JP3742619B2 - Low carbon steel slab manufacturing method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、加工性、成形性に優れた低炭素薄鋼板の溶製方法に関するものである。
【０００２】
【従来の技術】
転炉や真空処理容器で精錬された溶鋼中には、多量の溶存酸素が含まれており、この過剰酸素は酸素との親和力が強い強脱酸元素であるＡｌにより脱酸されるのが一般的である。しかし、Ａｌは脱酸によりアルミナ系介在物を生成し、これが凝集・合体して粗大なアルミナクラスターとなる。このアルミナクラスターは鋼板製造時に表面疵発生の原因となり、薄鋼板の品質を大きく劣化させる。また、溶鋼中のアルミナ系介在物は、タンディッシュノズル等の連続鋳造用ノズルに付着し易く、ノズルが閉塞した場合には、円滑な鋳造作業を困難にする。特に、炭素濃度が低く、精錬後の溶存酸素濃度が高い薄鋼板用素材である低炭素溶鋼では、アルミナクラスターの量が非常に多く、表面疵やノズル閉塞が極めて発生し易く、アルミナ系介在物の低減対策は大きな課題となっている。
【０００３】
これに対して、従来は特許文献１の介在物吸着用フラックスを溶鋼表面に添加してアルミナ系介在物を除去する方法、或いは特許文献２の注入流を利用してＣａＯフラックスを溶鋼中に添加し、これによりアルミナ系介在物を吸着除去する方法が提案、実施されてきた。一方、アルミナ系介在物を除去するのではなく、生成させない方法として、特許文献３にあるように溶鋼をＭｇで脱酸し、Ａｌでは殆ど脱酸しない薄鋼板用溶鋼の溶製方法も開示されている。
【０００４】
【特許文献１】
特開平５−１０４２１９号公報
【特許文献２】
特開昭６３−１４９０５７号公報
【特許文献３】
特開平５−３０２１１２号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、上述したアルミナ系介在物を除去する方法では、低炭素溶鋼中に多量に生成したアルミナ系介在物を表面疵やノズル閉塞が発生しない程度まで低減することは非常に難しい。また、アルミナ系介在物を全く生成しないＭｇ脱酸では、Ｍｇの蒸気圧が高く、溶鋼への歩留まりが非常に低いため、低炭素鋼のように溶存酸素濃度が高い溶鋼をＭｇだけで脱酸するには多量のＭｇを必要とし、製造コストを考えると実用的なプロセスとは言えない。
これらの問題を鑑み、本発明はアルミナ系介在物を生成させることがないように、Ｔｉを主とした脱酸を行うことにより、確実に表面疵とノズル閉塞を防止できる薄鋼板用低炭素鋼鋳片の製造方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記課題を解決するために、本発明は以下の構成を要旨とする。
（１）真空脱ガス処理により溶鋼中の炭素含有率を０．０１質量％以下まで脱炭した後、２回以上のＴｉの添加により予め設定された総Ｔｉ添加量を投入し、その後少なくともＬａ、Ｃｅを添加した溶鋼を鋳造する方法であって、１回目のＴｉ添加前にＡｌを添加して３分以上攪拌して予備脱酸処理を行い、１回目のＴｉ添加後の溶鋼中の溶存酸素を０．００１質量％以上から０．０１質量％以下とし、１回目のＴｉを添加した後、２回目のＴｉを添加するまでに、３０秒以上の介在物浮上時間を確保することを特徴とする低炭素鋼鋳片の製造方法。
【０００７】
【発明の実施の形態】
以下に本発明を詳細に説明する。本発明の溶製法では、転炉や電気炉等の製鋼炉で精錬し、或いはその後に真空脱ガス処理して炭素含有率を０．０１質量％以下に脱炭した溶鋼に、Ｔｉを２回以上添加し脱酸を行い、さらにその溶鋼中に少なくともＬａ、Ｃｅを添加する。
この溶製法の基本思想は、１回目のＴｉ添加により介在物を低融点化し浮上分離を促進することにより溶鋼の清浄性を高め、その上で２回目以降のＴｉ添加と、その後に少なくともＬａ、Ｃｅを添加することにより残りの介在物を微細に分散させ、無害化することにある。以下に詳細に説明する。
【０００８】
まず、本発明が対象とする脱炭溶鋼の炭素含有率は０．０１質量％以下とする。その理由として、自動車用外板向けの加工が厳しい極低炭素鋼板等では、加工性を付与するためにＣをできるだけ低くする必要があるためである。そこで、Ｃ濃度は０．０１質量％以下、好ましくは０．００５質量％以下にするのが良い。また、真空脱ガス装置を用いて脱炭しても良い。
【０００９】
次に、Ｔｉを２回以上添加することであるが、溶鋼中の溶存酸素濃度が高い状態で添加された１回目のＴｉは、急激に溶鋼中の溶存酸素と反応しチタニアとなるが、Ｔｉ添加後も溶存酸素を過飽和に残存させているため、チタニアがさらに溶鋼と反応し、最終的に酸化鉄・チタニア系の複合介在物となる。この介在物は溶鋼中で液相であり、凝集・合体で粗大化することにより殆ど浮上分離されるため、溶鋼中の溶存酸素の低下と共に、介在物濃度も大きく低下する。１回目のＴｉ添加は脱酸が主な目的であるが、上述したように比較的凝集・合体し易い低融点の介在物に組成制御し、浮上分離により介在物量をできるだけ低減させる役割も有している。このため、溶鋼中の溶存酸素をできるだけ低減し、且つ溶鋼中の介在物を浮上分離し易い酸化鉄・チタニア系の複合介在物に制御することが重要であり、この様なことを考慮して、１回目のＴｉ添加量を実験等により適宜設定すれば良い。
【００１０】
２回目以降に添加されたＴｉは、一部残った溶存酸素と反応してチタニア系介在物を生成するが、この介在物は酸化鉄・チタニア系の液相介在物とは異なり固相であり、且つ溶鋼との濡れ性がアルミナ系介在物に比べて良好であるため、比較的凝集・合体し難く、アルミナ系介在物に比べて微細である。２回目以降に添加するＴｉの添加回数は、必要に応じて複数回添加しても良い。この様にして得られた、チタニア系介在物でも一部凝集・合体が起こるため、チタニアクラスターを形成する。このため、最終Ｔｉ添加終了後に少なくともＬａ、Ｃｅを添加し、このチタニア系介在物を還元することにより、さらに微細なチタニア−セリュウムオキサイド系、チタニア−ランタンオキサイド系、或いはチタニア−ランタンオキサイド−セリュウムオキサイド系の複合介在物に改質する。その結果、アルミナ系介在物を生成することなく、溶鋼中の介在物を低減した上で、さらに介在物を微細化できるため、確実に表面疵とノズル閉塞を防止できる薄鋼板用素材の低炭素溶鋼を製造することができる。ここで、少なくともＬａ、Ｃｅを添加するというのは、Ｌａ、Ｃｅのいずれか一方または双方を添加するという意味である。
【００１１】
添加するＴｉはスポンジ状Ｔｉのように高純度Ｔｉに限られたものではなく、Ｆｅ−Ｔｉのような合金として添加しても上記効果は損なわれない。
また、少なくともＬａ、Ｃｅの添加量は、２回目以降に添加したＴｉと溶存酸素が反応して生成した少量のチタニア系介在物を還元するに必要な量以上であって、且つＬａ、Ｃｅが耐火物やモールドパウダーと反応して溶鋼を汚染させない量以下とすることが好ましい。すなわち、溶鋼中のＬａとＣｅの合計濃度で０．０００１〜０．０１質量％が適正範囲である。Ｌａ、Ｃｅの添加は、Ｔｉ添加後に実施すれば良く、インジェクション法、ワイヤー添加法等により、取鍋、タンディッシュ、連続鋳造鋳型等の何れかで添加すれば良い。さらに、Ｌａ、Ｃｅの添加は純Ｌａ、純Ｃｅで行うことも可能であるが、Ｌａ−Ｃｅ等の合金として添加しても良い。
【００１２】
次に、Ｔｉの総添加量は溶鋼中の溶存酸素を脱酸し、さらに材質を確保する上で溶鋼中の炭素と窒素を固定するに必要な量であることが好ましい。従って、この様なことを考慮して、予めＴｉの総添加量を設定することができる。脱ガス処理後の溶鋼中の溶存酸素量と炭素、窒素濃度にもよるが、溶鋼中の最終Ｔｉ濃度で０．００５質量％以上、好ましくは０．０１質量％以上になるように歩留まりを考慮して添加するのが良い。
この様に、２回以上のＴｉ添加量の合計が、予め設定された総Ｔｉ添加量の投入になる様に、Ｔｉを添加するものである。ここで、各添加ごとのＴｉ添加量は、上記に記載の通りである。
【００１３】
また、１回目のＴｉ添加量については、比較的凝集・合体し易い低融点の介在物に組成制御し、浮上分離により介在物量をできるだけ低減させるための、１回目のＴｉ添加後の好ましい溶存酸素量は、実験的検討から溶鋼中に０．００１質量％から０．０１質量％程度残すようにすることが効果的であることが判明した。ここで、溶存酸素量の測定方法としては、固体電解質を利用した酸素センサー等を活用すれば容易に測定できる。
さらに、１回目のＴｉを添加した後、２回目のＴｉ添加までに介在物の浮上分離時間を設けることが好ましく、この酸化鉄・チタニア系の介在物組成であれば３０秒以上確保すれば十分である。
【００１４】
溶鋼中にアルミナ系介在物を残さないためには、溶鋼中にＡｌを添加しないことが好ましいが、脱炭後の溶存酸素が高くなり過ぎると、この溶存酸素をＴｉだけで脱酸するのはコスト的に不利である。その場合、過剰な溶存酸素を一部Ａｌで予備脱酸し、Ｔｉ添加量を減少させることができる。
さらに、Ａｌ添加後の攪拌時間を３分以上確保することが、殆どのアルミナ系介在物を残留させないため好ましい。
【００１５】
【実施例】
以下に、実施例及び比較例を挙げて、本発明について説明する。
・実施例：転炉で精錬した２００ｔの溶鋼を、環流式真空脱ガス装置で炭素濃度０．００３質量％まで脱炭した。その時、取鍋内溶鋼の溶存酸素濃度は０．０５質量％であった。取鍋内の溶鋼に表１に示すＴｉ量を添加して脱酸した。一部、Ｔｉ添加前にＡｌによる予備脱酸も実施した。ここで、Ａｌとして金属Ａｌを、またＴｉとしてスポンジ状Ｔｉをそれぞれ用いた。
【００１６】
最初のＴｉ添加と２回目Ｔｉ添加との間隔は、１分間であった。２回目のＴｉ添加後に、取鍋内溶鋼中にＬａ、Ｃｅの混合物（質量比で６：４）を添加し、最終組成の溶鋼を溶製した。この溶鋼を連続鋳造法で鋳造し、厚み２５０mm、幅１８００mmのスラブを鋳造した。連続鋳造時におけるノズル開度は一定であり、ノズル閉塞は生じなかった。鋳造した鋳片は８５００mm長さに切断し、１コイル単位とした。このようにして得られたスラブは、常法により熱間圧延、冷間圧延し、最終的には０．７mm厚みで幅１８００mmコイルの冷延鋼板とした。鋳片品質については、冷間圧延後の検査ラインで目視観察を行い、１コイル当たりに発生する表面欠陥の発生個数を評価した。その結果、表面欠陥は発生しなかった。
【００１７】
【表１】
・比較例：転炉で精錬した２００ｔの溶鋼を、環流式真空脱ガス装置で炭素濃度３０ppmまで脱炭した後、取鍋内の溶鋼にＡｌを２００kg添加して脱酸し、その後直ちに４５kgのＴｉを加えて、Ａｌ濃度０．０４質量％、Ｔｉ濃度０．０２質量％の溶鋼に成分調整した。この溶鋼を連続鋳造法で鋳造し、厚み２５０mm、幅１８００mmのスラブを鋳造した。連続鋳造時におけるノズル開度は鋳造開始から徐々に開き、鋳造終了時には全開状態となり、ノズル閉塞が生じた。鋳造した鋳片は８５００mm長さに切断し、１コイル単位とした。このようにして得られたスラブは、常法により熱間圧延、冷間圧延し、最終的には０．７mm厚みで幅１８００mmコイルの冷延鋼板とした。鋳片品質については、冷間圧延後の検査ラインで目視観察を行い、１コイル当たりに発生する表面欠陥の発生個数を評価した。その結果、表面欠陥は１コイル当たり２０個も発生した。
【００１９】
【発明の効果】
以上に説明したように、本発明によると、アルミナ系介在物を生成することなく、溶鋼中の介在物を低減した上で、さらに介在物を微細化することができるため、確実に表面疵とノズル閉塞を防止できる加工性、成形性に優れた薄鋼板用の低炭素鋼鋳片を製造することが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for melting a low carbon thin steel sheet excellent in workability and formability.
[0002]
[Prior art]
The molten steel refined in a converter or vacuum processing vessel contains a large amount of dissolved oxygen, and this excess oxygen is generally deoxidized by Al, a strong deoxidizing element with a strong affinity for oxygen. Is. However, Al produces alumina inclusions by deoxidation, which aggregate and coalesce into coarse alumina clusters. This alumina cluster causes surface flaws during the production of the steel sheet and greatly deteriorates the quality of the thin steel sheet. In addition, alumina inclusions in the molten steel are likely to adhere to a continuous casting nozzle such as a tundish nozzle, and when the nozzle is blocked, smooth casting work becomes difficult. In particular, low carbon molten steel, which is a material for thin steel sheets with a low carbon concentration and a high dissolved oxygen concentration after refining, has a very large amount of alumina clusters, and surface flaws and nozzle clogging are very likely to occur. Measures to reduce this are a major issue.
[0003]
On the other hand, conventionally, the inclusion adsorption flux of Patent Document 1 is added to the molten steel surface to remove alumina inclusions, or the CaO flux is added to the molten steel using the injection flow of Patent Document 2. Thus, a method for adsorbing and removing alumina inclusions has been proposed and implemented. On the other hand, as a method that does not remove alumina inclusions but does not generate them, a method for melting molten steel for thin steel sheets that deoxidizes molten steel with Mg and hardly deoxidizes with Al as disclosed in Patent Document 3 is also disclosed. ing.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-104219 [Patent Document 2]
JP 63-149057 A [Patent Document 3]
Japanese Patent Laid-Open No. 5-302112
[Problems to be solved by the invention]
However, in the method of removing the alumina inclusions described above, it is very difficult to reduce the alumina inclusions generated in a large amount in the low carbon molten steel to the extent that surface flaws and nozzle clogging do not occur. In addition, Mg deoxidation that does not produce any alumina inclusions has a high vapor pressure of Mg and a very low yield to molten steel. Therefore, a molten steel with a high dissolved oxygen concentration such as low carbon steel can be deoxidized only with Mg. Therefore, a large amount of Mg is required, and it cannot be said that it is a practical process considering the manufacturing cost.
In view of these problems, the present invention is a low-carbon steel for thin steel sheets that can reliably prevent surface flaws and nozzle clogging by performing deoxidation mainly using Ti so as not to generate alumina inclusions. It aims at providing the manufacturing method of slab.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention has the following configuration.
(1) After decarburizing the carbon content in the molten steel to 0.01% by mass or less by vacuum degassing treatment, a total Ti addition amount set in advance by adding Ti twice or more is added, and then at least La , A method of casting molten steel to which Ce has been added , Al is added before the first Ti addition, and the mixture is stirred for 3 minutes or more, preliminarily deoxidized, and dissolved in the molten steel after the first Ti addition. Oxygen is 0.001 mass% or more to 0.01 mass% or less, and after the first Ti is added, the inclusion flotation time of 30 seconds or more is ensured until the second Ti is added. A method for producing a low carbon steel slab.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. In the melting method of the present invention, Ti is twice applied to molten steel that has been refined in a steelmaking furnace such as a converter or an electric furnace, or subsequently degassed by vacuum degassing to a carbon content of 0.01% by mass or less. Deoxidation is performed by adding the above, and at least La and Ce are added to the molten steel.
The basic idea of this melting method is to improve the cleanliness of molten steel by lowering the melting point of inclusions and promoting floating separation by the first addition of Ti, and then adding Ti for the second and subsequent times, and then at least La, By adding Ce, the remaining inclusions are finely dispersed and made harmless. This will be described in detail below.
[0008]
First, the carbon content of the decarburized molten steel targeted by the present invention is 0.01% by mass or less. This is because, in an extremely low carbon steel sheet or the like that is severely processed for an automobile outer plate, it is necessary to make C as low as possible in order to impart workability. Therefore, the C concentration is 0.01% by mass or less, preferably 0.005% by mass or less. Moreover, you may decarburize using a vacuum degassing apparatus.
[0009]
Next, Ti is added two or more times. The first Ti added in a state where the dissolved oxygen concentration in the molten steel is high reacts rapidly with the dissolved oxygen in the molten steel to become titania. Since dissolved oxygen remains supersaturated even after the addition, titania further reacts with the molten steel, and finally becomes iron oxide / titania composite inclusions. The inclusions are in a liquid phase in the molten steel, and are almost floated and separated by being coarsened by agglomeration and coalescence. Therefore, the inclusion concentration is greatly reduced as the dissolved oxygen in the molten steel is reduced. The primary purpose of the first Ti addition is deoxidation, but as described above, the composition is controlled to low melting point inclusions that are relatively easy to aggregate and coalesce, and the amount of inclusions is reduced as much as possible by flotation separation. ing. For this reason, it is important to reduce the dissolved oxygen in the molten steel as much as possible, and to control the inclusions in the molten steel to be iron oxide / titania composite inclusions that are easily levitated and separated. What is necessary is just to set the Ti addition amount of the 1st time suitably by experiment etc.
[0010]
Ti added after the second reaction reacts with the remaining dissolved oxygen to produce titania inclusions, which are solid phases unlike iron oxide / titania liquid phase inclusions. In addition, since wettability with molten steel is better than that of alumina inclusions, it is relatively difficult to agglomerate and coalesce and is finer than alumina inclusions. The number of additions of Ti added after the second time may be added a plurality of times as necessary. Even the titania inclusions obtained in this way partially aggregate and coalesce, so that titania clusters are formed. Therefore, by adding at least La and Ce after the final Ti addition is completed and reducing the titania inclusions, finer titania-cerium oxide, titania-lanthanum oxide, or titania-lanthanum oxide-cement. It is modified to a composite oxide inclusion of ruthenium oxide. As a result, the inclusions in the molten steel can be reduced without generating alumina inclusions, and the inclusions can be further refined, so the low carbon content of the thin steel sheet material can reliably prevent surface flaws and nozzle clogging. Molten steel can be manufactured. Here, adding at least La and Ce means adding one or both of La and Ce.
[0011]
Ti to be added is not limited to high-purity Ti like sponge-like Ti, and the above effect is not impaired even if it is added as an alloy such as Fe-Ti.
Further, at least the addition amount of La and Ce is not less than the amount necessary for reducing a small amount of titania inclusions produced by the reaction of Ti and dissolved oxygen added after the second time, and La and Ce are contained. It is preferable to make the amount less than that which does not contaminate molten steel by reacting with refractory or mold powder. That is, 0.0001-0.01 mass% is an appropriate range with the total density | concentration of La and Ce in molten steel. La and Ce may be added after adding Ti, and may be added in any of a ladle, a tundish, a continuous casting mold or the like by an injection method, a wire addition method, or the like. Furthermore, La and Ce can be added as pure La or pure Ce, but may be added as an alloy such as La-Ce.
[0012]
Next, the total addition amount of Ti is preferably an amount necessary for deoxidizing dissolved oxygen in the molten steel and securing carbon and nitrogen in the molten steel in order to secure the material. Therefore, in consideration of this, the total amount of Ti can be set in advance. Considering the yield so that the final Ti concentration in the molten steel is 0.005 mass% or more, preferably 0.01 mass% or more, depending on the dissolved oxygen content and carbon and nitrogen concentration in the molten steel after degassing treatment. To add.
In this manner, Ti is added so that the total of the two or more Ti addition amounts becomes the input of the preset total Ti addition amount. Here, the Ti addition amount for each addition is as described above.
[0013]
In addition, for the first Ti addition amount, preferable dissolved oxygen after the first Ti addition to control the composition to inclusions having a low melting point that are relatively easy to aggregate and coalesce, and to reduce the inclusion amount as much as possible by floating separation. From the experimental investigation, it has been found that it is effective to leave about 0.001% by mass to 0.01% by mass in the molten steel. Here, as a method for measuring the amount of dissolved oxygen, it can be easily measured by utilizing an oxygen sensor using a solid electrolyte.
Furthermore, it is preferable to provide a floating separation time for inclusions after the first Ti addition until the second Ti addition. If this iron oxide / titania inclusion composition is sufficient, it is sufficient to secure 30 seconds or more. It is.
[0014]
In order not to leave alumina inclusions in the molten steel, it is preferable not to add Al to the molten steel, but when the dissolved oxygen after decarburization becomes too high, it is possible to deoxidize this dissolved oxygen with only Ti. It is disadvantageous in cost. In that case, a part of the excess dissolved oxygen can be predeoxidized with Al to reduce the amount of Ti added.
Furthermore, it is preferable to secure a stirring time of 3 minutes or more after the addition of Al since most alumina inclusions do not remain.
[0015]
【Example】
Hereinafter, the present invention will be described with reference to examples and comparative examples.
Example: 200 t of molten steel smelted in a converter was decarburized to a carbon concentration of 0.003% by mass using a reflux vacuum degasser. At that time, the dissolved oxygen concentration of the molten steel in the ladle was 0.05 mass%. The amount of Ti shown in Table 1 was added to the molten steel in the ladle for deoxidation. In part, preliminary deoxidation with Al was also performed before Ti addition. Here, metal Al was used as Al, and sponge-like Ti was used as Ti.
[0016]
The interval between the first Ti addition and the second Ti addition was 1 minute. After the second addition of Ti, a mixture of La and Ce (6: 4 by mass ratio) was added to the molten steel in the ladle to melt the molten steel having the final composition. This molten steel was cast by a continuous casting method to cast a slab having a thickness of 250 mm and a width of 1800 mm. The nozzle opening during the continuous casting was constant, and no nozzle clogging occurred. The cast slab was cut to a length of 8500 mm to make one coil unit. The slab thus obtained was hot-rolled and cold-rolled by a conventional method, and finally formed into a cold-rolled steel sheet having a thickness of 0.7 mm and a coil width of 1800 mm. Regarding the slab quality, visual observation was performed on the inspection line after cold rolling, and the number of surface defects generated per coil was evaluated. As a result, no surface defects occurred.
[0017]
[Table 1]
・ Comparative example: After decarburizing 200t of molten steel smelted in a converter to a carbon concentration of 30ppm with a reflux vacuum degassing device, 200kg of Al was added to the molten steel in the ladle and immediately deoxidized. Ti was added to adjust the components to molten steel having an Al concentration of 0.04% by mass and a Ti concentration of 0.02% by mass. This molten steel was cast by a continuous casting method to cast a slab having a thickness of 250 mm and a width of 1800 mm. The nozzle opening at the time of continuous casting gradually opened from the start of casting and was fully opened at the end of casting, resulting in nozzle clogging. The cast slab was cut to a length of 8500 mm to make one coil unit. The slab thus obtained was hot-rolled and cold-rolled by a conventional method, and finally formed into a cold-rolled steel sheet having a thickness of 0.7 mm and a coil width of 1800 mm. Regarding the slab quality, visual observation was performed on the inspection line after cold rolling, and the number of surface defects generated per coil was evaluated. As a result, 20 surface defects were generated per coil.
[0019]
【The invention's effect】
As described above, according to the present invention, the inclusions in the molten steel can be reduced and the inclusions can be further refined without generating alumina inclusions, so that It becomes possible to produce a low carbon steel slab for a thin steel sheet excellent in workability and formability that can prevent nozzle clogging.
Claims (1)
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| JP5096779B2 (en) * | 2007-04-12 | 2012-12-12 | 株式会社神戸製鋼所 | Method of adding rare earth elements to molten steel |
| JP4879809B2 (en) * | 2007-04-17 | 2012-02-22 | 新日本製鐵株式会社 | Continuous casting method |
| CN110643783A (en) * | 2019-10-31 | 2020-01-03 | 达力普石油专用管有限公司 | Narrow range control method for Ti content of Ti microalloyed steel |
| CN114058786B (en) * | 2021-10-18 | 2023-03-17 | 首钢集团有限公司 | Alloying method in IF steel refining process |
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