JPH0730381B2 - Denitrification refining method for high chromium steel - Google Patents
Denitrification refining method for high chromium steelInfo
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- JPH0730381B2 JPH0730381B2 JP18925488A JP18925488A JPH0730381B2 JP H0730381 B2 JPH0730381 B2 JP H0730381B2 JP 18925488 A JP18925488 A JP 18925488A JP 18925488 A JP18925488 A JP 18925488A JP H0730381 B2 JPH0730381 B2 JP H0730381B2
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- carbon
- molten steel
- oxygen
- carbon concentration
- gas
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Description
この発明は真空精錬炉により高クロム鋼を溶製する際の
低窒素化精錬技術に係り、脱窒反応をより効果的に促進
させて窒素含有量の低減をはかる高クロム鋼の脱窒精錬
方法に関する。The present invention relates to a low-nitrogen refining technology for producing high-chromium steel in a vacuum refining furnace, which is a method for denitrifying and refining high-chromium steel by more effectively promoting the denitrification reaction and reducing the nitrogen content. Regarding
【従来の技術】 Cr 5〜35重量％（以下％表示は重量％を表わす）を含有
する合金鋼、フェライト系あるいはオーステナイト系ス
テンレス鋼等の高クロム鋼は、窒素溶解度が高いため低
窒素化には不利な鋼であるにもかかわらず、鋼質特性上
極低窒素化が要求される。 真空精錬法による溶製法はこのような要求に応える精錬
法の一つとして開発されたもので、その代表的な溶製法
としては、次の三つの方法を挙げることができる。 目的窒素値に応じ精錬初期炭素値を決める方法。 真空精錬炉に炉底からArガスを導入する方法。 高炭素濃度領域において、酸素吹精脱炭中にこれを中
断し高真空処理を施す方法。 すなわち、の方法は、減圧下、酸素吹精中に脱炭反応
と同時に起こる脱窒反応を期待したもので、初期炭素値
を高くすると脱炭中の脱窒量を増大できる。脱炭反応は
反応界面での酸素濃度を低下させるだけでなく、溶鋼中
に発生する大量のCOガスが反応界面積（単位溶鋼当りの
ガス−メタル界面積）を増大し、窒素分圧(PN2)の低いC
Oガス中に溶鋼中の窒素を移行させることにより脱窒を
促進させるものである。 の方法は、Arガスを溶鋼中に吹込むことにより窒素分
圧の低いArガス中に溶鋼中の窒素を移行させるとともに
反応界面積の増大効果も持たせて脱窒を促進させる方法
である。 の方法は、真空精錬炉で極低窒素鋼を溶製する際、脱
炭過程で酸素等の酸化性ガス、酸化剤等の供給を一時中
断して高真空度を確保する方法である（特開昭57-6362
0）。 この方法は、脱炭過程で溶鋼中に溶解した酸素あるいは
脱炭過程で生成した酸化物を脱炭反応のための酸素源と
し、高真空（臨界炭素濃度より高い炭素濃度領域で10mm
Hg以下の真空度）下で脱炭反応を生じさせると微細なCO
ガスが発生する。これによりガス−メタル反応界面積が
著しく増大するとともに、窒素ガス分圧(PN2)の低いCO
ガスを発生させることができ、さらに溶鋼中の酸素濃度
を低くできるので脱窒反応を促進できる。また、この方
法で脱窒反応を促進させるのに先立ち、Al,Ti,Zr等の脱
酸剤を添加することにより、溶鋼の酸素濃度を低く維持
する方法についても脱窒に効果がある。 なお、臨界炭素濃度とは、脱炭反応速度が酸素の供給律
速（酸素供給速度が一定の時脱炭速度は一定）である領
域から炭素濃度に比例する領域に移る点（炭素濃度）を
表わし、通常の転炉精錬では溶鋼中炭素（以下［Ｃ］と
表わす）は0.1〜0.2％近傍、VOD精錬ではCrを含有して
いるため［Ｃ］＝0.2〜0.4％近傍が臨界炭素濃度とな
る。2. Description of the Related Art Alloy steels containing 5 to 35% by weight of Cr (hereinafter% is% by weight) and high chromium steels such as ferritic or austenitic stainless steels have a high nitrogen solubility, so that they have a low nitrogen content. Despite being a disadvantageous steel, extremely low nitrogen content is required due to the steel quality characteristics. The smelting method by the vacuum smelting method was developed as one of the smelting methods that meet such requirements, and the following three methods can be given as typical smelting methods. A method of determining the initial refining carbon value according to the nitrogen value. A method of introducing Ar gas into the vacuum refining furnace from the bottom of the furnace. In the high carbon concentration range, a method of interrupting the oxygen-blown decarburization and performing high-vacuum treatment. That is, the method (1) expects a denitrification reaction that occurs at the same time as the decarburization reaction during oxygen blowing under reduced pressure, and the denitrification amount during decarburization can be increased by increasing the initial carbon value. The decarburization reaction not only lowers the oxygen concentration at the reaction interface, but also a large amount of CO gas generated in molten steel increases the reaction boundary area (gas-metal boundary area per unit molten steel), and the nitrogen partial pressure (PN 2 ) Low C
The denitrification is promoted by transferring nitrogen in the molten steel into O gas. The method (2) is a method of blowing nitrogen gas into molten steel to transfer nitrogen in the molten steel into Ar gas having a low nitrogen partial pressure, and at the same time having an effect of increasing a reaction interfacial area to accelerate denitrification. Is a method of securing a high degree of vacuum by temporarily interrupting the supply of oxidizing gas such as oxygen and oxidizing agent during the decarburization process when smelting ultra-low nitrogen steel in a vacuum refining furnace. Kaisho 57-6362
0). This method uses oxygen dissolved in molten steel in the decarburization process or oxides generated in the decarburization process as the oxygen source for the decarburization reaction, and high vacuum (10 mm in the carbon concentration region higher than the critical carbon concentration
When a decarburization reaction occurs under a vacuum of Hg or less), fine CO
Gas is generated. This significantly increases the gas-metal reaction interfacial area and reduces CO 2 with a low partial pressure of nitrogen gas (PN 2 ).
Since gas can be generated and the oxygen concentration in the molten steel can be lowered, the denitrification reaction can be promoted. Further, prior to accelerating the denitrification reaction by this method, a method of keeping the oxygen concentration of the molten steel low by adding a deoxidizing agent such as Al, Ti, Zr is also effective for denitrification. The critical carbon concentration represents the point (carbon concentration) at which the decarburization reaction rate shifts from a region in which the oxygen supply rate is controlled (the decarburization rate is constant when the oxygen supply rate is constant) to a region proportional to the carbon concentration. , Carbon in molten steel (hereinafter referred to as [C]) is around 0.1 to 0.2% in normal converter smelting, and Cr is contained in VOD smelting, so the critical carbon concentration is near [C] = 0.2 to 0.4% .
しかし、従来の前記の方法は、脱窒反応には有効で
あるが、次のような欠点を有する。 すなわち、酸素吹精中はガス発生速度が大きく、溶鋼の
流動およびスプラッシュ飛散のため高真空度を維持でき
ないこと、またそのために酸素吹精による脱炭中は溶鋼
の酸素濃度が高くなるため、脱窒反応速度が低下する。
また、減圧中に底吹Arガス量を増大することは、炉体耐
火物の維持に問題があるのみならず、大量のArガスを溶
鋼中に導入すると溶鋼の温度降下をもたらし、熱補償の
点でも不利である。さらに、Arガス導入中でも酸素吹精
期には前記したごとく高真空を維持することができな
い。 したがって、真空精錬炉で低窒素鋼を溶製する場合、酸
素吹精初期の炭素濃度を高くしたり、大量のArガスを導
入したりすることは、窒素含有量の低減に効果はあって
も、酸素吹精中に高真空にすることは前記の通り操業上
困難である。 また、の方法は、脱炭を中断し高真空に保持すること
を１回実施することにより、溶鋼中に溶解した酸素およ
び脱炭過程で生成した酸化物等の酸素源に見合うだけの
脱炭反応が起こるため、溶鋼中の炭素濃度が低下する。
すなわち、この方法の脱窒効率は、同じ炭素量であれば
酸素吹精脱炭により高効率となるが、初期炭素濃度によ
りこの方法の適用回数には制約がある。 通常、初期炭素濃度が１％程度であれば臨界炭素濃度以
上の領域での適用は高々３回程度である。しかし、脱窒
反応速度の小さい高クロム鋼の極低窒素化には、この３
回程度の適用では初期の目標窒素濃度に到達し得ないと
いう欠点がある。 さらに、脱酸剤の適用はこうした脱窒処理を効率よく行
なうだけでなく、脱炭反応による炭素濃度の低下防止を
目的としているが、脱酸剤添加量が多すぎるとガス−メ
タル界面積の低下につながり、他方少なすぎると溶鋼中
の酸素濃度抑制効果の低下につながるため、添加量の決
定は極めて難しいという問題がある。 この発明は従来の技術のこのような問題点を考慮してな
されたものであり、その目的とするところは従来技術の
中でも脱窒化促進法として有効なの方法を改善し、溶
鋼中の炭素濃度を低下させることなく脱窒反応速度を大
きくすることができる脱窒精錬方法を提案しようとする
ものである。However, although the above-mentioned conventional method is effective for the denitrification reaction, it has the following drawbacks. That is, the gas generation rate is high during oxygen sparging, and a high degree of vacuum cannot be maintained due to the flow and splash of molten steel, and therefore the oxygen concentration in molten steel becomes high during decarburization by oxygen sparging. Nitrogen reaction speed decreases.
In addition, increasing the amount of bottom-blowing Ar gas during depressurization not only poses a problem in maintaining the furnace refractory, but when introducing a large amount of Ar gas into the molten steel, it causes a temperature drop of the molten steel, which leads to thermal compensation. It is also disadvantageous. Furthermore, even when Ar gas is introduced, a high vacuum cannot be maintained as described above during the oxygen blowing period. Therefore, when smelting low-nitrogen steel in a vacuum refining furnace, increasing the carbon concentration in the initial stage of oxygen blowing or introducing a large amount of Ar gas is effective in reducing the nitrogen content. As mentioned above, it is difficult in operation to make a high vacuum during oxygen sparging. In the method, the decarburization is carried out once by interrupting the decarburization and maintaining it in a high vacuum, so that the decarburization corresponding to the oxygen dissolved in the molten steel and the oxygen source such as the oxides generated in the decarburization process is performed. Since the reaction occurs, the carbon concentration in the molten steel decreases.
That is, the denitrification efficiency of this method is high by oxygen-blown decarburization if the amount of carbon is the same, but the number of times this method is applied is limited by the initial carbon concentration. Normally, if the initial carbon concentration is about 1%, the application in the region above the critical carbon concentration is about 3 times at most. However, in order to achieve extremely low nitrogen in high chromium steel with a low denitrification reaction rate, this 3
There is a drawback that the initial target nitrogen concentration cannot be reached by applying it about once. Further, the application of the deoxidizing agent not only performs such denitrification treatment efficiently but also aims to prevent the carbon concentration from decreasing due to the decarburization reaction. However, if the amount of the deoxidizing agent added is too large, the gas-metal interfacial area is reduced. On the other hand, if the amount is too small, the effect of suppressing the oxygen concentration in the molten steel will be reduced, so there is the problem that the addition amount is extremely difficult to determine. The present invention has been made in consideration of such problems of the conventional technology, and the purpose thereof is to improve the method effective as the denitrification accelerating method among the conventional technology to improve the carbon concentration in molten steel. It is intended to propose a denitrification refining method capable of increasing the denitrification reaction rate without lowering it.
この発明は、Cr 5〜35％を含有する高クロム鋼を真空精
錬炉で溶製する際、酸化性ガスおよび／または酸化剤を
用いて脱炭処理する過程において、溶鋼中炭素濃度が臨
界炭素濃度以上の領域で、前記酸化性ガスおよび／また
は酸化剤の供給を一時中断し、炭素または炭素含有物を
添加しながら、高真空処理を施すことを要旨とするもの
である。 なお、炭素または炭素化合物としては、炭素粉の外に炭
素飽和鉄のような炭素を含有する合金粉、石灰粉、炭化
珪素等の炭化物等の炭素含有物を用いることができる。
無論、これらの混合物も使用できる。This invention is a process for decarburizing a high chromium steel containing Cr 5 to 35% in a vacuum refining furnace by using an oxidizing gas and / or an oxidizing agent, in which the carbon concentration in the molten steel is critical carbon. The gist of the present invention is to temporarily suspend the supply of the oxidizing gas and / or the oxidizer in a region where the concentration is equal to or higher than that, and perform high vacuum treatment while adding carbon or a carbon-containing material. In addition to carbon powder, carbon-containing materials such as alloy powder containing carbon such as carbon-saturated iron, lime powder, and carbides such as silicon carbide can be used as the carbon or carbon compound.
Of course, mixtures of these can also be used.
炭素または炭素含有物（以下「炭素源」と記す）の場合
は、Al,Si等の金属系脱酸剤と異なり、脱酸生成物がCO
またはCO2の気体となるため、ガス−メタルの脱窒反応
界面積が低下することはない。すなわち、溶鋼中の炭素
濃度を低下させることなく脱炭・脱窒反応を高真空下で
実施することがで１る。 高真空処理中に炭素源を添加する方法としては、減圧下
における粉体上吹添加法か、あるいは粉体を直接溶鋼中
に吹込む方法のいずれでもよい。 以下、この発明方法について詳細に説明する。 臨界炭素濃度以上の高炭素濃度領域における酸化性ガス
および／または酸化剤による脱炭処理過程において、こ
の酸化性ガスおよび／または酸化剤の供給を一時中断す
るのは、以下に示す理由による。 この脱炭処理過程は減圧下でありながら脱炭により発生
するガス量が多く、この時の真空度を100mmHgよりよく
することは難しい。したがってこの間、溶鋼中の酸素濃
度は100ppm以上となり、脱炭反応を抑制する作用を呈す
るが、この100ppm以上の溶鋼中酸素、および溶鋼表面等
に生成していることが推定される酸化物中の酸素が、高
真空処理中に添加する炭素源すなわち脱酸剤と反応し、
COまたはCO2ガスとなるので、酸化性ガスおよび／また
は酸化剤を用いた脱炭過程を中断させる必要がある。 すなわち、真空精錬炉内の溶鋼または溶鋼表面には、酸
素源の存在が必要であり、これが欠除している場合には
脱窒促進効果が低下するため、この発明の脱酸剤を添加
する際には酸化性ガおよび／または酸化剤の供給を一時
中断しなければならないのである。 炭素源の形態としては、溶鋼または溶鋼表面の酸素源と
反応しガスを発生させ、ガス−メタル界面積を低減させ
ることなく（脱窒反応界面積の確保）脱窒反応を促進で
き、かつ溶鋼中の炭素濃度を低下させないためには粉体
が好ましい。 炭素源は、その粉体がCO生成核となるだけでなく、溶鋼
中に分散された炭素粉体の周囲の炭素濃度が溶鋼平均の
濃度より極めて高くなり、見掛け上窒素溶解度を低下さ
せる効果を発揮するものと推察される。 すなわち、炭素源は溶鋼中に添加されると脱窒反応を促
進させるばかりでなく、溶鋼中の炭素濃度を低下させる
ことがないため、初期炭素濃度によらず、脱窒処理を繰
返すことが可能となるのである。 上記炭素源を溶鋼中に分散させたり、溶鋼表面に浮遊す
る酸化剤の反応をよくするためには、溶鋼中に気体を導
入し撹拌を行なうのが効果的である。 なお、臨界炭素濃度は装置および操業時の真空度により
若干異なるが、［Ｃ］＝0.1〜0.3％程度であり、これを
知る方法としては例えば下記３項目がある。 炉から排出される排ガスを、排ガス流量計で排ガス量
Ｖ（l/min）、排ガス分析器でCO,CO2濃度（体積％）を
測定するとともに、排ガス温度ｔ（℃）、排ガス圧力Ｐ
（torr）を測定し、下記（１）式より単位時間当りの脱
炭量Ａ（g/min）を算出する方法。 上記式により算出した炭素量Ａ（g/min）と、初期溶
銑重量Wo（ton）、酸素流量Q(Nm3/min)の値より、時々
刻々の脱炭速度-dc/do2(%/Nm3)を下記（２）式により算
出し、この値が減少しはじめる時刻における溶鋼炭素濃
を臨界炭素濃度とする方法。 過去の精錬チャージ（溶鉄成分，溶鉄温度，炉内圧
力，酸素流量等）を鋼種や精錬条件別に多数分類し、こ
の個々の分類より前記の-dc/do2および臨界炭素濃度
領域の関係から臨界炭素濃度領域に達するまでに必要と
する酸素量をあらかじめ定め、この酸素量Qo(Nm3)と精
錬中の酸素流量Q(Nm3/min)から臨界炭素濃度領域に至る
時間ｔを下記（３）式により求めて臨界炭素濃度領域と
する方法。 ｔ（min）＝Qo(Nm3)/Q(Nm3/min) ……（３） 精錬中に多数回溶鋼を採取し、発光分光分析等の迅速
分析により、その採取した溶鋼の炭素濃度Ci（重量％）
および採取時刻tiを求めるとともに、各採取間で脱炭速
度（−dc/dt）を下記（４）式により算出し、その減少
時間を臨界炭素濃度領域とする方法。 In the case of carbon or carbon-containing substances (hereinafter referred to as "carbon source"), the deoxidation product is CO, unlike metal deoxidizers such as Al and Si.
Alternatively, since it becomes a gas of CO 2, the denitrification reaction interface area of the gas-metal does not decrease. That is, the decarburization / denitrification reaction can be carried out under high vacuum without lowering the carbon concentration in the molten steel. The method of adding the carbon source during the high vacuum treatment may be either the powder top blowing addition method under reduced pressure or the method of directly blowing the powder into the molten steel. Hereinafter, the method of the present invention will be described in detail. The supply of the oxidizing gas and / or the oxidizing agent is temporarily interrupted in the decarburization process with the oxidizing gas and / or the oxidizing agent in the high carbon concentration region above the critical carbon concentration for the following reason. In this decarburization process, the amount of gas generated by decarburization is large even under reduced pressure, and it is difficult to improve the degree of vacuum at this time to better than 100 mmHg. Therefore, during this period, the oxygen concentration in the molten steel becomes 100 ppm or more, which exhibits the effect of suppressing the decarburization reaction, but the oxygen in the molten steel of 100 ppm or more, and in the oxides presumed to be generated on the molten steel surface, etc. Oxygen reacts with the carbon source or deoxidizer added during high vacuum processing,
Since it becomes CO or CO 2 gas, it is necessary to interrupt the decarburization process using the oxidizing gas and / or the oxidizing agent. That is, the presence of an oxygen source is required for the molten steel or the surface of the molten steel in the vacuum refining furnace, and if the oxygen source is lacking, the denitrification accelerating effect decreases, so the deoxidizing agent of the present invention is added. In this case, the supply of the oxidizing gas and / or the oxidizing agent must be temporarily stopped. As the form of the carbon source, it reacts with the molten steel or the oxygen source on the surface of the molten steel to generate a gas, which can promote the denitrification reaction without reducing the gas-metal interfacial area (securing the denitrification reaction interfacial area), and the molten steel. A powder is preferable in order not to lower the carbon concentration in the powder. As for the carbon source, not only does the powder become CO-generating nuclei, but the carbon concentration around the carbon powder dispersed in the molten steel becomes extremely higher than the average concentration of the molten steel, which apparently reduces the nitrogen solubility. It is speculated that it will work. That is, when the carbon source is added to the molten steel, it not only accelerates the denitrification reaction, but also does not lower the carbon concentration in the molten steel, so the denitrification treatment can be repeated regardless of the initial carbon concentration. It becomes. In order to disperse the carbon source in the molten steel and to improve the reaction of the oxidant floating on the surface of the molten steel, it is effective to introduce gas into the molten steel and perform stirring. The critical carbon concentration is about [C] = 0.1 to 0.3%, although it slightly varies depending on the apparatus and the degree of vacuum during operation, and there are the following three methods for knowing this. Exhaust gas discharged from the furnace was measured for exhaust gas amount V (l / min) with an exhaust gas flow meter, CO, CO 2 concentrations (volume%) with an exhaust gas analyzer, and exhaust gas temperature t (° C) and exhaust gas pressure P.
(Torr) is measured, and the decarburization amount A (g / min) per unit time is calculated from the following equation (1). From the carbon amount A (g / min) calculated by the above formula, the initial hot metal weight Wo (ton), and the oxygen flow rate Q (Nm 3 / min), the decarburization rate was changed every moment -dc / do 2 (% / Nm 3 ) is calculated by the following formula (2) and the molten steel carbon concentration at the time when this value begins to decrease is taken as the critical carbon concentration. A number of past refining charges (molten iron components, molten iron temperature, furnace pressure, oxygen flow rate, etc.) are classified according to steel type and refining conditions, and from these individual classifications, criticality is obtained from the relationship between -dc / do 2 and the critical carbon concentration region. The amount of oxygen required to reach the carbon concentration region is determined in advance, and the time t from the oxygen amount Qo (Nm 3 ) and the oxygen flow rate Q (Nm 3 / min) during refining to the critical carbon concentration region is given by (3 ) A method of determining the critical carbon concentration region by the formula. t (min) = Qo (Nm 3 ) / Q (Nm 3 / min) …… (3) Molten steel was sampled many times during refining, and the carbon concentration of the molten steel was measured by rapid analysis such as optical emission spectroscopy. (weight%)
And the sampling time ti and the decarburization rate (-dc / dt) between each sampling is calculated by the following equation (4), and the reduction time is set to the critical carbon concentration range.
実施例１ 2.5トン真空精錬炉で第１表に示す組成を有する粗溶鋼
（初期）を送酸速度0.45Nm3/min/tonで酸素上吹脱炭を5
0分間行ない、その脱炭過程で溶鋼中の炭素濃度が0.3％
のときに送酸を一時停止し、その後の高真空処理に際
し、炭素粉末を上吹ランスにて0.005kg/min/tonの供給
速度で、ランス高さ400mmから40分間上吹きした。 この高真空処理では処理度を1mmHg、溶鋼温度を1600〜1
620℃に制御した。この時の［Ｃ］，［Cr］および
［Ｎ］濃度を第１表に示す。 また、比較のため、上記と同様に酸素上吹脱炭後に炭素
濃度が0.3％のときに送酸を一時停止し、その後高真空
処理のみを行なった時の結果を第１表に併せて示す。 第１表より明らかなごとく、高真空処理中に炭素を添加
することにより溶鋼中の炭素濃度を効率よく脱窒するこ
とができた。 実施例２ 50トンVOD精錬炉で第２表に示す組成を有する粗溶鋼
（初期）を送酸速度0.45Nm3/min/tonで酸素上吹精を15
分間行ない、その脱炭過程で溶鋼中の炭素濃度が0.6％
のときに酸素吹精を１時中断し、その後の高真空処理
（到達真空度2mmHg）に際し、炭素粉末を0.05kg/min/to
nの供給速度で上吹ランス（高さ500mm）により約12分間
上吹した。 その後再び酸素吹精を行ない、さらに炭素濃度が0.4％
のときに酸素吹精を一時中断し、２回目の炭素粉末上吹
を６分間実施して高真空処理を行なった。その後、さら
に酸素吹精を行ない所定の炭素濃度0.02％とした。 本実施例における［Ｃ］，［Cr］，［Ｎ］濃度を第２表
に示す。 また、比較のため、炭素粉末を上吹添加しなかった場合
の結果を第２表に併せて示す。 第２表の結果より、本実施例においても高真空処理中に
炭素を添加することにより脱窒が促進され、また炭素濃
度を低下させることなく最終窒素濃度を低減できること
がわかる。 Example 1 In a 2.5-ton vacuum refining furnace, crude molten steel (initial) having the composition shown in Table 1 was subjected to oxygen top blowing decarburization at an acid transfer rate of 0.45 Nm 3 / min / ton.
The carbon concentration in the molten steel is 0.3% during the decarburization process for 0 minutes.
At that time, the acid feeding was temporarily stopped, and in the subsequent high vacuum treatment, the carbon powder was top-blown with a top-blowing lance at a feed rate of 0.005 kg / min / ton from a lance height of 400 mm for 40 minutes. In this high vacuum treatment, the treatment degree is 1 mmHg and the molten steel temperature is 1600 to 1
The temperature was controlled at 620 ° C. Table 1 shows the [C], [Cr] and [N] concentrations at this time. In addition, for comparison, similarly to the above, Table 1 also shows the results when the oxygen transfer was temporarily stopped after the oxygen top blowing decarburization and the carbon concentration was 0.3%, and then only high vacuum treatment was performed. . As is clear from Table 1, the carbon concentration in the molten steel could be efficiently denitrified by adding carbon during the high vacuum treatment. Example 2 In a 50 ton VOD refining furnace, crude molten steel (initial) having the composition shown in Table 2 was fed with oxygen at a rate of 0.45 Nm 3 / min / ton for 15 times.
The carbon concentration in the molten steel is 0.6% during the decarburization process.
At that time, oxygen sparging was interrupted at 1 o'clock, and during the subsequent high vacuum treatment (achieved vacuum degree of 2 mmHg), carbon powder was added at 0.05 kg / min / to
The top-blowing lance (height: 500 mm) was used to top-blown at a feeding rate of n for about 12 minutes. After that, oxygen was blown again and the carbon concentration was 0.4%.
At that time, the oxygen blowing was suspended, and the second carbon powder blowing was performed for 6 minutes to perform high vacuum treatment. After that, oxygen was blown further to a predetermined carbon concentration of 0.02%. Table 2 shows the [C], [Cr], and [N] concentrations in this example. In addition, for comparison, Table 2 also shows the results when the carbon powder was not added in a top blowing manner. From the results in Table 2, it can be seen that, also in this example, denitrification is promoted by adding carbon during the high vacuum treatment, and the final nitrogen concentration can be reduced without lowering the carbon concentration.
以上説明したごとく、この発明方法によれば、高クロム
鋼の低窒素化精錬において、酸化性ガス、酸化剤の供給
を一時中断して高真空度を得る従来の方法による到達窒
素濃度よりさらに効果的に低窒素化できるとともに、炭
素濃度を低下させることなく脱窒処理できるので実操業
での適用回数を増加することが可能となり、高クロム鋼
の低窒素化に大なる効果を奏するものである。As described above, according to the method of the present invention, in the nitrogen refining of high chromium steel, it is more effective than the reached nitrogen concentration by the conventional method of temporarily suspending the supply of the oxidizing gas and the oxidizing agent to obtain a high degree of vacuum. In addition to the ability to reduce nitrogen levels, the denitrification process can be performed without lowering the carbon concentration, which makes it possible to increase the number of times of application in actual operation, and it has a great effect on reducing nitrogen in high chromium steel. .
Claims (1)
空精錬炉で溶製する際、酸化性ガスおよび／または酸化
剤を用いて脱炭処理する過程において、溶鋼中炭素濃度
が臨界炭素濃度以上の領域で、前記酸化性ガスおよび／
または酸化剤の供給を一時中断し、炭素または炭素含有
物を添加しながら、高真空処理を施すことを特徴とする
高クロム鋼の脱窒精錬方法。1. When melting high chromium steel containing 5 to 35% by weight of Cr in a vacuum refining furnace in a decarburizing process using an oxidizing gas and / or an oxidizing agent, the carbon concentration in the molten steel is In the region above the critical carbon concentration, the oxidizing gas and / or
Alternatively, a method for denitrifying and refining high-chromium steel, characterized in that the supply of an oxidant is temporarily stopped and a high vacuum treatment is performed while adding carbon or a carbon-containing material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18925488A JPH0730381B2 (en) | 1988-07-28 | 1988-07-28 | Denitrification refining method for high chromium steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18925488A JPH0730381B2 (en) | 1988-07-28 | 1988-07-28 | Denitrification refining method for high chromium steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0238512A JPH0238512A (en) | 1990-02-07 |
| JPH0730381B2 true JPH0730381B2 (en) | 1995-04-05 |
Family
ID=16238216
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18925488A Expired - Fee Related JPH0730381B2 (en) | 1988-07-28 | 1988-07-28 | Denitrification refining method for high chromium steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0730381B2 (en) |
-
1988
- 1988-07-28 JP JP18925488A patent/JPH0730381B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0238512A (en) | 1990-02-07 |
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