JPH0585609B2 - - Google Patents
Info
- Publication number
- JPH0585609B2 JPH0585609B2 JP26349884A JP26349884A JPH0585609B2 JP H0585609 B2 JPH0585609 B2 JP H0585609B2 JP 26349884 A JP26349884 A JP 26349884A JP 26349884 A JP26349884 A JP 26349884A JP H0585609 B2 JPH0585609 B2 JP H0585609B2
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- ladle
- slag
- refining
- cao
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- 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
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は転炉の如き精錬炉において精錬の完了
した取鍋内の溶鋼を更に精錬し、高純度鋼を得る
ための取鍋精錬法に関する。Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a ladle refining method for further refining molten steel in a ladle that has been refined in a refining furnace such as a converter to obtain high-purity steel. .
（従来の技術）
近年、鉄鋼の品質も用途の多様化により益々高
級化してきた。例えば深絞り缶用では介在物によ
るクラツクの発生による疵落ちのないことが必要
でありこの点溶鋼の高清浄度化が要求されてい
る。又極低温帯で使用されるパイプや厚板につい
ても硫黄などの不純元素は極力低くしなければな
らずこの様な厳しい品質要求に対応すべく精錬過
程も複雑になつてきた。(Prior Art) In recent years, the quality of steel has become increasingly high quality due to diversification of its uses. For example, for deep-drawn cans, it is necessary that there be no defects caused by cracks caused by inclusions, and high cleanliness of the spot molten steel is required. In addition, impurity elements such as sulfur must be kept as low as possible in pipes and plates used in cryogenic temperatures, and the refining process has become more complex in order to meet these strict quality requirements.
この結果、精錬炉から出鋼された溶鋼を取鍋内
で精錬する二次精錬法も多岐に亘つている。即ち
真空機能を有し、溶鋼内脱ガスを行うもの、昇温
機能を有し精錬炉の負荷を軽減させるもの、介在
物浮上や合金添加成分調整を行うもの等がある。
また、本発明と同一目的の極低硫鋼を溶製する場
合の方法についても、例えば特開昭53−86613号
公報に示される如く、溶銑にCaOとCaC2の混合
物を添加して脱硫し、該脱硫溶銑を精錬炉（以下
単に転炉と称する）で溶製する方法、特開昭56−
14325号公報に示される如く取鍋内溶鋼中にCaO
を主成分とする脱硫剤を浸漬ランスで吹込む方法
（以下単にインゼクシヨン脱硫と称する）が提案
されている。 As a result, there is a wide variety of secondary refining methods in which molten steel discharged from a refining furnace is refined in a ladle. Specifically, there are those that have a vacuum function and perform degassing in molten steel, those that have a temperature raising function that reduce the load on the refining furnace, and those that float inclusions and adjust alloy additive components.
In addition, regarding the method for producing ultra-low sulfur steel for the same purpose as the present invention, for example, as shown in JP-A-53-86613, a mixture of CaO and CaC 2 is added to hot metal to desulfurize it. , A method for melting the desulfurized hot metal in a refining furnace (hereinafter simply referred to as a converter), JP-A-1988-
As shown in Publication No. 14325, CaO is present in the molten steel in the ladle.
A method has been proposed in which a desulfurization agent containing as a main component is injected using an immersion lance (hereinafter simply referred to as injection desulfurization).
このような方法によつて達成される工業的硫黄
レベルは溶銑脱硫後で20ppm、転炉溶製後で
40ppmとなる。このように転炉溶製後で溶銑より
も上昇する理由は、溶銑を転炉に装入する際に、
溶銑脱硫スラグが同時に転炉に装入されたり、硫
黄の高い屑鉄を使用したり又は転炉に当該チヤー
ジ以前に付着したスラグが当該チヤージ溶製中に
溶出する等種々の要因が重なつておこるものであ
る。 Industrial sulfur levels achieved by such methods are 20 ppm after hot metal desulfurization and 20 ppm after converter smelting.
It becomes 40ppm. The reason why the temperature rises higher than the hot metal after melting in the converter is that when charging the hot metal into the converter,
This can occur due to a combination of factors, such as hot metal desulfurization slag being charged into the converter at the same time, scrap iron with high sulfur content being used, or slag that was attached to the converter before the charge leaching out during the charge melting process. It is something.
転炉から取鍋に出鋼された硫黄含有量40ppmの
溶鋼は、インゼクシヨン脱硫精錬法で硫黄含有量
は10〜20ppmまで下げられる。しかしながら該イ
ンゼクシヨン脱硫精錬法は以下の３つの重大欠点
をを有している。 Molten steel with a sulfur content of 40 ppm is tapped from the converter into a ladle, and the sulfur content is reduced to 10 to 20 ppm using the injection desulfurization refining method. However, the injection desulfurization refining method has the following three major drawbacks.
すなわち第１点は設備費が300T／ch処理で４
億円という莫大な投資が必要であり、しかも著し
い作業費の上昇を伴うこと、第２点は、精錬中の
溶鋼温度降下が40〜50℃と極めて大きいこと、第
３点は、溶鋼中に吹込むためにCaOあるいはCa
脱硫剤を粉状にしなければならず原材料費が高価
で、かつ吸湿性が良く取扱いに十分注意が必要な
ことである。 In other words, the first point is that the equipment cost is 4 for processing 300T/ch.
The second point is that the molten steel temperature drop during refining is extremely large at 40 to 50 degrees Celsius, and the third point is that the molten steel CaO or Ca to infuse
The desulfurization agent must be in powder form, resulting in high raw material costs, and is highly hygroscopic, requiring careful handling.
（発明が解決しようとする問題点）
本発明は、前述の如き従来法の欠点である溶鋼
の脱硫に際して多大の設備費と大幅な作業費の上
昇を招くことなく、精錬中の溶鋼温度の低下を防
止して、容易に極低硫鋼を溶製できる溶鋼の精錬
法を提供することにある。(Problems to be Solved by the Invention) The present invention is capable of reducing the temperature of molten steel during refining without causing a large increase in equipment costs and work costs when desulfurizing molten steel, which is the drawback of the conventional method as described above. It is an object of the present invention to provide a method for refining molten steel that can easily melt ultra-low sulfur steel while preventing the above.
（問題点を解決するための手段）
以下本発明による取鍋精錬法について図に示す
一実施例に基づいて述べる。(Means for Solving the Problems) The ladle refining method according to the present invention will be described below based on an embodiment shown in the drawings.
本発明の取鍋精錬法は、第１図に示す如く、取
鍋１内溶鋼２の上面にキヤツプ型浸漬管３（以下
単に浸漬管と称する）を設置して実施される。し
かして該浸漬管３は副材投入管６と排煙吸引管７
から構成されている。又浸漬管３とは独立して昇
降する上吹酸素ランス４が図示の如く設備されて
おり例えば純酸素ガスあるいは酸素含有の酸化性
ガス（以下単に酸素と称する）500〜5000Nm3／
Ｈの可変吹酸が可能でである。取鍋１の底部には
ポーラスプラグ５が埋設されておりAr又はN2等
の不活性ガスを吹込み溶鋼２を撹拌出来る様にな
つている。 The ladle refining method of the present invention is carried out by installing a cap-type dip tube 3 (hereinafter simply referred to as dip tube) on the upper surface of the molten steel 2 in the ladle 1, as shown in FIG. Therefore, the immersion pipe 3 has an auxiliary material input pipe 6 and a smoke exhaust suction pipe 7.
It consists of In addition, a top-blown oxygen lance 4 that moves up and down independently of the immersion tube 3 is installed as shown in the figure, and is equipped with, for example, pure oxygen gas or oxygen-containing oxidizing gas (hereinafter simply referred to as oxygen) 500 to 5000 Nm 3 /
Variable blowing of H is possible. A porous plug 5 is embedded in the bottom of the ladle 1 so that an inert gas such as Ar or N2 can be blown into the ladle 1 to stir the molten steel 2.
浸漬管３を前記の如く溶鋼２上面に設置するに
はまず精錬に先だつて取鍋１の底部のポーラスプ
ラグ５から200〜400／分のArガスを吹込み溶
鋼２の上面に浮遊したスラグ８を排除した後に、
上部浸漬管３を下降浸漬させる。これは転炉スラ
グ中には高濃度の硫黄が含有されており、その後
の精錬作業に悪影響があるからである。この段階
で浸漬管３の内部の溶鋼１は取鍋１の底部から上
昇して来るArガスによつて激しく撹拌されてい
る。次いでAlを添加し、同時に吹ランス４から
吹酸することにより浸漬管３内部の溶鋼表面火点
は超高温となりAlは2Al＋3/2O2→Al2O3となる。
このような高温火点域に更にCaOを添加すること
により従来よりも高融点のCaO−Al2O3の形成が
極めて急速に起り得ることになる。 To install the dip tube 3 on the top surface of the molten steel 2 as described above, first, prior to refining, Ar gas is blown at 200 to 400/min from the porous plug 5 at the bottom of the ladle 1 to remove the slag 8 floating on the top surface of the molten steel 2. After eliminating the
The upper dipping tube 3 is dipped downward. This is because converter slag contains a high concentration of sulfur, which adversely affects subsequent refining operations. At this stage, the molten steel 1 inside the immersion tube 3 is being vigorously stirred by the Ar gas rising from the bottom of the ladle 1. Next, by adding Al and simultaneously blowing acid from the blowing lance 4, the molten steel surface fire point inside the immersion tube 3 becomes extremely high temperature, and the Al becomes 2Al+3/2O 2 →Al 2 O 3 .
By further adding CaO to such a high temperature boiling point region, the formation of CaO-Al 2 O 3 having a higher melting point than before can occur extremely rapidly.
本発明の骨子は溶鋼表面に上吹ランスから吹酸
するとともにAlを添加することにより、Alが燃
焼して2Al＋3/2O2→Al2O3となり、その際形成さ
れる超高温火点域によつて第２図に示す如く、脱
硫能はあるが、従来の精錬方式では滓化が困難で
あるかもしくは滓化しても粘性が高く溶鋼の脱硫
に不利となる組成のスラグを迅速に滓化せしめ、
しかも高流動性を保持して吹酸あるいは底吹ガス
撹拌による効果的な溶鋼２の脱硫に適したスラグ
８ａを形成することにある。 The gist of the present invention is to blow acid onto the surface of molten steel from a top-blowing lance and add Al, which causes the Al to burn and become 2Al + 3/2O 2 → Al 2 O 3 . Therefore, as shown in Figure 2, it is possible to quickly slag slag that has desulfurization ability but is difficult to sludge using conventional refining methods, or has a composition that is too viscous and disadvantageous for desulfurization of molten steel. Seshime,
Moreover, the purpose is to form a slag 8a that maintains high fluidity and is suitable for effectively desulfurizing the molten steel 2 by stirring with blown acid or bottom blown gas.
すなわち本発明者らは上吹酸素によりAlが燃
焼して2Al＋3/2O2→Al2O3となりかつ超高温が形
成されることに注目して種々のCaO／Al2O3比率
を造滓テストした結果、極めてスムーズに脱硫用
のスラグ８ａを形成し得るとともに、下記知見を
も得た。即ち造滓されたスラグ８ａの脱硫能は当
然CaOの比率が高い程良いが、この際にスラグ８
ａの融点も高くなつていき、ついには固化する様
になる。本発明では上吹酸素によるAlの高温燃
焼が特徴であり、そのためスラグ８ａの温度も高
温になつているのでAlの燃焼中は高いCaO比率
まで容易に溶融することが可能であるが、上吹酸
素の吹付けを停止し且つ、Alの燃焼も停止する
とスラグの温度は低下して溶鋼２の温度と同じに
なる。この際CaO比率が高いと固化することとな
る。しかしスラグ８ａの脱硫能や溶鋼中の介在物
の浮上捕捉にはスラグ８ａが溶融していることが
必要であり種々のテストの結果によるとスラグ中
のAl2O3／CaOが0.33以上であることが必要であ
り、浸漬管３内に添加するAlと生石灰（CaO）
の添加重量比は、Al／CaO≧0.15となる。また一
方では、スラグ８ａの脱硫能からAl／CaOの比
を高くすると該スラグ８ａの脱硫能の低下を招く
ことからAl／CaO≦0.26とすることが必要であ
る。このことから浸漬管３ａの限定域内でのラン
ス４による吹酸とAl酸化反応による高温域の利
点を活用して高い脱硫率を達成するには前記の
Al／CaOは0.15〜0.26、好ましくは0.18〜0.24に
するとより安定した精錬を行ない得る。 In other words, the present inventors conducted slag-making tests with various CaO/Al 2 O 3 ratios, focusing on the fact that top-blown oxygen burns Al to form 2Al + 3/2O 2 → Al 2 O 3 and an extremely high temperature is formed. As a result, the desulfurization slag 8a could be formed extremely smoothly, and the following findings were also obtained. In other words, the higher the CaO ratio, the better the desulfurization ability of the slag 8a, but in this case, the desulfurization ability of the slag 8a is better.
The melting point of a also increases, and it finally begins to solidify. The present invention is characterized by high-temperature combustion of Al by top-blown oxygen, and as a result, the temperature of the slag 8a is also high, so it is possible to easily melt Al to a high CaO ratio during combustion. When the blowing of oxygen is stopped and the combustion of Al is also stopped, the temperature of the slag decreases and becomes the same as the temperature of the molten steel 2. At this time, if the CaO ratio is high, solidification will occur. However, for the desulfurization ability of the slag 8a and for the floating capture of inclusions in molten steel, the slag 8a must be molten, and according to the results of various tests, the Al 2 O 3 /CaO in the slag is 0.33 or more. It is necessary to add Al and quicklime (CaO) into the immersion tube 3.
The addition weight ratio of Al/CaO≧0.15. On the other hand, since increasing the Al/CaO ratio leads to a decrease in the desulfurization ability of the slag 8a, it is necessary to set Al/CaO≦0.26. Therefore, in order to achieve a high desulfurization rate by taking advantage of the high temperature range caused by the acid blowing by the lance 4 and the Al oxidation reaction within the limited area of the immersion tube 3a, the above-mentioned method is necessary.
More stable refining can be achieved by setting Al/CaO to 0.15 to 0.26, preferably 0.18 to 0.24.
なお、本発明により生成するスラグは、CaO−
Al2O3−SiO2系の組成であるが、この他にMgO，
FeO，MnO等を含んだものでも同様の効果があ
り、又溶鋼中の介在物の捕捉のためにはAl，
CaOの他にCaF2を添加して更に粘性の低いスラ
グを造ることも効果がある。 Note that the slag produced by the present invention is CaO-
The composition is Al 2 O 3 −SiO 2 system, but in addition to this, MgO,
Products containing FeO, MnO, etc. have a similar effect, and Al,
It is also effective to add CaF 2 in addition to CaO to create a slag with even lower viscosity.
（実施例）
次に、本発明による取鍋内溶鋼の精錬法の一実
施例について述べる。(Example) Next, an example of the method for refining molten steel in a ladle according to the present invention will be described.
第１図は本発明の溶鋼精錬法を実施する装置の
断面図を示す。300T／ch取鍋１内の溶鋼２内に
浸漬させた浸漬管３の上方からランス４によつて
酸素を吹付けるが、先づ浸漬管３の下方の溶鋼表
面上のスラグを除去するため、取鍋底部に装着さ
れたポーラスプラグ５よりAr又はN2等の不活性
ガスを1.5〜2.5Nl／min・ｔで吹込み、露出した
溶鋼面に浸漬管３を下降浸漬させる。この際の浸
漬深さは浸漬管３内の溶鋼２が速やかに置換さ
れ、かつ下方流を形成することが好ましく100〜
200mmとした。 FIG. 1 shows a sectional view of an apparatus for implementing the molten steel refining method of the present invention. Oxygen is sprayed from above the immersion tube 3 immersed in the molten steel 2 in the 300T/ch ladle 1 using a lance 4. First, in order to remove the slag on the surface of the molten steel below the immersion tube 3, An inert gas such as Ar or N 2 is blown at 1.5 to 2.5 Nl/min·t through a porous plug 5 attached to the bottom of the ladle, and the immersion tube 3 is lowered into the exposed molten steel surface. At this time, the immersion depth is preferably 100 to 100 mm so that the molten steel 2 in the immersion tube 3 is quickly replaced and a downward flow is formed.
It was set to 200mm.
さらに、ポーラスプラグ５から不活性ガスを吹
込みつつ、取鍋１内の溶鋼２内に浸漬した浸漬管
内に70Kg／minの速度で投入管６からAl粒を添加
しその後速やかに上吹ランスから酸素を2500N
m3／Ｈで吹付け30秒後にCaOを400Kg／minの速
度で投入管６から添加してAl／CaOを0.20〜0.23
として５分間酸素を吹付けたところ溶鋼温度は25
℃上昇した。更にランス４からの酸素吹込を停止
した後、５分間ポーラスプラグ５から不活性ガス
を吹込み溶鋼２の撹拌を継続したところ溶鋼中の
〔Ｓ〕は33ppmから18ppmに低下し極めて良質の
鋼を製造することが出来た。 Furthermore, while blowing inert gas from the porous plug 5, Al grains are added from the injection pipe 6 at a rate of 70 kg/min into the immersion pipe immersed in the molten steel 2 in the ladle 1, and then immediately from the top blowing lance. Oxygen 2500N
After 30 seconds of spraying at m 3 /H, CaO was added from the input pipe 6 at a rate of 400 kg/min to give Al/CaO of 0.20 to 0.23.
When oxygen was sprayed for 5 minutes, the temperature of the molten steel was 25
℃ rose. Furthermore, after stopping the oxygen injection from the lance 4, inert gas was blown from the porous plug 5 for 5 minutes and stirring of the molten steel 2 was continued, and the [S] in the molten steel decreased from 33ppm to 18ppm, resulting in extremely high quality steel. I was able to manufacture it.
またこのように精錬した溶鋼の介在物を調査し
たところ12.5μm以下の介在物量が14個／cm2から
１個／cm2以下に減少しており十分な清浄度の鋼が
得られた。 Further, when the inclusions in the molten steel refined in this manner were investigated, the amount of inclusions of 12.5 μm or less was reduced from 14 inclusions/cm 2 to 1 inclusion/cm 2 or less, and steel with sufficient cleanliness was obtained.
（発明の効果）
以上述べた如く、本発明によれば多大の設備費
と作業費を必要とせずに、溶鋼を昇温しつつ、従
来滓化不良の領域組成の脱硫剤を用いて容易に脱
硫精錬を行なつて高清浄度の極低硫鋼を溶製する
ことができる。(Effects of the Invention) As described above, according to the present invention, it is possible to easily increase the temperature of molten steel and use a desulfurization agent having a composition in a region where conventional slag formation is difficult, without requiring a large amount of equipment and work costs. Highly clean, ultra-low sulfur steel can be produced by desulfurization refining.
第１図は本発明を実施する装置の一例を示す説
明図、第２図は本発明による溶鋼精錬の際のスラ
グ組成範囲の一実施例を示す三元状態図である。
１……取鍋、２……溶鋼、３……浸漬管、４…
…ランス、５……ポーラスプラグ、８ａ……スラ
グ。
FIG. 1 is an explanatory diagram showing an example of an apparatus for implementing the present invention, and FIG. 2 is a ternary phase diagram showing an example of the slag composition range during molten steel refining according to the present invention. 1... Ladle, 2... Molten steel, 3... Immersion tube, 4...
...Lance, 5...Porous plug, 8a...Slag.
Claims (1)
つつ撹拌するとともに、該取鍋内に浸漬管を挿入
し該浸漬管内の溶鋼表面に酸化性ガスを吹付ける
取鍋内溶鋼の精錬法において、該浸漬管内に添加
するAlとCaOの添加重量比をAl／CaO＝0.15〜
0.26とすることを特徴とする取鍋内溶鋼の精錬
法。1 A method for refining molten steel in a ladle, in which molten steel in a ladle is stirred while blowing inert gas from the bottom, and an immersion pipe is inserted into the ladle, and oxidizing gas is sprayed onto the surface of the molten steel in the immersion pipe. In this case, the weight ratio of Al and CaO added into the immersion tube is set to Al/CaO=0.15~
A method for refining molten steel in a ladle, characterized in that the molten steel is 0.26.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26349884A JPS61143510A (en) | 1984-12-13 | 1984-12-13 | Refining method of molten steel in ladle |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26349884A JPS61143510A (en) | 1984-12-13 | 1984-12-13 | Refining method of molten steel in ladle |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61143510A JPS61143510A (en) | 1986-07-01 |
| JPH0585609B2 true JPH0585609B2 (en) | 1993-12-08 |
Family
ID=17390357
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26349884A Granted JPS61143510A (en) | 1984-12-13 | 1984-12-13 | Refining method of molten steel in ladle |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61143510A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63216917A (en) * | 1987-03-05 | 1988-09-09 | Nippon Steel Corp | Method for refining molten steel in molten metal vessel |
| JP2617948B2 (en) * | 1987-10-12 | 1997-06-11 | 新日本製鐵株式会社 | Ladle refining method for molten steel |
| JP4345769B2 (en) * | 2006-04-07 | 2009-10-14 | 住友金属工業株式会社 | Melting method of ultra low sulfur high clean steel |
| CN101535508A (en) * | 2006-12-05 | 2009-09-16 | 住友金属工业株式会社 | Process for producing ingot of ultralow-sulfur high-cleanliness steel |
| JP5082417B2 (en) * | 2006-12-08 | 2012-11-28 | 住友金属工業株式会社 | Method of melting ultra low sulfur low nitrogen high cleanliness steel |
-
1984
- 1984-12-13 JP JP26349884A patent/JPS61143510A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61143510A (en) | 1986-07-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPH0585609B2 (en) | ||
| KR20200118191A (en) | How to make a lecture | |
| WO2022259806A1 (en) | Molten steel denitrification method and steel production method | |
| US3897244A (en) | Method for refining iron-base metal | |
| JPH0510406B2 (en) | ||
| JPH0245686B2 (en) | ||
| JPH09235611A (en) | Method for producing ultra-low-purity pure iron with high cleanliness | |
| JP2988305B2 (en) | Desulfurization method of molten steel | |
| JP3214730B2 (en) | Refining method of high purity steel using reflux type vacuum degasser | |
| JPH06228626A (en) | Method for reforming slag as pretreatment of desulfurization | |
| JP5061545B2 (en) | Hot metal dephosphorization method | |
| JPH0953109A (en) | Heated refining method for molten steel | |
| JP2001152234A (en) | Carbon adding method to molten steel in ladle | |
| JP3660040B2 (en) | Method of desulfurization of molten steel using RH vacuum degassing device | |
| KR100749022B1 (en) | Method for desulfurization of hot metal | |
| JP6273947B2 (en) | Desulfurization treatment method for molten steel | |
| JP2006283164A (en) | Desulfurization treatment method for chromium-containing hot metal | |
| JP4360239B2 (en) | Method for desulfurization of molten steel in vacuum degassing equipment | |
| JP4759832B2 (en) | Hot phosphorus dephosphorization method | |
| JP2897639B2 (en) | Refining method for extremely low sulfur steel | |
| JPH01100216A (en) | Ladle refining method for molten steel | |
| RU1794094C (en) | Method of producing steel in hearth furnace | |
| JPH08260025A (en) | Ultra low sulfur ultra low oxygen steel manufacturing method | |
| JP3371559B2 (en) | Heat refining method of molten steel | |
| WO2026004825A1 (en) | Method for manufacturing slab for non-oriented electrical steel sheet |