JP3574427B2 - Continuous casting powder and continuous casting method for Ti and Al-containing steel - Google Patents

Description

【００３４】
なお、溶鋼成分、パウダー成分およびパウダーの物性値は、以下の方法で評価した。
・溶鋼成分：蛍光Ｘ線分析装置により定量分析した。表１に示した成分の残部は、Ｆｅを主に含み、その他に、微量のＳｉ，Ｍｎ，Ｐ等を含んでいる。
・パウダー成分：Ｃは燃焼法により、その他の成分は化学分析により定量分析した。表１中に示す各成分の合計が、９６．２〜９９．９ｗｔ％となっているのは、これらの成分以外にも、ＭｇＯ，Ｆｅ_２Ｏ_３等の不可避的不純物を含むためである。
・粘度：回転円筒法により測定した。すなわち、鉄ルツボ中にパウダーを入れ、縦型抵抗炉内で溶解し、その後、鉄製のローターを挿入、回転することで、粘度を測定した。
・凝固温度：上記、粘度測定の際、温度を降下していくと急激に粘度の値が立ち上がる点が求まる。この変曲点を凝固温度とした。
【００３５】
表２には、表１に示した溶鋼を連続鋳造した際の、パウダーの組成変化と凝固した時の結晶相、連続鋳造における異常有無および得られたスラブの表面品質と研削後のスラブ歩留りの結果をまとめて示した。
ここで、それぞれの評価は以下の方法で行った。
・パウダーの組成変化：鋳型内からサンプルを採取し、化学分析により定量分析した。
・結晶相：鋳込み後のパウダーフイルムを採取し、Ｘ線回折することで結晶相を特定した。
・表面欠陥：鋳込み後のスラブを観察し特定した。
・スラブ研削歩留：研削前後での重量変化より測定した。
【００３６】
【表２】

【００３７】
表２から判るように、本発明例の１〜８では、いずれもパウダーの組成変化が少なく、トラブルなく鋳造を行うことができた。また、得られたスラブも表面欠陥を発生することなく、スラブ研削での歩留りも９０％以上と良好な結果であった。
それに対して、比較例の９〜１７は、スラグ成分、物性値および鋳造条件のいずれかが本発明の制限範囲を外れているため、鋳造においてブレークアウト、ノズル詰まり等のトラブルが発生し、あるいは、完鋳しても縦割れ等の表面欠陥を引き起こす結果となった。表面欠陥が発生すると、スラブ研削歩留りが９０％未満となってしまい、製造コストの上昇を招く。
【００３８】
以下にそれぞれの失敗原因を説明する。
・Ｎｏ．１０は、パウダー中のＣａＯ，ＳｉＯ_２，Ｎａ_２Ｏ濃度の範囲が外れているため、塩基度が低く、粘度も高い。その結果、ＴｉＯ_２およびＡｌ_２Ｏ_３のピックアップ量の合計が３０％を超えたため、ブレークアウトしてしまった。
・Ｎｏ．１１では、パウダーは適正なものを用いたが、引抜速度が速すぎたため、ブレークアウトした。
・Ｎｏ．１２では、パウダーは適正なものを用いたが、溶鋼過熱度が２℃と低かったことと、引抜速度が５５０ｍｍ／分と遅かったため、浸漬ノズルが詰まり鋳造停止となってしまった。
・Ｎｏ．１３では、パウダーは適正なものを用いたが、溶鋼過熱度が８０℃と高すぎたため、パウダー中のＴｉＯ_２およびＡｌ_２Ｏ_３のピックアップ量の合計が３０ｗｔ％を超えたため、表面欠陥が発生した。
・Ｎｏ．１４では、パウダー成分が適正ではなく、塩基度が２．２２と高く、粘度、凝固温度とも高いものを使用したため、表面欠陥が発生した。
・Ｎｏ．１５では、パウダー成分が適正ではなく、塩基度が０．４５と低く、凝固温度も低いものを使用した。その結果、凝固シェル／鋳型間に流入したパウダーフイルムがガラス質となり、表面欠陥が発生した。
・Ｎｏ．１６では、骨材Ｃが低すぎたため、流入量が過剰となり、表面欠陥が発生した。
・Ｎｏ．１７では、骨材Ｃが高すぎたため、流入量が少なすぎ、ブレークアウトしてしまった。
【００３９】
【発明の効果】
以上説明したように、本発明によれば、ＴｉおよびＡｌ含有鋼の鋳造に当たり、ブレークアウト等の事故がなくなり、安定した連続鋳造が可能となる。さらに、本発明に係るパウダーを用いて鋳造したスラブは、表面性状に優れているため、研削歩留りが良好となり、生産性の向上、さらには、製造コストの低減が実現できる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a powder for continuous casting used for continuously casting steel containing Ti and Al, particularly stainless steel, heat-resistant steel, super-corrosion-resistant steel, and the like, and to continuously cast a slab having no surface defects using the powder. A suggestion on how to do it.
[0002]
[Prior art]
As the powder for continuous casting of steel, one composed of an oxide such as CaO, SiO ₂ , Na ₂ O, Al ₂ O ₃ , and F is generally used. However, in the case of such a powder, when steel containing active elements such as Ti and Al is continuously cast, these elements react with SiO ₂ contained in the powder (hereinafter simply referred to as “powder”). Then, oxides such as TiO ₂ and Al ₂ O ₃ are generated, and these are picked up in the powder (slag). For this reason, there is a problem that the composition of the powder changes greatly, and the physical properties such as the viscosity and the solidification temperature also change, deviating from the physical property range suitable for casting. As a result, slab surface defects such as depletion, vertical cracking, and bleeding are caused, and in the worst case, a breakout is caused to stop the casting.
[0003]
In order to cope with such a problem, for example, in Japanese Patent Application Laid-Open No. Hei 4-100660, a powder having a basicity of CaO / SiO ₂ of 0.4 or less and a solidification temperature of 790 to 835 ° C. is cast, and the powder changes in composition. A technique has been proposed in which the physical property value is kept within an appropriate range even if the above occurs. However, since this technique induces a lower basicity and a lower solidification temperature, the crystallinity of the powder is lost and vitrification occurs, and the flow of molten powder between the solidified shell and the copper mold is greatly increased. However, there is a problem that uneven cooling is caused.
[0004]
Japanese Patent Application Laid-Open No. 7-32091 discloses a powder having a basicity CaO / SiO of 0.4 to 0.7 for a steel type having a Ti concentration of 0.1 to 0.5 wt%. The gazette discloses a technique of casting using powders each having a basicity of CaO / SiO of 0.2 to 0.6. However, these techniques also have a problem in that since the basicity is low, the crystallinity of the powder is lost and vitrification occurs, the amount of powder flowing in is greatly increased, and uneven cooling is caused.
[0005]
Contrary to the above technique, Japanese Patent Application Laid-Open No. Hei 7-116797 proposes a technique of casting using a powder whose basicity CaO / SiO is adjusted to a high value of 1.8 to 2.5. When the basicity of the powder is increased as described above, the reaction between Ti or Al as a molten steel component and SiO ₂ in the powder is suppressed, and a change in the physical properties of the powder can be prevented. However, since this powder has a remarkably high basicity, the coagulation temperature becomes high, and an appropriate inflow of the powder cannot be ensured, which may cause problems such as sticking. In addition, this powder requires addition of an expensive flux such as Li ₂ O or Na ₂ O in order to optimize the coagulation temperature and viscosity, so that there is a problem that the cost is high.
[0006]
Note that Ti-containing steel has a problem that the yield during refining is poor because Ti is a highly active element. Therefore, deoxidation of the Ti-containing steel is performed with Al, and the concentration of Al is as low as about 0.02 wt% and as high as about 0.8 wt%. As a result, Al ₂ O ₃ is picked up in the powder, which has a great influence on the physical properties of the powder. However, each of the above prior arts does not take this point into consideration.
[0007]
[Problems to be solved by the invention]
As described above, conventionally, when continuously casting steel containing active Ti or Al, in the conventional powder, SiO ₂ is reduced during casting, and TiO ₂ or Al ₂ O ₃ is picked up. As a result, As described above, there has been a problem that surface defects such as depletion, vertical cracks, bleeding, etc. are caused, and in some cases, casting is stopped due to breakout.
[0008]
An object of the present invention is to provide a powder for continuous casting suitable for casting of a steel containing Ti and Al, and to propose a method for continuously casting a slab having no surface defects.
[0009]
[Means for Solving the Problems]
In contact with the above-mentioned problem of the prior art, the present inventors first contain at least 0.08 to 3.0 wt% of Ti and 0.02 to 0.8 wt% of Al, and additionally contain Fe and various additives. A study was made on what physical properties of the powder for continuous casting are suitable for continuous casting of steel composed of components and unavoidable elements. For the study, the inventors conducted a solidification test of molten steel such as thermal analysis. As a result, a powder having a viscosity of 1 to 4 poise at 1300 ° C. and a solidification temperature of 900 to 1300 ° C., and further having a property of crystallizing a crystal phase such as caspidyne, nepheline, or perovskite at the time of solidification is used in the present invention. It became clear that the Ti and Al-containing steel to be treated can be cast without any surface defects.
[0010]
Next, the viscosity and the solidification temperature were measured for powders having various component compositions in order to find out what chemical components and compositions should be used for the powders satisfying the above physical properties. As a _{result, CaO: 25~40wt%, SiO 2} : 25~40wt%, Na 2 O: 10~20wt%, Al 2 O 3: 10wt% or less, F: powder component composition containing 5 to 10 wt% is It was found that the above physical properties and properties were satisfied.
[0011]
Subsequently, in a high-frequency induction furnace, a reaction experiment was performed between powder for continuous casting having various component compositions and molten steel containing 0.08 to 3.0% of Ti and 0.02 to 0.8% of Al. . As a result, when the degree of superheat of the molten steel is set to 50 ° C. or less and the basicity of the powder satisfies 0.7 <CaO / SiO ₂ <1.8, TiO ₂ and Al ₂ O in the powder are It was found that the pickup of No. ₃ could be suppressed to a range not exceeding the casting suitability range (30% or less in total).
[0012]
The powder developed based on such knowledge was finally used in an actual machine, and test casting was performed under various casting conditions. As a result, using a powder for continuous casting containing 1 to 3.5 wt% of C as an aggregate in addition to the above component composition, controlling the superheat of molten steel to 5 to 50 ° C and controlling the drawing speed to 600 to 900 mm / min. By performing continuous casting, it became clear that both the melting speed of the powder and the inflow amount of the molten powder were within appropriate ranges.
[0013]
The present invention positively, which has been developed based on the above findings and test results, the has as summary and construction, also a small Ti: 0.08~3.0wt%, Al: containing 0.02～0.8Wt% a powder for use in continuous casting of steel which, this _{powder, CaO: 25~40wt%, SiO 2} : 25~40wt%, Na 2 O: 10~20wt%, Al 2 O 3: 10wt% or less, F : Has a composition of 5 to 10% by weight and 1 to 3.5 % by weight of C as an aggregate, has a basicity of 0.7 <CaO / SiO ₂ <1.8, a viscosity of 1 to 4 poise at 1300 ° C., and solidifies When the temperature is 900 to 1300 ° C. and flows between the mold and the solidified shell, on the side in contact with the mold, at a thickness of 15 to 75% of the total thickness of the powder, any one of caspidyne, nepheline, perovskite or It is to have the property of crystallizing a crystalline phase composed of two or more.
[0015]
In addition, the present invention provides C ≦ 1.0 wt%, Si ≦ 2.0 wt%, Mn ≦ 2.0 wt%, Ni ≦ 85 wt%, Cr ≦ 30 wt%, Ti: 0.08-3.0 wt%, Al: The above-mentioned powder for continuous casting is prepared by subjecting molten steel consisting of 0.02 to 0.8 wt%, the balance being Fe and unavoidable impurities, to a drawing speed of 600 to 900 mm / min and a superheat of molten steel of 5 to 50 ° C. This is a method of continuous casting using
[0016]
In the present invention, the molten steel may further include one or more selected from Mo: 0.5 to 5 wt%, Cu: 0.5 to 5 wt%, V: 0.5% or less, and B: 100 ppm or less. It is preferable to include two or more types.
[0017]
In the present invention, the casting is preferably performed so that the total amount of TiO ₂ and Al ₂ O ₃ in the powder during continuous casting is 30 wt% or less.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
As described above, the powder for continuous casting according to the present invention has been developed through experiments, and is basically composed of a CaO—SiO ₂ —Na ₂ O—Al ₂ O ₃ —F system, It has characteristics of a viscosity of 1 to 4 poise at 1300 ° C. and a solidification temperature of 900 to 1300 ° C., and is characterized by crystallization during solidification. Hereinafter, the reason for limiting the physical properties and properties of the powder of the present invention as described above will be described.
[0019]
Viscosity at 1300 ° C: 1-4 poise
If the powder viscosity is too low, such as less than 1 poise, or more than 4 poise, surface defects such as depletion, vertical cracking, and bleeding occur, and the amount of slab grinding increases and the yield decreases. In the worst case, it causes a breakout. From this, the viscosity at 1300 ° C. is set to 1 to 4 poise. Preferably it is 1.2 to 3.7 poise, more preferably 1.5 to 2.5 poise.
[0020]
Solidification temperature: 900-1300 ° C
If the solidification temperature is too low (less than 900 ° C.) or too high (more than 1300 ° C.), surface defects such as depletion, vertical cracks, and bleeding occur, and the slab grinding amount increases and the yield decreases. In the worst case, it causes a breakout. For this reason, the solidification temperature is set to 900 to 1300 ° C. Preferably it is 950-1280 degreeC, More preferably, it is 980-1250 degreeC.
[0021]
Crystallization Behavior Oxides or oxyfluorides generally crystallize or vitrify during solidification. The molten powder flows between the solidified shell and the copper mold during casting and at least partially solidifies. At this time, if the powder of the solidified layer is crystallized without vitrification, the powder film is formed uniformly, and uniform cooling of the slab is realized. Therefore, as a characteristic of the powder, it is necessary that at least the side in contact with the mold at the time of solidification be crystallized with a predetermined thickness. The composition of the crystal phase generated when the powder is solidified, Kasupidain _{(3CaO · 2SiO 2 · CaF 2} ), nepheline _{(Na 2 O · Al 2 O} 3 · 2SiO 2), perovskite (CaO · _TiO 2) It is desirable that any one or more of the above be used. The perovskite is generated when TiO ₂ is picked up in the powder.
[0022]
The thickness (proportion) of the crystal phase formed on the side in contact with the mold in the solidified phase is a thickness occupying 15 to 75 % of the total thickness of the solidified layer. However, the reason for such a solidified layer, when the proportion of the crystalline phase is less than 1 5%, most to show the behavior of the glass, causing uneven cooling for the reasons described above. Conversely, if it exceeds 75 %, the thickness of the molten powder layer becomes thin, and the lubrication of the solidified shell deteriorates. In each of these cases, the risk of introducing surface defects is extremely high. Therefore, the properties of the powder according to the present invention are such that the ratio of the crystal phase of the powder flowing between the mold and the solidified shell accounts for 15 to 75 % of the total thickness of the solidified layer. This _{property, CaO, SiO 2, Al 3} O 2, Na 2 O, can be controlled by optimizing the F content. Name your, total of powder that has flowed between the mold / solidified shell thickness optic lobe, and 0 .5~3mm.
[0023]
Next, the reason why the composition of the powder according to the present invention is limited as described above will be described. _{CaO: 25~40wt%, SiO 2:} 25~40wt%, Na 2 O: 10~20wt%, Al 2 O 3: 10wt% or less, F: 5~10wt%;
All of these components are necessary to achieve the above-mentioned physical properties and crystallization behavior. Of these, even if Al ₂ O ₃ is not contained, the physical property value and the crystallization behavior can be kept in appropriate ranges, so that the content is set to 10 wt% or less. Other CaO, SiO ₂ , Na ₂ O, and F were each controlled within the above ranges in order to make the solidification temperature, viscosity, and crystallization behavior appropriate.
[0024]
Basicity: 0.7 <CaO / SiO ₂ <1.8
When the basicity is 0.7 or less, the activity of SiO _{2 in} the powder increases, so that the following reaction occurs, and TiO ₂ and Al ₂ O ₃ are picked up in the powder. If the pickup amount of one or both of TiO ₂ and Al ₂ O ₃ exceeds 10%, the physical property values deviate from the casting suitability range. As a result, surface defects such as depletion, vertical cracks, and bleeding are generated, and the amount of grinding of the slab increases, and the yield decreases. In the worst case, it causes a breakout.
(SiO ₂ ) + Ti = (TiO ₂ ) + Si (1)
3 (SiO ₂ ) +4 Al = 2 (Al ₂ O ₃ ) +3 Si (2)
Here, () indicates a component in the powder, and an underlined portion indicates a component in the molten steel.
When the basicity of the powder is low, the powder tends to be vitrified, and the viscosity tends to be high, so that it is difficult to adjust the physical properties. When the basicity is 1.8 or more, the above physical property values cannot be obtained. Therefore, the range of the basicity was set to be more than 0.7 and less than 1.8. Preferably it is 0.75 or more and 1.5 or less, more preferably 0.8 or more and 1.3 or less.
[0025]
C as an aggregate: 1 to 5 wt%
C is added in order to control the melting rate of the powder, and if it is less than 1 wt%, the melting is too fast, causing excessive inflow, generating surface defects such as depletion, longitudinal cracking, bleeding, and the like, and increasing the slab yield. Decreases. In the worst case, it causes a breakout. Conversely, if C is higher than 5 wt%, the melting rate becomes too slow to keep up with the inflow, causing surface defects such as depletion, vertical cracking, and bleeding, and lowering the slab yield. In the worst case, it causes a breakout.
[0026]
Further, the present invention proposes a continuous casting method of Ti, Al-containing steel using the above powder.
The target steel types in which the powder according to the present invention is effectively used include C ≦ 1.0 wt%, Si ≦ 2.0 wt%, Mn ≦ 2.0 wt%, Ni ≦ 85 wt%, Cr ≦ 30 wt%, and Ti: 0. 0.08-3.0 wt%, Al: 0.02-0.8 wt%, the balance being molten steel composed of Fe and unavoidable impurities. When casting the molten steel, the drawing speed is limited to 600 to 900 mm / min, and the degree of superheat of the molten steel is limited to 5 to 50 ° C. That is, by performing continuous casting under the above conditions using the powder of the present invention, it is possible to suppress the total pickup amount of TiO ₂ and Al ₂ O _{3 in} the powder to 30 wt% or less, As a result, there is no surface defect, and it is possible to secure a yield in slab grinding of 90% or more. Hereinafter, the reasons for each limitation will be described.
[0027]
The target steel types are, for example, C: 0.0005 to 0.1 wt%, Si: 0.01 to 2.0 wt%, Mn: 0.01 to 2.0 wt%, Ni: 5 to 85 wt%, Cr: 13 to 30 wt%. %, 0.08 to 3.0 wt% of Ti, 0.02 to 0.8 wt% of Al, and if necessary, 0.5 to 5 wt% of Mo, 0.5 to 5 wt% of Cu, and V: It is preferable to use stainless steel, heat-resistant steel, and super-corrosion-resistant steel containing one or more selected from 0.5 wt% or less and B: 100 ppm or less.
[0028]
In the above component composition, C is useful for maintaining the strength of the material, and Si and Mn are elements useful for deoxidation. Ni is useful for keeping the structure austenite, and Cr is an element useful for corrosion resistance and heat resistance. Ti and Al are elements useful for heat resistance, high temperature oxidation resistance, or deoxidation. In addition, Mo, Cu, and V are useful for controlling corrosion resistance and crystal grain size, and can be added as needed. B is a component that may be added for improving hot workability.
[0029]
Drawing speed: 600 to 900 mm / min When the drawing speed is less than 600 mm / min, the residence time of the slab in the mold becomes longer, the cooling becomes more powerful, the renewal of the molten powder becomes slower, and depletion, longitudinal cracking, Surface defects such as bleeding occur, and the amount of grinding of the slab increases, and the yield decreases. Conversely, if the drawing speed exceeds 900 mm / min, the growth of the shell in the mold cannot catch up, causing a breakout. Therefore, the drawing speed is limited to 600 to 900 mm / min. Preferably, it is 650-880 mm / min, more preferably 700-850 mm / min.
[0030]
Superheat degree of molten steel: 5 to 50 ° C
If the degree of superheat of the molten steel is lower than 5 ° C., the molten steel solidifies in the immersion nozzle, causing nozzle blockage, and stopping casting. Conversely, when the degree of superheat is higher than 50 ° C., the reactions of the above equations (1) and (2) become active, and the pickup of TiO ₂ and Al ₂ O ₃ becomes severe. If the total amount of both TiO ₂ and Al ₂ O ₃ pickup exceeds 30 wt%, the physical properties deviate from the suitable range for casting. As a result, surface defects such as depletion, vertical cracks, and bleeding are generated, the slab grinding amount increases, and the yield decreases. In the worst case, it causes a breakout. Therefore, the degree of superheat of molten steel is limited to 5 to 50 ° C. Preferably it is 10-45 degreeC, More preferably, it is 15-40 degreeC.
[0031]
Total pick-up amount of TiO ₂ and Al ₂ O ₃ in powder: 30 wt% or less As described above, when the total pick-up amount of oxides of TiO ₂ and Al ₂ O ₃ exceeds 30 wt%, the physical property value is cast. It deviates from the appropriate range. As a result, surface defects such as depletion, vertical cracks, and bleeding occur, and the slab yield decreases. In the worst case, it causes a breakout. For this reason, the total pickup amount of TiO ₂ and Al ₂ O _{3 in} the powder is limited to 30 wt% or less. It is preferably at most 28 wt%, more preferably at most 25 wt%.
At the time of this continuous casting, an exothermic powder may be added at the very beginning of the casting to help melting.
[0032]
【Example】
A slab was obtained by smelting molten steel having the component composition shown in Table 1 and continuously casting it using the powder shown in Table 1.
In the smelting, raw materials such as iron scrap, pure nickel, ferrochrome, and stainless scrap were melted in an electric furnace and refined using one or both of AOD and VOD to obtain predetermined components. Melting the steel species, [NCF800H, NCF825, Inkoro Lee 840], SUH660, including SUS321 and Ti and Al 18Cr - a 8Ni stainless steel. Table 1 also shows the composition of the powder used in the continuous casting, the physical properties thereof, and the conditions for the continuous casting.
[0033]
[Table 1]

[0034]
The physical properties of the molten steel component, the powder component, and the powder were evaluated by the following methods.
-Molten steel component: Quantitatively analyzed by a fluorescent X-ray analyzer. The balance of the components shown in Table 1 mainly includes Fe, and also includes trace amounts of Si, Mn, P, and the like.
-Powder component: C was quantitatively analyzed by a combustion method, and other components were quantitatively analyzed by a chemical analysis. The sum of the components shown in Table 1, has become a 96.2～99.9Wt%, in addition to these components, in order to contain MgO, unavoidable impurities such as _Fe 2 _{O 3.}
Viscosity: measured by a rotating cylinder method. That is, the powder was put in an iron crucible, melted in a vertical resistance furnace, and then the viscosity was measured by inserting and rotating an iron rotor.
Solidification temperature: In the above viscosity measurement, a point at which the value of the viscosity rises sharply as the temperature is lowered is determined. This inflection point was taken as the solidification temperature.
[0035]
Table 2 shows the change in powder composition and the crystal phase when solidified during continuous casting of the molten steel shown in Table 1, the presence or absence of abnormalities in continuous casting, the surface quality of the obtained slab, and the slab yield after grinding. The results are shown together.
Here, each evaluation was performed by the following methods.
-Powder composition change: A sample was collected from the inside of the mold and quantitatively analyzed by chemical analysis.
Crystal phase: The powder phase after casting was sampled, and the crystal phase was identified by X-ray diffraction.
-Surface defect: The slab after casting was observed and specified.
Slab grinding yield: Measured from the weight change before and after grinding.
[0036]
[Table 2]

[0037]
As can be seen from Table 2, in each of Examples 1 to 8 of the present invention, there was little change in the composition of the powder, and casting could be performed without any trouble. Further, the obtained slab did not cause any surface defects, and the yield in slab grinding was a good result of 90% or more.
On the other hand, in any of Comparative Examples 9 to 17, any one of the slag component, the physical property value, and the casting condition is out of the range of limitation of the present invention, so that a trouble such as breakout or nozzle clogging occurs in casting, or However, even when casting was completed, surface defects such as vertical cracks were caused. When a surface defect occurs, the slab grinding yield becomes less than 90%, which leads to an increase in manufacturing cost.
[0038]
The causes of each failure will be described below.
・ No. Sample No. 10 has a low basicity and a high viscosity because the concentration of CaO, SiO ₂ , and Na ₂ O in the powder is out of the range. As a result, the total pickup amount of TiO ₂ and Al ₂ O ₃ exceeded 30%, resulting in a breakout.
・ No. In 11, the powder used was appropriate, but the drawing-out speed was too fast, so a breakout occurred.
・ No. In No. 12, an appropriate powder was used. However, since the degree of superheat of molten steel was as low as 2 ° C. and the drawing speed was as low as 550 mm / min, the immersion nozzle was clogged and the casting was stopped.
・ No. In No. 13, the powder used was appropriate, but the superheat degree of the molten steel was too high at 80 ° C., and the total amount of TiO ₂ and Al ₂ O ₃ pickup in the powder exceeded 30 wt%, and surface defects occurred. did.
・ No. In No. 14, since the powder component was not appropriate, the basicity was as high as 2.22, and the viscosity and the coagulation temperature were both high, surface defects occurred.
・ No. In No. 15, the powder component was not appropriate, the basicity was as low as 0.45, and the coagulation temperature was low. As a result, the powder film flowing between the solidified shell and the mold became vitreous, and surface defects occurred.
・ No. In No. 16, since the aggregate C was too low, the inflow amount became excessive, and surface defects occurred.
・ No. In No. 17, since the aggregate C was too high, the inflow amount was too small and a breakout occurred.
[0039]
【The invention's effect】
As described above, according to the present invention, when casting a steel containing Ti and Al, accidents such as breakouts can be eliminated, and stable continuous casting can be performed. Furthermore, since the slab cast using the powder according to the present invention has excellent surface properties, the grinding yield is good, and the productivity can be improved and the manufacturing cost can be reduced.

Claims (4)

Least be Ti: 0.08~3.0wt%, Al: a powder for use in continuous casting of steel containing 0.02~0.8wt%, this powder, CaO: 25~40wt%, SiO 2 : 25~40wt% , Na ₂ O: 10 to 20 wt%, Al ₂ O ₃ : 10 wt% or less, F: 5 to 10 wt%, C: 1 to 3.5 wt%, and a basicity of 0.7 <CaO / SiO ₂ <1.8, a viscosity at 1300 ° C. of 1 to 4 poise, a solidification temperature of 900 to 1300 ° C., and a powder total thickness (0. 15-75% of the 5 to 3 mm) is Kasupidain, nepheline, continuous for Ti and Al-containing steel, characterized in that it is of even that produce crystals of either one or crystalline phase comprising two or more of perovskite Casting powder. C ≦ 1.0wt%, Si ≦ 2.0wt%, Mn ≦ 2.0wt%, Ni ≦ 85wt%, Cr ≦ 30wt%, Ti: 0.08-3.0wt%, Al: 0.02-0.8wt%, balance Fe and inevitable A continuous casting of molten steel comprising impurities using the continuous casting powder according to claim 1 under the conditions of a drawing speed: 600 to 900 mm / min and a degree of superheating of the molten steel: 5 to 50 ° C. And continuous casting method for Al-containing steel. The molten steel further comprises one or more selected from the group consisting of Mo: 0.5 to 5 wt%, Cu: 0.5 to 5 wt%, V: 0.5 wt% or less, and B: 100 ppm or less. Item 4. A continuous casting method for a Ti and Al-containing steel according to Item 2 . _3. The continuous casting method for Ti and Al-containing steel according to claim 2 , wherein the total amount of the powdered TiO ₂ and Al ₂ O ₃ pickup during the continuous casting is 30 wt% or less.