CN112218965A - Stainless steel material having excellent slag point generation inhibiting ability, welded structural member, and method for producing same - Google Patents
Stainless steel material having excellent slag point generation inhibiting ability, welded structural member, and method for producing same Download PDFInfo
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- CN112218965A CN112218965A CN201880068466.1A CN201880068466A CN112218965A CN 112218965 A CN112218965 A CN 112218965A CN 201880068466 A CN201880068466 A CN 201880068466A CN 112218965 A CN112218965 A CN 112218965A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
- B23K31/02—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups relating to soldering or welding
- B23K31/027—Making tubes with soldering or welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
- B23K35/3053—Fe as the principal constituent
- B23K35/308—Fe as the principal constituent with Cr as next major constituent
- B23K35/3086—Fe as the principal constituent with Cr as next major constituent containing Ni or Mn
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
Abstract
A stainless steel material having, in mass%, C: 0.005-0.100%, Si: 0.10 to 3.00%, Mn: 0.10-6.50%, P: 0.001-0.050%, S: 0.0001-0.0200%, Ni: 0-20.00%, Cr: 10.50-26.00%, N: 0.005-0.200%, O: 0.0030 to 0.0150%, and a chemical composition containing Mo, Cu, Nb, V, Zr, W, Co, B, Ti, Al, Ca, Mg, REM (rare earth element except Y), Y, and the balance Fe and inevitable impurities in a predetermined range as required, wherein the average CaO/(SiO) of oxide inclusions observed in the metallographic structure is CaO/(SiO)2+ MnO + CaO) of 0.40 or less and an average CaO/MnO mass ratio of 15.0 or less, and can stably and remarkably suppress generation of slag spots in arc welding.
Description
Technical Field
The present invention relates to a stainless steel material in which a defect called "slag point (slag point)" or "black point" which is one type of welding defect generated in an arc bead is less likely to be generated. Also disclosed are a welded structural member using such a steel material and a method for producing the same.
Background
When arc welding is performed using a stainless steel material as a base material, a defect called "slag point" may occur in which an oxide aggregate is scattered on a weld bead. Fig. 1 shows and exemplifies a photograph of the appearance of a weld bead with a slag spot generated as disclosed in non-patent document 1. According to the description of non-patent document 1, the slag point is considered to be a minute slag that remains floating on the bead at intervals of several mm to several cm in an island-like or spot-like shape. It is considered that oxygen in the air intruded into the molten pool during the arc welding reacts with active elements such as Al, Ca, Ti and the like which are trace components in the steel material and remains as slag points; in particular, in high-speed TIG welding in which sufficient gas shielding of the molten pool is difficult, the generation of slag spots tends to become significant.
Fig. 2 illustrates an appearance of slag spots observed on a bead of a steel pipe manufactured by TIG welding. The number of slag points having a size of 1.0mm or more in the major axis direction of the steel pipe per 1m in the longitudinal direction of the bead (hereinafter referred to as "slag point generation rate") was 0.7/m.
When slag spots frequently occur on the weld bead, for example, the following problems occur. (i) The beauty of the weld bead portion is impaired. (ii) In order to remove the bead, complicated finishing such as polishing of the bead surface may be required. (iii) In the production of welded steel pipes, there is also a use in which a bead on the inner surface of a steel pipe is pressed down to reduce the height of the bead, and then the inner surface is polished. In this case, when the bead portion on the inner surface of the steel pipe is pressed down, the slag point is pressed in to form a recess in the metal surface of the bead, and a grinding residue (non-ground portion) is generated in the subsequent grinding step. (iv) Interstitial corrosion sometimes occurs between foreign matter constituting slag spots and the metal surface of the bead. (v) In the case of welded steel pipes, slag spots formed on the inner surface beads fall off during use of the steel pipes, and cause foreign matter to be mixed into the fluid flowing therein. (vi) When foreign matter causing slag spots during arc welding is aggregated in the molten metal pool, the arc becomes unstable, and the bead shape is easily disturbed.
Therefore, there is a demand for the development of a stainless steel material which can significantly suppress the generation of slag spots when used as a base material for arc welding.
Patent documents 1 and 2 disclose ferritic stainless steels in which the content of Al, Ti, Si, and Ca, which are easily oxidizable elements, is adjusted to an optimized steel composition, thereby reducing the generation of slag spots (black spots). However, according to the investigation of the inventors, only the steel composition is adjusted, the effect of suppressing the slag point is limited, and there is room for further improvement.
Patent document 3 describes that, in an austenitic Fe — Ni — Cr alloy for a coated pipe, foreign matter on the surface of a welded portion, which becomes a starting point of a machining crack, is reduced. Teaches that: since the foreign matter adhering to the surface of the welded material is mainly composed of oxides and nitrides of Al, Ti, Si, Ca, Mg, etc., and the nonmetallic inclusions present in the base material are generally high in melting point, they float and aggregate on the surface of the molten metal without melting at the time of welding, and remain on the surface directly at the time of solidification to form irregularities (paragraph 0035). Further, it is considered that the foreign matter adhering to the surface of the welded portion is derived from the nonmetallic inclusions present in the base material (paragraph 0038). In the technique disclosed in patent document 3, the amount of Al, Ti, and Si is reduced as much as possible, and Ca, Mg, N, and O, which are other inclusion constituent elements, are also reduced, thereby reducing the number of inclusions present in the base metal, and thus reducing the foreign matter observed on the weld metal surface (paragraph 0039). However, according to the studies of the inventors, it has been difficult to stably obtain an arc welding bead with extremely few foreign matters (slag spots) required for a welded steel pipe used in, for example, a food processing line or a semiconductor manufacturing facility, by simply reducing the number of non-metallic inclusions present in a stainless steel material. Further, the amount of non-metallic inclusions present in the stainless steel material is significantly reduced, which increases the load in the steel making process and causes an increase in the steel material cost. Therefore, it is desired to develop a new method capable of reducing slag point without depending on a method of reducing the amount of inclusions.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent application No. 2010-202973
Patent document 2: japanese laid-open patent publication No. 2012 and 36444
Patent document 3: japanese patent laid-open No. 2014-84493
Non-patent document
Non-patent document 1: the stainless Steel Association, "stainless Steel Messaging 3 rd edition", journal Industrial News agency, 1995, p.1030-1031
Disclosure of Invention
Problems to be solved by the invention
Examples of a welding method effective in reducing the slag point of the arc bead include a method of using a welding wire for an electrode and a method of adding a solder (filler metal). It is also effective to use a flux-containing wire. On the other hand, arc welding using a non-consumable electrode type electrode such as TIG welding is also widely performed, and solder is often not used.
The present invention is intended to provide a technique capable of stably and remarkably suppressing the generation of slag spots in various stainless steel types regardless of austenite type and ferrite type, regardless of the use of a wire or a solder, even when a non-consumable electrode type arc welding method is employed.
Means for solving the problems
As a result of detailed studies, the inventors have found that the above-mentioned object can be achieved by adopting a method of reducing the amount of non-metallic inclusions present in the stainless steel base material and controlling the composition of oxide-based inclusions. In the present specification, the following invention is disclosed.
[1]A stainless steel material having a composition comprising, in mass%, C: 0.005-0.100%, Si: 0.10 to 3.00%, Mn: 0.10-6.50%, P: 0.001-0.050%, S: 0.0001-0.0200%, Ni: 0-20.00%, Cr: 10.50 to 26.00%, Mo: 0-2.50%, Cu: 0 to 3.50 percent,Nb: 0-0.500%, V: 0-0.500%, Zr: 0-0.500%, W: 0-0.500%, Co: 0-0.500%, B: 0-0.020%, N: 0.005-0.200%, Ti: 0-0.050%, Al: 0-0.100%, Ca: 0-0.0010%, Mg: 0 to 0.0010%, REM (rare earth element other than Y): 0-0.050%, Y: 0-0.050%, O: 0.0030 to 0.0150%, and the balance Fe and inevitable impurities, wherein oxide inclusions containing Mn are present, and the contents of Si, Mn and Ca in the oxide inclusions are respectively converted into SiO2Average CaO/(SiO) of oxide inclusions observed in the metallographic structure in the inclusion composition at the mass ratio of MnO to CaO2+ MnO + CaO) is 0.40 or less and the average CaO/MnO mass ratio is 15.0 or less.
[2] A base material for arc welding comprising the stainless steel material according to [1 ].
[3] A steel plate base material for arc welding pipe production, comprising the stainless steel material according to [1 ].
[4] An arc welding structural member using the steel material according to [1] as a base material.
[5] An arc-welded steel pipe using the steel material according to [1] above as a base material.
[6] A method for producing a welded structural member, wherein the stainless steel material according to [1] above is used as a base material, and non-consumable electrode type arc welding is performed without adding a solder.
[7] A method for producing a welded steel pipe, wherein the stainless steel sheet according to [1] is used as a base material, and the welded steel pipe is formed by non-consumable electrode arc welding without adding a solder.
Here, the content of each steel component described above is the total content of the element present in the steel. Therefore, a part of the metal element present in the form of oxide, the content of oxygen, includes the amount present in the form of oxide. Average CaO/(SiO) of oxide inclusions2+ MnO + CaO) mass ratio and the average CaO/MnO mass ratio can be determined as follows. The arc welding structural member is a member having a welded portion formed by arc welding. Similarly, an arc-welded steel pipe is a steel pipe having a welded portion formed by arc welding. These welding parts can be provided withA "solder-free solder joint" (i.e., a solder joint formed without added solder).
[ average CaO/(SiO)2Method for calculating mass ratio of + MnO + CaO) and average CaO/MnO mass ratio]
In SEM observation of a cross section of a steel material, 30 or more particles were randomly selected from the oxide-based inclusion particles present in the cross section, and composition analysis was performed by EDX (energy dispersive X-ray analysis). The contents of Si, Mn, Ca, Al, Mg, Ti, Cr and Fe in the respective particles were converted to SiO oxides2、MnO、CaO、Al2O3、MgO、TiO2、Cr2O3The mass ratio of the SiO in the 8 oxides to FeO2The mass ratios of MnO and CaO are set as SiO of the particles2Content (mass%), MnO content (mass%) and CaO content (mass%). By mixing SiO of the respective particles2The content, MnO content and CaO content were weighted-averaged, respectively, to calculate SiO for all the measured particles2Average content (mass%) of MnO and CaO. The average CaO/(SiO) was determined by substituting the value of the average content (mass%) of each oxide of the following formula (1) into the position of the chemical formula of the oxide2+ MnO + CaO) mass ratio. Similarly, the average CaO/MnO mass ratio was determined by substituting the value of the above average content (mass%) of each oxide of the following formula (2) into the position of the chemical formula of the oxide.
CaO/(SiO2+MnO+CaO) (1)
CaO/MnO (2)
Effects of the invention
According to the present invention, the generation of slag spots in the arc welding of stainless steel materials can be stably and significantly suppressed. This technique can be applied to various stainless steel grades regardless of the austenitic and ferritic systems, and is particularly effective in TIG welding performed without adding a solder.
Drawings
Fig. 1 is a photograph showing the appearance of a weld bead with slag spots generated as disclosed in non-patent document 1.
Fig. 2 is a photograph showing the appearance of slag spots on a bead of a steel pipe produced by TIG welding.
FIG. 3 shows the average CaO/(SiO) of oxide inclusions2+ MnO + CaO) mass ratio and slag point generation rate.
FIG. 4 is a graph showing the relationship between the average CaO/MnO mass ratio of oxide inclusions and the slag point generation rate.
FIG. 5 is an enlarged graph showing a region where the average CaO/MnO mass ratio of FIG. 4 is low.
FIG. 6 is a graph showing the relationship between the total oxygen content in the steel material and the average CaO/MnO mass ratio of the oxide-based inclusions.
FIG. 7 is an enlarged graph showing a region where the average CaO/MnO mass ratio of FIG. 6 is low.
FIG. 8 is a graph showing the relationship between the total oxygen content in the steel material and the slag point generation rate.
Fig. 9 is a graph showing the relationship between the slag basicity and the slag point generation rate during refining.
Detailed Description
[ composition of Steel ]
In the present invention, various steel grades are suitable regardless of the austenitic system and the ferritic system. According to the study of the inventors, the slag point suppressing effect by the composition control of inclusions described later can be obtained in the following composition range.
In mass%, C: 0.005-0.100%, Si: 0.10 to 3.00%, Mn: 0.10-6.50%, P: 0.001-0.050%, S: 0.0001-0.0200%, Ni: 0-20.00%, Cr: 10.50 to 26.00%, Mo: 0-2.50%, Cu: 0 to 3.50%, Nb: 0-0.500%, V: 0-0.500%, Zr: 0-0.500%, W: 0-0.500%, Co: 0-0.500%, B: 0-0.020%, N: 0.005-0.200%, Ti: 0-0.050%, Al: 0-0.100%, Ca: 0-0.0010%, Mg: 0 to 0.0010%, REM (rare earth element other than Y): 0-0.050%, Y: 0-0.050%, O: 0.0030 to 0.0150% and the balance of Fe and inevitable impurities.
The content of P, S in the steel is generally preferably low, but since excessive dephosphorization and desulfurization increase the steel making load and make it uneconomical, P, S content is limited to steel having the above-mentioned range. Ni, Mo, Cu, Nb, V, Zr, W, Co, B, Ti, Al, Ca, Mg, REM (rare earth elements other than Y), Y is any element contained. These are general elements which are added to stainless steel as appropriate for improving hot workability and various properties of the steel material, and if the content is within the above range, the slag point suppressing effect of the arc welding bead is not inhibited if the average CaO/MnO mass ratio of the oxide-based inclusions is controlled to be within a predetermined range described later. If the content of Ti and Al is excessive, the inclusion composition may be adversely affected, which may cause generation of slag spots, and therefore, Ti is limited to 0.050% or less and Al is limited to 0.100% or less, respectively. More preferably, the composition is adjusted so that Ti is less than 0.010% and Al is 0.007% or less. In order to sufficiently reduce the Al content, it is desirable to perform Si deoxidation in refining.
[ composition of oxide-based inclusions ]
The following modes are considered as the main cause of generation of slag spots generated in arc welding beads in which stainless steel is used as a base material.
(mode 1) the oxidizable elements (Al, Ca, Ti, etc.) in the base material form oxides in the areas where the gas barrier is insufficient, and remain on the beads.
(mode 2) the nonmetallic inclusions present in the base material and having a high dissociation temperature are aggregated and floated by the scanning of the arc, and when the aggregated particles are large to a certain extent, they are left from the scanning of the arc and remain on the bead.
According to the study of the inventors, slag spots are generated even when the gas shielding is sufficiently performed, and therefore, in order to stably and remarkably suppress the generation of slag spots, it is necessary to overcome the generation cause of the above-described mode 2. The main cause of the mode 1 can be eliminated by limiting the content of the easily oxidizable element or the like in the steel composition of the base material to the above range.
As a countermeasure for the main cause of the mode 2, it is important to control inclusions in the base material. Among the nonmetallic inclusions, the nonmetallic inclusions which cause slag inclusions are oxide-based inclusions having a high dissociation temperature. In the steel compositionIn the case of stainless steel (2), a typical constituent component of oxide inclusions present in the steel material is SiO2、MnO、CaO、Al2O3MgO, and the like. Among these, CaO has a high dissociation temperature and is not reduced during welding and exists in an oxide state. When the metal melted by the heat of the arc is aggregated, the metal is cooled and appears as slag points. MnO and SiO on the other hand2Since the dissociation temperature of (b) is relatively low, Mn and Si constituting oxides are reduced to metals during welding and easily dissolved in molten metals. Thus, MnO and SiO2Is not easy to become the main cause of slag points.
The inventors examined the composition of oxide inclusions contained in the steel material in detail for various stainless steel types within the above-described steel composition range. As a result, it was found that oxide inclusions existing in general stainless steel materials are mostly SiO2And a type having a large content of CaO. Further, it was confirmed that the composition of inclusions can be controlled by changing the refining conditions so as to decrease the CaO content of the inclusions and increase the MnO content instead. Further, it is known that SiO is increased in the composition of inclusions2When the content of MnO coexists with CaO, generation of slag points can be remarkably suppressed in spite of the presence of CaO. SiO is then reacted with2And a general type of oxide-based inclusion containing a large amount of CaO is referred to as "SiO" for convenience2CaO type, which is a type of oxide-based inclusion in which a decrease in Ca concentration and an increase in Mn concentration are achieved by controlling the composition of the inclusion, is referred to as "SiO" for convenience2-MnO-CaO type ".
Metal oxides typically dissociate into metal and oxygen as the temperature increases. For example, if it is assumed in an Ellingham Diagram (Ellinghan diagram) that the partial pressure of oxygen is 10-12The dissociation temperature at atm is estimated to be SiO2: about 1530 ℃, MnO: about 1380 ℃, CaO: about 2100 ℃ and Al2O3: about 2020 deg.c. Mixing SiO2The CaO type inclusions are changed to SiO as much as possible2MnO-CaO type, i.e., making the composition of inclusions SiO2The MnO-CaO type is relatively advantageous,this contributes to the suppression of slag points. Here, Al2O3The steel material adjusted to the above steel composition, however, has Al at a high dissociation temperature2O3The amount of the carbon dioxide is small, and therefore, the generation of slag is difficult to be a main cause.
Quantitatively indicating SiO in the composition of inclusions2CaO type and SiO2An indication of the relative dominance of the MnO-CaO type, in the present invention, the "average CaO/MnO mass ratio" is used. The smaller the value, the evaluated as SiO2The inclusion composition of MnO-CaO type is relatively dominant, which is advantageous for suppressing the generation of slag spots. The average CaO/MnO mass ratio can be determined by the above-mentioned method. As a result of detailed examination, in the stainless steel in which the steel composition is adjusted to the above-mentioned range, when the average CaO/MnO mass ratio is 15.0 or less, a remarkable effect of reducing the slag point can be seen as compared with the conventional stainless steel. More preferably, the average CaO/MnO mass ratio is 10.0 or less, and can be controlled to 6.0 or less.
On the other hand, even when the MnO content of the oxide-based inclusion is high, if the CaO content is too high, the slag point generation-suppressing effect cannot be sufficiently obtained. As a result of the investigation, it is desirable to set the average CaO/(SiO)2+ MnO + CaO) of 0.40 or less. Average CaO/(SiO)2The mass ratio of + MnO + CaO) can be determined by the above-mentioned method.
[ composition control of inclusions ]
Average CaO/(SiO) of oxide inclusions2+ MnO + CaO) mass ratio and the average CaO/MnO mass ratio the above-described stainless steel material, of which the mass ratio of + MnO + CaO) and the average CaO/MnO mass ratio are optimized, can be manufactured using a general stainless steel melting facility. Representative are VOD process and AOD process. In either case, first, decarburization is performed by blowing oxygen into Cr-containing molten iron, and molten steel (C content, for example, 0.20% or less) having Cr oxide-containing slag on the molten steel surface is produced by a conventional method. Since the molten steel at this stage is the molten steel in which decarburization by blowing oxygen is completed, the oxidizable elements Si, Ti, Al, Ca, Mg, and the like are oxidized and removed from the molten steel. That is, Si, Ti, Al, Ca and Mg are hardly present in the molten steel. In addition, Cr contained in a large amount in molten steel is partially oxidized,slag is formed on the surface of the molten steel in the form of Cr oxides. On the other hand, a large amount of oxygen blown into the molten steel for decarburization is dissolved therein. Therefore, deoxidation is required before casting. The final composition adjustment was performed using a FeSi alloy as a deoxidizer instead of Al.
To simultaneously obtain the average CaO/(SiO) content of oxide inclusions2+ MnO + CaO) mass ratio of 0.40 or less, and sufficiently reducing the average CaO/MnO mass ratio, it was found that refining to satisfy, for example, the following 3 points was very effective in deoxidation and final component adjustment.
(1) Refining is performed so that the oxygen content in the steel (including the total oxygen content of oxygen present as an oxide) is 0.0030% (30ppm) or more. When the oxygen content is less than 0.0030%, it becomes difficult to perform refining such that the average CaO/MnO mass ratio is stabilized to 15.0 or less. When the average CaO/MnO mass ratio is reduced to 10.0 or less or 6.0 or less, the oxygen content is more preferably adjusted to 0.0040% (40ppm) or more. However, when the oxygen content is too high, a large amount of inclusions containing a large amount of Cr oxides are produced, which causes deterioration of product quality. The oxygen content is limited to 0.0150% (150ppm) or less, and more preferably 0.0100% (100ppm) or less. Can be controlled to 0.0060% (60ppm) or less.
(2) Si deoxidation is performed using a high-purity FeSi alloy having a Ca content of, for example, 0.20% or less.
(3) The alkalinity of the slag is CaO/SiO2The range of 1.20 to 1.60.
Examples
Stainless steel shown in table 1 was melted by a VOD process to obtain a continuously cast slab. In the final refining process, the total oxygen content in the steel, the kind of FeSi alloy as a deoxidizer, and the slag basicity (CaO/SiO) are changed2) Under the conditions of (1), attempts have been made to control inclusions. The respective conditions are shown in table 2. The oxygen content in table 2 again reveals the values of table 1. The FeSi alloy as the deoxidizer is a high purity product or a normal product with a small impurity content. The high-purity product has a Ca content of 0.20 mass% or less. The Ca content of the usual product is about 0.5 to 1.5 mass%. Slag alkalinity on samples taken from the slagAnd (4) analyzing and obtaining.
Using the obtained continuously cast slab, a cold-rolled annealed steel sheet having a thickness of 0.5 to 1.5mm is obtained by a process including hot rolling and cold rolling. The cold-rolled annealed steel sheet was observed in a cross section (L cross section) parallel to the rolling direction and the sheet thickness direction by SEM (scanning electron microscope), and the composition of oxide inclusions was analyzed by EDX (energy dispersive X-ray analysis) with SEM. Based on the measurement values of 30 randomly selected oxide inclusions, the "average CaO/(SiO)" was determined as described above2The method for determining the mass ratio of + MnO + CaO) and the average CaO/MnO Mass ratio to determine the average CaO/(SiO)2+ MnO + CaO) and an average CaO/MnO mass ratio. The results are shown in table 2.
Each cold-rolled annealed steel sheet was used as a raw material, and a welded steel pipe was produced under normal conditions by TIG welding. The outer diameter of the tube is in the range of 25-51 mm. No solder is added during soldering. Samples were randomly taken from the obtained steel pipe products, and the occurrence of slag spots was examined for a continuous bead having a length of 50m or more. The number of slag points having a major diameter (diameter of the longest part of the particles) of 1.0mm or more was counted, and the number of slag points generated per 1m was defined as a slag point generation rate (number/m). If the slag point generation rate is 0.30 pieces/m or less, it is estimated that the generation of slag points is suppressed more greatly than in the conventional case. Therefore, the slag point generation rate of 0.30 pieces/m or less was judged as passed. These results are shown in table 2.
TABLE 1
TABLE 2
The steel composition satisfies the specified range of the present invention and the average CaO/(SiO) of the oxide inclusions2+ MnO + CaO) and the average CaO/MnO mass ratio are controlled to be within the ranges specified in the present invention, the generation of slag spots is very small.
In contrast, in comparative examples Nos. 21 to 23, the slag basicity was high during refining, so that the average Cao/MnO mass ratio of oxide-based inclusions was high, and the generation of slag spots was large. In Nos. 24 to 26, the total oxygen content in the steel was too low, and the slag basicity during the melting was high, so that the average Cao/MnO mass ratio of the oxide-based inclusions was significantly higher than that of the other examples, and the slag point suppression effect was not obtained. In Nos. 27 to 30, since FeSi alloys using "usual products" as the deoxidizer were used, the desired inclusion control could not be performed, the average CaO/MnO mass ratio of oxide-based inclusions became high, and the generation of slag spots was large.
In FIG. 3, the average CaO/(SiO) of the oxide inclusions is shown for each example2+ MnO + CaO) mass ratio and slag point generation rate. The black dots are an example of the FeSi alloy using the "high-purity product" as the deoxidizer, and the white dots are an example of the "normal product" (the same applies to fig. 4 to 9 below). In addition, fig. 4 and 5 show the relationship between the average CaO/MnO mass ratio of the oxide-based inclusions and the slag point generation rate for each example. FIG. 5 is an enlarged view showing a region where the average CaO/MnO mass ratio of FIG. 4 is low. Therefore, the following steps are carried out: by making the average CaO/(SiO) of oxide inclusions2+ MnO + CaO) of 0.40 or less and an average CaO/MnO mass ratio of 15.0 or less, the slag point generation suppressing effect was remarkably improved.
FIGS. 6 and 7 show the relationship between the total oxygen content in the steel materials and the average CaO/MnO mass ratio of oxide inclusions in the examples. FIG. 7 is an enlarged view of the region of FIG. 6 where the average CaO/MnO mass ratio is low. Therefore, the following steps are carried out: it is extremely effective to control the average CaO/MnO mass ratio of the oxide inclusions to be low by setting the oxygen content to 0.0030% or more.
Fig. 8 shows the relationship between the total oxygen content in the steel material and the slag point generation rate for each example. Therefore, the following steps are carried out: it is effective to suppress the generation of slag points by using a FeSi alloy as a deoxidizer "high purity product" so that the oxygen content is 0.0030% or more.
Fig. 9 shows the relationship between the slag basicity and the slag point generation rate during refining. Therefore, the following steps are carried out: the use of a FeSi alloy as a deoxidizer in "high purity products" is effective in suppressing the generation of slag spots by adjusting the basicity of the slag to a range of 1.20 to 1.60.
Claims (7)
1. A stainless steel material having a composition comprising, in mass%, C: 0.005-0.100%, Si: 0.10 to 3.00%, Mn: 0.10-6.50%, P: 0.001-0.050%, S: 0.0001-0.0200%, Ni: 0-20.00%, Cr: 10.50 to 26.00%, Mo: 0-2.50%, Cu: 0 to 3.50%, Nb: 0-0.500%, V: 0-0.500%, Zr: 0-0.500%, W: 0-0.500%, Co: 0-0.500%, B: 0-0.020%, N: 0.005-0.200%, Ti: 0-0.050%, Al: 0-0.100%, Ca: 0-0.0010%, Mg: 0 to 0.0010%, rare earth elements REM other than Y: 0-0.050%, Y: 0-0.050%, O: 0.0030 to 0.0150%, and the balance Fe and inevitable impurities, wherein oxide inclusions containing Mn are present, and the contents of Si, Mn and Ca in the oxide inclusions are respectively converted into SiO2Average CaO/(SiO) of oxide inclusions observed in the metallographic structure in the inclusion composition at the mass ratio of MnO to CaO2+ MnO + CaO) is 0.40 or less and the average CaO/MnO mass ratio is 15.0 or less.
2. A base material for arc welding comprising the stainless steel material according to claim 1.
3. A steel plate base material for arc welding pipe, comprising the stainless steel material according to claim 1.
4. An arc welding structural member using the steel material according to claim 1 as a base material.
5. An arc-welded steel pipe using the steel product according to claim 1 as a base material.
6. A method for producing a welded structural member, wherein the stainless steel material according to claim 1 is used as a base material, and non-consumable electrode type arc welding is performed without adding a solder.
7. A method for producing a welded steel pipe, wherein the stainless steel sheet according to claim 1 is used as a base material, and the welded steel pipe is formed by non-consumable electrode arc welding without adding a solder.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017206555A JP7042057B2 (en) | 2017-10-25 | 2017-10-25 | Stainless steel materials and welded structural members with excellent slag spot generation suppression ability and their manufacturing methods |
| JP2017-206555 | 2017-10-25 | ||
| PCT/JP2018/018480 WO2019082427A1 (en) | 2017-10-25 | 2018-05-14 | Stainless steel material having excellent slag spot occurrence prevention performance, welded structural member and method for producing same |
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| CN112218965A true CN112218965A (en) | 2021-01-12 |
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| CN201880068466.1A Pending CN112218965A (en) | 2017-10-25 | 2018-05-14 | Stainless steel material having excellent slag point generation inhibiting ability, welded structural member, and method for producing same |
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| JP (1) | JP7042057B2 (en) |
| KR (1) | KR102391566B1 (en) |
| CN (1) | CN112218965A (en) |
| TW (1) | TWI694160B (en) |
| WO (1) | WO2019082427A1 (en) |
Cited By (2)
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| CN112941403A (en) * | 2021-01-14 | 2021-06-11 | 上海欣冈贸易有限公司 | Sulfur-free low-carbon steel metal alloy for welding and composition thereof |
| CN115466909A (en) * | 2022-10-26 | 2022-12-13 | 浦项(张家港)不锈钢股份有限公司 | Austenitic stainless steel, preparation process and application |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20220115104A (en) * | 2020-01-15 | 2022-08-17 | 닛테츠 스테인레스 가부시키가이샤 | Ferritic stainless steel |
| JP7243950B1 (en) * | 2021-10-01 | 2023-03-22 | 日本製鉄株式会社 | duplex stainless steel pipe |
| WO2023054599A1 (en) * | 2021-10-01 | 2023-04-06 | 日本製鉄株式会社 | Duplex stainless steel pipe |
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Also Published As
| Publication number | Publication date |
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| JP2019077925A (en) | 2019-05-23 |
| KR102391566B1 (en) | 2022-04-29 |
| KR20200067886A (en) | 2020-06-12 |
| TWI694160B (en) | 2020-05-21 |
| JP7042057B2 (en) | 2022-03-25 |
| WO2019082427A1 (en) | 2019-05-02 |
| TW201923108A (en) | 2019-06-16 |
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