JP4183524B2 - Manufacturing method of high cleanliness steel - Google Patents

Description

【００１２】
本発明は、図１に示す従来法による特徴を生かし、非金属介在物を少なくした高清浄度鋼の製造方法を提供しようとするものである。
【００１３】
【課題の解決手段】
請求項１に係わる発明は、予備処理で脱硫した未脱珪溶銑又は、該溶銑と冷鉄源を一定量配合した主原料を用い、転炉にて吹錬して〔Ｃ〕：０．０３〜０．１５％、〔Ｐ〕：０．０１０〜０．０２０％まで脱珪、脱炭、脱隣したのち、取鍋に移し、真空二次精錬装置にて最終脱炭、合金調整、脱酸を行う〔Ｃ〕：０．０３％以上の鋼の製造方法において、転炉にて脱珪、脱炭、脱隣したのち、取鍋に移す際、スラグカット手段によりスラグをカットして取鍋へのスラグの流出を一定量とし、取鍋へのスラグの流出を抑制し、かつ真空二次精錬工程の脱酸後かつ工程終了の期間に取鍋へＣａＦ _２ またはＡｌ _２ Ｏ _３ を４０〜５０重量％含有したＣａＯ系フラックスからなるスラグ改質剤を添加して真空二次精錬後の（Ｔ．Ｆｅ）を６〜１２％としたことを特徴とする。
【００１４】
真空二次精錬後の（Ｔ．Ｆｅ）の範囲は、転炉吹錬後の（Ｔ．Ｆｅ）およびスラグ流出量の範囲に起因するものである。段落番号０００９で説明したように、真空二次精錬後の（Ｔ．Ｆｅ）が低い程清浄度が高くなり、１２％を超えると清浄度が低く満足しうる品質とならない。また、更に（Ｔ．Ｆｅ）を低減させるためには取鍋スラグの除去、およびスラグ改質剤の増加が必要になり、製造・作業コストの増加、熱バランス低下、耐火物の溶損増加、および処理時間増加による生産能力の低下が懸念されるため、６％を下限としてよい。
【００１５】
本発明は以上のように、図１に示す従来法において、スラグカット手段と、スラグ改質剤とを併用し、取鍋へのスラグの流量を少なくすると共に、スラグを無害化又は改質することにより、非金属介在物の少ない高清浄度鋼を得ることができる。
【００１６】
本発明で用いるスラグカット手段としては、例えばスラグダーツ、スラグストッパー、スラグボール、不活性ガス、スラグ流出検知器等を用いることができるが、このなかではスラグ、溶鋼との比重差によるスラグカットを利用した、簡単かつ命中率の高いスラグダーツが好ましい。
【００１７】
スラグ改質剤としては、例えばＣａＯ、Ａｌ _２ Ｏ _３ 、ＣａＦ _２ の一種以上を主成分とするフラックス、金属Ａｌを含有するＡｌドロス等を用いることができるが、金属Ａｌは還元力は強いものゝ、スラグ中のＰ _２ Ｏ _５ を還元して鋼中に復燐し、鋼中の燐含有量が多くなること、及びＡｌ _２ Ｏ _３ となって非金属介在物になる可能性が高いため、高清浄度を得るには、前者のフラックスを使用するのが望ましい。
【００１８】
本発明のように、脱酸後、溶鋼中の〔Ｏ〕濃度が十分に低下したのちにスラグ改質剤を添加すると、スラグ改質剤がフラックスである場合、反応が穏やかになり、スロッピングや発塵の発生を抑制することができる。
【００１９】
請求項２に係わる発明は、請求項１に係わる発明において、スラグカット手段がスラグダーツであることを特徴とする。スラグダーツを用いることにより命中精度が高く、スラグ流出量をほゞ一定にすることができ、スラグ流出量をほゞ一定にすることにより脱酸剤も鋼種に応じて調整する程度で、同じ鋼種では一定にすることができる。
【００２０】
請求項１又は２に係わる発明において、真空二次精錬がＲＨ真空精錬装置を用いて行われ、該ＲＨ真空精錬装置を用いて最終脱炭、合金調整、脱酸を行った後、真空槽内へスラグ改質剤を添加し、その後環流することとすれば、ＲＨ真空精錬装置内での環流は、ガス吹き込み装置によるガス撹拌に比べ、取鍋全体を撹拌しないため、スラグと溶鋼の界面付近を集中的に改質し、スラグカットすることと相まってスラグ改質剤の使用量を少なくすることができ、また撹拌が穏やかであり、Ａｒバブリングのようにスラグを強撹拌して鋼中にスラグを巻込む可能性も少ない。
なお、環流は従来でも脱酸後、Ａｌ_２Ｏ_３を浮上促進させるために行われており、この環流を利用することができるので、時間延長の問題を生じない。
【００２１】
【発明の実施の形態】
予備処理で脱硫した未脱珪溶銑（〔Ｓｉ〕：０．２〜０．８％、〔Ｍｎ〕：０．１５〜０．３０％、〔Ｐ〕：０．０８０〜０．１００％）と冷鉄源としてのスクラップを一定量配合した主原料に生石灰、石灰石、ドロマイト、Ｍｎ鉱石、焼結鉱、蛍石等の溶媒剤を添加し、上底吹き転炉型反応容器で吹練して〔Ｃ〕：０．０５〜０．１０％、〔Ｐ〕：０．０１０〜０．０２０％まで脱珪、脱炭、脱燐した。このとき反応容器内で生成するスラグは、溶鋼ｔ当り６０〜１２０kg、(Ｔ．Ｆｅ)は１０〜１７％であった。
【００２２】
次に反応容器の溶鋼を取鍋へ移す際、図３に示すように、反応容器１の容器口２より棒鋼と耐火物よりなるスラグダーツ３をブーム４の先端に取付けて挿入し、反応容器１のスラグ５上に投入した。
スラグダーツを投入するタイミングは、反応容器１に投入された溶鋼量と、出鋼時の溶鋼の流速とで出鋼終了時間を予測し、終了１、２分前にブーム４よりダーツ３を放すことにより行われる。
【００２３】
ここでスラグダーツ３の比重は、溶鋼６の比重とスラグ５の比重の中間になるように設定することにより、スラグダーツ３を溶鋼６とスラグ５の間にとどめることができるようになり、これにより約９０％と高い成功率でスラグカットを行うことができ、またスラグ改質剤の使用も少なくできる。そしてスラグダーツ実施以前は、取鍋７へのスラグ流出量が溶鋼ｔ当り５〜２６kg（平均１６kg）であったものが、スラグダーツを用いてスラグカットしたことにより、取鍋７へのスラグ流出量を溶鋼ｔ当り５〜１６kg（平均１０kg）に低減された。図中、8は出鋼孔を示す。
【００２４】
取鍋へ移された溶鋼は、つづいてＲＨ真空精錬装置を用いて最終脱炭、合金調整、脱酸を行ったのち、ＣａＦ₂又はＡｌ₂Ｏ_３を４０〜５０％含有したＣａＯ系フラックスを溶鋼ｔ当り２．７kg真空槽内に添加し、添加後、槽内で６〜１２分環流した。環流後の(Ｔ．Ｆｅ)は、６〜１２％に低減し、フラックス添加により(Ｔ．Ｆｅ)は平均で約３０％低下した。またスラグカットを行ってスラグ流出量を低減させることにより見かけ上のフラックス原単位が増加し、スラグカットと、フラックスを併用したことにより、(Ｔ．Ｆｅ)は平均で約４０％低下した（図４）。
【００２５】
また図５は、スラグカットとフラックス添加を行わない従来法におけるＵＳＴ個数（鋳造・圧延後の鋼板中に含まれる介在物の個数を表す指標）を１００とした場合に、フラックス添加によるスラグ改質のみの個数と、スラグダーツを使用してスラグカットし、かつフラックスを添加してスラグ改質した場合の個数を示すものである。図に示されるように、スラグカットと、フラックスを併用した場合のＵＳＴ個数がスラグカットとフラックス添加を行わない従来法はもとよりのこと、フラックスを添加してスラグ改質を行った場合に比べ、鋼種Ａ、Ｂ共、特にＢについては格段に減少した。なお、鋼種Ａ、Ｂはそれぞれ〔Ｃ〕：０.０８〜０.１２％、〔Ｍｎ〕：１.００〜１.６０％、〔Ｓｉ〕：０.００〜０.３０％、〔Ｐ〕：≦０.２０％のそれぞれ成分の異なる鋼種である。
【００２６】
【発明の効果】
請求項１及び２に係わる発明によると、図１に示す従来法による特徴、すなわち予備処理での負荷が小さく、熱ロスも小さいうえ、熱バランスもよく、生産能力も高い、という特徴を保持し、スラグカットとスラグ改質剤を併用したことにより、非金属介在物が少ない高清浄度鋼を得ることができる。
【００２７】
また、スラグ改質剤を真空二次精錬の脱酸後に添加することにより、スロッピングや発塵の発生を抑制し、或いは鋼中の非金属介在物を少なくし、清浄度の高い鋼を得ることができる。
【００２８】
請求項１又は２に係わる発明において、真空二次精錬がＲＨ真空精錬装置を用いて行われ、該ＲＨ真空精錬装置を用いて最終脱炭、合金調整、脱酸を行った後、真空槽内へスラグ改質剤を添加し、その後環流することとすれば、ガス撹拌に比べ、スラグの巻き込みが少なくなり、清浄度の高い鋼を得ることができる。
また、スラグと溶鋼の界面付近を集中的に改質することができ、スラグカットすることと相まってスラグ改質剤の使用量を少なくすることができる。また撹拌が穏やかなため、スラグを強撹拌して鋼中にスラグを巻込むのをすくなくできる。
【図面の簡単な説明】
【図１】従来法の製鋼プロセスを示す図。
【図２】近年多用されている製鋼プロセスを示す図。
【図３】スラグダーツを挿入した状態を示す図。
【図４】フラックス量と(Ｔ．Ｆｅ)の関係を示す図。
【図５】従来法及びスラグ改質とダーツを使用した場合のＵＳＴ指数を示す図。
【符号の説明】
１・・反応容器
２・・容器口
３・・スラグダーツ
５・・スラグ
６・・溶鋼
７・・取鍋[0001]
[Technical field to which the invention belongs]
The present invention uses a main raw material in which a certain amount of undesiliconized hot metal or non-desiliconized hot metal and a cold iron source is blended, and a converter reactor (hereinafter referred to as “converter reactor”) is simply indicated as “converter”. In this case, the molten steel that has been desiliconized, decarburized, and adjoined by vacuum refining in the steel is reduced to reduce non-metallic inclusions C ≧ 0.03% by weight (hereinafter “wt%” is simply “%”. And a method for producing a high cleanliness low carbon steel or medium carbon steel.
[0002]
[Prior art]
Conventionally, the hot metal discharged from the blast furnace is pretreated in a hot metal ladle and desulfurized as shown in Fig. 1, and then transferred to the converter, where it is desiliconized, decarburized, and dephosphorized, and then removed. It was transferred to a pan, vacuum secondary refining was performed in a vacuum degassing treatment device, decarburized, alloy adjusted and deoxidized, then transferred to tundish and continuously cast, but in recent years it has been removed from the blast furnace as shown in FIG. After desiliconization, de-adjacent, and desulfurization of the molten iron in the preliminary treatment process, it is transferred to a converter, decarburized in the converter, transferred to a ladle, and then vacuumed with a vacuum degassing treatment device. Subsequent refining is followed by decarburization, alloy adjustment and deoxidation, then transferred to tundish, and a method of continuous casting is frequently used.
[0003]
Patent Document 1 listed below relates to this method in the converter [C]: 0.03 to 0.06%, [Mn]: 0.01 to 0.2%, [Si]: 0. After refining to 01-0.03%, slag is cut and the slag is discharged into a ladle with a slag amount of 8-12 kg per t of molten steel, and then RH vacuum degassing equipment [C]: ≤0.005% After decarburizing until decarburized, deoxidize by adding Al, then move to Ar bubbling device, add slag modifier consisting of a predetermined amount of aluminum ash according to the oxygen concentration in the molten steel, then slag reforming A method is disclosed in which Ar gas is blown into molten steel to promote the reaction and gas stirring is performed, and the concentration of (FeO + MnO) in slag by slag modification is at least 10% or less, preferably 5% or less. Has been. Here, [] represents a component in molten steel, and () represents a component in slag.
[0004]
Patent Document 2 discloses a chemical composition of [C]: 0.02 to 0.06%, [Mn]: 0.01 to 0.2%, and [Si]: 0.01 to 0.03% from the converter. After the slag is discharged as much as possible in the ladle, the slag modifier consisting of Al ash and Al-CaO flux is added, and then the carbon content is reduced under vacuum using RH. Disclosed is a method in which decarburization treatment is performed until 0.005% or less, Al is added and deoxidation is performed, and a catalyst agent is added and refluxed. The concentration of (FeO + MnO) in the slag after slag reforming is disclosed. Is 5.3 to 11.0%.
[0005]
Further, in Patent Document 3, 2.6 kg of CaO-Al ₂ O ₃ flux per molten steel t is added to [C]: 0.1% molten steel that has been removed from the converter to the ladle, and Ar gas is applied under reduced pressure. After decarburizing and refining while blowing in, a method of deoxidizing by adding Al as a deoxidizing agent is disclosed, [C] after decarburizing and refining is 0.07%, total Fe concentration in slag (hereinafter referred to as , (T.Fe)) is 3%.
[0006]
In Patent Document 4, [P] ≤ 0.030% hot metal pre-treated in hot metal is blown out in a converter and undeoxidized to the steel in the ladle. When a slag outflow of a level or more is detected, a method is disclosed in which a slag stopper is operated to perform slag cut, and then Al ash is added according to the slag outflow amount to deoxidize the slag, and (FeO), (MnO ) Can also be reduced stably.
[0007]
[Patent Document 1]
JP 2001-98316 A [Patent Document 2]
JP 2000-178634 A [Patent Document 3]
JP-A-10-152719 [Patent Document 4]
Japanese Patent Laid-Open No. 6-235017
[Problems to be solved by the invention]
In the conventional method shown in FIG. 1, desiliconization and dephosphorization are performed in a converter, and only desulfurization is performed in the pretreatment, so the load of the pretreatment is small and the heat loss of the pretreatment is small. Considering that dephosphorization in the pretreatment causes light decarburization and the amount of carbon as a heat source in the converter is reduced, it is better to dephosphorize in the converter in terms of heat balance. Since the converter is faster than the pretreatment, the production capacity is improved, but on the other hand, the desiliconization load in the converter is large, the amount of slag generation is large, the dephosphorization load in the converter is large, (T.Fe) increases, and there are difficulties such as an increase in non-metallic inclusions.
[0009]
The relationship between (T.Fe) and non-metallic inclusions is such that, for example, as shown in formula (1), Al for deoxidation is reoxidized and the generated Al ₂ O ₃ is cast in a state suspended in molten steel. It is said that the quality after rolling is lowered, and the lower the (T.Fe), the higher the cleanliness.
3 (FeO) +2 [Al] = (Al ₂ O ₃ ) + 3Fe (1)
[0010]
In this regard, in the method shown in FIG. 2, compared to the conventional method shown in FIG. 1, there is no desiliconization load in the converter, the amount of slag generation is reduced, the dephosphorization load in the converter is small, and (T. Fe) is low, and there are advantages such as reducing non-metallic inclusions, but the pretreatment load is large, the production capacity is low, and the heat loss in the pretreatment is also large, and dephosphorization is performed in the pretreatment. Therefore, there is a drawback that the heat balance is also bad.
Table 1 compares the method shown in FIG. 1 with the method shown in FIG.
[0011]
[Table 1]

[0012]
The present invention is intended to provide a method for producing a high cleanliness steel that makes use of the characteristics of the conventional method shown in FIG. 1 and reduces non-metallic inclusions.
[0013]
[Means for solving problems]
In the invention according to claim 1, undesiliconized hot metal desulfurized by pretreatment or a main raw material containing a certain amount of the hot metal and a cold iron source is blown in a converter [C]: 0.03 ~ 0.15%, [P]: After desiliconization, decarburization, deneighboring up to 0.010-0.020%, move to ladle, final decarburization, alloy adjustment, desorption in vacuum secondary refining equipment performing acid [C]: in the manufacturing method of 0.03% or more steel, desiliconization, decarburization in a converter furnace, after Datsutonari, when passing the ladle, collected by cutting slugs by slug cut means The amount of slag flowing into the ladle is set to a fixed amount, the outflow of slag into the ladle is suppressed, and 40F of CaF ₂ or Al ₂ O ₃ is added to the ladle after the deoxidation of the vacuum secondary refining process and during the end of the process. (T.Fe) after secondary vacuum refining by adding a slag modifier composed of CaO-based flux containing ~ 50 wt% to 6-12% It is characterized by that.
[0014]
The range of (T.Fe) after vacuum secondary refining is due to the range of (T.Fe) and slag outflow after converter blowing. As explained in paragraph 0009, the lower the (T.Fe) after vacuum secondary refining, the higher the cleanliness, and if it exceeds 12%, the cleanliness is low and satisfactory quality is not achieved. Furthermore, in order to further reduce (T.Fe), it is necessary to remove the ladle slag and increase the slag modifier, increase the manufacturing / working costs, decrease the heat balance, increase the refractory melting loss, Further, since there is a concern about a decrease in production capacity due to an increase in processing time, 6% may be set as the lower limit.
[0015]
As described above, the present invention uses the slag cutting means and the slag modifier in combination with the conventional method shown in FIG. 1 to reduce the flow rate of the slag to the ladle and to make the slag harmless or reformed. Thus, it is possible to obtain a high cleanliness steel with less non-metallic inclusions.
[0016]
As the slag cutting means used in the present invention, for example, a slag dart, a slag stopper, a slag ball, an inert gas, a slag outflow detector, etc. can be used. In this, slag cut by a difference in specific gravity between slag and molten steel is performed. A simple and highly accurate slag dart used is preferred.
[0017]
As the slag modifier, for example, a flux mainly composed of one or more of CaO, Al ₂ O ₃ , and CaF ₂ , Al dross containing metallic Al, etc. can be used, but metallic Al has a strong reducing power. た め , P ₂ O ₅ in the slag is reduced and rephosphorized in the steel, so that the phosphorus content in the steel increases, and Al ₂ O ₃ is likely to be a non-metallic inclusion. In order to obtain high cleanliness, it is desirable to use the former flux.
[0018]
When the slag modifier is added after the [O] concentration in the molten steel is sufficiently lowered after deoxidation as in the present invention, when the slag modifier is a flux, the reaction becomes gentle and slopping is performed. And generation of dust can be suppressed.
[0019]
The invention according to claim 2 is the invention according to claim 1, wherein the slag cutting means is a slag dart. By using slag darts, hit accuracy is high, slag outflow can be made almost constant, and deoxidizer can be adjusted according to steel grade by making slag outflow almost constant. Then it can be fixed.
[0020]
In the invention according to claim 1 or 2 , vacuum secondary refining is performed using an RH vacuum refining apparatus , and after performing final decarburization, alloy adjustment, and deoxidation using the RH vacuum refining apparatus, slag Aratameshitsuzai added to, if possible refluxing after thereof, reflux in the RH vacuum refining apparatus, compared with the gas stirred by the gas blowing device, since no stirring the entire ladle, the interface of the slag and the molten steel It is possible to reduce the amount of slag modifier used in combination with intensive slag cutting and slag cutting in the vicinity. Also, the stirring is gentle and the slag is vigorously stirred like Ar bubbling into the steel. There is little possibility of entraining slag.
Incidentally, the reflux is conventionally performed to promote the floating of Al ₂ O ₃ after deoxidation, and since this reflux can be used, there is no problem of time extension.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Non-desiliconized hot metal desulfurized by pretreatment ([Si]: 0.2 to 0.8%, [Mn]: 0.15 to 0.30%, [P]: 0.080 to 0.100%) Solvent agent such as quick lime, limestone, dolomite, Mn ore, sintered ore and fluorite is added to the main raw material containing a certain amount of scrap as a cold iron source, and blown in an upper bottom blown converter reactor. [C]: 0.05 to 0.10%, [P]: 0.010 to 0.020% desiliconized, decarburized, and dephosphorized. At this time, the slag produced in the reaction vessel was 60 to 120 kg per t of molten steel, and (T.Fe) was 10 to 17%.
[0022]
Next, when the molten steel in the reaction vessel is transferred to the ladle, as shown in FIG. 3, a slag dart 3 made of a steel bar and a refractory is attached to the tip of the boom 4 and inserted from the vessel port 2 of the reaction vessel 1. 1 was put on the slag 5.
The timing at which the slag dart is introduced is based on the amount of molten steel charged into the reaction vessel 1 and the flow rate of the molten steel at the time of steel extraction. Is done.
[0023]
Here, by setting the specific gravity of the slag dart 3 to be between the specific gravity of the molten steel 6 and the specific gravity of the slag 5, the slag dart 3 can be kept between the molten steel 6 and the slag 5. Therefore, the slag can be cut with a high success rate of about 90%, and the use of the slag modifier can be reduced. And before slag darts implementation, slag outflow to ladle 7 was 5 to 26 kg (average 16 kg) per t of molten steel, but slag outflow to ladle 7 was made by slag cutting using slag darts The amount was reduced to 5 to 16 kg (average 10 kg) per t steel. In the figure, 8 indicates a steel hole.
[0024]
The molten steel transferred to the ladle is subsequently subjected to final decarburization, alloy adjustment and deoxidation using an RH vacuum refining device, and then CaO-based flux containing 40-50% of CaF ₂ or Al ₂ O ₃ is used. It added in the 2.7kg vacuum tank per molten steel t, and after the addition, it circulated in the tank for 6 to 12 minutes. (T.Fe) after reflux was reduced to 6 to 12%, and (T.Fe) was reduced by about 30% on average by addition of flux. In addition, by reducing the amount of slag outflow by performing slag cut, the apparent flux intensity increases, and by using slag cut and flux together, (T.Fe) is reduced by about 40% on average (Fig. 4).
[0025]
FIG. 5 shows slag modification by adding flux when the number of USTs (an index indicating the number of inclusions contained in the steel sheet after casting / rolling) in the conventional method in which slag cutting and flux addition are not performed is 100. The number of slags and the number of slag cuts using slag darts and the slag modification by adding flux are shown. As shown in the figure, the number of USTs when slag cut and flux are used together is not limited to the conventional method in which slag cut and flux addition are performed, compared with the case where slag modification is performed by adding flux, Both steel types A and B, especially B, decreased significantly. Steel types A and B are [C]: 0.08 to 0.12%, [Mn]: 1.00 to 1.60%, [Si]: 0.000 to 0.30%, [P]. : ≦ 0.20% of different steel types.
[0026]
【The invention's effect】
The invention according to claims 1 and 2 retains the characteristics of the conventional method shown in FIG. 1, that is, that the load in the pretreatment is small, the heat loss is small, the heat balance is good, and the production capacity is high. By using a slag cut and a slag modifier in combination, a high cleanliness steel with less non-metallic inclusions can be obtained.
[0027]
In addition, by adding a slag modifier after deoxidation in vacuum secondary refining, the generation of slopping and dust generation is suppressed, or non-metallic inclusions in the steel are reduced to obtain a steel with high cleanliness. be able to.
[0028]
In the invention according to claim 1 or 2, vacuum secondary refining is performed using an RH vacuum refining apparatus, and after performing final decarburization, alloy adjustment, and deoxidation using the RH vacuum refining apparatus, to the addition of slag Aratameshitsuzai, if to reflux after the, compared to the gas agitation, inclusion of the slag is reduced, it is possible to obtain a highly clean steel.
Further, the vicinity of the interface between the slag and molten steel can be intensively reformed, and the amount of slag modifier used can be reduced in combination with slag cutting. In addition, since the stirring is gentle, it is possible to eliminate the need to slag intensively into the steel by slag stirring.
[Brief description of the drawings]
FIG. 1 is a view showing a conventional steelmaking process.
FIG. 2 is a diagram showing a steel making process that is frequently used in recent years.
FIG. 3 is a view showing a state where a slag dart is inserted.
FIG. 4 is a graph showing the relationship between the flux amount and (T.Fe).
FIG. 5 is a diagram showing a UST index when a conventional method and slag reforming and darts are used.
[Explanation of symbols]
1 ··· Reaction vessel 2 · · Vessel port 3 · · Slag darts 5 · · Slag 6 · · Molten steel 7 · · Ladle

Claims (2)

Using undesiliconized hot metal desulfurized by pretreatment or a main raw material in which a certain amount of the hot metal and a cold iron source are blended, the molten steel components are [C]: 0.03 to 0 by blowing in a converter reactor. 15% by weight, [P]: After desiliconization, decarburization, and deneighboring to 0.010 to 0.020% by weight, move to ladle and use final vacuum decarburization, alloy adjustment, desorption in vacuum secondary refining equipment. Performing acid [C]: In a method for producing 0.03% by weight or more of steel, after desiliconization, decarburization, and deneighboring in a converter reactor, slag is removed by slag cutting means when transferred to a ladle. and a certain amount of outflow of the slag to the ladle is cut to suppress the outflow of slag into the ladle, and CaF _2, or Al ₂ to ladle deoxidation after and duration of step is completed the vacuum secondary refining step In slag after vacuum refining by adding a slag modifier comprising CaO-based flux containing 40 to 50% by weight of O ₃ (T.Fe) of 6 to 12% by weight, A method for producing a high cleanliness steel.   The method for producing a high cleanliness steel according to claim 1, wherein the slag cutting means is a slag dart.

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