags, and center segregation are also good (by ◎), and the r value, which is a processability index, is also called good. (Indicated by ◎). Relatively speaking, 'Comparative Example 1 is a rotating piece in which the number of inclusions contained in a cast piece is set to 70 pieces / cm2' and the size of the inflammable pieces is less than 10 inches. Its equiaxed crystal rate is 27%, and the average equiaxed crystal diameter is 2.5mm. The paper size is applicable to China National Standard (CNS) A4 specification (210 X 297 mm) --- I ------ ---- * 1 III --- Order --- I --- (Please read the notes on the back before filling this page) 89

V. Description of the invention (87) As far as the slab is concerned, surface defects such as cracks and sunken flaws (indicated by X) occur, and cracks and loose cores inside the slab occur, such as 'central segregation?' 4 3 4 0 5 9 ΑΓ internal defect (indicated by X). In addition, using the cast steel after calendering, surface peeling defects, bulging, and seam defects (indicated by χ) occurred, and internal defects such as cracks, voids, and segregation also deteriorated (indicated by X). The Γ value of the processability index is also not good (indicated by X). Comparative Example 2 is a slab composed of 45 / cm2 in the surface layer portion of the metal compound present per unit area of the slab, and the number of metal compounds below 10 / zm is in the surface layer portion. The slab in which the maximum equiaxed grain size and the internal equiaxed grain size are enlarged. For this slab, internal defects such as cracks and sags, and internal defects such as cracks, center sags, and segregation (indicated by X) also occurred. Also, 'the rolled steel using this slab has surface defects such as spalling and cracking, and internal defects such as cracking, center sag, and center segregation (represented by X)', which is also the r value of the processability index. Good (indicated by χ). Embodiment 4 This embodiment relates to the slab D of the present invention. After adding 0.005% mass of Mg to the molten steel in the gate plate, continuous casting is performed in a casting mold with a size of 1200 mm and a thickness of 250 mm. The blade is cooled by the cooling of the die and the scattered water from the support segment. It is allowed to solidify, and the pressing section is subjected to a pressing process of 3 to 7 mm, and then pulled out through a sagittal roller. This paper is again suitable for China National Standard (CNS) A4 (210 X 297 mm) I I L .. installed! — F · — Order -------- ί (Please read the notes on the back before filling out this page) Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 90 A? V. Description of Invention (88) Then 'will The slab was cut to investigate the size of the equiaxed crystals in the solidified structure of the thickness section and the defects in the surface layer and the interior. In addition, the cast piece was heated to 125 ° C. and then subjected to rolling processing, and defects and processing characteristics on the surface layer and inside of the steel material were investigated.

Table 6 Number of metal compounds (pcs / cm2) Maximum equiaxed grain size (mm) Internal defects and surface defects of cast slabs and steels r-values of steel (a) Surface layer part (b) Internal (b) / (a) Surface layer Internal Examples 1 50 66 1.32 1.7 4,9 〇 Example 2 95 130 1.37 1.1 3.1 〇Comparative Example 1 45 46 1.02 1.8 5.5 XX Comparative Example 2 97 Bu 6 1.19 1.2 4.2 〇X • II-— -II -1III1 --- (Please read the precautions on the back before filling out this page) ▲ _ -Example 1 in Table 6 printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, which is among the metal compounds contained in the cast The number of metal compounds below 10 em is 50 pieces / cm2 in the surface layer portion and 66 pieces / cm2 in the inside, which are cast pieces formed by good equiaxed crystals. As far as the cast is concerned, the occurrence of cracks and sags, as well as internal defects such as bulging and side seam flaws, cracks, center sags and center segregation, etc. In addition, there are not many internal defects (such as 0) in the surface of the steel sheet 'rolled and edge seam flaws, cracks, center depression, and center segregation, etc. after using the cast sheet. The ^ value of the indicator is good (indicated by 0). In Example 2, among the metal compounds present per unit area of the town sheet, 'the number of metal compounds below 10 # m is 95 in the surface layer portion / cm2, and 130 in the inner portion are formed by good equiaxed crystals' The slab caster. With regard to the cast, the occurrence of cracks and sags, as well as bulging and edge seam defects, etc. The paper size applies the Chinese National Standard (CNS) A4 specification (210 297 mm) 1 ^ ·-line 91 • 434059

V. Description of the invention (89) The employee cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs have fewer prints, and there are not many internal defects such as cracks, center depression and center segregation. In addition, using this cast steel after calendering and rolling, there are not many internal defects such as bulging and side seam fatigue, cracks, center depression and center segregation (indicated by 0), and Γ values are also good (indicated by 〇 means). Comparatively speaking, the comparative example relates to a slab of metal compounds per unit area of the slab, so that the number of metal compounds below 10 &quot; m is 45 / cm2 in the surface layer portion and 46 / cm2 in the inside. , Is the slab in which the maximum equiaxed grain size in the surface layer portion and the maximum equiaxed grain size in the interior are enlarged. As for the slab, surface defects such as cracks and sags, and internal defects such as cracks, center sags, and center segregation occurred, and peeling defects and cracks occurred on the steel after the slabs were calendered. Surface defects and internal defects such as cracks, center depression, and center segregation (represented by χ), and r values are also not good (represented by X). Comparative Example 2 is related to the presence of metal compounds per unit area of cast slabs. The number of metal compounds below 10 / im is 97 / {; 〇12 in the surface layer portion, and 116 pieces / cm2 in the inside, and the thickness of the surface layer portion and the inside is reduced. . Although the occurrence of surface defects and internal defects in this slab and the steel material produced by the slab is good (indicated by 0), the r value is not good (indicated by X). In addition, Example 1 and Example 2 have the same ratio of the number of metal compounds of 10 Åm or less 'for the slabs after the masses of Mg0', MgAla〇4, TiN, and TiC 0.06¾ added as the metal compound, and After the sheet is processed by rolling, etc., the equiaxed crystal size of the solidified structure and the surface and internal defects are investigated. Then, the cast sheet is heated to 125 °. This paper is in accordance with China National Standard (CNS) A4. (21.0 X 297 public love) (Please read the precautions on the back before filling out this page) Install -------- Order -------! Line 4 92 A7 _____ B7____ 5. Explanation of the invention (90) ° c and then calendering, investigating defects and processing characteristics on the surface and inside of the steel can obtain good results. Example 5 This example relates to the treatment method I of the present invention. The dissolved steel in the dishwasher does not contain Ca, and the dissolved steel contains 0.0002% by mass and 0.0005 of the total Ca. / 〇quality, 0.0006% quality, and 10000001 / 〇 quality situation 'Add 0.005% mass Mg to molten steel, respectively, and then the front washes continuously in a mold with a size of 1200mm and a thickness of 250mm.' Through the cooling of the mold and the cooling by the scattered water of the support section to solidify the ballast, the pressing section is used to perform a pressing process of 3 to 7 mm and then pulled out by the pinch roller. Next, "the main components of oxides in the dissolved steel before the addition of Mg, and the micronization of the main components of oxides in the dissolved steel after the addition of Mg were investigated. The results are shown in Table 7. ------------ I -------- Order --------- line (Please read the precautions on the back before filling this page). # 济 部 智慧Printed on the paper by the Consumers' Cooperative of the Property Bureau, the paper size is applicable to Chinese national standards (CNS &gt; A4 specification (210 * 297 public love) 93 434059 A7 B7 V. Description of the invention (91) Inclusions in dissolved steel before addition of Mg Total evaluation of the fineness of the solidification structure of inclusion slabs in dissolved steel after addition of Mg Ίτ Example 1 0,0000% AUO, A1203-MgO, MgO extremely fine (particle size &lt; lmm) ◎ 2 0.0002% auo3 Al2〇3 * MgO, MgO very fine (particle size &lt; lmm) ◎ 3 but 0.005% ΑΙΑ A1203 'MgO * MgO extremely fine (particle size &lt; lmm) ◎ 0.0006% Al2〇3 · CaO (CaO% or less) Al2〇3 · MgO -CaO MgO · CaO (CaO% or less) Fine (particle size &lt; 3mm) 〇5 0.0010% Al2〇3 * CaO (CaO% or less) AI2 03 · MgO • CaO MgO ♦ CaO (CaO %% or less) Fine (particle size &lt; 3mm) 〇 Comparative Example 0.0012% AU〇, CaO Al2 03 MgO * CaO Coarse X 2 0.0015% Al, 〇.. CaO Al2 03 MgO • CaO Coarse X 3 0.0023% Α] 2〇3 · CaO Al203 MgO • CaO Coarse x (Please read the precautions on the back before filling out this page) Installation -------- Order ------ --- Line '<Example 1 in Table 7 printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economics, in the case where the molten steel does not contain C a, and before the addition of Mg, the dissolved steel is mainly composed of the inclusion A1203. Oxide, so the inclusions in the dissolved steel after adding Mg are oxides with A1203. MgO and MgO as the main components. The solidification structure of the slab obtained by casting this molten steel is extremely fine, and the overall evaluation is excellent ( (Expressed as ◎). Example 2, In the case where the dissolved steel contains 0.0002% by mass Ca, the inclusions in the dissolved steel before adding Mg are oxides containing Al2O3 as the main component, and the loss in dissolved steel after adding Mg is Miscellaneous matter is the case where Al2O3. MgO and MgO are the main component oxides. As far as the molten steel is concerned, calcium is not formed. The aluminate paper size applies the Chinese national standard &lt; CNS) A4 specification (210 X 297 mm) 94: Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the Invention (92) Salt. Solidification of the cast slab is formed to obtain extremely fine, very excellent evaluation sum (expressed in ◎). Example 3 In the case where the molten steel contains Ca 5% by mass, the inclusions in the dissolved steel before the addition of Mg are oxides whose main component is 丨 203, and the inclusions in the dissolved steel are added after the addition of Mg. It is the case of oxides with ai203, MgO and MgO as the main components. In this molten steel, calcium and aluminate were not formed, and the solidification structure of the slab obtained by casting the molten steel was extremely fine, and the overall evaluation was excellent (indicated by ◎). In Example 4, the molten steel contained 0.0006 /. In the case of mass Ca, the inclusions in the dissolved steel before addition of Mg, in addition to the main component 8 2203, still contain CaO oxides of less than / 0; and the inclusion content in the dissolved steel after addition of Mg A1203. MgO. CaO and MgO. CaO as the main component oxide of CaO below %% CaO has been detected in the inclusions before and after the addition of Mg. number. / 〇 or less, when the molten steel is solidified, the inoculation effect is exhibited. Therefore, when the molten steel was cast to obtain a solidified structure of a cast slab, and the fineness was formed, the total evaluation was good (indicated by 0). 6 Example 5 The Ca contained in the molten steel was 0.0000. / 〇 In the case of mass, the inclusions in the dissolved steel before adding Mg, in addition to the main component a 丨 203, contain oxides of CaO below / 0: and the inclusions in the dissolved steel after adding Mg ' This is the case where AIOA containing Ca0 or less; MgO, CaO, and MgO · CaO are the main components of the oxide. As far as the molten steel is concerned, although the inclusions before and after the addition of Mg are also tested, the paper size is applicable to the Chinese national standard (CiS; S) A4 specification (2) 0 * 297 mm> --------- ---- Equipment -------- Order --------- line (Please read the notes on the back before filling this page) 95 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs

f 4 3 4 ύ 5 S. A7 ____B7_ V. Description of the Invention (93) CaO, but its content ’is less than a few%, so its inoculation effect can be exhibited when the molten steel solidifies. Therefore, when the solidified structure of the slab obtained by casting the molten steel was refined, the overall evaluation was good (indicated by 0). Relatively speaking, 'Ca in the molten steel of Comparative Example 1 is 0.001% by mass.' The inclusions in the molten steel before the addition of Mg are oxides containing A1203 as the main component, and The inclusions in the dissolved steel after adding Mg are oxides with CaO-A! 203-MgO as the main component. The solidification structure of each of the slabs produced by this> Gu Gang was coarsened, and the overall evaluation was poor (indicated by X). Comparative Example 2 In the case where Ca contained in the molten steel was 0.015% by mass, the inclusions in the molten steel with Mg added were oxides containing A1ζ〇3-CaO (calcium aluminate) as the main component, and Inclusions in dissolved steel after Mg are oxides with CaO-Al / VMgO as the main component. The solidified structure of the slab produced by casting the molten steel was coarsened, and the overall evaluation was poor (indicated by X). In Comparative Example 3, when Ca contained in the dissolving steel was 0.023% by weight, the impurities in the dissolving steel before adding Mg were oxides containing A12〇3_Ca〇 (calcium. Aluminate) as the main component, and Mg was added. The impurities in the later dissolved steel are oxides with CaO-AerMgO as the main component. The solidified structure of the slab obtained by casting the molten steel was coarsened, and the overall evaluation was poor (indicated by X). Embodiment 6 This embodiment relates to the processing method π of the present invention. (Please read the precautions on the back before filling this page) ------ II ^ 11111111 96 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the invention (94) The decarbonization refining composition adjustment will be made 150 tons of the later molten steel was cast into the molten iron tank, and A1 and Ti were added to the molten steel to change the addition conditions. At the same time, the porous pipe plug installed in the molten iron tank was deoxidized while blowing argon gas while stirring. Then supply 0.75 ~ 15kg Mg in molten steel. Next, the presence or absence of defects in the surface layer and the inside of the slab, and the fineness of the solidified structure obtained by continuous casting using the molten steel were adjusted. The results are shown in Table 8. Table 8

Project Example Comparative Example 1 2 3 1 2 Amount of dissolved steel (ton) 150 150 150 150 150 Amount of deoxidizer in deoxidizing conditions (kg) Metal A1 50 Metal A] 75 Fe-Ti 50 Fe-Ti 50 Metal Al 75 Metal A1 75 The amount of metal Mg (kg) after adding metal A175 after adding Fe-Ti 50 and metal Mg 15 at the same time as metal Mg 0.75. Metal Mg 0,75 Metal Mg 15 Metal Mg 15 Are there any surface defects and internal defects? No, no, no, yes, no, no, no, no, no, no, no, no, no, no, no, no, no, no (all) good evaluation of the solidified structure. XXXX As for Example 1 in Example 8, after adding 50 kg of A1 for deoxygenation treatment, 0.75 kg of Mg was added. There are no defects on the surface and inside of the slab. The solidification structure of the slab has been fully refined, and the overall evaluation can be called a good one (indicated by 0). In Example 2, after adding 75 kg of A1 and 50 kg of Fe-Ti alloy to perform deoxidation treatment, 15 kg of Mg was added. There are no defects on the surface layer and the inside of the slab. The solidification structure of the slab has been sufficiently refined, and the overall evaluation is good (indicated by 0). This paper size applies to China National Standard (CNS) A4 (210 X 297 cm) I--If —--- III * 11 I--1! · --- II I-- (Please read the note on the back first Please fill in this page again) 97 Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs and Consumer Cooperatives I 43405 9 A7 ------- V. Description of the Invention (95) Example 3, after adding 50kg Fe-Ti alloy, and then add A1: 75 kg for deoxidation treatment, followed by 15 kg of Mg. There are no defects on the surface and inside of the slab. The solidification structure of the slab has been fully refined, and the overall evaluation is good (indicated by 0). In the case of any of Examples 1 to 3, as shown in FIG. 9, the solidified structure of the slab is formed into an equiaxed crystal inside and is refined. In contrast, Comparative Example 1 is a case where A1 75 kg and Mg 0.75 kg are added to the dissolving steel for deoxidation treatment. Although the dissolving steel generates a composite oxide of Mg0 and Al203, the surface structure of the MgO-containing oxide, The proportion of MgO is less than 10%, and the degree of lattice integration between 5 pure grain iron is not good, which is not suitable as a solidified core. As a result, defects occur on the surface and inside of the slab. As shown in Figure 7, solidification The structure is also coarsened, and the overall evaluation is poor (indicated by X). Comparative Example 2 is a case where 50 kg of Fe-Ti alloy is added, 15 kg of Mg is added, and then 75 kg of A1 is added for deoxidation treatment. The gaseous substance 'has MgO in the center, and because it produces a1203 on the surface, it does not act as a solidification nucleus. As a result, defects occur in the surface layer and the interior of the slab, and the solidified structure is also coarsened. The overall evaluation system is poor (indicated by X). Example 7 This example relates to the treatment method I and the treatment method Π of the present invention, and the oxides such as slag and deoxidation products contained in the molten steel are added and added. Mg is generated when the steel is dissolved The oxide 'system is added with a predetermined amount of Mg to the molten steel to satisfy the following (1) and (2) formulas (% mole of k-type oxide). The paper size is in accordance with the Chinese National Standard (CNS) A4 specification (210 X 297 mm) ------------ {Installation -------- Order --------- Edge r (Please read the precautions on the back before filling in this Page) 98 A7 B7 V. Description of the invention (96) method: a = 17.4 (kAl2O3) +3.9 (kMgO) +0.3 (kMgAl2O4) + 18.7 (kCaO) ^ 500… ⑴ β = (kAi203) + (kMg0) + ( kMgAI204) + (kCa0) ^ 95… (2) Using an upper-bottom blowing chain converter, put 50 tons of molten steel containing 10 ~ 23% of chromium in a molten iron tank, and blow argon through the porous pipe plug side. While adding 100 kg of A1 from the hopper, the molten steel was uniformly mixed for deoxidation treatment. After that, the molten steel was sampled and the oxide composition was measured by using EPMA to adjust the amount of Mg added to satisfy the above (1) and (2), and the composite oxide is formed. Then, slabs are produced by continuous casting of molten steel. Next, the internal defects such as internal cracks, center segregation, and center porosity of the slabs are investigated. Presence or absence, good or not of the solidified structure 'Surface properties and workability of the steel after processing. The results are shown in Table 9. ----- I --- I-装 ----- 1-- Order ·!- --· Line (please read the precautions on the back before filling this page) • Printed on 5 sheets of printed paper by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs (CNS) A4 (210 X 297 mm) 99 4340 5 A7 B7 V. Description of the invention (9?) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economy rr £ &gt; z ττ 1 1 CD SS if Ιφ U) Ui &gt; 1! ΈΜ £ 1 | | S g 戋 bo U u &gt; 1 g Ik) lu 1 f ϊο Lj 豕 6〇g A 8 S bo C Da a cc awa \ Ε »s ft Kun · S a repeated py Λ: Dance E f; &amp;f; w φ 鲞 X * Η- eto * C; B »I ii * 1 XX 〇〇 ： £ II --------- L equipment · ------- order --------- V ( Please read the notes on the back before filling in this page) This paper size applies the Chinese National Standard (CNS) A4 specifications &lt; 210 X 297 mm) 100 A7 B7 V. Description of the invention (98) Example 1 in Table 9, Adding 125kg of Mg to molten steel and blending molten steel α value of the composite oxide (the left side of the above (1) formula. An indicator of the degree of lattice mismatch between the oxide and 5 pure grain iron) was formed in the case of 3 26 ', and no internal defects occurred in the slab, and the solidified structure was refined.' The surface properties and workability of the steel are also good , The overall evaluation is good (indicated by 0). In Example 2, 30 kg of Mg was added and the molten steel was stirred, and the α value of the composite oxide contained in the molten steel was set to 497. No defects on the surface and inside of the slab occurred as shown in FIG. 9 It shows that the solidification structure of the steel has been refined, the surface properties and workability of the steel are also good, and the overall evaluation is good (indicated by 0). Comparatively speaking, 'Comparative Example 1 and Comparative Example 2 were made by adding 85 kg and 30 kg of Mg and dissolving the steel without considering the composition of the oxide contained in the molten steel before adding Mg. As a result, the alpha value of the composite oxide contained in the molten steel exceeded 500, and internal defects occurred in the slab. In short, the solidified structure was coarsened and deteriorated as shown in Section 7 (b), and the overall evaluation system was poor (indicated by X). ). Example 8 This example relates to the processing method 羾 of the present invention. Cr concentration after decarburization and removal of impurities such as phosphorus, sulfur, etc. using an upper-bottom blowing chain converter: 0 to 23% by mass of molten steel casted into a molten iron tank of 150 ton, and argon gas is blown through the porous pipe plug while blowing Add Fe-Ή alloy and N-Mn alloy 'to limit the Ti concentration of the molten steel to 0.013 ~ 0 · 125 ° / 〇 mass and N concentration to 0.0012 ~ 0.024% by mass' and then add Mg for continuous conversion' to make this paper scale Applicable to China National Standard (CNS) A4 specification (210 X 297 mm) • ------------- install i — ί Please read the precautions on the back before filling this page)

-SJ-Line • Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 101 434-0 5 9 A7

Fifth, the invention (&quot;) into a cast piece. Therefore, we investigated the stability of the operation during casting, the fineness of the solidification structure of the slab, the internal defects of the slab, and the presence of surface defects on the steel. The results are shown in Table 10. Printed by the Intellectual Property Bureau of the Ministry of Economy ’s Consumer Cooperatives. The paper size is applicable to the Chinese National Standard (CNS) A4 (210 X 297 mm). 102. 5. Description of the invention (100) A7 B7. M to one NJ — g falling steel 5-〇CriM (mass 1%) 0.198 0.021 0.125 0.020 0.013 Ti impurity (mass%) 0.038 0.023 0.022 0.024. 0.012 NiM (mass%) No addition 0.0025 0.0015! ____ 0.0035 _1 Mgxian (ft%) The stability of the operation is good or not. The microstructure of the solidification structure is fine: whether the internal slab of the slab is open or not. The surface defects of the Xie Cai are present. The nozzles are X. X. 〇〇〇〇 ------------ Installation -------- Order --------- Line (Please read the notes on the back before filling this page) This paper size is applicable to China National Standard (CNS) A4 Specification (210 X 297 mm) 103 434059 A7 B7 Printed by the Intellectual Property Office of the Ministry of Economic Affairs and Consumer Cooperation Du V. Description of Invention (101) Example 1 in Table 10, the Cr concentration is 0% The Ti concentration of the dissolved steel is limited to 0.013% by mass and the Ni concentration is 0.012% by mass. By adding the situation after the Mg 0.0035% quality. The casting operation was stable, and the solidification structure of its slabs was refined, and no defects were found in the slabs and steels. The overall evaluation was good (indicated by 0). In Example 2, the Cr concentration of the dissolved steel was limited to 10% by mass, the Ti concentration was 0.020% by mass, and the N concentration was 0.024% by mass, and then Mg was added to 0-0015% by mass. The casting operation was stable, and the solidified structure of the cast slab was finer. The cast slab and the steel had no defects, and the overall evaluation was good (indicated by 0). In the third embodiment, the Cr concentration: 23% by mass of molten steel is limited to 0.125% by mass, the N concentration is 0.022% by mass, and then Mg0 0_0025% by mass is added. When the town was built, the operation was stable. The solidification structure of the cast piece was refined, and the recording and steel were free of defects. The overall evaluation was good (indicated by 0). In contrast, Comparative Example 1 limited the Cr concentration of the molten steel to 10% by mass, the Ti concentration to 0.021% by mass, and the N concentration to 0.023% by mass without adding Mg. When casting occurs, such as nozzle blockage, etc., which causes operational instability, the solidification structure of the slab is coarsened as shown in Fig. 7. Both the slab and the steel are defective, and the overall evaluation is poor (indicated by X). In Comparative Example 2, the Cr concentration of the molten steel was limited to 23% by mass, the Ti concentration of the molten steel was 0.198% by mass, and the N concentration was 0.038% by mass, and the solubility product of the two elements ([% Ti] X [% N]) It is set in a range where TiN does not crystallize and Mg is not added. In the case of the comparative example, although the size of the solidified paper is in accordance with Chinese National Standard (CNS) A4 (210 X 297 mm) -111 --------! III (Please read the precautions on the back before (Fill in this page) Order ----- 4 104 A7 B7 V. Description of the invention (102) After refinement, 'but nozzle clogging occurred during casting, which caused instability in operation. Defects caused by coarse TiN occurred on the surface of the steel. , The overall evaluation is generally poor (indicated by △). Example 9 This example relates to the processing method IV of the present invention. 150 tons of molten steel is cast in a molten iron tank to form a thickness of 100 mm of slag covering the molten steel, and the total mass of FeO, Fe203, MnO, and SiO is adjusted to a predetermined range. Then, Mg alloy wire is supplied and penetrates the slag to make The Mg content in the molten steel was 50 kg (0.0333% by mass). Next, the molten steel was cast using a continuous casting device having a thickness of 250 mm and a width of 1200 mm in a mold and a casting speed of 0.6 m / min. Yu Xuan investigated the Mg% mass in the molten steel after Mg treatment, the Mg ° / 0 mass in the slab, and the state of refinement of the solidified structure of the slab. The results are shown in Table 11. ------------- I -------- (Please read the notes on the back before filling out this page) Total mass% of FeO, Fe: 05, MnO and SiO in the slag before Mg addition \ %% by mass in molten steel after Mg treatment \ 1 & %% by mass in slabs Refinement of solidified structure 1 2.5 0.0041 0.0015 Fineness 2 11.3 0.0061 0.0020 Fineness Example 3 16.1 0.0065 0.0035 Fineness 4 22.4 0.0063 0.0031 Fineness 5 28.5 0.0036 0.0019 Fineness comparison 0.5 0.0025 0.0009 Partial coarseness example 2 36.3 0.0028 0.0008 Partial coarseness This paper scale applies Chinese National Standards &lt; CNS) A4 specification (210 X 297 mm) 105 4 3 4 0 5 9 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7_____ 5. Description of the invention (103) Example 1 in Table 11 is before Mg will be added The total mass of FeO, {^ 2〇3,] ^ 0, 8 丨 02 in the slag was set at 2.5. / 〇quality situation. The solidification structure of the cast slab can be made fine by setting Mg in molten steel to 0.0041% by mass and Mg in slab to 0.0015% by mass. In Examples 2, 3 and 4, the total mass of FeO, Fe203, MnO and SiO2 in the slag before Mg was added was limited to 11.3% by mass, 16.1% by mass, and 22.4% by mass. Mg in molten steel is 0.0061% mass, 0.0065% mass, 0.0063% mass, and Mg in cast slabs is 0.0020% mass, 0.0035% mass, and 0.0031% mass, respectively. The content rates are high and stable. The solidified structure has also been refined. In Example 5, the total mass of FeO, Fe203, MnO, and SiOz in the slag before Mg was limited to 28.5% by mass. The Mg in the molten steel can be set to 0.00036. The mass of the cast slab is 0 0019 // mass, and the solidification structure of the cast slab is refined. In contrast, Comparative Example 1 is a case where the total mass of FeO, FeA3, MnO, and SiO2 in the slag before Mg is added is limited to 0.5% by mass. The Mg in the molten steel is 0.0025% by mass, and the Mg in the prayer sheet is 0.0009% by mass. The content of Mg is poor, and the solidified structure of the slab is locally coarsened. Comparative Example 2 is a case where the total mass of Fe0, Fe2O3, Mn0, and Si02 in the slag before the addition of Mg is limited to 36.3% by mass. A &quot; § in molten steel is 0.0028% by mass, and casting The content of ^ in the sheet was 0.0008% by mass, and the content of Mg was not good. As for the solidified structure of the cast sheet, localized coarsening was formed. Example 10 This paper size applies to China National Standard (CNS) A4 (210 X 297) ------ 1 --- IL ^ -------- Order ------ --- line- r (Please read the notes on the back before filling out this page) 106, printed by A7 B7, Consumer Cooperative of Intellectual Property Bureau of the Ministry of Economic Affairs V. Description of the invention (104) This embodiment is related to the invention Processing method v. 150 tons of molten steel was cast in a molten iron tank, the thickness of the slag covering the molten steel was 1000 mm, the activity of CaO in the slag and the range of the slag were adjusted, and Mg alloy iron wires were supplied to the molten steel through the collapse. Medium and dissolved, it is made by adding Mg with an Mg purity of 50 kg to molten steel. Further, the molten steel was fabricated by using a continuous casting apparatus having a thickness of 2500 mm and a width of 1200 mm in a mold, and was cast at a casting speed of 0.6 m / min. Then, "the mass of Mg% in the molten steel after the Mg treatment and the micronized state of the solidified structure of the cast slab were investigated. The results are shown in Table 12. Table η

CaO activity in the project slag Slag salinity (Ca0 / Si02) Mg concentration (% by mass) in molten steel Total evaluation of the solidification structure of the ball 1 0.20 3 0.0010 ◎ ——— 2 2 0.25 7 0.0020 ◎ ———-- ---- ◎ Example 3 0.30 10 0.0020 ◎ ◎ Comparative Example 1 0.36 15 0.0050 XX 2 0.42 20 0.0100 XX In Example 1, the CaO activity in the slag was set to 0.2, and the shout level was set to 3 and added. In the case of Mg alloy wire. The Mg concentration in the molten steel after the Mg treatment is 0.001% by mass, and the solidified structure of the slab can be made finer (indicated by ◎), and the overall evaluation is excellent (indicated by ◎). In Examples 2 and 3, the Ca0 activity in the slag was set to 0.25 and 0.30, respectively, and the slag reduction was set to 7 and 10, respectively. The concentration of Mg in the molten steel is also high, and the solidified structure of the slab is also fine (to ◎ this paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) ill --- I It ------ ------- ^ --- I I --- I ^ &lt; Please read the notes on the back before filling out this page) 107 Printed by the Intellectual Property Bureau Employee Consumer Cooperatives of the Ministry of Economic Affairs Α7 Β7 ______ 5. Description of the invention ( 105)), and the overall evaluation is excellent (indicated by ◎). Comparatively speaking, in Comparative Example 1, the CaO activity in the slag was set to 0-36, the alkalinity was set to 15 and the Mg alloy iron wire was added, so that the Mg in the molten steel after the Mg treatment became 0,0050% by mass. Situation. The solidification structure of the slab is coarsened (indicated by X), and the overall evaluation is poor (indicated by X). In Comparative Example 2, the CaO activity in the slag was set to 0.42, the alkalinity of the slag was set to 20, and the Mg alloy iron wire was added so that Mg in the molten steel after the Mg treatment became 0.0100% by mass. The solidification structure of the slab was coarsened (indicated by X), and the overall evaluation was poor (indicated by X). Embodiment 11 This embodiment relates to a continuous casting method for manufacturing the slabs A to D of the present invention. After adding MgO.005% by mass to molten steel containing 16.5% by mass, 'continuous casting is performed using a vibrating mold with a width of 1200mm and a thickness of 250mm, and the mold is cooled through cooling of the mold and cooling water from the supporting section. The sheet solidifies' and is then scooped out by a pinch roller. Next, the number of defects and inclusions on the surface and inside of the slab, and the solidified structure were investigated. In addition, this cast piece was heated to 25 ° C and then rolled into A steel. The surface resistance and the occurrence of corrugation flaws (bulges) were investigated. The results are shown in Table 13. Paper only applies to China National Standard (CNS) A4 specifications (210 X 297)

It —---- I --- L--— — — — — 11111111 I (Please read the notes on the back before filling out this page) 108 A7 B7 V. Description of the invention (I〇6) Table 13 Project implementation Examples Comparative Example 1 Comparative Example 2 __ Mg is added with or without electromagnetic stirring with or without slab surface inclusions are small. There is no solidified structure. Fine and fine surface cracks. No A 4 1 .. There are no internal inclusions. There are no solidified structures. No cracking, no center segregation, slight slightness, significant surface surface, good name, bad, good time delay, ripple defects, good, good, bad. The example in Table 13 is to set the electromagnetic stirring device at a position of 500mm on the meniscus downstream side in the mold The formation of the magnetic core occurs when the molten steel is mixed and cast. In this embodiment, the number of M gO-containing oxides (inclusions) located on the surface layer of the cast slab is reduced, and the solidified structure on the surface layer is formed to be fine. This can prevent defects such as surface cracking. In addition, the number of MgO-containing oxides (inclusions) in the slab is increased, and fine equiaxed crystals can be obtained. As a result, internal cracks are eliminated, and slight central segregation can be formed. Further, the steel material obtained by calendering the cast slab had good surface resilience, and there was no corrugation or the like caused by coarsening of the solidified structure. In contrast, Comparative Example 1 does not use an electromagnetic stirring device to stir the molten steel. In the surface layer and the interior of the cast slab, the number of MgO-containing compounds (inclusions) is increased. Although the solidified structure located in the surface layer and the interior can be refined, the surface of the steel after rolling is found to Contains 1 ^ § oxygen I--lit ------------ order ------- I f (Please read the notes on the back before filling out this page). Staff of Intellectual Property Bureau, Ministry of Economic Affairs Printed by the Consumer Cooperative 109 '434〇59 A7 ------- B7_; _____ V. Description of the invention (丨 〇7) The existence of corrosion spots starting from compounds. This steel is not practically practical. Comparative Example 2 'was a case where Mg was not added, but the molten steel was stirred by using an electromagnetic stirring device. The coarsening of the solidified structure located inside the slab has internal cracks and center segregation; the steel produced by processing the slab has corrugation defects caused by coarsening of the solidified structure. Example 12 This %% 'is related to the above-mentioned continuous casting of the present invention, which is applicable to the casting of pure grain iron-based stainless steel molten steel, and the seamless steel pipe is manufactured from the cast slab. It is in a molten steel containing 13.0% by mass of chromium, 0.0010% by mass of Mg is added, and then continuous casting is performed using a vibration mold with a width of 60mm and a thickness of 250mm, and cooling through the mold and cooling water from the supporting section Treatment 'set the slab to solidify and then pull it out through the pinch roller. Next ', investigate the solidification structure of the slab and the occurrence of surface and internal defects of the seamless steel pipe after the perforation process &lt; = and show the results in Table 14

Middle D Table 14 ---------- IX ^ --------- Order --------- line, 』(Please read the precautions on the back before filling this page ) The amount of molten steel Mg added (mass%) printed by the project of the Intellectual Property Bureau of the Ministry of Economic Affairs and the Consumer Cooperative Cooperative Society. The internal and surface defects of the solidified structure steel tube of the cast slab under the condition of electromagnetic stirring and soft pressing were evaluated. Reduction amount (mm) Example 1 0.0010 None---〇〇—- 〇2 0.0010 With the meniscus liquid level 0.5 6 ◎ ◎ ◎ ---- 1 ◎ 3 0.0010 None-0.4 7 〇 ◎ Comparative Example 1 No added with downstream side 500mm--XXX 2 No added without-0.4 7 XXX This paper is suitable for medium solid standard (CNS) A4 specification (210 X 297 mm) 110 Α7 Α7 'Employee of Intellectual Property Bureau, Ministry of Economic Affairs Printed by a consumer cooperative. 5. Description of the invention (10¾ Example 1 in Table 14 is a case where seamless steel pipes are manufactured by adding 0.0010% by mass of Mg to molten steel and casting. The solidification structure of the cast slabs is refined (by 〇), cracks and peeling defects on the surface and inside of the steel pipe during perforation None (indicated by 0), and the overall evaluation is good (indicated by 0). Example 2 'The electromagnetic stirring device is set at a position 500 mm away from the meniscus on the downstream side of the mold to form the core center, which generates agitated molten steel. When one side is cast, and the light pressing process is started from the position where the solid phase ratio is formed to 0. The number of Mg-containing compounds in the surface layer of the ball is reduced, and the solidified structure of the entire cast is fine. (Indicated by ◎); on the surface and inside of the steel pipe during perforation processing, there are no cracks and peeling flaws (indicated by ◎) 'Excellent overall evaluation (indicated by ◎)' Example 3, added to molten steel Mg 〇.〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇１０ ％ 〇)), and there were no cracks or peeling defects on the surface and inside of the steel pipe during perforation processing (indicated by ◎), and the overall evaluation was excellent (indicated by ◎). Comparative Example 1 was based on the fact that the molten steel was not added. MMg Casting, and electromagnetic stirring at a position 500mm away from the meniscus on the downstream side, and then through perforation. The solidification structure of the slab is coarsened (indicated by χ). During the perforation process, turtles are generated on the surface and inside of the steel pipe. Cracking and spalling defects (expressed as X) 'The overall evaluation is poor (expressed as X). Comparative Example 2 is based on the casting of molten steel, and the solid phase rate ranges from 0.4 to solidification. The paper size of the depth of 7001 is applicable to the Chinese national standard (CNS &gt; A4 specification (210 X 297)) ------------ Shang -------- Order --------- Line (please read the precautions on the back before filling this page) 111 '434059 A7: ----- ~~ ----; __ V. Description of the invention (10S) Processing sentiment. The solidification structure of the slab is coarsened (indicated by X), and cracks and peeling defects (indicated by X) occur on the surface and inside of the steel pipe during perforation processing. The overall evaluation (indicated by X) is not good. INDUSTRIAL APPLICABILITY The ball chip of the present invention is designed to suppress surface defects such as cracks and depressions caused by deformation and stress in the solidification process, surface defects such as inclusions, surface defects caused by inclusions, and internal cracks and centers. Occurrence of internal defects such as looseness (central depression) and central segregation. Therefore, the slabs of the present invention have good processing characteristics and quality characteristics. Moreover, it is unnecessary to prepare slabs for grinding and the like, and they have high productivity due to extremely reduced fragmentation. In the processing method of the present invention, in order to refine the solidified structure during the solidification of the molten steel, and adjust the characteristics of the molten steel and the shape of the inclusions in the molten steel, in order to obtain the slab of the present invention, it is a very useful molten steel processing method. . Further, the continuous casting method for manufacturing the slab of the present invention, the effect of the molten steel provided by the processing method of the present invention is further improved during continuous casting. Therefore, the steel sheet, steel pipe, and other steel materials produced by processing the ball sheet of the present invention are formed by suppressing the occurrence of surface defects and internal defects in the same way as the cast sheet, and the processing characteristics and quality characteristics are also excellent. . This paper size applies to Chinese national standards (CNS> A4 size (210 X 297 mm) (Please read the precautions on the back before filling out this page)) ------------ Order --------- Printed by the Consumers' Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 112. 5. Description of invention (uo) 10 ... continuous casting device 11 ... molten steel 12 ... fishing port 13 ... mold 14 ... spout 15 ... immersion nozzle 16 ... electromagnetic stirring device 17 … Support section 18… slab 19… press sections 20, 21… pinch pro 22… support roller 23… projection (lower roller) 24… lower roller 25 ··· processing device A7 --- -Component number comparison 2 6 * · Hot metal tanks 27, 28 ... Storage hopper 29 ... Drain trough 30 ... Iron wire 31 ... Supply device 32 ... Guide line 33 ... Slag 35 ... Processing device 36 ... Blow-in spray gun 13a, 13b ... Long pieces of town molds 13c, 13cl ... Short films of molds 16a, 16b ... Solenoid coils 16d, 16c ... Solenoid coils 18a, 18b ... Solidified shell 18b ... Unsolidified part of the cast piece I --- 11-- I ----- install --- f Please read the notes on the back before filling in this page) ^] ·-· LINE_ With China National Standard (CNS) A4 (210 X 297 mm) 113

Claims (1)

4340 5 9 A8 BS C8 D8 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 6. Application for patent scope 1. A township with excellent processing characteristics, characterized by ... 60% μ of the entire cross section of the cast Those who satisfy the following formula: D &lt; 1.2XW3 + 0.75 [where the diameter of the D-series crystal is the same as the diameter of the isospheric crystal of the structure (mm), and the distance of X-series from the surface of the slab (mm)] 2. A casting slab with excellent processing characteristics, characterized in that the maximum value of the crystal grain size located at the same depth on the surface of the sacrifice sheet is within 3 times the average crystal grain size of its depth. 3. The slabs with excellent processing characteristics as described in item 2 of the patent application are characterized by: * 60% or more of the cross-sections in the thickness direction of the ball are equiaxed. 4. ·. A slab with excellent quality and processing characteristics, characterized in that the inclusions below the degree of lattice inconsistency between the 6 pure grain irons formed during solidification of the steel are 100 or more per cm2 . 5. The slab with excellent quality and processing characteristics according to item 4 of the patent application is characterized in that the above-mentioned inclusions include those having a size of 10 &quot; mW and more than 100 / cm2. 6. A slab with excellent quality characteristics, which is a slab cast by adding a metal or a metal compound to the molten steel to form a solidified core during the solidification of the molten steel, which is characterized in that it is relative to the surface portion of the cast The number of metal compounds having a size of 10 or less and the number of metal compounds having a size of 10 # m or less contained in the inside is 1.3 times or more than the surface layer portion. 7. If the cymbals with excellent processing characteristics and / or quality characteristics according to any of the claims in the scope of the patent application No. 丨 ~ 6, it is characterized in that the town film contains M§〇 --------- --- 4k -------- order --------- line "(Please read the notice on the back before filling out this page) 114 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs AS BS C8 ______DS 6. Scope of patent application and / or those containing MgO oxide. 8. If applying for a patent. Casting slabs with excellent processing characteristics and / or quality characteristics in any one of the scope 1 to 6 'are characterized by : This cast piece is a prayer piece of pure grain iron which is not too steel. 9_ A method for dissolving steel, which is to dissolve the steel to refine the solidified structure of the cast piece, is characterized by: The total amount of Ca is set to less than 100% by mass; and then, a predetermined amount of Mg is added to the molten steel. I 〇—The treatment method of molten steel is to refine the solidification structure of the slab. Dissolved steel processor; It is characterized in that: before adding a predetermined amount of Mg to the molten steel, 'the predetermined amount containing eight Those who dissolve the alloy in the molten steel for deoxidation treatment. II. The method for dissolving the molten steel in item 10 of the patent application scope, characterized in that: before adding a predetermined amount of Mg to the molten steel, in addition to the predetermined amount of the alloy containing A1 Those who have added a predetermined amount of Ti-containing alloys for deoxidation treatment. 12. For example, the treatment method of the molten steel in item 9 or 10 of the scope of the patent application is characterized by the slag and deoxidation products contained in the molten steel. The oxides and oxides generated when Mg is added to the molten steel are those that satisfy the following formulas (1) and (2) and are added with a predetermined amount of Mg to the molten steel; 17.4 (kAI203) +3.9 ( kMgO) +0.3 (kMgAl2O3) + 18.7 (kCaO) ^ 500… ⑴ (kAl203) + (kMg0) + (kMgAl203) + (kCa0) ^ 95… (2) This paper size applies the Chinese National Standard (CNS) A4 specification ( 210 X 297 Public Love> ----------------- II ί ^ ---------- (Please read the precautions on the back before filling this page) 115 434059 A8 BS C8 D8 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 6. Scope of patent application [of which k / oxide is 0/0 mole] D 13-such as The method for treating molten steel in the 9th or 10th patent scope is characterized in that the Mg added to the molten steel is in the range of 0.001 to 100% by mass. 14 ' The method for treating molten steel of item 9 or item 10, characterized in that the molten steel is a pure steel of a pure iron type and the molten steel is a molten steel. 15. Kind of steel processing method, which is to dissolve steel in order to refine the solidification structure of scales. It is characterized by: Ti concentration above the liquidus temperature of molten steel and satisfying the solubility product of TiN crystals. And N concentration of the dissolved steel 'add a given amount of'§. 16. For example, the treatment method of the molten steel of item 5 of the patent scope is characterized in that the Ti concentration [% Ti] and N concentration [% N], [% Ti) X [% N] [〇 / 〇Cr] 2 · 5 + 150) χ 10-6 [of which [% Ή] is Ti% mass in molten steel, [% Ν [] Mass of N% in molten steel '[% Cr] is mass of cr% in molten steel]. 17- The method for processing molten steel in the 15th or 16th of the scope of patent application, characterized in that the molten steel contains Crl0 ~ 23% mass pure steel iron stainless steel dissolving steel. 18. —A dissolving steel treatment method is a dissolving steel treatment to refine the solidification structure of the slab, which is characterized in that The slag 'makes it contain tritium compounds that have been recovered by Mg! ~ 300 / 〇 quality. 19. If you apply for special The processing method of molten steel in item 18 of the scope, its characteristics This paper size applies the Chinese National Standard (CNS) A4 specification (210x297 mm) --It --------- 4 ^ &lt; I --- ! —Order · -11-11 Line JLΊ (please read the note on the back? Matters before filling out this page) 116. The scope of patent application is: The oxides returned by Mg are Fe 0, Fe 2 03, One or two or more of Mn〇 and Si〇2. 20. The processing method of molten steel in the 18th or 19th of the scope of the patent application of Shenqiao is characterized in that it is A ^ 〇3 contained in the molten steel. It is limited to those with a mass of 0. 05 to 0. 10%. 21. —A treatment method for molten steel 'is a treatment for melting steel in order to refine the solidification structure of a cast slab, and is characterized by adding a predetermined amount Before dissolving Mg, the CaO activity in the slag covering the molten steel is set to be less than 0.3. 22. The method for dissolving molten steel in item 21 of the application for printing, which is characterized by the alkali in the slag The degree is set below 丨 〇. 23. If the method for processing molten steel in the scope of patent application No. 21 or 22 is characterized by: A steel-based pure-grain iron-based stainless steel. 24'A continuous casting method of a slab, which continuously casts a slab having a solidified structure after miniaturization treatment ', characterized in that: it contains Mg0 and / Or a molten steel containing MgO oxide is cast into a mold, and an electromagnetic stirring device is used to cast the molten steel while stirring the molten steel. 25. The continuous casting method of a slab, such as the 24th claimed in the patent, is characterized by: The electromagnetic mixing device is set at a distance of 2.5m from the meniscus in the scale mold to the downstream side. 26. The continuous front making method of slabs as claimed in item 24 or 25 of the scope of patent application, characterized in that it uses an electromagnetic stirring device to impart the flow velocity of the molten steel's stirring flow, which is above I0cm / sec. The A8 B8 C8 D8 t printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, and the scope of patent application 27. For the continuous casting method of the slab of the application for the scope of the patent No. 24, characterized in that the molten steel is pure grain iron stainless steel molten steel . 28. The method for continuous casting of slabs as claimed in item 27 of the scope of patent application, characterized in that the aforementioned dissolving steel is a pure grain iron-based stainless steel containing 10 to 23% by mass of chromium and Mg 0.0005 to 0.010% by mass By. 29. For the continuous casting method of slabs as claimed in item 27 of the patent application, it is characterized by the use of an electromagnetic stirring device, while the molten steel is searched and mixed, and the pound is processed. 30. The continuous casting method of a slab, such as the scope of application for patent No. 27, is characterized in that the solid phase rate of the slab starts from the range of 0.2 to 0.7, and the light-down processing of the slab is started. 31—A kind of steel with excellent processing characteristics and quality characteristics, which is characterized in that: the casting slabs with excellent processing characteristics and / or quality characteristics as described in any of claims 1 to 6 of the scope of patent application are heated to 1 100 ~ 13 50. (: Manufactured by subsequent processing such as calendering. 32_ —Seamless steel pipe 'is characterized in that it is a continuous casting method using a continuous casting method such as the slab of item 28 in the scope of patent application. The sheet is processed after perforation. This paper size is applicable to China National Standard (CNS) A4 (210 X 297 mm) --- Order --------- Line L 1 (Please read the notice on the back before filling this page) 118