JP2897639B2 - Refining method for extremely low sulfur steel - Google Patents
Refining method for extremely low sulfur steelInfo
- Publication number
- JP2897639B2 JP2897639B2 JP6716594A JP6716594A JP2897639B2 JP 2897639 B2 JP2897639 B2 JP 2897639B2 JP 6716594 A JP6716594 A JP 6716594A JP 6716594 A JP6716594 A JP 6716594A JP 2897639 B2 JP2897639 B2 JP 2897639B2
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- desulfurization
- ladle
- immersion
- steel
- 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
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- Treatment Of Steel In Its Molten State (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、清浄性に優れた極低硫
鋼の精錬方法、特に真空昇熱処理と組合わせた真空脱硫
処理による極低硫鋼の精錬方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining ultra-low sulfur steel having excellent cleanliness, and more particularly to a method for refining ultra-low sulfur steel by vacuum desulfurization treatment combined with vacuum heat treatment.
【０００２】[0002]
【従来の技術】極低硫鋼の溶製には、通常、大気圧下で
取鍋内溶鋼の上に脱硫フラックスを置いた状態でガス攪
拌する方法、あるいはガス攪拌しながら脱硫用粉体を溶
鋼中にインジェクションする方法が行われている。この
場合、大気中の空気との接触による溶鋼の空気酸化ある
いは窒素濃度の上昇を避けるために、取鍋蓋を使用する
こともある。2. Description of the Related Art In general, ultra-low sulfur steel is melted by a method in which gas is stirred under a condition in which a desulfurization flux is placed on molten steel in a ladle under atmospheric pressure, or powder for desulfurization is stirred while gas is stirred. A method of injecting into molten steel has been used. In this case, a ladle lid may be used to avoid air oxidation of the molten steel or an increase in the nitrogen concentration due to contact with air in the atmosphere.
【０００３】これらの脱硫処理によれば、大気圧下でガ
ス攪拌あるいは粉体吹込みを行うため、攪拌力が十分で
なく、したがって脱硫速度をあまり速くすることができ
ない。そのため、溶鋼中の硫黄濃度を例えば10ppm 以下
というように極低硫領域まで下げようとする場合には、
その処理時間が長く、その間に溶鋼温度が低下してしま
う。すると、今度は溶鋼温度が低いためさらに反応速度
が遅くなってしまい、その繰り返しで、結局、目的とす
る程度までの脱硫が達成されないことになる。According to these desulfurization treatments, gas stirring or powder blowing is performed under atmospheric pressure, so that stirring power is not sufficient, so that the desulfurization rate cannot be made too high. Therefore, when trying to reduce the sulfur concentration in the molten steel to an extremely low sulfur region such as 10 ppm or less,
The processing time is long, during which the temperature of the molten steel drops. Then, the reaction rate is further reduced due to the low temperature of the molten steel, and the repetition of the reaction does not eventually achieve the desired degree of desulfurization.
【０００４】このように、上記の従来の脱硫方法では、
脱硫時の温度降下が大きいために、極低硫化とするには
脱硫処理に先立って出鋼温度を高める必要がある。しか
しながら、出鋼温度を余り高めると転炉耐火物の溶損が
大きくなり、転炉炉寿命の低下をきたしてしまう。ま
た、出鋼温度を高めるためには転炉において冷材である
スクラップの添加量を減らしたり、転炉吹錬において吹
き下げ操業を行う必要がある。これらはそれぞれ溶銑率
の上昇や鉄分歩留の低下などにつながり、生産性の低下
やコストアップをもたらしてしまう。そこで、転炉出鋼
温度を過度に高めないためには、取鍋精錬にて溶鋼昇熱
をする必要がある。As described above, in the above-mentioned conventional desulfurization method,
Since the temperature drop during desulfurization is large, it is necessary to raise the tapping temperature prior to the desulfurization treatment to achieve extremely low sulfurization. However, if the tapping temperature is raised too much, the erosion of the converter refractory increases, and the life of the converter furnace is shortened. Further, in order to increase the tapping temperature, it is necessary to reduce the amount of scrap, which is a cold material, in the converter, or to perform a blow-down operation in the converter blowing. These respectively lead to an increase in the hot metal ratio and a decrease in the yield of iron, resulting in a decrease in productivity and an increase in cost. Therefore, it is necessary to raise the temperature of the molten steel by ladle refining in order not to excessively raise the converter tapping temperature.
【０００５】ところで、大気圧下での溶鋼昇熱方法とし
て、取鍋底部から不活性ガスを吹き込んで溶鋼を攪拌し
つつ溶鋼に浸漬した浸漬管内に酸化反応剤を添加しつつ
酸素ガスを吹き付けて溶鋼を加熱する方法が提案されて
いる。また、真空下での溶鋼昇熱法として、真空槽溶鋼
内へ酸素ガスを導入するとともに真空槽底部から不活性
ガスを吹き込んで攪拌する方法が提案されている。As a method for heating molten steel under atmospheric pressure, an inert gas is blown from the bottom of a ladle to stir the molten steel while adding an oxidizing agent to an immersion tube immersed in the molten steel while blowing oxygen gas. A method of heating molten steel has been proposed. As a method for heating molten steel under vacuum, a method has been proposed in which oxygen gas is introduced into molten steel in a vacuum tank and an inert gas is blown from the bottom of the vacuum tank to stir the molten steel.
【０００６】例えば、特開昭63−266017号公報では、
「取鍋内溶鋼に大型浸漬管を浸漬させて、発熱剤と酸素
ガスとを供給することにより溶鋼昇熱させ、この昇熱の
前後に、造滓剤を投入しパウダーインジェクションを行
い取鍋内溶鋼の昇熱精錬を行う方法」が提案されてい
る。For example, in JP-A-63-266017,
"Immerse a large immersion tube in the molten steel in the ladle, heat the molten steel by supplying a heating agent and oxygen gas, and before and after this heating, add a slag-making agent and perform powder injection to perform ladle injection. Method for Performing Heat Refining of Molten Steel "has been proposed.
【０００７】特開平４−253213号公報では、「一本足浸
漬管を取鍋内溶鋼に浸漬し、浸漬管内を真空排気して攪
拌ガスを吹込みつつ酸素ガスを供給することを特徴とす
る取鍋内溶鋼の加熱方法」が提案されている。[0007] Japanese Patent Application Laid-Open No. 4-253213 discloses a method characterized in that a single-leg immersion pipe is immersed in molten steel in a ladle, the inside of the immersion pipe is evacuated, and oxygen gas is supplied while blowing a stirring gas. Method of heating molten steel in ladle "has been proposed.
【０００８】一方、取鍋における脱硫法としては、例え
ば、特開平１−100216号公報が、「取鍋内溶鋼に浸漬管
を浸漬せしめて、該浸漬管内に発熱剤を添加しつつ、上
方より吹酸昇熱するとともに、該浸漬管投影下面域で、
かつ前記吹酸に伴う火点形成域より下方に脱硫剤を吹き
込むことを特徴とする溶鋼の取鍋精錬法」を提案してい
る。これは、溶鋼昇熱と脱硫を同時に行うもので、総処
理時間を短くできるという利点がある。On the other hand, as a desulfurization method using a ladle, for example, Japanese Unexamined Patent Publication No. 1-100216 discloses a method in which a dip tube is immersed in molten steel in a ladle and a heating agent is added to the dip tube from above. While heating with blowing acid, in the lower surface area of the immersion tube projection,
And a ladle refining method for molten steel characterized by blowing a desulfurizing agent below a flash point forming region associated with the blowing acid. This has the advantage that the heating of molten steel and desulfurization are performed simultaneously, and the total processing time can be shortened.
【０００９】特開平１−92314 号公報では、「一本足浸
漬管を取鍋内溶鋼に浸漬し、浸漬管内を真空排気して攪
拌ガスを吹き込みつつ脱硫する方法」が提案されてい
る。また、溶鋼を収容した取鍋全体を真空槽内に取り込
み、真空槽内を排気減圧した状態で、ガス攪拌あるいは
ガス攪拌とともに脱硫剤インジェクションによって極低
硫鋼を精錬する方法も提案されている。JP-A-1-92314 proposes a "method of immersing a single-leg immersion tube in molten steel in a ladle, evacuating the immersion tube and desulfurizing while blowing a stirring gas". A method has also been proposed in which the entire ladle containing molten steel is taken into a vacuum chamber, and the vacuum chamber is evacuated and depressurized, and the ultra-low sulfur steel is refined by gas agitation or gas agitation together with a desulfurizing agent injection.
【００１０】[0010]
【発明が解決しようとする課題】しかし、前述した従来
方法では以下の問題点がある。特開昭63−266017号で
は、その実施例に示されるように大気圧下で酸素ガス供
給による溶鋼昇熱を行うため、低級酸化物が多量に生成
し、脱硫に不利な条件となってしまう。However, the above-mentioned conventional method has the following problems. In Japanese Patent Application Laid-Open No. 63-266017, as shown in the example, since the molten steel is heated by supplying oxygen gas under atmospheric pressure, a large amount of lower oxides is generated, which is a disadvantageous condition for desulfurization. .
【００１１】特開平４−253213号では、真空下での溶鋼
昇熱が開示されており、発熱反応剤の利用効率が極めて
高く低級酸化物の生成が抑制されているが、これは単に
溶鋼の加熱を目的としたもので、清浄性が改善されるこ
とは開示されているが、極低硫鋼を溶製する点に関して
は何の言及もされていない。Japanese Patent Application Laid-Open No. Hei 4-253213 discloses heating of molten steel under vacuum, and the utilization efficiency of the exothermic reactant is extremely high and the formation of lower oxides is suppressed. It is aimed at heating and it is disclosed that the cleanliness is improved, but nothing is mentioned about melting ultra-low sulfur steel.
【００１２】一方、特開平１−100216号では、吹酸昇熱
する火点形成域より下方に脱硫剤を吹き込むため、脱硫
剤が溶鋼中を上昇する過程で一時的なトランジトリーの
脱硫反応が生じるものの、この脱硫剤は溶鋼表面の火点
形成域に到達した後、過酸化状態である火点で復硫して
しまい、総合的な脱硫効率が極めて低下するという極低
硫鋼溶製に対して大きな問題が生じる。On the other hand, in JP-A-1-100216, since a desulfurizing agent is blown below a hot spot forming region in which blowing acid is heated, temporary desulfurization reaction of a transient occurs during a process in which the desulfurizing agent rises in molten steel. However, this desulfurization agent reaches the hot spot formation area on the molten steel surface, and then resulfurizes at the hot flash point, which is a peroxide state, resulting in extremely low overall desulfurization efficiency. A big problem arises.
【００１３】特開平１−92314 号では、大気圧下で同様
な処理をする場合よりも脱硫率が向上するとしている
が、例えば硫黄重量濃度５ppm 以下の極低硫鋼を溶製す
る場合は、このように脱硫効率が高い処理においても、
処理時間が延びてしまい、処理中の温度降下が大きくな
ってしまう。温度補償をする場合に、転炉出鋼温度上昇
や大気圧下での酸素ガス吹込みによる取鍋溶鋼加熱では
すでに述べた問題点が同じように生じてしまう。Japanese Patent Application Laid-Open No. 1-92314 discloses that the desulfurization rate is improved as compared with the case where the same treatment is performed under the atmospheric pressure. For example, when extremely low sulfur steel having a sulfur concentration of 5 ppm or less is melted, Even in such a process with high desulfurization efficiency,
The processing time increases, and the temperature drop during the processing increases. In the case of temperature compensation, the above-mentioned problems occur in the same way in the case of ladle molten steel heating by raising the converter output temperature or injecting oxygen gas under atmospheric pressure.
【００１４】このように、従来技術においても極低硫鋼
の取鍋精錬法についてはいくつか提案されているが、極
低硫化と清浄性とを同時に満足したものはなく、またＳ
≦10ppm かつ清浄度指数1.0 以下の極低硫清浄鋼のより
経済的な精錬法はまだ開発されていない。「清浄度指
数」は、圧延後のサンプルをミクロ検鏡し、大型介在物
の単位面積当たりの個数を指標とした数値である。As described above, some ladle refining methods for ultra-low sulfur steel have been proposed in the prior art, but none of them has simultaneously satisfied ultra-low sulfuration and cleanliness.
More economical refining processes for ultra-low sulfur clean steel with ≤10 ppm and cleanliness index less than 1.0 have not been developed yet. The “cleanness index” is a numerical value obtained by microscopically examining a sample after rolling and using the number of large inclusions per unit area as an index.
【００１５】ここに、本発明の目的は、清浄性に優れた
極低硫鋼の効率的かつ安価な精錬方法を提供する事であ
る。さらに具体的には、本発明の目的は、真空下での脱
硫処理をより効果的に行うことでさらに効率的で安価に
実施できる清浄度指数1.0 以下かつＳ≦10ppm の極低硫
鋼の精錬方法を提供することである。Here, an object of the present invention is to provide an efficient and inexpensive refining method of ultra-low sulfur steel having excellent cleanliness. More specifically, an object of the present invention is to refining ultra-low sulfur steel having a cleanliness index of 1.0 or less and S ≦ 10 ppm, which can be performed more efficiently and inexpensively by performing desulfurization treatment under vacuum more effectively. Is to provide a way.
【００１６】[0016]
【課題を解決するための手段】本発明者らは、かかる課
題を解決すべく、種々検討を重ね、次のような知見を得
て本発明を完成した。 炉経済性を考えると、浸漬管内径と取鍋内径との比Ｄ
1/Ｄ2 を0.5 〜0.8 とすることが有利であること。 そのような前提で、昇温後に脱硫を行うことが有利で
あること。 溶鋼の昇温と脱硫とを組合わせるに際して、大気圧下
で昇熱を行うとむしろ、脱硫効率が低下するとともに鋼
の清浄性が劣化するが、真空下で昇熱した溶鋼に同じく
真空下で脱硫処理を行うと、予想外にもＳ≦10ppm 、特
にＳ≦５ppm を短時間で達成でき、清浄性も確保できる
こと。 脱硫後溶鋼バブリングを継続することでスラグ改質を
図り、復硫を可及的に小とすること。Means for Solving the Problems The present inventors have conducted various studies in order to solve the above problems, and have obtained the following findings to complete the present invention. Considering the furnace economy, the ratio D of the inner diameter of the immersion tube to the inner diameter of the ladle is D
It 1 / D 2 to be from 0.5 to 0.8 is advantageous. Under such a premise, it is advantageous to perform desulfurization after heating. When combining the temperature rise of molten steel with desulfurization, if the temperature is raised under atmospheric pressure, the desulfurization efficiency is reduced and the cleanliness of the steel is deteriorated, but the molten steel heated under vacuum is also subjected to vacuum. When desulfurization treatment is performed, unexpectedly, S ≦ 10 ppm, particularly S ≦ 5 ppm, can be achieved in a short time, and cleanliness can be secured. Continue slag reforming by continuing molten steel bubbling after desulfurization to minimize resulfurization.
【００１７】ここに、本発明の要旨とするところは、取
鍋内に収容した溶鋼に１本足からなる筒状浸漬管を浸漬
し、浸漬管内を真空排気して溶鋼を浸漬管内に吸い上げ
た状態で浸漬管の投影面下の取鍋内下部から不活性ガス
を吹き込む極低硫鋼の精錬方法において、前記浸漬管内
径Ｄ1 と取鍋内径Ｄ2 との比Ｄ1 ／Ｄ2 が0.5 以上0.8
以下の値となるような浸漬管の内径を定め、前記浸漬管
内に吸い上げられた溶鋼にAlを一括あるいは分割もしく
は連続添加するとともに、該溶鋼に酸化性ガスを供給す
ることにより溶鋼を昇熱してから引き続き溶鋼を脱硫精
錬し、その後前記浸漬管内を大気圧に復圧し、浸漬管の
浸漬深さを0.5 ｍ以内にしてガス攪拌処理を行うことを
特徴とする極低硫鋼の精錬方法である。Here, the gist of the present invention is that a one-legged cylindrical immersion pipe is immersed in molten steel accommodated in a ladle, and the interior of the immersion pipe is evacuated to suck the molten steel into the immersion pipe. in the state in refining method very low硫鋼blowing inert gas from ladle bottom of under the projection surface of the dip tube, the ratio D 1 / D 2 of the dip tube inner diameter D 1 and the ladle inner diameter D 2 of 0.5 0.8 or more
Determine the inner diameter of the immersion pipe so as to have the following values, while adding Al to the molten steel sucked into the immersion pipe in a lump or divided or continuous, and by heating the molten steel by supplying an oxidizing gas to the molten steel And then subjecting the molten steel to desulfurizing and refining, and then returning the pressure in the dip tube to atmospheric pressure, performing a gas agitation treatment with the dip depth of the dip tube within 0.5 m, and performing gas agitation treatment. .
【００１８】本発明の好適態様によれば、前記の脱硫精
錬後、浸漬管内を大気圧の状態にまで復圧してから、金
属Ca含有物質を、上吹き、インジェクション、ワイヤー
形状物による添加あるいは溶鋼上部より押込む等の手段
でもって溶鋼に供給するようにしてもよい。According to a preferred embodiment of the present invention, after the desulfurization refining, the pressure in the immersion pipe is restored to atmospheric pressure, and then the metal Ca-containing substance is blown upward, injected, added by a wire-shaped material or molten steel. You may make it supply to molten steel by means, such as pushing from the upper part.
【００１９】また、溶鋼への酸化性ガスおよびAlの供給
は、上吹きランスあるいはインジェクションランスある
いは浸漬管内側に設置した浸漬羽口もしくは上吹き羽口
から行えばよく、特に制限はない。The supply of the oxidizing gas and Al to the molten steel may be carried out from an upper blowing lance, an injection lance, or an immersion tuyere or an upper blowing tuyere provided inside the immersion tube, and there is no particular limitation.
【００２０】同様に、上記脱硫処理時に脱硫用粉体は、
浸漬管内に設置した上吹きランスあるいはインジェクシ
ョンランスあるいは浸漬管内側の浸漬羽口、もしくは上
吹羽口から添加するようにしてもよく、特に制限はな
い。Similarly, during the desulfurization treatment, the powder for desulfurization is
The addition may be made from an upper blowing lance or injection lance installed in the immersion tube, or from the immersion tuyere inside the immersion tube, or from the upper blowing tuyere, and there is no particular limitation.
【００２１】本発明の別の好適態様によれば、溶鋼昇熱
後に浸漬管内を100 Torr以下の条件で真空精錬処理する
ことにより溶鋼中の水素濃度を低減させてもよい。本発
明のさらに別の好適態様によれば、溶鋼脱硫後に浸漬管
内を100 Torr以下の条件で真空精錬処理することにより
溶鋼中の水素濃度を低減させてもよい。本発明のなおさ
らに別の好適態様によれば、溶鋼昇熱前に浸漬管内を大
気圧とし、浸漬管の浸漬深さを0.5 ｍ以内にしてガス攪
拌処理を行ってもよい。According to another preferred embodiment of the present invention, the hydrogen concentration in the molten steel may be reduced by performing a vacuum refining process under a condition of 100 Torr or less in the immersion tube after heating the molten steel. According to still another preferred embodiment of the present invention, the hydrogen concentration in the molten steel may be reduced by subjecting the interior of the immersion pipe to vacuum refining treatment at 100 Torr or less after the desulfurization of the molten steel. According to still another preferred embodiment of the present invention, the gas agitation treatment may be performed before the heat of the molten steel is heated, by setting the inside of the immersion pipe to the atmospheric pressure and setting the immersion depth of the immersion pipe to 0.5 m or less.
【００２２】[0022]
【作用】次に、本発明の操作を添付図面を参照しながら
簡単に説明し、次いで本発明において上述のように各処
理条件を限定した理由をその作用とともに詳述する。添
付図面の図１は、転炉( 図示せず）から取鍋10に出鋼し
た溶鋼12は、通常1620〜1670℃程度であるが、これに浸
漬管14を浸漬する。この浸漬管14には、図示例では、酸
化性ガス上吹きランス16、合金投入口18、および適宜真
空装置( 図示せず) に接続された排気口20が設けられて
いる。Next, the operation of the present invention will be briefly described with reference to the accompanying drawings, and then the reason for limiting the respective processing conditions in the present invention as described above will be described in detail together with its operation. In FIG. 1 of the accompanying drawings, the molten steel 12 that has been tapped from the converter (not shown) to the ladle 10 is usually at about 1620 to 1670 ° C., and the immersion pipe 14 is immersed therein. In the illustrated example, the immersion tube 14 is provided with an oxidizing gas upper blowing lance 16, an alloy charging port 18, and an exhaust port 20 appropriately connected to a vacuum device (not shown).
【００２３】取鍋内の溶鋼12には吹き込みランス22が浸
漬管14の投影面内に浸漬されており、不活性ガスを溶鋼
内に吹き込んでいる。別法として取鍋底部にポーラスプ
ラグ24を設けてもよい。A blowing lance 22 is immersed in the molten steel 12 in the ladle in the projection plane of the immersion pipe 14, and an inert gas is blown into the molten steel. Alternatively, a porous plug 24 may be provided at the bottom of the ladle.
【００２４】まず、本発明は、取鍋10内に収容した溶鋼
12に１本足からなる筒状浸漬管14を浸漬し、この浸漬管
14内を真空排気して、浸漬管の投影面下の取鍋内下部か
ら吹込みランス22またはポーラスプラグ24を経て不活性
ガスを吹き込む方法である。Arガスなどのこの不活性ガ
スの吹き込みは、好ましくは取鍋精錬開始から終了時点
まで継続され、本発明における真空処理はいずれもこの
不活性ガスの吹き込みの下で行われる。First, according to the present invention, molten steel contained in a ladle 10
12 is immersed in a cylindrical immersion tube 14 consisting of one foot.
This is a method in which the inside of 14 is evacuated and an inert gas is blown from the lower part of the ladle below the projection plane of the immersion tube via the blowing lance 22 or the porous plug 24. The blowing of the inert gas such as Ar gas is preferably continued from the start to the end of the ladle refining, and all the vacuum treatments in the present invention are performed under the blowing of the inert gas.
【００２５】その際、浸漬管内径Ｄ1 と取鍋の内径Ｄ2
との比Ｄ1 ／Ｄ2 が0.5 以上0.8 以下の値となるような
浸漬管の内径を定めた理由は、以下の通りである。脱硫
反応が生じる浸漬管内の面積が大きいほど浸漬管内の反
応界面積が増大し、脱硫反応速度は増加する。ただし、
必要以上に浸漬管内径を大きくすると浸漬管の溶損速度
が高まり、耐火物の補修頻度が増加したり浸漬管寿命が
低下するなどの問題も生じる。At this time, the inner diameter D 1 of the immersion tube and the inner diameter D 2 of the ladle
The reason why the inner diameter of the immersion tube is determined so that the ratio D 1 / D 2 to the value of 0.5 to 0.8 is as follows. The larger the area in the immersion tube where the desulfurization reaction occurs, the larger the reaction interface area in the immersion tube and the higher the desulfurization reaction rate. However,
If the inner diameter of the immersion tube is made larger than necessary, the erosion speed of the immersion tube increases, and problems such as an increase in the frequency of repair of refractories and a decrease in the life of the immersion tube also occur.
【００２６】浸漬管内径と取鍋内径との比Ｄ1 ／Ｄ2 と
(A)脱硫速度、 (B)浸漬管補修頻度指数の関係を250 ト
ン取鍋内に収容した溶鋼を用いて調査した。その結果、
この(A)(B)の２つを同時に満足のいくレベルにするため
の最適範囲として浸漬管内径Ｄ1 と取鍋の内径Ｄ2 との
比Ｄ1 ／Ｄ2 が0.5 以上0.8 以下を選定したのである。
好ましくは 0.6〜0.75である。The ratio D 1 / D 2 between the inner diameter of the immersion tube and the inner diameter of the ladle is
The relationship between (A) desulfurization rate and (B) submerged pipe repair frequency index was investigated using molten steel stored in a 250-ton ladle. as a result,
The (A) (B) selecting the ratio D 1 / D 2 of the dip tube inner diameter D 1 and the inner diameter D 2 of the ladle as the optimum range for the same time satisfactory level two is 0.5 to 0.8 of It was done.
Preferably it is 0.6 to 0.75.
【００２７】次に、まず真空下で溶鋼にAlを一括あるい
は分割もしくは連続的に添加し、同時に酸化性ガス、つ
まり酸素ガスまたは酸素含有ガスを、通常は上吹きラン
スあるいはインジェクションあるいは浸漬管内側に設置
した浸漬羽口または上吹き羽口から、溶鋼に供給するこ
とにより溶鋼を昇熱した後、引き続き真空下で溶鋼を脱
硫精錬する。図示例では酸化性ガス上吹き羽口を設けて
いる。Next, first, Al is added to molten steel in a lump, dividedly or continuously under vacuum, and at the same time, an oxidizing gas, that is, an oxygen gas or an oxygen-containing gas is usually added to the inside of a top-blowing lance, injection or immersion tube. After the molten steel is heated by supplying it to the molten steel from the installed immersion tuyere or the upper blowing tuyere, the molten steel is desulfurized and refined under vacuum. In the example shown in the figure, a tuyere is provided above the oxidizing gas.
【００２８】このときのAlおよび酸化性ガスの投入量は
制限されないが、その目的は後続の脱硫時の温度低下を
補償するものであるから、通常は溶鋼温度を1620〜1700
℃程度にまで高めるに必要かつ十分な量だけ投入すれば
よい。なお、Alは好ましくは粉末状で添加される。At this time, the input amounts of Al and the oxidizing gas are not limited. However, since the purpose is to compensate for the temperature drop during the subsequent desulfurization, the molten steel temperature is usually set to 1620 to 1700.
What is necessary is just to throw in the quantity necessary and sufficient to raise to about ° C. Note that Al is preferably added in powder form.
【００２９】本発明では昇熱が真空下で行われるため、
従来の大気圧下での昇熱に比べて低級酸化物(FeO、MnO
等) の生成が抑制されるのである。溶鋼昇熱後に脱硫処
理を行えば、溶鋼昇熱時にAlと酸素との反応によって生
じたアルミナ等である溶鋼中に懸濁する介在物は、脱硫
処理に用いる脱硫剤または脱硫スラグに吸着分離され溶
鋼中から分離除去することが可能である。しかし、先に
脱硫処理を行いその後に溶鋼昇熱をすると、昇熱時に生
じたアルミナ系介在物の一部はスラグに吸着され分離除
去が可能であるが、その大部分は溶鋼中に残留し、鋼の
清浄性を悪化させてしまう。したがって、このように溶
鋼昇熱後に脱硫処理を行うことにしたのである。また、
これにより極低硫鋼溶製時のように脱硫処理時間が非常
に長い場合でも、転炉出鋼温度を高めることなく脱硫処
理をすることが可能となるのである。In the present invention, since the heating is performed under vacuum,
Compared with conventional heating under atmospheric pressure, lower oxides (FeO, MnO
) Is suppressed. If the desulfurization treatment is performed after the heating of the molten steel, inclusions suspended in the molten steel such as alumina generated by the reaction between Al and oxygen during the heating of the molten steel are adsorbed and separated by a desulfurizing agent or desulfurization slag used for the desulfurization treatment. It is possible to separate and remove from the molten steel. However, when the desulfurization treatment is performed first and then the molten steel is heated, some of the alumina-based inclusions generated during the heating are adsorbed by the slag and can be separated and removed, but most of them remain in the molten steel. However, the cleanliness of the steel is deteriorated. Therefore, the desulfurization treatment is performed after the heating of the molten steel. Also,
As a result, even when the desulfurization treatment time is very long, such as in the case of melting extremely low sulfur steel, desulfurization treatment can be performed without increasing the converter tapping temperature.
【００３０】本発明において使用する脱硫剤はCaO2-CaF
系、CaO-Al2O3 系、CaO-Al2O3-CaF2系等、慣用のものを
使用できる。これにより、本発明ではＳ≦10ppm までの
脱硫が可能となり、脱硫終了時の溶鋼温度は1590〜1620
℃程度とすることができる。The desulfurizing agent used in the present invention is CaO 2 -CaF
System, CaO-Al 2 O 3 system, CaO-Al 2 O 3 -CaF 2 system and the like, those commonly available. Thus, in the present invention, desulfurization up to S ≦ 10 ppm becomes possible, and the molten steel temperature at the end of desulfurization is 1590 to 1620.
° C.
【００３１】なお、真空下で溶鋼昇熱するのは、特開平
４−253213号に示される如く、大気圧下よりも昇熱時の
低級酸化物生成が抑制され、鋼の清浄性が確保できると
ともに、その後の脱硫処理が有利となるためである。As described in Japanese Patent Application Laid-Open No. Hei 4-253213, the formation of a lower oxide during heating at a pressure higher than the atmospheric pressure is suppressed, and the cleanliness of the steel can be ensured. In addition, the subsequent desulfurization treatment is advantageous.
【００３２】また、真空下で溶鋼脱硫処理するのは、特
開平１−92314 号に示される如く、特に攪拌動力が増加
する点で大気圧下よりも脱硫効率が向上するためであ
る。脱硫後、浸漬管14の内部を大気圧に復圧し、大気圧
下でしかも浸漬管14の浸漬深さＤ3 を0.5 ｍ以下の状態
で吹込みランス22またはポーラススラグ24からの不活性
ガス吹込みを継続してガス攪拌処理を行う。この理由は
以下の通りである。Further, the desulfurization treatment of molten steel under vacuum is because the desulfurization efficiency is more improved than under atmospheric pressure, particularly in the point that the stirring power is increased, as shown in JP-A-1-92314. After desulfurization, Fukuoshi the interior of the dip tube 14 to the atmospheric pressure, an inert gas blown from the blowing lance 22 or a porous slug 24 in immersion depth D 3 of the following 0.5 m state of the atmospheric pressure addition dip tube 14 Gas stirring process is continued. The reason is as follows.
【００３３】脱硫反応を促進させるためにはスラグメタ
ル界面の酸素ポテンシャルを低減する必要があるが、そ
のためにはスラグ中の低級酸化物を低減する必要があ
る。また、スラグ中の低級酸化物は溶鋼再酸化の原因と
なり、溶鋼の清浄性を低下させるため、これを極力低減
する必要がある。In order to accelerate the desulfurization reaction, it is necessary to reduce the oxygen potential at the interface of the slag metal, but it is necessary to reduce the lower oxides in the slag. In addition, the lower oxides in the slag cause reoxidation of the molten steel, which lowers the cleanliness of the molten steel.
【００３４】浸漬管内を真空下にした状態で脱硫処理を
行う場合、浸漬管内のスラグの攪拌は良好であるが、浸
漬管外側のスラグの攪拌が不十分となる。また、浸漬管
内を大気圧で処理した場合でも、浸漬管の浸漬深さが大
きいとやはり浸漬管外側のスラグの攪拌は不十分とな
る。When the desulfurization treatment is performed in a state where the inside of the immersion tube is kept under vacuum, the slag inside the immersion tube is well stirred, but the slag outside the immersion tube is insufficiently stirred. Further, even when the inside of the immersion tube is treated at atmospheric pressure, if the immersion depth of the immersion tube is large, the agitation of the slag outside the immersion tube also becomes insufficient.
【００３５】そこで、本発明者らは浸漬管内を大気圧と
し、浸漬管の浸漬深さがスラグ中の低級酸化物濃度に及
ぼす影響を調査した。その結果、浸漬深さが0.5 ｍ超の
場合には浸漬管内外のスラグ中の低級酸化物濃度に差が
あり、0.5 ｍ以内にするとその濃度差は著しく小さくな
った。これは不活性ガス吹き込みにより生じた溶鋼の上
昇流が浸漬管内浴表面で浸漬管内壁に向かう水平流とな
り、浸漬管の浸漬深さが0.5 ｍ超ではその溶鋼流が浸漬
管内壁で完全に下降流へと変化するのに対し、浸漬深さ
が0.5 ｍ以内ではその水平溶鋼流が完全な下降流には変
化せず、浸漬管外側での溶鋼流を形成し、したがってス
ラグの攪拌が可能となるためである。Therefore, the present inventors investigated the influence of the immersion depth of the immersion tube on the lower oxide concentration in the slag by setting the inside of the immersion tube to atmospheric pressure. As a result, when the immersion depth was more than 0.5 m, there was a difference in the lower oxide concentration in the slag inside and outside the immersion tube, and when the immersion depth was less than 0.5 m, the difference in the concentration was significantly small. This is because the upward flow of the molten steel caused by the injection of the inert gas becomes a horizontal flow toward the inner wall of the immersion pipe at the bath surface of the immersion pipe, and when the immersion depth of the immersion pipe exceeds 0.5 m, the flow of the molten steel falls completely at the inner wall of the immersion pipe. When the immersion depth is less than 0.5 m, the horizontal molten steel flow does not change to a complete downward flow, but forms a molten steel flow outside the immersion pipe, thus enabling the slag to be stirred. It is because it becomes.
【００３６】本発明の好適態様によれば、浸漬管内を復
圧し、ガス攪拌処理しながら、あるいはガス攪拌処理を
してから、溶鋼に例えばCa−Si、Fe−Ca、Fe−Ca−Ni、
Ca−Alなどの金属Ca含有物質を上吹き、インジェクショ
ン、ワイヤー添加あるいは溶鋼上部より押し込むなどの
手段で供給してもよいが、これは同一装置で真空下およ
び大気圧下で処理を行える本発明の本精錬方法の特徴を
生かし、耐HIC 鋼を溶製するためである。According to a preferred embodiment of the present invention, the pressure in the immersion tube is restored, and the molten steel is subjected to, for example, Ca-Si, Fe-Ca, Fe-Ca-Ni,
The metal Ca-containing substance such as Ca-Al may be supplied by means of upward blowing, injection, addition of wire or pushing from the top of molten steel, but this is the present invention which can be processed under vacuum and atmospheric pressure by the same apparatus. The purpose of this refining method is to melt HIC-resistant steel.
【００３７】これにより、介在物形態制御用の金属Ca添
加を必要とする耐ＨＩＣ鋼においても単なるＲＨ脱ガス
処理のようにCa歩留を低下させることなく、つまり蒸発
ロスを少なくし、単一プロセスで処理を完了させること
が可能となるのである。As a result, even in a HIC-resistant steel which requires the addition of metallic Ca for controlling the form of inclusions, the yield of Ca is not reduced as in the case of simple RH degassing, that is, the evaporation loss is reduced, and The process can complete the process.
【００３８】真空脱硫処理時に脱硫剤粉体を浸漬管内に
設置した上吹きランスあるいはインジェクションランス
あるいは浸漬管内側の浸漬羽口もしくは上吹き羽口から
添加するのは、脱硫処理時の脱硫速度、脱硫率を向上さ
せるためである。During the vacuum desulfurization treatment, the desulfurizing agent powder is added from the upper blowing lance or the injection lance installed in the immersion tube or the immersion tuyere or the upper wing tuyere inside the immersion tube because of the desulfurization rate during the desulfurization treatment, the desulfurization This is to improve the rate.
【００３９】脱硫処理時に真空度100 Torr以下で処理す
るのは、真空下でガスを吹き込むため、その浸漬管内の
圧力が高くなるほど (真空度が悪化するほど) 吹き込み
ガスの攪拌力が弱くなり、また平衡水素濃度が上昇する
ため、脱水素速度が著しく低下し、脱水素に不利となる
ためである。したがって、本発明では真空度100 Torr以
下で脱水素処理をするのである。When the desulfurization treatment is performed at a degree of vacuum of 100 Torr or less, the gas is blown under vacuum, so that the higher the pressure in the immersion tube (the worse the degree of vacuum), the weaker the agitation power of the blown gas. In addition, since the equilibrium hydrogen concentration increases, the dehydrogenation rate significantly decreases, which is disadvantageous for dehydrogenation. Therefore, in the present invention, the dehydrogenation treatment is performed at a degree of vacuum of 100 Torr or less.
【００４０】脱硫処理後に真空度100 Torr以下で処理す
るのは、真空下での脱硫処理時に同時に生じる脱水素反
応では十分な溶鋼中水素濃度を得ることができない場合
があり、脱硫後に引続き真空下脱水素処理する必要があ
るからである。真空度を100Torr以下としたのは上記と
同様の理由である。The treatment at a degree of vacuum of 100 Torr or less after the desulfurization treatment may not be able to obtain a sufficient concentration of hydrogen in the molten steel due to the dehydrogenation reaction that occurs simultaneously during the desulfurization treatment under vacuum. This is because it is necessary to perform a dehydrogenation treatment. The reason why the degree of vacuum is set to 100 Torr or less is the same as above.
【００４１】本発明の変更例では、昇熱処理前に浸漬管
内を大気圧でかつ浸漬管の浸漬深さを0.5 ｍ以内にした
状態でガス攪拌処理を行ってもよいが、これは本発明の
処理前のスラグ中の低級酸化物が非常に高い場合は、そ
の後の処理だけでは完全に浸漬管外側取鍋スラグ改質が
十分にできないことがあり、その対策のためである。次
に、実施例によって本発明の具体的作用効果について説
明する。In a modified example of the present invention, the gas agitation treatment may be performed before the heat treatment by heating the inside of the immersion tube at atmospheric pressure and the immersion depth of the immersion tube within 0.5 m. If the lower oxide in the slag before the treatment is very high, the subsequent treatment alone may not be enough to completely modify the ladder outside ladle slag, and this is for the purpose. Next, specific working effects of the present invention will be described with reference to examples.
【００４２】[0042]
(実施例１)本例では、図１に示す装置を用い、250 ton
取鍋に収容した1620℃の溶鋼中に１本足浸漬管を浸漬
し、浸漬管内を100Torr 以下に真空排気した状態で取鍋
の底吹きポーラスプラグからアルゴンガスを3 Nm3/min
吹き込んで、溶鋼のガス攪拌を行った。このようにして
ガス攪拌を行っている期間中に、真空下で1670℃にまで
溶鋼昇熱処理を行い、引続き100 Torr以下の真空下で脱
硫処理を行った。(Example 1) In this example, the device shown in FIG.
The single-footed immersion tube is immersed in molten steel at 1620 ° C stored in a ladle, and 3 Nm 3 / min of argon gas is blown from the bottom blown porous plug of the ladle while the interior of the immersion tube is evacuated to 100 Torr or less.
The gas was blown to stir the molten steel. While the gas was being stirred in this manner, the molten steel was heat-treated to 1670 ° C. under vacuum, and then desulfurized under vacuum of 100 Torr or less.
【００４３】本例における処理前の溶鋼中硫黄濃度は20
〜50ppm 、処理前溶鋼中水素濃度は５〜15ppm であっ
た。脱硫後、浸漬管の浸漬深さを0.5 ｍ以内にしてガス
攪拌を行った。本例では溶鋼の昇熱は、Al粉末を溶鋼に
合金投入口より添加するとともに、酸化性ガス上吹きラ
ンスからは酸化性ガスとして酸素ガスを溶鋼に供給し
た。In this example, the sulfur concentration in the molten steel before the treatment was 20
The hydrogen concentration in the molten steel before the treatment was 5 to 15 ppm. After desulfurization, gas agitation was performed with the immersion tube having an immersion depth of 0.5 m or less. In this example, the heat of the molten steel was increased by adding Al powder to the molten steel from the alloy inlet, and supplying oxygen gas as oxidizing gas to the molten steel from the oxidizing gas upper blowing lance.
【００４４】溶鋼昇熱前に昇熱量に応じてAlを160 〜80
0 kg添加し、酸素ガス流量は50Nm3/min で各チャージで
酸素ガスを２分から10分供給した結果、昇熱速度は各チ
ャージとも約8 ℃／min であった。Before heating the molten steel, Al is added in an amount of 160 to 80 in accordance with the heat amount.
0 kg was added, the oxygen gas flow rate was 50 Nm 3 / min, and oxygen gas was supplied at each charge for 2 to 10 minutes. As a result, the heating rate was about 8 ° C./min for each charge.
【００４５】なお、取鍋内径は4 ｍで一定とし、浸漬管
内径を1.5 、1.8 、2 、2.5 、3 、3.5 ｍの各条件で低
水素極低硫鋼を溶製した。また、脱硫フラックスとして
CaO 85重量％、CaF215重量％から成る脱硫剤10kg／Ｔを
昇熱後に浸漬管の合金投入口から添加した。結果は表１
にまとめて示す。The inner diameter of the ladle was kept constant at 4 m, and the low hydrogen extremely low sulfur steel was melted under the conditions of 1.5, 1.8, 2, 2.5, 3, and 3.5 m. Also, as desulfurization flux
10 kg / T of a desulfurizing agent composed of 85% by weight of CaO and 15% by weight of CaF 2 was added from the alloy inlet of the dip tube after heating. Table 1 shows the results
Are shown together.
【００４６】表１に示すように、100 Torr以下の真空下
脱硫時間は13〜15分であり、Ｄ1 ／Ｄ2 が0.5 以上が脱
硫条件として望ましいことがわかる。また、その真空下
脱硫処理時の脱水素挙動を表２に示すが、Ｄ1 ／Ｄ2 が
0.5以上が脱水素条件として望ましいことがわかる。As shown in Table 1, the desulfurization time under vacuum of 100 Torr or less is 13 to 15 minutes, and it is found that desulfurization conditions of D 1 / D 2 of 0.5 or more are desirable. Although showing a dehydrogenation behavior during the vacuum desulfurization in Table 2, the D 1 / D 2
It turns out that 0.5 or more is desirable as a dehydrogenation condition.
【００４７】浸漬管寿命および浸漬管補修頻度をＤ1 ／
Ｄ2 ＝0.375 の場合を基準にして指数化した値を表３に
表示した。表３からＤ1 ／Ｄ2 が0.8 超で浸漬管の寿命
および補修頻度が著しく増加することがわかる。The life of the immersion tube and the frequency of repair of the immersion tube are represented by D 1 /
Table 3 shows values indexed based on the case of D 2 = 0.375. From Table 3, it can be seen that when D 1 / D 2 exceeds 0.8, the life and repair frequency of the immersion tube are significantly increased.
【００４８】(実施例２)実施例１の脱硫終了後のガス攪
拌の後にCa−Siを溶鋼１トン当たり0.8kg 投入し、Ca処
理を行った。その結果、得られた鋼材は次のようなＮＡ
ＣＥ条件を満足した。(Example 2) After gas stirring after completion of desulfurization in Example 1, 0.8 kg of Ca-Si was charged per 1 ton of molten steel, and Ca treatment was performed. As a result, the obtained steel material has the following NA
The CE condition was satisfied.
【００４９】ＮＡＣＥ条件: 溶液：５％NaCl＋0.8 ％CH3COOH 温度：24±2.8 ℃ ｐＨ：max 4.5 時間：96時間 H2S 濃度： H2S飽和 〃 流量： 100〜200 cc/min。 NACE conditions : Solution: 5% NaCl + 0.8% CH 3 COOH Temperature: 24 ± 2.8 ° C. pH: max 4.5 hours: 96 hours H 2 S concentration: H 2 S saturation 流量 Flow rate: 100-200 cc / min.
【００５０】(比較例１)本例では表１中No.4とほぼ同じ
Ｄ1 ／Ｄ2 ＝0.625 の条件で実施例１を繰り返したが、
昇熱と脱硫操作を同時に行った。結果を表４にまとめて
示す。Comparative Example 1 In this example, Example 1 was repeated under the condition that D 1 / D 2 = 0.625, which is almost the same as No. 4 in Table 1.
Heating and desulfurization operations were performed simultaneously. The results are summarized in Table 4.
【００５１】(比較例２)本例では表１中No.4とほぼ同じ
Ｄ1 ／Ｄ2 ＝0.625 の条件で実施例１を繰り返したが、
昇熱を大気圧下で行い、次いで減圧して100 Torr以下の
高真空下で脱硫を行った。結果を同じく表４にまとめて
示す。参考までに真空昇温だけ行った例についてもその
結果を示す。(Comparative Example 2) In this example, Example 1 was repeated under the condition of D 1 / D 2 = 0.625, almost the same as No. 4 in Table 1.
The heating was performed under atmospheric pressure, and then the pressure was reduced to perform desulfurization under a high vacuum of 100 Torr or less. The results are also summarized in Table 4. For reference, the results are also shown for an example in which only the temperature was raised in vacuum.
【００５２】(比較例３)本例でも表１中No.4とほぼ同じ
Ｄ1 ／Ｄ2 ＝0.625 の条件で実施例１を繰り返したが、
脱硫後の大気圧下ガス攪拌を省略した。結果を表４にま
とめて示す。(Comparative Example 3) In this example, Example 1 was repeated under the condition of D 1 / D 2 = 0.625, almost the same as No. 4 in Table 1.
Gas stirring under atmospheric pressure after desulfurization was omitted. The results are summarized in Table 4.
【００５３】(比較例４)本例でも表１中No.4とほぼ同じ
Ｄ1 ／Ｄ2 ＝0.625 の条件で実施例１を繰り返したが、
昇熱に先立って脱硫を行った。結果は表４にまとめて示
す。(Comparative Example 4) In this example, Example 1 was repeated under the condition of D 1 / D 2 = 0.625 which is almost the same as that of No. 4 in Table 1.
Desulfurization was performed prior to heating. The results are summarized in Table 4.
【００５４】[0054]
【表１】 [Table 1]
【００５５】[0055]
【表２】 [Table 2]
【００５６】[0056]
【表３】 [Table 3]
【００５７】[0057]
【表４】 [Table 4]
【００５８】[0058]
【発明の効果】以上述べた如く、本発明による極低硫鋼
の精錬方法を用いることにより、真空下での脱硫速度を
高位に安定させ、取鍋スラグ全体の低級酸化物濃度を低
下せしめることにより極低硫鋼で得られる硫黄濃度レベ
ルを低減し、それと同時に耐火物の損耗等をも抑制する
ことができた。また、真空処理時の真空度を制御するこ
とにより同時に低水素鋼も精錬できる。As described above, by using the method for refining ultra-low sulfur steel according to the present invention, the desulfurization rate under vacuum is stabilized at a high level, and the lower oxide concentration in the entire ladle slag is reduced. As a result, the sulfur concentration level obtained from the extremely low sulfur steel was reduced, and at the same time, the wear of the refractory was suppressed. Further, by controlling the degree of vacuum during the vacuum processing, low hydrogen steel can be refined at the same time.
【図１】本発明を実施する取鍋と浸漬管との設置状況の
概略説明図である。BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic explanatory view showing a setting state of a ladle and a dip tube for implementing the present invention.
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.6，ＤＢ名) C21C 7/00 C21C 7/10 ──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. 6 , DB name) C21C 7/00 C21C 7/10
Claims (2)
筒状浸漬管を浸漬し、浸漬管内を真空排気して溶鋼を浸
漬管内に吸い上げた状態で浸漬管の投影面下の取鍋内下
部から不活性ガスを吹き込み、ガス攪拌処理を行いなが
ら行う極低硫鋼の精錬方法において、前記浸漬管内径Ｄ
1 と取鍋内径Ｄ2 との比Ｄ1 ／Ｄ2 が0.5 以上0.8 以下
の値となるような浸漬管の内径を定め、前記浸漬管内に
吸い上げられた溶鋼にAlを一括あるいは分割もしくは連
続添加するとともに、該溶鋼に酸化性ガスを供給するこ
とにより溶鋼を昇熱し、次いで溶鋼を脱硫精錬し、その
後前記浸漬管内を大気圧に復圧し、浸漬管の浸漬深さを
0.5 ｍ以内にして取鍋内下部からの前記不活性ガスの吹
き込みによるガス攪拌処理を継続することを特徴とする
極低硫鋼の精錬方法。A immersion pipe having a single foot is immersed in molten steel accommodated in a ladle, and the interior of the immersion pipe is evacuated to a vacuum and the molten steel is sucked into the immersion pipe. In the refining method of ultra-low sulfur steel, which is performed by blowing an inert gas from a lower part of the pot and performing a gas stirring process,
The inner diameter of the immersion pipe is determined so that the ratio D 1 / D 2 of 1 to the ladle inner diameter D 2 becomes a value of 0.5 or more and 0.8 or less, and Al is added to the molten steel sucked into the immersion pipe all at once or divided or continuously added. At the same time, the molten steel is heated by supplying an oxidizing gas to the molten steel, then the molten steel is desulfurized and refined, and then the inside of the dip tube is restored to the atmospheric pressure, and the dip depth of the dip tube is reduced.
A method for refining ultra-low sulfur steel, wherein the gas agitation treatment is continued by blowing the inert gas from the lower part of the ladle within 0.5 m.
大気圧の状態に復圧してから、金属Ca含有物質を溶鋼に
供給することを特徴とする極低硫鋼の精錬方法。2. A method for refining ultra-low sulfur steel, wherein after the desulfurization refining according to claim 1, the pressure inside the immersion pipe is restored to the atmospheric pressure, and then the metal Ca-containing substance is supplied to the molten steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6716594A JP2897639B2 (en) | 1994-04-05 | 1994-04-05 | Refining method for extremely low sulfur steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6716594A JP2897639B2 (en) | 1994-04-05 | 1994-04-05 | Refining method for extremely low sulfur steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07278639A JPH07278639A (en) | 1995-10-24 |
| JP2897639B2 true JP2897639B2 (en) | 1999-05-31 |
Family
ID=13337020
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6716594A Expired - Lifetime JP2897639B2 (en) | 1994-04-05 | 1994-04-05 | Refining method for extremely low sulfur steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2897639B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100214927B1 (en) * | 1995-08-01 | 1999-08-02 | 아사무라 타카싯 | Vacuum refining method of molten metal |
| JP2000073118A (en) * | 1998-08-26 | 2000-03-07 | Nippon Steel Corp | Simple ladle refining method |
-
1994
- 1994-04-05 JP JP6716594A patent/JP2897639B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07278639A (en) | 1995-10-24 |
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