JP3044642B2 - Decarburization refining method of chromium-containing molten steel - Google Patents
Decarburization refining method of chromium-containing molten steelInfo
- Publication number
- JP3044642B2 JP3044642B2 JP5115074A JP11507493A JP3044642B2 JP 3044642 B2 JP3044642 B2 JP 3044642B2 JP 5115074 A JP5115074 A JP 5115074A JP 11507493 A JP11507493 A JP 11507493A JP 3044642 B2 JP3044642 B2 JP 3044642B2
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- Prior art keywords
- gas
- concentration
- refining
- molten steel
- decarburization
- Prior art date
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- Treatment Of Steel In Its Molten State (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は含クロム溶鋼の脱炭精錬
において、溶鋼中の［Ｃｒ］の酸化を抑え、効率よく高
速で脱炭を行い、かつ極低炭素濃度まで脱炭を行う含ク
ロム溶鋼の脱炭精錬法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the decarburization and refining of chromium-containing molten steel, in which oxidation of [Cr] in the molten steel is suppressed, decarburization is performed efficiently and at high speed, and decarburization is performed to an extremely low carbon concentration. The present invention relates to a method for refining chrome molten steel.
【０００２】[0002]
【従来の技術】従来ステンレス鋼のごとき１１ｍａｓｓ
％以上のクロムを含むような含クロム溶鋼の脱炭法とし
ては、浴面下より酸素ガスまたは酸素ガス（以下、単に
酸素という）と不活性ガスの混合ガスを吹込むＡＯＤ法
が広く用いられている。ＡＯＤ法においては、脱炭が進
行して溶鋼中の［Ｃ］濃度が低下してくると［Ｃｒ］が
酸化されやすくなることから、［Ｃ］濃度の低下にとも
なって吹込みガス中のＡｒガスのような不活性ガスの比
率を高く、酸素の比率を低くして、［Ｃｒ］の酸化を抑
える方法がとられている。しかし、高［Ｃ］濃度域では
浴面下からのみの酸素の供給では供給量を十分にとるこ
とができず、脱炭効率の向上も望めない。また、低
［Ｃ］濃度域では脱炭速度が低下するために所望の
［Ｃ］濃度に到達するのに長時間を要し、かつ吹込みガ
ス中の不活性ガスの比率を高くするために、不活性ガス
の消費量が大幅に増大することから経済的にも不利にな
る。2. Description of the Related Art Conventionally, 11 mass such as stainless steel is used.
As a method for decarburizing chromium-containing molten steel containing chromium of at least%, an AOD method in which oxygen gas or a mixed gas of oxygen gas (hereinafter, simply referred to as oxygen) and an inert gas is blown from below a bath surface is widely used. ing. In the AOD method, when the decarburization proceeds and the [C] concentration in the molten steel decreases, [Cr] is easily oxidized. Therefore, as the [C] concentration decreases, the Ar in the blown gas increases. A method of suppressing the oxidation of [Cr] by increasing the ratio of an inert gas such as a gas and decreasing the ratio of oxygen is used. However, in a high [C] concentration region, supply of oxygen only from below the bath surface cannot provide a sufficient supply amount, and improvement in decarburization efficiency cannot be expected. Further, in the low [C] concentration region, it takes a long time to reach a desired [C] concentration because the decarburization rate is reduced, and in order to increase the ratio of the inert gas in the blown gas. However, since the consumption of the inert gas is greatly increased, it is economically disadvantageous.
【０００３】高［Ｃ］濃度域で効率よく脱炭を行う方法
としては、例えば、特開昭５５−１５８２１３号公報に
は浴面下に酸素および不活性ガスを吹込んで脱炭を行う
と同時に該酸素量の少なくとも０．２倍に相当する量を
浴面上より供給し、浴面上より供給した酸素の二次燃焼
反応熱によって、脱炭を促進させる方法が記載されてい
る。該方法は二次燃焼を促進させるために多量の酸素を
費やすので、酸素の供給量に限界がある場合には浴面に
供給される酸素の量が少なくなるため、脱炭速度の低下
を招くことがある。As a method for efficiently decarburizing in the high [C] concentration range, for example, Japanese Patent Application Laid-Open No. 55-158213 discloses a method of blowing deoxygenated gas by blowing oxygen and an inert gas under a bath surface. A method is described in which an amount corresponding to at least 0.2 times the amount of oxygen is supplied from a bath surface, and decarburization is promoted by a secondary combustion reaction heat of the oxygen supplied from the bath surface. Since this method consumes a large amount of oxygen to promote secondary combustion, when the supply amount of oxygen is limited, the amount of oxygen supplied to the bath surface is reduced, and the decarburization rate is reduced. Sometimes.
【０００４】また、低［Ｃ］濃度域における脱炭を促進
する方法としては、真空精錬法の利用が挙げられる。例
えば、特公昭６０−１００８７号公報には、高クロム・
ステンレス鋼を０．０３ｍａｓｓ％以下の低［Ｃ］濃度
まで脱炭するために、大気圧下での酸素による脱炭を
［Ｃ］＝０．２〜０．４ｍａｓｓ％まで行い、その後は
非酸化性ガスによる攪拌は続けるが酸素吹込みは停止
し、鋼浴上の圧力を約１０Ｔｏｒｒまで連続的に低下さ
せてボイリングを起こさせることによって所望の脱炭を
行う方法が記載されている。該方法は、比較的高［Ｃ］
濃度より酸素の供給を止めるために、［Ｃｒ］の酸化に
よる損失は少なくなるが、急激な真空精錬の適用によ
り、ＣＯガスを大量に発生し、爆発の危険を招く。これ
を回避するため真空吸引をゆるやかにすれば危険はなく
なるが、経過時間が長くなって溶鋼温度が低下し、かつ
反応が遅くなる。また、圧力を１０Ｔｏｒｒ以下の高真
空にすれば、溶鋼のスプラッシュが激しくなり、合金材
料投入用ホッパーの閉塞などの問題が生じる。[0004] As a method of promoting decarburization in a low [C] concentration region, use of a vacuum refining method can be cited. For example, Japanese Patent Publication No. 60-10087 discloses a high chromium
In order to decarburize stainless steel to a low [C] concentration of 0.03 mass% or less, decarburization with oxygen under atmospheric pressure is performed until [C] = 0.2 to 0.4 mass%, and then non-oxidized. A method is described in which a desired decarburization is carried out by continuing stirring with an inert gas but stopping oxygen blowing and continuously reducing the pressure on the steel bath to about 10 Torr to cause boiling. The method has a relatively high [C]
Since the supply of oxygen is stopped at a concentration lower than the concentration, the loss due to oxidation of [Cr] is reduced. However, rapid application of vacuum refining generates a large amount of CO gas, which may cause an explosion. To avoid this, if the vacuum suction is made slow, there is no danger, but the elapsed time becomes longer, the temperature of the molten steel decreases, and the reaction slows down. Further, when the pressure is set to a high vacuum of 10 Torr or less, the splash of molten steel becomes severe, and problems such as blockage of a hopper for charging the alloy material occur.
【０００５】前記の問題点を解決する方法として、特開
平３−６８７１３号公報および特開平４−２５４５０９
号公報記載の方法が開示されている。これらに記載され
ている含クロム溶鋼の精錬方法は［Ｃ］濃度０．２〜
０．０５ｍａｓｓ％までは吹込みガスとして非酸化性ガ
スと酸素の混合ガスを使用し、［Ｃ］濃度がこの範囲内
に低下した後は、２００〜１５Ｔｏｒｒに減圧し、かつ
吹込みガスとして非酸化性ガスのみを使用するものであ
る。該方法は、比較的低［Ｃ］濃度まで大気圧下で精錬
を行うために、［Ｃｒ］の酸化損失が大きくなる。また
真空下での脱炭処理においては不活性ガスのみを用いる
ことで［Ｃｒ］の酸化は抑えられるが、脱炭の酸素源が
溶鋼中の［Ｏ］あるいはスラグ中の酸素のみとなって酸
素の供給速度が遅くなるために脱炭速度が低下し、効率
的な脱炭精錬法とは言えない。As a method for solving the above problems, Japanese Patent Laid-Open Nos. 3-68713 and 4-254509.
Discloses a method described in Japanese Patent Application Laid-Open Publication No. H11-260, 1988. The smelting method of chromium-containing molten steel described in these methods has a [C] concentration of 0.2 to
A mixed gas of a non-oxidizing gas and oxygen is used as the blowing gas up to 0.05 mass%, and after the [C] concentration falls within this range, the pressure is reduced to 200 to 15 Torr, and the blowing gas is a non-oxidizing gas. Only an oxidizing gas is used. In this method, refining is performed under atmospheric pressure to a relatively low [C] concentration, so that the oxidation loss of [Cr] increases. In the decarburization treatment under vacuum, the oxidation of [Cr] can be suppressed by using only an inert gas, but the oxygen source of decarburization is only [O] in the molten steel or oxygen in the slag, and The decarburization rate is reduced due to the slower supply rate of the gas, which is not an efficient decarburization refining method.
【０００６】[0006]
【発明が解決しようとする課題】本発明は同一精錬容器
内で大気圧下脱炭処理後、減圧下脱炭処理（真空精錬）
を行う含クロム溶鋼の脱炭精錬において、大気圧下での
脱炭条件、真空精錬を開始する［Ｃ］濃度、真空精錬時
の真空度および真空精錬時に吹込むガスの条件を好適な
範囲に維持することにより、溶鋼中の［Ｃｒ］の酸化を
抑え、効率よく脱炭を行い、併せて還元用Ｓｉ原単位の
低減、精錬時間の短縮および極低炭素濃度鋼の精錬を可
能にする含クロム溶鋼の脱炭精錬方法を提供することを
目的とするものである。SUMMARY OF THE INVENTION In the present invention, after decarburizing under atmospheric pressure in the same refining vessel, decarburizing under reduced pressure (vacuum refining)
In the decarburization refining of chromium-containing molten steel, the decarburization conditions under atmospheric pressure, the [C] concentration at which vacuum refining is started, the degree of vacuum during vacuum refining, and the conditions of the gas blown during vacuum refining are within suitable ranges. By maintaining it, the oxidation of [Cr] in the molten steel can be suppressed, decarburization can be performed efficiently, and at the same time, reduction of the basic unit of Si for reduction, reduction of refining time, and refining of ultra-low carbon steel can be performed. It is an object of the present invention to provide a method for decarburizing and refining chromium molten steel.
【０００７】[0007]
【課題を解決するための手段】本発明は前記の課題を有
利に解決するものであり、その要旨とするところは下記
のとおりである。 （１）同一精錬容器内で大気圧下での脱炭処理後、減圧
下での脱炭処理を行う含クロム溶鋼の精錬法において、
大気圧下での脱炭処理は［Ｃ］濃度が０．５ｍａｓｓ％
以上で行い、かつ浴面上および浴面下より酸素ガスまた
は酸素ガスと不活性ガスの混合ガスを吹込む方法で行
い、減圧下での脱炭処理は［Ｃ］濃度がこの値未満に低
下した後に容器内を３００Ｔｏｒｒ以下に減圧して行
い、かつ浴面下のみより、［Ｃ］濃度０．１ｍａｓｓ％
までは酸素ガスまたは酸素ガスと不活性ガスの混合ガス
を吹込み、［Ｃ］濃度０．１ｍａｓｓ％以下では不活性
ガスのみを吹込むことを特徴とする含クロム溶鋼の脱炭
精錬法。SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and the gist thereof is as follows. (1) In a refining method of chromium-containing molten steel, which is subjected to decarburization treatment under reduced pressure after decarburization treatment under atmospheric pressure in the same refining vessel,
The decarburization treatment under atmospheric pressure has a [C] concentration of 0.5 mass%
The above procedure is performed, and oxygen gas or a mixed gas of oxygen gas and inert gas is blown from above and below the bath surface. In the decarburization treatment under reduced pressure, the [C] concentration falls below this value. After that, the pressure in the container was reduced to 300 Torr or less, and the concentration of [C] was 0.1 mass% from below the bath surface only.
A decarburizing refining method for molten chromium-containing steel, characterized by blowing oxygen gas or a mixed gas of oxygen gas and inert gas, and blowing only inert gas at a [C] concentration of 0.1 mass% or less.
【０００８】（２）大気圧下での脱炭処理における浴面
上からのガス吹込みは上吹きランスで行うとともに上吹
きランスのノズルからのガス噴出速度は音速以上であ
り、かつ上吹きランスのノズルから噴出されたガスの流
路において、ガス速度が音速以下になっている領域の長
さｈと上吹きランスのノズル最小径ｄO との比ｈ／ｄO
が４０以上８０以下であることを特徴とする前項１記載
の含クロム溶鋼の脱炭精錬法。(2) In the decarburization process under atmospheric pressure, gas is blown from above the bath surface by the upper blowing lance, and the gas blowing speed from the nozzle of the upper blowing lance is higher than the sound speed, and the upper blowing lance is used. Ratio h / d O between the length h of the region where the gas velocity is equal to or lower than the sonic speed in the flow path of the gas ejected from the nozzle and the nozzle minimum diameter d O of the upper blowing lance.
3. The method for decarburizing and refining chromium-containing molten steel according to the above item 1, wherein the ratio is from 40 to 80.
【０００９】（３）真空下での脱炭処理において浴面下
より供給するガスの流量が溶鋼１トン当り０．１Ｎｍ3
／ｍｉｎ以上であることを特徴とする前項１または２記
載の含クロム溶鋼の脱炭精錬法。 以下本発明について詳細に説明する。本発明の含クロム
溶鋼の脱炭精錬は図１に例示するような精錬方法であ
る。精錬容器（１）内で含クロム溶鋼（４）中に底吹き
羽口（２）を通して、精錬ガス（５）を吹込む。また、
精錬容器（１）は脱着可能な排気フード（３）を有して
おり、３００Ｔｏｒｒ以下の減圧が可能である。また、
精錬容器（１）の上部には上吹きランス（６）を有して
おり、高［Ｃ］濃度側では浴面下および浴面上からのガ
ス供給が可能である。(3) In the decarburization treatment under vacuum, the flow rate of gas supplied from below the bath surface is 0.1 Nm 3 per ton of molten steel.
3. The method for decarburizing and refining chromium-containing molten steel according to the above 1 or 2, wherein the rate is not less than / min. Hereinafter, the present invention will be described in detail. The decarburization refining of the chromium-containing molten steel of the present invention is a refining method as illustrated in FIG. The refining gas (5) is blown into the chromium-containing molten steel (4) through the tuyere (2) in the refining vessel (1). Also,
The refining vessel (1) has a removable exhaust hood (3), and can reduce the pressure to 300 Torr or less. Also,
An upper blowing lance (6) is provided at the upper part of the refining vessel (1), and gas can be supplied from below and above the bath surface on the high [C] concentration side.
【００１０】本発明は真空精錬を用いる含クロム溶鋼の
脱炭精錬において、高炭域では浴面上（上吹き）および
浴面下（底吹き）より酸素を供給する複合吹錬法で行
い、かつ比較的高［Ｃ］濃度の０．５ｍａｓｓ％未満で
も真空度３００Ｔｏｒｒ未満であれば、吹込みガスとし
て酸素または酸素と不活性ガスを用いることで、溶鋼中
［Ｃｒ］の酸化を抑え、脱炭速度を高位に保つことが可
能であることに着目したものである。The present invention relates to a decarburization refining of chromium-containing molten steel using vacuum refining, which is performed by a combined blowing method in which oxygen is supplied from above the bath surface (upward blowing) and below the bath surface (bottom blowing) in a high-carbon region, In addition, when the degree of vacuum is less than 300 Torr even if the concentration of [C] is relatively low and less than 0.5 mass%, the oxidation of [Cr] in the molten steel is suppressed by using oxygen or oxygen and an inert gas as the blowing gas, and the degassing is performed. It focuses on the fact that it is possible to keep the coal speed high.
【００１１】図２にＳＵＳ３０４ステンレス鋼を処理し
た場合の大気圧下精錬における［Ｃ］濃度と脱炭酸素効
率の関係を示す。なお、脱炭酸素効率は吹込み酸素のう
ちで脱炭に使用された酸素の割合を示す。また吹錬前の
［Ｓｉ］濃度は０．１ｍａｓｓ％以下であり、吹込みガ
スとして浴面下より酸素とＡｒガスを用い、Ｏ2 ／Ａｒ
比＝４／１で吹錬を行った場合の結果である。図２より
［Ｃ］濃度０．５ｍａｓｓ％未満で脱炭酸素効率が急激
に低下する。従って、［Ｃ］濃度０．５ｍａｓｓ％未満
で真空精錬を適用すれば脱炭酸素効率の低下を防止する
ことが可能になることがわかる。FIG. 2 shows the relationship between [C] concentration and decarbonation efficiency in refining under atmospheric pressure when SUS304 stainless steel is treated. The decarboxylation efficiency indicates the ratio of oxygen used for decarburization in the injected oxygen. The [Si] concentration before blowing is less than 0.1mass%, using oxygen and Ar gas from the bath surface under a blow gas, O 2 / Ar
This is the result when blowing was performed at a ratio of 4/1. As shown in FIG. 2, when the [C] concentration is less than 0.5 mass%, the decarboxylation efficiency sharply decreases. Therefore, it is understood that if vacuum refining is applied at a [C] concentration of less than 0.5 mass%, it is possible to prevent a decrease in decarbonation efficiency.
【００１２】複合吹錬法は上吹きによる高温火点での反
応を効率よく進めることが可能であれば、同一送酸量で
底吹き単独に比べ、脱炭速度の向上が可能である。図３
にＳＵＳ３０４ステンレス鋼を全送酸量４０００Ｎｍ3
／Ｈｒ一定として、大気圧下で［Ｃ］濃度０．５ｍａｓ
ｓ％まで複合吹錬を実施した場合のｈ／ｄO とｄＣ／ｄ
Ｏ2 の関係を示す。なお複合吹．開始時の［Ｃ］濃度は
１．５ｍａｓｓ％、［Ｓｉ］濃度は０．１ｍａｓｓ％以
下であった。また、ｄＣ／ｄＯ2 は吹込み酸素１Ｎｍ3
当りの脱炭量を示し、単位はｋｇ／Ｎｍ3 で示してお
り、この値が大きいほど脱炭効率が高いことを表してい
る。なお底吹き単独ではこの値が０．７０〜０．７２ｋ
ｇ／Ｎｍ3 であった。図よりｈ／ｄO ＝４０〜８０の範
囲でｄＣ／ｄＯ2 が底吹き単独よりも大きくなってお
り、かつｈ／ｄO が小さい方がｄＣ／ｄＯ2 が向上して
いる。なお、ｈ／ｄO の下限を４０とする理由は、ｈ／
ｄO が４０未満になると溶鋼表面の凹みが大きくなりす
ぎ、溶鋼表面からのスプラッシュが大きくなって、操業
に支障をきたすためである。In the combined blowing method, if the reaction at the high-temperature fire point by top blowing can be efficiently promoted, the decarburization speed can be improved as compared with bottom blowing alone with the same amount of acid supply. FIG.
SUS304 stainless steel with total acid supply of 4000Nm 3
/ Hr constant, [C] concentration 0.5mass under atmospheric pressure
h / d O and dC / d when combined blowing up to s%
The relationship of O 2 is shown. Combined blowing. At the start, the [C] concentration was 1.5 mass%, and the [Si] concentration was 0.1 mass% or less. In addition, dC / dO 2 is 1 Nm 3 of blown oxygen.
The decarburization amount per unit is shown in kg / Nm 3 , and the larger the value, the higher the decarburization efficiency. In the case of bottom blow alone, this value is 0.70 to 0.72 k
g / Nm 3 . As shown in the figure, dC / dO 2 is larger than that of sole blown in the range of h / d O = 40 to 80, and dC / dO 2 is improved as h / d O is smaller. The reason for setting the lower limit of h / d O to 40 is that
If d O is less than 40, the dent on the surface of the molten steel becomes too large, and the splash from the surface of the molten steel becomes large, thereby hindering the operation.
【００１３】ここで、ｈ／ｄO は図４に示すように自由
噴流域の長さを示す指標であり、、式で与えられ
る。 ｈ／ｄO ＝Ｈ／ｄO −ＨC ／ｄO … ＨC ／ｄO ＝４．１２Ｐa −１．８６ … ここで、ｈは自由噴流長（ｍｍ）、Ｈはランス・ギャッ
プ（ｍｍ）、ＨC はジェットコア域の長さ（ｍｍ）、Ｐ
a は上吹き吹錬圧力（ｋｇ／ｃｍ2 ）、ｄO は上吹きノ
ズルの最小経（ｍｍ）を示す。Here, h / d O is an index indicating the length of the free jet region as shown in FIG. 4 and is given by an equation. h / d O = H / d O -H C / d O ... H C / d O = 4.12P a -1.86 ... here, h is free jet length (mm), H is Lance gap (mm ), H C is the length of the jet core region (mm), P
a indicates the top blowing pressure (kg / cm 2 ), and d O indicates the minimum diameter (mm) of the top blowing nozzle.
【００１４】図５に同一の上吹きノズルを用いて、種々
の上吹き条件で複合吹錬を行った場合の上吹き酸素中の
二次燃焼反応に使用された酸素量とｈ／ｄO の関係を示
す。おな、二次燃焼反応とは脱炭反応により生成したＣ
Ｏが酸素と反応してＣＯ2 を生成する反応であり、式
で表される。 ＣＯ＋１／２Ｏ2 ＝ＣＯ2 … 図よりｈ／ｄO が小さくなるほど二次燃焼に消費される
酸素量が低減されている。従って、ｈ／ｄO を４０〜８
０の範囲に維持することは、上吹き酸素の二次燃焼に使
用される量を極力抑え、かつ安定した状態で、効率よく
脱炭反応を進行させる条件である。FIG. 5 shows the relationship between the amount of oxygen used for the secondary combustion reaction in the top-blown oxygen and h / d O when combined blowing is performed under various top-blown conditions using the same top-blown nozzle. Show the relationship. The secondary combustion reaction is C generated by the decarburization reaction.
O is a reaction in which oxygen reacts with oxygen to generate CO 2 , and is represented by a formula. CO + ／ O 2 = CO 2 ... As shown in the figure, the smaller the value of h / d O , the smaller the amount of oxygen consumed for the secondary combustion. Therefore, h / d O is 40 to 8
Maintaining the value in the range of 0 is a condition for minimizing the amount of oxygen used for the secondary combustion of the top-blown oxygen and for efficiently promoting the decarburization reaction in a stable state.
【００１５】以上の結果より、［Ｃ］濃度０．５ｍａｓ
ｓ％以上では複合吹錬法を適用し、かつｈ／ｄO を４０
〜８０とすることで効率的な脱炭が可能となった。図６
にＳＵＳ３０４ステンレス鋼をＯ2 ／Ａｒガス比率＝４
／１で処理した場合の真空度と［Ｃ］濃度＝０．３〜
０．５ｍａｓｓ％の範囲における脱炭酸素効率の関係に
ついて示す。真空度３００Ｔｏｒｒ以下で脱炭酸素効率
は高位に安定する。なお、真空度の低下にともない脱炭
酸素効率は向上する傾向にある。[0015] From the above results, [C] concentration 0.5mass
At s% or more, the combined blowing method is applied and h / d O is 40
By setting it to ~ 80, efficient decarburization became possible. FIG.
SUS304 stainless steel with O 2 / Ar gas ratio = 4
Degree of vacuum and [C] concentration = 0.3-
The relationship of the decarboxylation efficiency in the range of 0.5 mass% will be described. At a degree of vacuum of 300 Torr or less, the decarbonation efficiency is stabilized at a high level. In addition, the decarbonation efficiency tends to increase as the degree of vacuum decreases.
【００１６】従って、真空精錬で適用する真空度は３０
０Ｔｏｒｒ以下が必要である。なお、急激な真空度の上
昇は溶鋼スプラッシュを大量に発生するために、真空精
錬では［Ｃ］濃度の低下にともない３００Ｔｏｒｒから
徐々に低下させることが好ましい。図７にＳＵＳ３０４
ステンレス鋼を１００〜２００Ｔｏｒｒの真空下で処理
した場合の［Ｃ］濃度と脱炭酸素効率の関係について、
吹込みガスのＯ2 ／Ａｒ比率を１／１，１／４の２水準
でふらした結果を示す。なお、全吹込みガス流量は０．
３Ｎｍ3 ／ｍｉｎ・Ｔであった。図より吹込みガスとし
て酸素を混合する場合には［Ｃ］濃度０．１ｍａｓｓ％
以下で急激に脱炭酸素効率が低下する。従って、［Ｃ］
濃度０．１ｍａｓｓ％以下では吹込みガスとして不活性
ガスを用いた方が効率的な脱炭が可能となる。Therefore, the degree of vacuum applied in vacuum refining is 30
0 Torr or less is required. Since a sudden increase in the degree of vacuum generates a large amount of molten steel splash, it is preferable to gradually decrease the degree of vacuum from 300 Torr with a decrease in the [C] concentration in vacuum refining. FIG. 7 shows SUS304.
Regarding the relationship between the [C] concentration and the decarbonation efficiency when stainless steel is processed under a vacuum of 100 to 200 Torr,
The results of varying the O 2 / Ar ratio of the blown gas at two levels of 1/1 and 1/4 are shown. In addition, the total flow rate of the blown gas is 0.1.
It was 3 Nm 3 / min · T. According to the figure, when oxygen is mixed as the blowing gas, the [C] concentration is 0.1 mass%.
Below, the decarboxylation efficiency drops sharply. Therefore, [C]
At a concentration of 0.1 mass% or less, the use of an inert gas as the blowing gas enables more efficient decarburization.
【００１７】図８にＳＵＳ３０４ステンレス鋼を１００
〜２００Ｔｏｒｒの真空下でＡｒガスのみを吹込んで処
理した場合の［Ｃ］濃度０．０５〜０．１０ｍａｓｓ％
の範囲における吹込みガス流量と脱炭速度指数の関係を
示す。なお、脱炭速度指数はガス流量０．２Ｎｍ3 ／ｍ
ｉｎ・Ｔでの平均脱炭速度を１００として換算した値で
ある。図よりガス流量０．１Ｎｍ3 ／ｍｉｎ・Ｔ未満で
急激に脱炭速度が低下する。従って、高速で脱炭を行う
には吹込みガス流量として０．１Ｎｍ3 ／ｍｉｎ・Ｔ以
上が必要である。FIG. 8 shows that SUS304 stainless steel
[C] concentration of 0.05 to 0.10 mass% when only Ar gas is blown under a vacuum of ~ 200 Torr for treatment
Shows the relationship between the blown gas flow rate and the decarburization rate index in the range of. The decarburization rate index is a gas flow rate of 0.2 Nm 3 / m
It is a value obtained by converting the average decarburization rate in inT to 100. As shown in the figure, when the gas flow rate is less than 0.1 Nm 3 / min · T, the decarburization speed sharply decreases. Therefore, in order to perform decarburization at high speed, the flow rate of the blown gas needs to be 0.1 Nm 3 / min · T or more.
【００１８】以上より、溶鋼中の［Ｃｒ］の酸化を抑
え、効率よく含クロム溶鋼の脱炭を行うには［Ｃ］濃度
０．５ｍａｓｓ％未満では真空精錬を適用し、３００Ｔ
ｏｒｒ以下に減圧して、吹込みガスとして酸素または酸
素と不活性ガスの混合ガスを使用する必要がある。ま
た、［Ｃ］濃度０．１ｍａｓｓ％以下では不活性ガスの
みを吹込む。なお、ガス流量としては０．１Ｎｍ3 ／ｍ
ｉｎ・Ｔ以上が必要である。As described above, in order to suppress the oxidation of [Cr] in the molten steel and efficiently decarburize the chromium-containing molten steel, vacuum refining is applied when the [C] concentration is less than 0.5 mass%, and 300T
It is necessary to reduce the pressure to orr or less and use oxygen or a mixed gas of oxygen and an inert gas as the blowing gas. When the [C] concentration is 0.1 mass% or less, only an inert gas is blown. The gas flow rate was 0.1 Nm 3 / m
more than in · T is required.
【００１９】操業においては［Ｃ］濃度の時間変化は予
測できることから、粗溶鋼の装入時の溶鋼組成および溶
鋼温度を把握し、真空精錬を開始する時期を決定する。
高炭域では吹込み酸素流量とランスのノズル形状より、
ｈ／ｄO を好適な範囲に保持するように上吹きランスギ
ャップを制御して吹錬を行う。また、真空精錬中は炉内
状況を把握して、ガス吹込み条件および真空度の条件を
決定することが可能である。該操業方法により、溶鋼の
スプラッシュの大量発生は防止可能であり、安定した操
業が可能である。In the operation, since the time change of the [C] concentration can be predicted, the composition of the molten steel and the temperature of the molten steel at the time of charging the crude molten steel are grasped, and the timing for starting the vacuum refining is determined.
In the high coal area, based on the oxygen flow rate and the lance nozzle shape,
Blowing is performed by controlling the top blowing lance gap so as to maintain h / d O within a suitable range. Further, during vacuum refining, it is possible to determine the conditions of gas injection and the degree of vacuum by grasping the conditions inside the furnace. According to the operation method, it is possible to prevent a large amount of splashes of molten steel from occurring, and a stable operation is possible.
【００２０】[0020]
【作用】含クロム溶鋼の脱炭精錬では、下記式で示さ
れる脱炭反応と同時に式で示される溶鋼中［Ｃｒ］の
酸化反応も進行する。なお、式の反応平衡定数Ｋは
式で表される。 ［Ｃ］＋１／２Ｏ2 （ｇ）＝ＣＯ（ｇ） …In the decarburization refining of chromium-containing molten steel, the oxidation reaction of [Cr] in the molten steel represented by the following formula proceeds simultaneously with the decarburization reaction represented by the following formula. The reaction equilibrium constant K in the equation is represented by the equation. [C] + 1 / 2O 2 (g) = CO (g)
【００２１】[0021]
【数１】 (Equation 1)
【００２２】 ２［Ｃｒ］＋３／２Ｏ2 （ｇ）＝（Ｃｒ2 Ｏ3 ） … ここで、ａC は溶鋼中［Ｃ］の活量、ＰO2は雰囲気中の
Ｏ2 ガス分圧、ＰCOは雰囲気中のＣＯガス分圧を示す。
脱炭反応は［Ｃ］濃度によって律速過程が変化する。
［Ｃ］濃度０．７ｍａｓｓ％以上の高炭域では酸素供給
律速、［Ｃ］濃度０．３ｍａｓｓ％以下の低炭域では
［Ｃ］の移動律速と言われ、［Ｃ］濃度０．３〜０．７
ｍａｓｓ％の領域では混合律速と言われている。従っ
て、［Ｃ］濃度０．７ｍａｓｓ％以上で真空精錬を適用
しても効果が少ない。本発明では［Ｃ］濃度０．５ｍａ
ｓｓ％未満で適用することが効果的な条件であることを
見出した。2 [Cr] + 3 / 2O 2 (g) = (Cr 2 O 3 ) where a C is the activity of [C] in the molten steel, P O2 is the partial pressure of O 2 gas in the atmosphere, and P CO indicates the partial pressure of CO gas in the atmosphere.
In the decarburization reaction, the rate-determining process changes depending on the [C] concentration.
[C] It is said that oxygen supply is rate-determining in a high coal area having a concentration of 0.7 mass% or more, and [C] is movement-limiting rate in a low coal area having a concentration of 0.3 mass% or less. 0.7
In the mass% region, it is said that mixing is rate-determining. Therefore, even if vacuum refining is applied at a [C] concentration of 0.7 mass% or more, the effect is small. In the present invention, the [C] concentration is 0.5 ma.
It has been found that applying at less than ss% is an effective condition.
【００２３】また、［Ｃ］濃度０．５ｍａｓｓ％以上の
高炭域では上吹きと底吹きを併用する複合吹錬法を用い
ることで、上吹きによって生成する２１００℃以上の高
温火点での反応および底吹きの攪拌によって［Ｃ］の移
動が促進される条件を見出した。次に、低［Ｃ］濃度側
で脱炭を促進するには、式よりＰO2，ＰCOを低下さ
せることが有効である。しかし、ＰO2＝０、つまり非酸
化性ガスのみでは酸素の供給が遅れるために非酸化性ガ
スに酸素を混合する方が有効であり、［Ｃ］濃度０．１
ｍａｓｓ％以下で非酸化性ガスのみを用いることが効果
的であることを見出した。また、真空度としては図６に
示したように、３００Ｔｏｒｒ以下で効果的であり、
［Ｃ］濃度の低下にともない真空度を低下させることが
好ましいことを見出した。[0023] In a high-carbon region having a [C] concentration of 0.5 mass% or more, by using a combined blowing method in which both top blowing and bottom blowing are used, a high-temperature fire point of 2100 ° C. or more generated by top blowing is used. The present inventors have found a condition in which the movement of [C] is promoted by the reaction and stirring at the bottom. Next, in order to promote decarburization on the low [C] concentration side, it is effective to lower P O2 and P CO from the formula. However, since P O2 = 0, that is, the supply of oxygen is delayed with only the non-oxidizing gas, it is more effective to mix oxygen with the non-oxidizing gas.
It has been found that it is effective to use only a non-oxidizing gas at a mass% or less. Further, as shown in FIG. 6, the degree of vacuum is effective at 300 Torr or less.
[C] It has been found that it is preferable to lower the degree of vacuum as the concentration decreases.
【００２４】[0024]
【実施例】ＳＵＳ３０４ステンレス鋼（８ｍａｓｓ％Ｎ
ｉ−１８ｍａｓｓ％Ｃｒ）６０ｔｏｎの処理を図１に示
す実施態様で実施した。図９に本発明法による実施例−
１を示す。脱炭開始時の［Ｃ］濃度は１．５ｍａｓｓ％
であり、［Ｃ］濃度０．５ｍａｓｓ％までは大気圧下で
の複合吹錬法による脱炭を行い、その後真空精錬を適用
した。複合吹錬法ではｈ／ｄO を５０に保持し、また底
吹きのＯ2 ／Ａｒ比を１／０から４／１に低下させた。
真空精錬中Ｏ2 ／Ａｒガスの比率は１／１から１／４お
よび０／１に、真空度は２００から１００および５０Ｔ
ｏｒｒまで低下させて、［Ｃ］０．０４ｍａｓｓ％まで
脱炭した。その後、真空度を大気圧まで戻しながら、脱
炭中に酸化したクロムを還元するための還元材としてＦ
ｅ−Ｓｉを添加して、Ａｒガスのみの吹込みにより還元
処理を行い、取鍋へ出鋼した。[Example] SUS304 stainless steel (8 mass% N
(i-18 mass% Cr) 60 ton was carried out in the embodiment shown in FIG. FIG. 9 shows an embodiment according to the method of the present invention.
1 is shown. [C] concentration at the start of decarburization is 1.5 mass%
Decarburization was performed by a combined blowing method under atmospheric pressure until the [C] concentration reached 0.5 mass%, and then vacuum refining was applied. In the combined blowing method, h / d O was maintained at 50, and the O 2 / Ar ratio of the bottom blow was reduced from 1/0 to 4/1.
During vacuum refining, the ratio of O 2 / Ar gas is from 1/1 to 1/4 and 0/1, and the degree of vacuum is from 200 to 100 and 50T.
orr, and decarburized to [C] 0.04 mass%. Then, while reducing the degree of vacuum to atmospheric pressure, F is used as a reducing agent for reducing chromium oxidized during decarburization.
e-Si was added, a reduction treatment was performed by blowing only Ar gas, and the steel was poured into a ladle.
【００２５】図１０には本発明法による実施例−２を示
す。［Ｃ］濃度０．５ｍａｓｓ％までは複合吹錬法にて
底吹きＯ2 ／Ａｒ比を一定の状態で行い、［Ｃ］濃度
０．５ｍａｓｓ％未満で真空精錬を適用し、［Ｃ］濃度
の低下にともないＯ2 ／Ａｒ比は１／１，１／４，０／
１、真空度は３００，２００，１００，５０Ｔｏｒｒと
低下させた。還元処理は実施例−１と同一の方法で行っ
た。FIG. 10 shows an embodiment-2 according to the method of the present invention. [C] The bottom blown O 2 / Ar ratio is kept constant by the combined blowing method until the concentration reaches 0.5 mass%, and the vacuum refining is applied at the [C] concentration of less than 0.5 mass%, and the [C] concentration is applied. The O 2 / Ar ratio becomes 1/1, 1/4, 0 /
1. The degree of vacuum was reduced to 300, 200, 100, and 50 Torr. The reduction treatment was performed in the same manner as in Example 1.
【００２６】図１１には［Ｃ］濃度０．５ｍａｓｓ％ま
では大気圧下での処理を行ったが、底吹き単独で処理し
た比較例−１を示す。なお、真空下での処理は実施例−
１と同一の処理パターンで行った。図１２には従来法と
して示されている特開平３−６８７１３号公報記載の方
法に従った比較例−２を示す。本方法では［Ｃ］濃度
０．１０ｍａｓｓ％までは大気圧下で精錬し、［Ｃ］濃
度０．１０ｍａｓｓ％以下で真空度を１００Ｔｏｒｒか
ら５０Ｔｏｒｒに低下させる条件で、Ａｒガス吹込みで
０．０４ｍａｓｓ％までの脱炭処理を行い、その後大気
圧下での還元処理を行い、取鍋に出鍋した。FIG. 11 shows Comparative Example 1 in which the treatment under atmospheric pressure was performed up to the concentration of [C] of 0.5 mass%, but the treatment was performed solely by bottom blowing. The processing under vacuum is described in Example-
1 was performed in the same processing pattern. FIG. 12 shows Comparative Example-2 according to the method described in Japanese Patent Application Laid-Open No. 3-68713, which is shown as a conventional method. In this method, refining is performed under atmospheric pressure until the [C] concentration reaches 0.10 mass%, and the degree of vacuum is reduced from 100 Torr to 50 Torr at a [C] concentration of 0.10 mass% or less. %, Followed by a reduction treatment under atmospheric pressure, and the mixture was placed in a ladle.
【００２７】図９，１０，１１，１２には各実施例にお
ける精錬時間、［Ｃ］および［Ｃｒ］濃度の推移も示し
ているが、従来法に比べ本発明の方が全精錬時間が短く
なり、かつ［Ｃｒ］濃度の低下量も小さくなった。これ
らの精錬結果をまとめて表１に示す。なお、表１の値は
実施例−１による結果を１００とした指数で示す。9, 10, 11, and 12 also show the refining time and the transition of the [C] and [Cr] concentrations in each embodiment, but the total refining time of the present invention is shorter than that of the conventional method. And the decrease in the [Cr] concentration was also small. Table 1 summarizes the results of the refining. The values in Table 1 are shown as indices with the result of Example-1 taken as 100.
【００２８】[0028]
【表１】 [Table 1]
【００２９】[0029]
【発明の効果】本発明によると含クロム溶鋼の脱炭精錬
において、脱炭酸素効率が向上するために同一酸素供給
量で脱炭速度の向上がはかれる。また、還元用Ｓｉ原単
位が低減するとともに、精錬時間が短縮できるために、
大幅な精錬コストの低減および生産性の向上がはかれ
る。According to the present invention, in the decarburization and refining of chromium-containing molten steel, the decarburization rate is improved with the same oxygen supply in order to improve the decarbonation efficiency. In addition, since the reduction Si unit consumption is reduced and the refining time can be shortened,
Significant reduction in refining costs and improvement in productivity.
【００３０】さらに、真空処理を用いるのでＡｒガスの
代替としての窒素ガスの使用の拡大および、例えば
［Ｃ］濃度０．０１ｍａｓｓ％以下の極低炭素域までの
精錬が容易になる。Further, since the vacuum treatment is used, the use of nitrogen gas as an alternative to Ar gas can be expanded and, for example, refining up to an extremely low carbon region having a [C] concentration of 0.01 mass% or less can be facilitated.
【図１】本発明の実施態様例の精錬容器を示す図であ
る。FIG. 1 is a view showing a smelting vessel according to an embodiment of the present invention.
【図２】本発明における真空精錬の開始［Ｃ］濃度の限
定理由を示す図である。FIG. 2 is a diagram showing the reason for limiting the concentration [C] at the start of vacuum refining in the present invention.
【図３】本発明における大気圧下精錬時の上吹きｈ／ｄ
O の限定理由を示す図である。FIG. 3 shows the top blowing h / d during refining under atmospheric pressure in the present invention.
It is a figure showing the reason for limitation of O.
【図４】上吹きのｈ／ｄO の定義を示す図である。FIG. 4 is a diagram showing the definition of h / d O of the upper blowing.
【図５】大気圧下精錬時の上吹きｈ／ｄO と二次燃焼用
酸素量の関係を示す図である。FIG. 5 is a diagram showing the relationship between the upper blowing h / d O and the amount of oxygen for secondary combustion during refining under atmospheric pressure.
【図６】本発明における真空精錬時の真空度の限定理由
を示す図である。FIG. 6 is a diagram showing the reason for limiting the degree of vacuum during vacuum refining in the present invention.
【図７】本発明における真空精錬時の酸素ガスの吹込み
［Ｃ］濃度範囲の限定理由を示す図である。FIG. 7 is a diagram showing the reason for limiting the oxygen gas blowing [C] concentration range during vacuum refining in the present invention.
【図８】本発明における真空精錬時のガス吹込み流量の
限定理由を示す図である。FIG. 8 is a diagram showing the reason for limiting the gas injection flow rate during vacuum refining in the present invention.
【図９】本発明の実施例−１の精錬パターンを示す図で
ある。FIG. 9 is a diagram showing a refining pattern according to Example 1 of the present invention.
【図１０】本発明の実施例−２の精錬パターンを示す図
である。FIG. 10 is a diagram showing a refining pattern according to Example 2 of the present invention.
【図１１】従来法による実施例の精錬パターン（比較例
−１）を示す図である。FIG. 11 is a view showing a refining pattern of an example according to the conventional method (Comparative Example-1).
【図１２】従来による実施例の精錬パターン（比較例−
２）を示す図である。FIG. 12 shows a refining pattern of a conventional example (Comparative Example-
FIG.
１ 精錬容器 ２ 底吹き羽口 ３ 排気フード ４ 溶鋼 ５ ガス ６ 上吹きランス ７ ジェットコア域 ８ 自由噴流域 Reference Signs List 1 refining vessel 2 bottom blowing tuyere 3 exhaust hood 4 molten steel 5 gas 6 top blowing lance 7 jet core area 8 free jet area
フロントページの続き (72)発明者 岩崎 央 山口県光市大字島田3434番地 新日本製 鐵株式会社光製鐵所内 (58)調査した分野(Int.Cl.7，ＤＢ名) C21C 7/068 C21C 7/00 C21C 7/10 Continuation of the front page (72) Inventor Hiroshi Iwasaki 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Nippon Steel Corporation Hikari Works (58) Fields investigated (Int. Cl. 7 , DB name) C21C 7/068 C21C 7/00 C21C 7/10
Claims (3)
後、減圧下での脱炭処理を行う含クロム溶鋼の精錬法に
おいて、大気圧下での脱炭処理は［Ｃ］濃度が０．５ｍ
ａｓｓ％以上で行い、かつ浴面上および浴面下より酸素
ガスまたは酸素ガスと不活性ガスの混合ガスを吹込む方
法で行い、減圧下での脱炭処理は［Ｃ］濃度がこの値未
満に低下した後に容器内を３００Ｔｏｒｒ以下に減圧し
て行い、かつ浴面下のみより、［Ｃ］濃度０．１ｍａｓ
ｓ％までは酸素ガスまたは酸素ガスと不活性ガスの混合
ガスを吹込み、［Ｃ］濃度０．１ｍａｓｓ％以下では不
活性ガスのみを吹込むことを特徴とする含クロム溶鋼の
脱炭精錬法。In a refining method for chromium-containing molten steel, which is decarburized under atmospheric pressure in the same refining vessel and then decarburized under reduced pressure, the decarburizing process under atmospheric pressure is carried out at a concentration of [C]. Is 0.5m
as% or more, and oxygen gas or a mixed gas of oxygen gas and inert gas is blown from above and below the bath surface, and the decarburization treatment under reduced pressure has a [C] concentration less than this value. After that, the pressure in the vessel was reduced to 300 Torr or less, and the concentration of [C] was 0.1mass only from under the bath surface.
a decarburizing refining method for chromium-containing molten steel, characterized by blowing oxygen gas or a mixed gas of oxygen gas and inert gas up to s%, and blowing only inert gas at [C] concentration of 0.1 mass% or less. .
らのガス吹込みは上吹きランスで行うとともに上吹きラ
ンスのノズルからのガス噴出速度は音速以上であり、か
つ上吹きランスのノズルから噴出されたガスの流路にお
いて、ガス速度が音速以下になっている領域の長さｈと
上吹きランスのノズル最小径ｄO との比ｈ／ｄO が４０
以上８０以下であることを特徴とする請求項１記載の含
クロム溶鋼の脱炭精錬法。2. In the decarburization process under atmospheric pressure, gas is injected from above the bath surface by an upper blowing lance, and the gas blowing speed from the nozzle of the upper blowing lance is higher than the sonic speed. In the flow path of the gas ejected from the nozzle, the ratio h / d O of the length h of the region where the gas velocity is equal to or lower than the sound velocity to the nozzle minimum diameter d O of the upper blowing lance is 40.
2. The method for decarburizing and refining chromium-containing molten steel according to claim 1, wherein the number is 80 or less.
供給するガスの流量が溶鋼１トン当り０．１Ｎｍ3 ／ｍ
ｉｎ以上であることを特徴とする請求項１または２記載
の含クロム溶鋼の脱炭精錬法。3. The flow rate of gas supplied from below the bath surface in a decarburization treatment under vacuum is 0.1 Nm 3 / m per ton of molten steel.
3. The method for decarburizing and refining chromium-containing molten steel according to claim 1 or 2, wherein the ratio is at least in.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5115074A JP3044642B2 (en) | 1993-05-17 | 1993-05-17 | Decarburization refining method of chromium-containing molten steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5115074A JP3044642B2 (en) | 1993-05-17 | 1993-05-17 | Decarburization refining method of chromium-containing molten steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06330141A JPH06330141A (en) | 1994-11-29 |
| JP3044642B2 true JP3044642B2 (en) | 2000-05-22 |
Family
ID=14653537
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5115074A Expired - Lifetime JP3044642B2 (en) | 1993-05-17 | 1993-05-17 | Decarburization refining method of chromium-containing molten steel |
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| Country | Link |
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Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6190435B1 (en) | 1996-11-20 | 2001-02-20 | Nippon Steel Corporation | Method of vacuum decarburization/refining of molten steel |
| JP2003096515A (en) * | 2001-09-20 | 2003-04-03 | Nippon Steel Corp | Method for refining molten extra-low carbon chromium- containing steel |
| JP4895446B2 (en) * | 2001-09-20 | 2012-03-14 | 新日本製鐵株式会社 | Method for refining chromium-containing molten steel |
| BRPI0216050B1 (en) | 2001-09-20 | 2015-12-29 | Nippon Steel & Sumitomo Metal Corp | refining apparatus for cast chrome steels |
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1993
- 1993-05-17 JP JP5115074A patent/JP3044642B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| JPH06330141A (en) | 1994-11-29 |
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