JPH11279630A - Method for smelting highly cleaned steel - Google Patents
Method for smelting highly cleaned steelInfo
- Publication number
- JPH11279630A JPH11279630A JP7972398A JP7972398A JPH11279630A JP H11279630 A JPH11279630 A JP H11279630A JP 7972398 A JP7972398 A JP 7972398A JP 7972398 A JP7972398 A JP 7972398A JP H11279630 A JPH11279630 A JP H11279630A
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- steel
- molten steel
- ton
- stirring
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、高清浄度鋼の溶製
方法に係わり、詳しくは、ＶＯＤ等の底吹きガス撹拌機
能を有する減圧製錬装置を用いた所謂二次精錬の末期
に、脱炭済みの溶鋼を脱酸剤で脱酸するにあたり、溶鋼
中へのスラグの巻き込み量を低減し、非金属介在物の少
ない鋼を溶製する技術に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for smelting high cleanliness steel, and more particularly, to the so-called secondary refining using a vacuum smelting apparatus having a function of stirring a bottom-blown gas such as VOD. The present invention relates to a technique for reducing the amount of slag entrained in molten steel and for producing steel with less nonmetallic inclusions when deoxidizing molten steel that has been decarburized with a deoxidizing agent.
【０００２】[0002]
【従来の技術】溶鋼中の酸素は、溶鋼に溶解した所謂フ
リー酸素、脱酸剤と反応して生成した脱酸生成物系介在
物及び精錬で生じたスラグの巻き込みによって生じたス
ラグ系介在物のいずれかの形態で存在する。そして、こ
の溶鋼中の酸素は、該溶鋼を鋳造、圧延して製造する製
品鋼材の品質に悪影響を及ぼすので、通常は、転炉精錬
の後に二次精錬を行って、できるだけ低くするようにし
ている。なお、この二次精錬に用いられる装置の一つ
に、図３に示すようなＶＯＤ（Vacuum Oxygen Decarbur
ization ノ 略) 方式の減圧精錬装置７がある。それは、
溶鋼１を収容した取鍋２の周囲を密封容器３で囲み、該
容器３内を減圧できるようになっている。また、その容
器３内には、ランス４を介して酸素ガス５を溶鋼１に吹
き付け、脱炭を行う機能と、取鍋２の底から不活性ガス
６を吹込み、該底吹きガス６で溶鋼１を撹拌する機能と
を備えている。2. Description of the Related Art Oxygen in molten steel is composed of so-called free oxygen dissolved in molten steel, deoxidized product-based inclusions produced by reacting with a deoxidizing agent, and slag-based inclusions produced by entrainment of slag produced by refining. In any form. And since the oxygen in this molten steel has a bad influence on the quality of the product steel material produced by casting and rolling the molten steel, usually, secondary refining is performed after the converter refining, so as to be as low as possible. I have. One of the devices used for this secondary refining is a VOD (Vacuum Oxygen Decarbur) as shown in FIG.
There is a decompression smelting apparatus 7 of the type. that is,
The periphery of the ladle 2 containing the molten steel 1 is surrounded by a sealed container 3 so that the pressure inside the container 3 can be reduced. In addition, the oxygen gas 5 is blown into the molten steel 1 through the lance 4 into the container 3 to perform decarburization, and the inert gas 6 is blown from the bottom of the ladle 2 and the bottom blown gas 6 A function of stirring the molten steel 1.
【０００３】従来、かかるＶＯＤ精錬装置を用いた溶鋼
中酸素の低減方法としては、溶鋼表面上に形成するスラ
グの塩基度（ＣａＯ／ＳｉＯ2 ）を高くし、そのスラグ
とメタル間の反応で決まる溶鋼中の平衡酸素濃度が低い
ことを利用して、所謂フリー酸素を低減する方法と共
に、底吹きガス撹拌を強化して、脱酸生成物を浮上分離
する方法が採用されていた。Conventionally, as a method of reducing oxygen in molten steel using such a VOD refining apparatus, the basicity (CaO / SiO 2 ) of slag formed on the surface of molten steel is increased, and it is determined by a reaction between the slag and metal. Utilizing the fact that the equilibrium oxygen concentration in molten steel is low, a method of reducing so-called free oxygen and a method of flotation separation of deoxidized products by strengthening bottom-blowing gas stirring have been adopted.
【０００４】しかしながら、このような減圧精錬処理で
は、溶鋼１の表面上に溶融したスラグ８が存在するの
で、底吹きガス６で溶鋼１を過度に強撹拌すると、該ス
ラグ８が必ず溶鋼１中に巻き込まれる。その際、巻き込
まれたスラグ８の粒子が大きい時は、溶鋼１中で再度浮
上し、容易に除去される。ところが、数１０μｍ以下の
大きさの粒子は、浮上し難く除去できないことが多いの
で、溶鋼１中の酸素濃度を増加し、製品鋼材に欠陥をも
たらす原因となる。それでも、底吹きガス６による撹拌
は、スラグ−メタル反応によるスラグ８の還元促進やフ
リー酸素低下には欠かすことができないので、減圧精錬
では、溶鋼１へのスラグ８の巻き込みを如何に改善する
かが問題となっていた。However, in such a vacuum refining process, the molten slag 8 is present on the surface of the molten steel 1. Therefore, if the molten steel 1 is excessively agitated with the bottom blown gas 6, the slag 8 is necessarily in the molten steel 1. Get caught in At this time, when the particles of the slag 8 entrained are large, the slag 8 floats again in the molten steel 1 and is easily removed. However, particles having a size of several tens of μm or less are difficult to float and cannot be removed in many cases, so that the oxygen concentration in the molten steel 1 increases, which causes defects in the product steel material. Nevertheless, stirring with the bottom blown gas 6 is indispensable for promoting the reduction of the slag 8 and reducing free oxygen by the slag-metal reaction. Was a problem.
【０００５】[0005]
【発明が解決しようとする課題】本発明は、かかる状況
に鑑み、ＶＯＤのような減圧精錬装置を用い、溶鋼中の
脱酸生成物及びスラグ巻き込みに起因した非金属介在物
を従来より低減できる高清浄度鋼の溶製方法を提供する
ことを目的としている。SUMMARY OF THE INVENTION In view of the above circumstances, the present invention can reduce deoxidation products in molten steel and nonmetallic inclusions caused by slag entrainment in molten steel by using a vacuum refining apparatus such as VOD. It is an object of the present invention to provide a method for melting high cleanliness steel.
【０００６】[0006]
【課題を解決するための手段】発明者は、上記目的を達
成するため、ＶＯＤ減圧精錬装置を用い、溶鋼のフリー
酸素濃度が低く、且つ脱酸生成物やスラグの巻き込み量
の少ない鋼の製造をいかにすれば良いか研究を重ねた。
そして、該二次精錬のうちの末期、つまり金属Ａｌ，Ｆ
ｅ−Ｓｉ等での脱酸還元処理時における、溶鋼の撹拌方
法に着眼し、本発明を完成させた。Means for Solving the Problems In order to achieve the above object, the present inventor uses a VOD vacuum refining apparatus to produce steel having a low free oxygen concentration in molten steel and a small amount of deoxidized products and slag involved. I researched how to do it.
And the last stage of the secondary refining, that is, metal Al, F
The present invention was completed by focusing on the method of stirring molten steel during deoxidation reduction treatment with e-Si or the like.
【０００７】すなわち、本発明は、底吹きガス撹拌機能
を有する減圧製錬装置内で脱炭した溶鋼に、引き続き脱
酸剤を投入して脱酸処理する溶鋼の精錬方法において、
前記脱酸剤の投入から少なくとも５分間は、前記溶鋼を
下記（１）式で定義される撹拌動力密度（ε）が３００
ワット／トン−ｓｔｅｅｌ以上となる条件で撹拌し、そ
の後は、前記撹拌動力密度が２５０ワット／トン−ｓｔ
ｅｅｌ以下となる条件での撹拌を少なくとも５分間行う
ことを特徴とする高清浄度鋼の溶製方法である。That is, the present invention relates to a method for refining molten steel in which a deoxidizing agent is continuously added to molten steel decarburized in a vacuum smelting apparatus having a bottom-blown gas stirring function, followed by a deoxidizing treatment.
For at least 5 minutes after the introduction of the deoxidizing agent, the molten steel has a stirring power density (ε) defined by the following formula (1) of 300.
Stirring is performed under the condition of watt / ton-steel or more, and thereafter, the stirring power density is 250 watt / ton-st
This is a method for melting high cleanliness steel, wherein stirring under a condition of not more than eel is performed for at least 5 minutes.
【０００８】 ε＝０．０２８５・Ｑ・Ｔ／Ｗ・ｌｏｇ（１＋Ｚ／１４８×７６０／Ｐ） …（１） ε：撹拌動力密度（ワット／トン−ｓｔｅｅｌ） Ｑ：底吹きガス流量（ノルマル・リットル／分） Ｔ：鋼浴温度（Ｋ°） Ｗ：鋼浴重量（トン） Ｚ：浴深さ（ｃｍ） Ｐ：真空度（ｔｏｒｒ）また、本発明は、前記減圧製錬
装置をＶＯＤとすることを特徴とする高清浄度鋼の溶製
方法である。Ε = 0.0285 · Q · T / W · log (1 + Z / 148 × 760 / P) (1) ε: stirring power density (watt / ton-steel) Q: bottom blown gas flow rate (normal (Liter / minute) T: Steel bath temperature (K °) W: Steel bath weight (ton) Z: Bath depth (cm) P: Degree of vacuum (torr) Also, in the present invention, the vacuum smelting apparatus is defined as VOD. This is a method for smelting high cleanliness steel.
【０００９】本発明では、脱酸生成物ができ、スラグに
十分に吸収される間は強撹拌し、脱酸生成物が十分浮上
し、スラグが均一化した後は弱撹拌するようにしたの
で、溶鋼への脱酸生成物やスラグの巻き込みが抑制でき
るようになる。その結果、従来より清浄な溶鋼が得られ
るようになる。In the present invention, vigorous stirring is performed while the deoxidized product is formed and sufficiently absorbed by the slag, and after the deoxidized product sufficiently floats and the slag is homogenized, weak stirring is performed. As a result, entrapment of deoxidized products and slag in the molten steel can be suppressed. As a result, molten steel that is cleaner than before can be obtained.
【００１０】[0010]
【発明の実施の形態】以下、図面を参照し、本発明の実
施の形態を説明する。まず、転炉等の製鋼炉（図示せ
ず）で粗脱炭された溶鋼１を取鍋２に出鋼し、該取鍋２
を、底吹きガス６による撹拌機能を有する減圧精錬装置
７に移行する。なお、ここでは、該減圧精錬装置７とし
て、図３に示したＶＯＤを採用している。Embodiments of the present invention will be described below with reference to the drawings. First, molten steel 1 roughly decarburized in a steelmaking furnace (not shown) such as a converter is tapped into ladle 2 and
Is transferred to a vacuum refining device 7 having a stirring function with the bottom blown gas 6. Here, the VOD shown in FIG. 3 is adopted as the vacuum refining device 7.
【００１１】このＶＯＤでは、減圧精錬の第一段階とし
て、密封容器３内を減圧すると共に、ランス４を介して
酸素ガス５を溶鋼に吹き付け、目標炭素濃度まで脱炭が
行われる。この酸素吹錬脱炭に引き続き、上吹酸素を停
止して、溶鋼中の溶存酸素による所謂「Ｃ−Ｏ脱炭」を
行うこともある。そして、脱炭が終了してから、第二段
階として、溶鋼１中に金属Ａｌ，ＳｉあるいはＦｅ−Ｓ
ｉ等の脱酸剤を投入し、脱酸処理が実施される。本発明
は、この脱酸処理中の溶鋼１の撹拌を、従来とは異なる
方法で行い、得られる溶鋼１の酸素濃度を従来より低減
し、非金属介在物の溶鋼への混入を抑制するものであ
る。In this VOD, as a first stage of vacuum refining, the pressure in the sealed vessel 3 is reduced, and oxygen gas 5 is blown to molten steel through a lance 4 to decarbonize to a target carbon concentration. Subsequent to the oxygen blowing decarburization, the so-called "CO decarburization" may be performed by stopping the upper blowing oxygen and dissolving oxygen in the molten steel. Then, after the decarburization is completed, as a second stage, metal Al, Si or Fe-S
A deoxidizing agent such as i is charged, and a deoxidizing treatment is performed. The present invention stirs the molten steel 1 during this deoxidation treatment by a method different from the conventional method, thereby reducing the oxygen concentration of the obtained molten steel 1 as compared with the conventional method, and suppressing mixing of nonmetallic inclusions into the molten steel. It is.
【００１２】具体的には、脱酸剤の投入から少なくとも
５分間を強く撹拌し、その後少なくとも５分間を弱く撹
拌して、スラグ８の巻き込みを抑制する。その一例を、
時間と撹拌動力密度との関係として図１に示す。図１で
は、撹拌動力密度を一度だけ階段状に変更しているが、
本発明は、この変更方法はこの例に限るものではない。
つまり、複数回の変更を行っても良いし、また該動力密
度を連続的に低下させても良い。More specifically, the stirring of the slag 8 is suppressed by vigorously stirring for at least 5 minutes after the addition of the deoxidizing agent, and then weakly for at least 5 minutes. One example is
FIG. 1 shows the relationship between the time and the stirring power density. In FIG. 1, the stirring power density is changed stepwise only once,
In the present invention, this changing method is not limited to this example.
That is, the change may be performed a plurality of times, or the power density may be continuously reduced.
【００１３】脱酸剤の投入から少なくとも５分間を、撹
拌動力密度３００ワット／トン−ｓｔｅｅｌ以上とする
理由は、次の通りである。脱酸剤投入直後には、非金属
介在物の浮上分離もさることながら、まず、脱酸剤によ
ってスラグ自体を十分に且つ均一に還元することが肝要
である。この段階でスラグの還元が不十分であると、た
とえ介在物を浮上分離させても、スラグ中の酸化クロ
ム、酸化鉄、マンガン酸化物などの低級酸化物が解離し
て溶鋼中にフリー酸素を供給し続けることになり、精錬
の終了後に溶鋼を再酸化し、新たに非金属酸化物が生成
する原因となる。この反応は、すべて溶鋼の撹拌の強さ
に依存しており、とりわけ３００ワット／トン−ｓｔｅ
ｅｌ以上という強撹拌条件で、その効果が顕著となる。
この強撹拌処理を少なくとも５分間行うのは、脱酸剤と
スラグの反応を十分に行わせ、スラグを均一化しておく
ためである。なお、撹拌動力密度の上限は、特に設けな
いが、あまりに撹拌が激しいと、溶鋼容器から外に溶鋼
が噴出したり、容器の蓋に地金が付着したりして操業を
阻害するので、５００ワット／トン−ｓｔｅｅｌ程度に
とどめておくのが望ましい。また、処理時間の上限は、
特に定めないが、あまり長時間になると、スラグによる
溶鋼容器の内張り耐火物の溶損が発生するので、３０分
程度、より好ましくは２０分程度にとどめるのが好まし
い。The reason why the stirring power density is set to 300 watts / ton-steel or more for at least 5 minutes after the addition of the deoxidizing agent is as follows. Immediately after the addition of the deoxidizing agent, it is important to sufficiently and uniformly reduce the slag itself with the deoxidizing agent, as well as the floating separation of nonmetallic inclusions. If the slag is not sufficiently reduced at this stage, even if the inclusions are floated and separated, lower oxides such as chromium oxide, iron oxide, and manganese oxide in the slag are dissociated to generate free oxygen in the molten steel. The supply will be continued, and the molten steel will be re-oxidized after the refining is completed, which causes a new nonmetal oxide to be generated. This reaction all depends on the strength of the agitation of the molten steel, especially 300 watts / ton-ste.
The effect is remarkable under strong stirring conditions of el or more.
The reason why the strong stirring treatment is performed for at least 5 minutes is to sufficiently react the deoxidizing agent and the slag to make the slag uniform. The upper limit of the stirring power density is not particularly set. However, if the stirring is too severe, molten steel may squirt out of the molten steel container or metal may adhere to the lid of the container, thereby hindering the operation. It is desirable to keep it on the order of watts / ton-steel. The upper limit of the processing time is
Although not particularly defined, if the time is too long, the slag may cause erosion of the refractory lining of the molten steel container. Therefore, it is preferable that the time is about 30 minutes, more preferably about 20 minutes.
【００１４】一方、上記の処理後に、撹拌動力密度で２
５０ワット／トン−ｓｔｅｅｌ以下の撹拌処理を少なく
とも５分間以上行うのは、次の理由による。この時期に
は、もはやスラグの還元や均一化は重要でなく、溶鋼中
の非金属介在物及び上記強撹拌の際に溶鋼中に巻き込ま
れたスラグの浮上をはかり、溶鋼を清浄化することが大
切である。そして、鋼浴面上のスラグが新たに溶鋼中に
巻き込まれることは、極力避けなければならない。撹拌
動力密度が２５０ワット／トン−ｓｔｅｅｌを超える
と、上記スラグ巻き込みの速度が、スラグや介在物の浮
上速度より勝ってしまうので、この時期の撹拌動力密度
は、２５０ワット／トン−ｓｔｅｅｌを上限とする。撹
拌動力密度の下限は、特に設けるものではないが、撹拌
によるスラグや非金属介在物の浮上分離が所定時間内に
十分なされることが必要であるから、１０ワット／トン
−ｓｔｅｅｌ以上で行うのが良い。On the other hand, after the above treatment, the stirring power density is 2
The reason why the stirring treatment of 50 watts / ton-steel or less is performed for at least 5 minutes or more is as follows. At this time, it is no longer important to reduce or homogenize the slag, and it is necessary to clean up the molten steel by measuring the nonmetallic inclusions in the molten steel and the slag entrained in the molten steel during the above-mentioned strong stirring. It is important. And it must be avoided as much as possible that slag on the steel bath surface is newly caught in the molten steel. If the stirring power density exceeds 250 watts / ton-steel, the speed of the slag entrainment exceeds the floating speed of the slag and inclusions, so the stirring power density at this time has an upper limit of 250 watts / ton-steel. And Although the lower limit of the stirring power density is not particularly set, since it is necessary that the floating separation of the slag and the nonmetallic inclusions by the stirring is sufficient within a predetermined time, it is performed at 10 watt / ton-steel or more. Is good.
【００１５】この相対的に弱撹拌の時期は、少なくとも
５分間行うが、これは、介在物や巻き込みスラグを十分
に浮上分離させるために最低限５分間の処理が必要だか
らである。この処理時間も特に上限を定めるものではな
いが、前述の処理と同様に、あまり長時間になると、ス
ラグによる溶鋼容器の内張り耐火物の溶損が発生するの
で、３０分程度、より好ましくは２０分程度にとどめる
のが望ましい。なお、前記（１）式の撹拌動力密度は、
真空下でのガス撹拌エネルギーを表わすものとして公知
であるので、説明を省略する。[0015] The relatively weak stirring is performed for at least 5 minutes, because at least 5 minutes of treatment is required to sufficiently float and separate inclusions and entrained slag. There is no particular upper limit for this treatment time, but, similarly to the above-mentioned treatment, if the treatment time is too long, the slag may cause erosion of the refractory lining of the molten steel container. It is desirable to keep it to about a minute. In addition, the stirring power density of the formula (1) is:
Since it is well known that the gas stirring energy under vacuum is represented, the description is omitted.
【００１６】次に、発明者は、かかる本発明の実施効果
をＳＵＳ３０４のステンレス鋼で確認した。当該鋼種
は、Ｃａ処理を実施しないため、溶鋼中にＣａ成分は元
来存在しないが、スラグ中にはＣａＯが含まれているこ
とを利用した。つまり、溶鋼中へのスラグの巻き込み量
を、溶鋼中のＴｏｔａｌ．Ｃａの濃度で比較したのであ
る。Next, the inventor has confirmed the effect of the present invention with SUS304 stainless steel. Since the steel type does not carry out the Ca treatment, the Ca component was originally not present in the molten steel, but the fact that CaO was contained in the slag was used. In other words, the amount of slag involved in the molten steel is determined by the total amount of slag in the molten steel. The comparison was based on the Ca concentration.
【００１７】その結果を図２に示す。図２に示す従来法
とは、脱酸・還元処理期間中を３００ワット／トン・ｓ
ｔｅｅｌと一定で強撹拌した場合であり、本発明法と
は、十数分の強撹拌後に２５０ワット／トン・ｓｔｅｅ
ｌ以下にした場合である。図２より、本発明法の適用
で、従来法の強撹拌で一定に処理する場合よりも還元・
脱酸処理終了後の溶鋼中のＴ．Ｃａ濃度が低下する。こ
の鋼種の精錬条件では、溶鋼中のＴｏｔａｌ Ｃａ源と
しては、スラグ中のＣａＯしかありえない。従って、こ
の結果から、スラグ８の溶鋼１への巻き込みが減ること
が明らかである。FIG. 2 shows the result. Compared to the conventional method shown in FIG.
The method of the present invention refers to 250 watts / ton.
1 or less. From FIG. 2, it can be seen that the application of the method of the present invention is more effective in reducing and reducing the amount of water than the conventional method in which the treatment is carried out uniformly with strong stirring.
T. in molten steel after completion of deoxidation treatment Ca concentration decreases. Under the refining conditions of this steel type, the only source of Total Ca in molten steel is CaO in slag. Therefore, it is clear from this result that the slag 8 is less likely to be entrained in the molten steel 1.
【００１８】[0018]
【実施例】（実施例１）転炉で粗脱炭を行った溶鋼１６
０トンを取鍋２に出鋼し、その後ＶＯＤ真空精錬装置で
酸素吹錬を行い、Ｃ：０．０５５重量％、Ｃｒ：１８．
２重量％の溶鋼１を得た。しかる後、該溶鋼１にＦｅ−
Ｓｉ合金を９５０ｋｇ添加し、装置内の真空度を３ｔｏ
ｒｒに減圧し、底吹きガス６としてＡｒガスを５００ノ
ルマル・リットル／分で吹込み、所謂脱酸・還元処理を
開始した。従って、開始当初の撹拌動力密度は、４２０
ワット／トン−ｓｔｅｅｌである。EXAMPLES (Example 1) Molten steel 16 subjected to rough decarburization in a converter
0 tons were tapped into ladle 2, and then oxygen was blown with a VOD vacuum refining apparatus, C: 0.055% by weight, Cr: 18.
2% by weight of molten steel 1 was obtained. Then, Fe-
950 kg of Si alloy was added, and the degree of vacuum in the device was 3 to
The pressure was reduced to rr, and Ar gas was blown as the bottom blow gas 6 at 500 normal liters / minute to start a so-called deoxidation / reduction treatment. Therefore, the stirring power density at the beginning is 420
Watts / ton-steel.
【００１９】この状態を１５分間続けた後、装置内の真
空度を４０ｔｏｒｒにまで下げ、Ａｒガスを１００Ｎリ
ットル／分に変更して、撹拌動力密度を４７ワット／ト
ン・ｓｔｅｅｌとして７分間の弱撹拌を行った。その結
果、Ｃ：０．０５２重量％、Ｃｒ：１８．３重量％、Ｓ
ｉ：０．３５重量％、Ｏ：４５ｐｐｍ、およびＴ．Ｃ
ａ：１ｐｐｍのスラグ巻き込みの少ないステンレス溶鋼
を得ることができた。また、この溶鋼で得た鋳片を切断
し、断面を顕微鏡観察で調査したが、存在する非金属介
在物の面積率は、極めて少なかった。After maintaining this state for 15 minutes, the degree of vacuum in the apparatus is reduced to 40 torr, the Ar gas is changed to 100 Nl / min, and the stirring power density is set to 47 watts / ton. Stirring was performed. As a result, C: 0.052% by weight, Cr: 18.3% by weight, S
i: 0.35% by weight; O: 45 ppm; C
a: It was possible to obtain a molten stainless steel with a slag entrainment of 1 ppm. Further, the slab obtained from the molten steel was cut, and the cross section was examined by microscopic observation. As a result, the area ratio of the existing nonmetallic inclusions was extremely small.
【００２０】（実施例２）実施例１と同様に、転炉で粗
脱炭を行った溶鋼１６０トンを取鍋２に出鋼し、その後
ＶＯＤ真空精錬装置で酸素吹錬を行い、Ｃ：０．０６重
量％、Ｃｒ：１８．１重量％の溶鋼を得た。しかる後、
該溶鋼１にＦｅ−Ｓｉ合金１０００ｋｇを添加し、該装
置内の真空度を３ｔｏｒｒに減圧し、底吹きガス６のＡ
ｒガスを５００ノルマル・リットル／分で吹込み、撹拌
動力密度を４２０ワット／トン・ｓｔｅｅｌの脱酸・還
元処理を開始した。(Example 2) In the same manner as in Example 1, 160 tons of molten steel which had been roughly decarburized in a converter were tapped into a ladle 2 and then subjected to oxygen blowing with a VOD vacuum refining apparatus. 0.06% by weight and Cr: 18.1% by weight of molten steel were obtained. After a while
1000 kg of an Fe-Si alloy was added to the molten steel 1, the degree of vacuum in the apparatus was reduced to 3 torr, and
r gas was blown in at 500 normal liters / minute, and a deoxidizing / reducing treatment with a stirring power density of 420 watts / ton steel was started.
【００２１】この状態を１５分間継続した後、装置内の
真空度を３ｔｏｒｒとしたまま、Ａｒガスを６０ノルマ
ル・リットル／分に変更し、撹拌動力密度を５０ワット
／トン・ｓｔｅｅｌで８分間の弱撹拌を行った。その結
果、Ｃ：０．０５６重量％、Ｃｒ：１８．２重量％、Ｓ
ｉ：０．３８重量％、Ｏ：４７ｐｐｍ、およびＴ．Ｃ
ａ：１ｐｐｍのスラグ巻き込みの少ないステンレス溶鋼
を得ることができた。また、この溶鋼で得た鋳片を切断
し、断面を顕微鏡観察で調査したが、非金属介在物の面
積率は、実施例と同程度であり、極めて少なかった。After maintaining this state for 15 minutes, the Ar gas was changed to 60 normal liters / minute while maintaining the degree of vacuum in the apparatus at 3 torr, and the stirring power density was set to 50 watts / ton steel for 8 minutes. Light stirring was performed. As a result, C: 0.056% by weight, Cr: 18.2% by weight, S
i: 0.38% by weight, O: 47 ppm, and T.I. C
a: It was possible to obtain a molten stainless steel with a slag entrainment of 1 ppm. Further, the slab obtained from the molten steel was cut, and the cross section was examined with a microscope. The area ratio of the nonmetallic inclusions was almost the same as that of the example and was extremely small.
【００２２】（従来例）実施例１と同様に、転炉で粗脱
炭を行った溶鋼１６０トンを取鍋２に出鋼し、その後Ｖ
ＯＤ真空精錬装置で酸素吹錬を行い、Ｃ：０．０６重量
％、Ｃｒ：１８．１重量％の溶鋼を得た。しかる後、該
溶鋼１にＦｅ−Ｓｉ合金１０００ｋｇを添加し、該装置
内の真空度を３ｔｏｒｒに減圧し、底吹きガス６のＡｒ
ガスを５００ノルマル・リットル／分で吹込み、撹拌動
力密度を４２０ワット／トン・ｓｔｅｅｌの脱酸・還元
処理を開始した。そして、この状態を１５分間継続した
後、出鋼した。その結果、溶鋼成分は、Ｃ：０．０５６
重量％、Ｃｒ：１８．２重量％、Ｓｉ：０．３８重量
％、Ｏ：５０ｐｐｍ、およびＴ．Ｃａ：７ｐｐｍであ
り、そのＴｏｔａｌ Ｃａ濃度からスラグ起因の介在物
の巻き込みがあることが明らかになった。また、この溶
鋼で得た鋳片を切断し、断面を顕微鏡観察で調査したと
ころ、非金属介在物の面積率は、実施例１、２の５倍で
あり、清浄度が劣るものであった。(Conventional Example) As in Example 1, 160 tons of molten steel that had been roughly decarburized in a converter were tapped into ladle 2 and then V
Oxygen blowing was performed by an OD vacuum refining apparatus to obtain molten steel of C: 0.06% by weight and Cr: 18.1% by weight. Thereafter, 1000 kg of an Fe-Si alloy is added to the molten steel 1, the degree of vacuum in the apparatus is reduced to 3 torr, and Ar gas of the bottom blow gas 6 is reduced.
Gas was blown in at 500 normal liters / minute, and a deoxidizing / reducing treatment with a stirring power density of 420 watts / ton steel was started. After this state was continued for 15 minutes, tapping was performed. As a result, the molten steel component was C: 0.056
Wt%, Cr: 18.2 wt%, Si: 0.38 wt%, O: 50 ppm, and T.O. Ca: 7 ppm, and it was clear from the total Ca concentration that inclusion of inclusions caused by slag was present. The slab obtained from the molten steel was cut and the cross section was examined by microscopic observation. The area ratio of the nonmetallic inclusions was 5 times that of Examples 1 and 2, and the cleanliness was poor. .
【００２３】[0023]
【発明の効果】以上述べたように、本発明では、脱酸生
成物ができ、スラグに十分に吸収される間は強撹拌し、
スラグが溶鋼に巻き込まれ易くなってからは弱撹拌する
ようにしたので、溶鋼への脱酸生成物やスラグの巻き込
みが抑制できるようになる。その結果、非金属介在物が
従来より少ない、つまり清浄な溶鋼が安定して得られる
ようになった。As described above, in the present invention, strong stirring is performed while a deoxidized product is produced and sufficiently absorbed by the slag.
Since the slag is weakly stirred after the slag is easily entrained in the molten steel, the deoxidation products and slag entrainment in the molten steel can be suppressed. As a result, the amount of nonmetallic inclusions is smaller than before, that is, clean molten steel can be obtained stably.
【図１】従来法と本発明法とで、還元・脱酸処理中の撹
拌動力密度パターンを比較した図であり、（ａ）が本発
明法、（ｂ）が従来法のものである。FIG. 1 is a diagram comparing a stirring power density pattern during a reduction / deoxidation treatment between a conventional method and the method of the present invention, wherein (a) is the method of the present invention, and (b) is that of the conventional method.
【図２】還元・脱酸処理中の溶鋼の撹拌動力密度と処理
後の溶鋼中Ｔｏｔａｌ．Ｃａ濃度との関係図である。FIG. 2 shows the stirring power density of molten steel during the reduction / deoxidation treatment and the total power in the molten steel after the treatment. It is a relation diagram with Ca concentration.
【図３】ＶＯＤ減圧精錬装置を示す図である。FIG. 3 is a diagram showing a VOD vacuum refining device.
１ 溶鋼 ２ 取鍋 ３ 密封容器 ４ ランス ５ 酸素ガス ６ 不活性ガス（底吹きガス） ７ 減圧精錬装置（二次精錬装置） ８ スラグ DESCRIPTION OF SYMBOLS 1 Molten steel 2 Ladle 3 Sealed container 4 Lance 5 Oxygen gas 6 Inert gas (bottom blowing gas) 7 Decompression refining equipment (secondary refining equipment) 8 Slag
Claims (2)
置内で脱炭した溶鋼に、引き続き脱酸剤を投入して脱酸
処理する溶鋼の精錬方法において、 前記脱酸剤の投入から少なくとも５分間は、前記溶鋼を
下記（１）式で定義される撹拌動力密度（ε）が３００
ワット／トン−ｓｔｅｅｌ以上となる条件で撹拌し、そ
の後は、前記撹拌動力密度が２５０ワット／トン−ｓｔ
ｅｅｌ以下となる条件での撹拌を少なくとも５分間行う
ことを特徴とする高清浄度鋼の溶製方法。 ε＝０．０２８５・Ｑ・Ｔ／Ｗ・ｌｏｇ（１＋Ｚ／１４８×７６０／Ｐ） …（１） ε：撹拌動力密度（ワット／トン−ｓｔｅｅｌ） Ｑ：底吹きガス流量（ノルマル・リットル／分） Ｔ：鋼浴温度（Ｋ°） Ｗ：鋼浴重量（トン） Ｚ：浴深さ（ｃｍ） Ｐ：真空度（ｔｏｒｒ）1. A method for refining molten steel, in which a deoxidizing agent is continuously added to molten steel decarburized in a vacuum smelting apparatus having a bottom-blowing gas stirring function to deoxidize the molten steel. For 5 minutes, the stirring power density (ε) defined by the following formula (1) is 300
Stirring is performed under the condition of watt / ton-steel or more, and thereafter, the stirring power density is 250 watt / ton-st
A method for melting high cleanliness steel, wherein stirring under conditions of not more than eel is performed for at least 5 minutes. ε = 0.0285 · Q · T / W · log (1 + Z / 148 × 760 / P) (1) ε: stirring power density (watt / ton-steel) Q: bottom blown gas flow rate (normal liter / minute) ) T: Steel bath temperature (K °) W: Steel bath weight (ton) Z: Bath depth (cm) P: Degree of vacuum (torr)
特徴とする請求項１記載の高清浄度鋼の溶製方法。2. The method according to claim 1, wherein the vacuum smelting apparatus is a VOD.
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|---|---|---|---|
| JP07972398A JP3903580B2 (en) | 1998-03-26 | 1998-03-26 | Method of melting high cleanliness steel |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07972398A JP3903580B2 (en) | 1998-03-26 | 1998-03-26 | Method of melting high cleanliness steel |
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| Publication Number | Publication Date |
|---|---|
| JPH11279630A true JPH11279630A (en) | 1999-10-12 |
| JP3903580B2 JP3903580B2 (en) | 2007-04-11 |
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ID=13698130
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP07972398A Expired - Fee Related JP3903580B2 (en) | 1998-03-26 | 1998-03-26 | Method of melting high cleanliness steel |
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| Country | Link |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000239730A (en) * | 1999-02-25 | 2000-09-05 | Kawasaki Steel Corp | METHOD FOR MELTING Ag-CONTAINING STEEL |
| JP2007231410A (en) * | 2006-03-03 | 2007-09-13 | Kobe Steel Ltd | Method for producing high cleanliness steel |
| JP2008240126A (en) * | 2007-03-28 | 2008-10-09 | Jfe Steel Kk | Method for refining molten stainless steel |
| JP2010070815A (en) * | 2008-09-19 | 2010-04-02 | Jfe Steel Corp | Ladle for refining molten steel and method for refining molten steel |
| JP2011214084A (en) * | 2010-03-31 | 2011-10-27 | Kobe Steel Ltd | Method for producing high cleanliness steel |
| JP2012172218A (en) * | 2011-02-23 | 2012-09-10 | Sumitomo Metal Ind Ltd | Method of melting low-al steel |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000239730A (en) * | 1999-02-25 | 2000-09-05 | Kawasaki Steel Corp | METHOD FOR MELTING Ag-CONTAINING STEEL |
| JP2007231410A (en) * | 2006-03-03 | 2007-09-13 | Kobe Steel Ltd | Method for producing high cleanliness steel |
| JP2008240126A (en) * | 2007-03-28 | 2008-10-09 | Jfe Steel Kk | Method for refining molten stainless steel |
| JP2010070815A (en) * | 2008-09-19 | 2010-04-02 | Jfe Steel Corp | Ladle for refining molten steel and method for refining molten steel |
| JP2011214084A (en) * | 2010-03-31 | 2011-10-27 | Kobe Steel Ltd | Method for producing high cleanliness steel |
| JP2012172218A (en) * | 2011-02-23 | 2012-09-10 | Sumitomo Metal Ind Ltd | Method of melting low-al steel |
| CN103225009A (en) * | 2012-01-27 | 2013-07-31 | Jfe钢铁株式会社 | Method for producing high-cleanness steel |
| US9752202B2 (en) | 2012-05-14 | 2017-09-05 | Posco | High cleanliness molten steel production method and refining device |
| CN102748578A (en) * | 2012-07-09 | 2012-10-24 | 巩义市众鑫钙业有限公司 | Seamless ferroaluminum wire and preparation method thereof |
| CN106995868A (en) * | 2017-05-27 | 2017-08-01 | 马鞍山华盛冶金科技发展有限公司 | A kind of method of use agent for purifying molten steel refining liquid steel |
| WO2021177021A1 (en) * | 2020-03-06 | 2021-09-10 | Ｊｆｅスチール株式会社 | Method for producing low-carbon ferromanganese |
| JPWO2021177021A1 (en) * | 2020-03-06 | 2021-09-10 |
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