JPH0633133A - Production of ultralow carbon steel - Google Patents
Production of ultralow carbon steelInfo
- Publication number
- JPH0633133A JPH0633133A JP18920792A JP18920792A JPH0633133A JP H0633133 A JPH0633133 A JP H0633133A JP 18920792 A JP18920792 A JP 18920792A JP 18920792 A JP18920792 A JP 18920792A JP H0633133 A JPH0633133 A JP H0633133A
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- decarburization
- vacuum
- oxygen
- treatment
- 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.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は、溶鋼を真空脱炭処理
して極低炭素鋼を製造する方法、特に、脱炭処理を早
く、かつ処理時間の変動を小さくして行うことができる
極低炭素鋼の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultra-low carbon steel by subjecting molten steel to vacuum decarburization treatment, and more particularly to an ultralow-carbon method capable of performing decarburization treatment quickly and with a small variation in treatment time. The present invention relates to a method for manufacturing low carbon steel.
【０００２】[0002]
【従来の技術】極低炭素鋼は、製鋼炉を用いて溶製した
低炭素溶鋼を真空脱ガス装置を用いて減圧下で目的の炭
素濃度まで脱炭し、その後脱酸剤を添加して脱酸処理を
行って製造される。真空脱ガス装置としては一般にはＲ
Ｈ脱ガス装置あるいはＤＨ脱ガス装置が用いられてい
る。2. Description of the Related Art Ultra-low carbon steel is obtained by decarburizing low-carbon molten steel produced by using a steelmaking furnace under a reduced pressure using a vacuum degassing device, and then adding a deoxidizing agent. It is manufactured by performing deoxidation treatment. R is generally used as a vacuum degassing device.
An H 2 degassing device or a DH degassing device is used.
【０００３】ＲＨ脱ガス装置では、図２に示すように、
２本の浸漬管を有する真空槽を取鍋内溶鋼に浸漬し、一
方の浸漬管内から環流用ガスを導入して溶鋼循環を生じ
させながら脱ガスを行う。ＤＨ脱ガス装置では、図３に
示すように、真空槽の一本の浸漬管を取鍋内溶鋼に浸漬
し、真空槽または取鍋を上、下に反復昇降させて溶鋼を
真空槽内と取鍋内とに反復導入して脱ガスを行う。この
とき真空槽の昇降を行わず、真空槽内に溶鋼を導入し、
取鍋下部の羽口またはランスを用いて浸漬管下部からガ
ス攪拌しながら脱ガスを促進する方法もある。In the RH degasser, as shown in FIG.
A vacuum tank having two dip tubes is immersed in molten steel in a ladle, and a gas for reflux is introduced from one of the dip tubes to perform degassing while causing molten steel circulation. In the DH degasser, as shown in FIG. 3, a single dip tube in a vacuum tank is immersed in molten steel in a ladle, and the vacuum tank or ladle is repeatedly moved up and down to move the molten steel into the vacuum tank. Degas by repeatedly introducing into and out of the ladle. At this time, without moving up and down the vacuum tank, introduce molten steel into the vacuum tank,
There is also a method of promoting degassing while stirring gas from the lower part of the dip tube using tuyere or lance at the bottom of the ladle.
【０００４】上述のような真空脱ガス装置を用いて、製
鋼炉で溶製した低炭素溶鋼から極低炭素鋼を製造する
際、脱炭速度を向上させて処理時間を短縮する方法が種
々提案されている。Various methods have been proposed for improving the decarburization rate and shortening the treatment time when producing ultra-low carbon steel from low-carbon molten steel produced in a steelmaking furnace by using the vacuum degassing apparatus as described above. Has been done.
【０００５】ＲＨ脱ガス装置での脱炭速度は、一般に下
記(1) 式で示される。 Ｋ＝（Ｖ／Ｗ）・ａｋ／（Ｖ＋ａｋ） ・・・(1) ただし、Ｋ：脱炭速度定数、 Ｖ：溶鋼環流速度、 Ｗ：処理溶鋼量、 ａｋ：真空槽内脱炭容量係数 ここで、浸漬管径の拡大は溶鋼環流速度Ｖを増大させ、
真空槽内ガス攪拌は真空槽内脱炭容量係数ａｋを増大さ
せるので、脱炭速度改善方法としては浸漬管径の拡大
（例えば特開昭59−85815 号公報）、環流ガス流量増加
による真空槽内ガス攪拌の強化（例えば特開昭58−1172
1 号公報）などが提案されている。The decarburization rate in the RH degasser is generally expressed by the following equation (1). K = (V / W) ・ ak / (V + ak) (1) However, K: decarburization rate constant, V: molten steel reflux velocity, W: amount of treated molten steel, ak: decarburization capacity coefficient in vacuum chamber here Then, the expansion of the immersion pipe diameter increases the molten steel circulation velocity V,
Since the gas stirring in the vacuum tank increases the decarburization capacity coefficient ak in the vacuum tank, the methods for improving the decarburization rate are to increase the diameter of the dipping pipe (for example, Japanese Patent Laid-Open No. 59-85815), and to increase the reflux gas flow rate by the vacuum tank. Strengthening internal gas agitation (for example, JP-A-58-1172
No. 1) is proposed.
【０００６】更に、ＲＨ式脱ガス装置の環流上昇管から
低圧および高圧の二系統のガスを吹き込んで上昇管断面
に均一に気泡を分散させて溶鋼環流量を増大させて脱炭
速度を改善する方法が特開平１−168809号公報に開示さ
れている。これらの従来のＲＨ脱炭速度改善対策は物理
的な条件（環流や攪拌）の改善を主眼としたものであ
る。Furthermore, low-pressure and high-pressure two-system gases are blown from the reflux riser of the RH type degasser to evenly disperse bubbles in the cross section of the riser to increase the flow rate of molten steel and improve the decarburization rate. The method is disclosed in JP-A-1-168809. These conventional measures for improving the RH decarburization rate are aimed mainly at improving physical conditions (reflux and stirring).
【０００７】一方、特開平２−77518 号公報には、真空
槽内の溶鋼の浴面上方から酸素ガスを溶鋼表面に吹付
け、溶鋼の脱炭反応を進行させるとともに、排ガス中の
(CO＋CO2)の割合が５％以上となり、かつ排ガス中のCO
2/(CO ＋CO2)比が約30％以上となる時期に溶鋼表面近傍
で脱ガス処理中に発生するCOガスを燃焼させて、溶鋼温
度の降下量を低減させる方法が開示されている。この方
法により、溶鋼の温度降下を防止するとともに、酸素供
給高さを変更して脱炭速度も制御可能としている。しか
し酸素供給高さの変更は、COガス燃焼と脱炭速度とに同
時に影響を及ぼすので両者を同時に改善するのは難しい
と思われる。On the other hand, in Japanese Unexamined Patent Publication (Kokai) No. 2-77518, oxygen gas is blown onto the molten steel surface from above the molten steel bath surface in a vacuum chamber to allow the decarburization reaction of the molten steel to proceed and
The ratio of (CO + CO 2 ) is 5% or more, and CO in exhaust gas
A method is disclosed in which the CO gas generated during the degassing process is burned in the vicinity of the molten steel surface at a time when the 2 / (CO + CO 2 ) ratio is about 30% or more to reduce the amount of decrease in the molten steel temperature. By this method, the temperature drop of molten steel is prevented and the decarburization rate can be controlled by changing the oxygen supply height. However, since changing the oxygen supply height affects CO gas combustion and decarburization rate at the same time, it seems difficult to improve both at the same time.
【０００８】[0008]
【発明が解決しようとする課題】最近では、例えば転炉
において高速吹錬技術が発達し、連続鋳造機での鋳込み
速度の高速化およびスラブ幅の拡大により、１ヒート当
たりの吹錬時間および連続鋳造時間は短縮されており、
転炉−連続鋳造プロセスの中間プロセスである真空脱ガ
ス工程での処理時間の短縮が要請されている。Recently, for example, a high-speed blowing technique has been developed in a converter, and by increasing the casting speed and expanding the slab width in a continuous casting machine, the blowing time per heat and continuous Casting time has been shortened,
There is a demand for reduction of processing time in a vacuum degassing process which is an intermediate process of a converter-continuous casting process.
【０００９】更に近年、極低炭素鋼に要求される炭素濃
度が従来の 30ppm以下から 20ppm以下と低下しつつあ
り、今後も要求炭素濃度の低下傾向が続くことが予想さ
れる。Further, in recent years, the carbon concentration required for ultra-low carbon steel is decreasing from the conventional 30 ppm or less to 20 ppm or less, and it is expected that the demand carbon concentration will continue to decrease.
【００１０】一般に、真空脱ガス装置では炭素濃度が低
下するにともない脱炭速度が著しく低下する。そのた
め、要求される炭素濃度が低いほど脱ガスに要する処理
時間が長くなる。Generally, in a vacuum degassing apparatus, the decarburization rate significantly decreases as the carbon concentration decreases. Therefore, the lower the required carbon concentration, the longer the processing time required for degassing.
【００１１】上記のような背景から、脱炭速度を大きく
して脱ガス処理時間を短縮する技術が強く求められてい
る。From the above background, there is a strong demand for a technique for increasing the decarburization rate and shortening the degassing treatment time.
【００１２】本発明者らも、ＲＨ脱ガス装置の浸漬管径
の拡大や真空槽内ガス攪拌などの改善対策を試み、相当
の脱炭速度向上の効果を得た。しかしながら、これらの
脱炭速度向上対策を講じても、真空脱ガス装置での脱炭
速度にはヒートごとのばらつきが多く、脱炭速度が遅い
ものでは処理時間を限界まで延長しても到達炭素濃度が
20 ppm 程度までしか下がらない場合があった。その場
合、ＲＨ処理時間の延長に合わせて連続鋳造機の鋳込み
速度を低下させなければならず、生産性の低下を招いて
しまう。さらに、真空脱炭処理の長時間化が著しい場合
には、処理ヒートを連続鋳造工程に送るのが遅れて、予
定の連々鋳の数に満たずに鋳込みを終了しなければなら
ない。このように連々鋳の数が予定数に満たない場合に
は、前の製鋼工程および後続の圧延工程のスケジュール
に狂いが出て、工程管理上、多大な支障がおきる。The inventors of the present invention also tried to improve the dipping pipe diameter of the RH degassing device and agitate the gas in the vacuum tank, and obtained a considerable improvement in the decarburizing rate. However, even if these measures to improve the decarburization rate are taken, the decarburization rate in the vacuum degasser varies widely from heat to heat. Concentration
In some cases, it dropped only to about 20 ppm. In that case, the casting speed of the continuous casting machine must be reduced in accordance with the extension of the RH treatment time, resulting in a decrease in productivity. Further, when the vacuum decarburization treatment is remarkably prolonged, it is delayed in sending the treatment heat to the continuous casting step, and the casting must be completed without reaching the planned continuous casting number. If the number of continuous castings is less than the planned number in this way, the schedules of the previous steel making process and the subsequent rolling process are out of order, which causes a great obstacle in process control.
【００１３】本発明は上記の問題を解決することを課題
としてなされたもので、具体的な目的は、製鋼炉で溶製
された低炭素溶鋼を真空脱炭処理する際の処理時間を短
縮し、しかも処理時間の大きな変動なしに確実に目標炭
素濃度まで下げることができる方法を提供することにあ
る。The present invention has been made to solve the above problems, and a specific object of the present invention is to reduce the processing time when vacuum decarburizing a low carbon molten steel produced in a steelmaking furnace. Moreover, it is an object of the present invention to provide a method capable of surely lowering the target carbon concentration without a large change in the treatment time.
【００１４】[0014]
【課題を解決するための手段】本発明は、『真空脱炭処
理後の溶鋼中の活量酸素が 350〜500 ppm となるように
脱炭処理前の溶鋼または脱炭処理中の溶鋼の酸素含有量
を調整して脱炭処理を行うことを特徴とする極低炭素鋼
の製造方法』を要旨とする。[Means for Solving the Problems] The present invention relates to "oxygen of molten steel before decarburization or molten steel during decarburization so that the activity oxygen in the molten steel after vacuum decarburization is 350 to 500 ppm. A method for producing an ultra-low carbon steel characterized by performing decarburization treatment by adjusting the content ”.
【００１５】具体的には、真空脱炭処理前の溶鋼中の
活量酸素が過剰な場合にはその溶鋼に脱酸剤を添加し、
真空脱炭処理前の溶鋼中の活量酸素が過少な場合には
脱炭処理前または脱炭処理中の溶鋼に酸素含有物質を添
加する、といういずれかの方法によって、真空脱炭処理
後の溶鋼中の活量酸素が 350〜500 ppm となるように調
整して脱炭処理を行う。Specifically, when the activity oxygen in the molten steel before the vacuum decarburization treatment is excessive, a deoxidizing agent is added to the molten steel,
If the activity oxygen in the molten steel before vacuum decarburization treatment is too low, the oxygen-containing substance is added to the molten steel before or during decarburization treatment. Decarburization is performed by adjusting the activity oxygen in the molten steel to 350 to 500 ppm.
【００１６】真空脱ガス装置で真空脱炭処理をするに際
して、取鍋内の溶鋼中活量酸素を定期的または連続的に
測定するのが望ましい。そして、脱炭処理後の溶鋼中活
量酸素が350ppm未満に低下することが予測される場合に
は、真空槽内の溶鋼に酸化性ガスを吹き込むか、または
固体酸化物を添加して、真空脱炭処理後の溶鋼中の活量
酸素が 350〜500ppmになるように調整しつつ脱炭処理を
行うのが、本発明の一つの望ましい実施態様である。When carrying out the vacuum decarburizing treatment with the vacuum degassing apparatus, it is desirable to measure the activity oxygen in the molten steel in the ladle periodically or continuously. Then, if it is predicted that the activity oxygen in the molten steel after decarburization will be reduced to less than 350 ppm, an oxidizing gas is blown into the molten steel in the vacuum tank, or a solid oxide is added, and a vacuum is added. It is one desirable embodiment of the present invention to carry out the decarburization treatment while adjusting the active oxygen in the molten steel after the decarburization treatment to be 350 to 500 ppm.
【００１７】本発明方法において、脱炭処理の対象とな
る鋼は、転炉または電気炉などで溶製された低炭素溶鋼
である。また、真空脱ガス処理装置としてはＲＨ脱ガス
装置またはＤＨ脱ガス装置などの冶金用真空脱ガス装置
を用いることができる。In the method of the present invention, the steel to be decarburized is a low carbon molten steel produced by a converter or an electric furnace. A vacuum degassing device for metallurgy such as a RH degassing device or a DH degassing device can be used as the vacuum degassing device.
【００１８】本発明で使用する脱酸剤は、金属Al、金属
Si、AlまたはSiを主成分とする合金鉄、炭素材など、製
鋼用脱酸剤として一般に使用されるものである。The deoxidizer used in the present invention is metal Al, metal
It is commonly used as a deoxidizing agent for steelmaking, such as iron alloy containing Si, Al or Si as a main component and carbon material.
【００１９】溶鋼中の活量酸素は、取鍋内の溶鋼中に固
体電解質型酸素センサーが先端に取付けられた測定ラン
スを浸漬することによって実測することができる。The active oxygen in the molten steel can be measured by immersing a measuring lance having a solid electrolyte type oxygen sensor attached at its tip in the molten steel in the ladle.
【００２０】酸素含有物質としては、純O2、CO2 等の酸
化性ガス、酸化鉄（鉄鉱石）、酸化マンガン（マンガン
鉱石）等の塊状または粉粒状の固体酸化物がある。As the oxygen-containing substance, there are oxidative gases such as pure O 2 and CO 2 , and solid or powdery solid oxides such as iron oxide (iron ore) and manganese oxide (manganese ore).
【００２１】[0021]
【作用】図１は、本発明者らが行った試験結果をまとめ
たもので、（ａ）は転炉で溶製した低炭素溶鋼中の活量
酸素と真空脱炭処理後の極低炭素溶鋼中の活量酸素との
関係を示す図、（ｂ）は極低炭素溶鋼中の活量酸素と脱
炭速度定数との関係を示す図である。なお脱炭速度定数
ＫC は取鍋内炭素濃度が200ppmから20ppm になるまでの
脱炭速度定数を示し、下記 (2)式で定義される。FIG. 1 is a summary of the test results conducted by the present inventors. (A) shows active oxygen in low carbon molten steel melted in a converter and very low carbon after vacuum decarburization treatment. FIG. 3 is a diagram showing a relationship between activity oxygen in molten steel and (b) is a diagram showing a relationship between activity oxygen in ultra-low carbon molten steel and a decarburization rate constant. The decarburization rate constant K C indicates the decarburization rate constant until the carbon concentration in the ladle changes from 200 ppm to 20 ppm, and is defined by the following equation (2).
【００２２】ＫC ＝ln（200/20）／ｔ ・・・(2) ただし、ｔ：炭素濃度が200ppmから20ppm に到達するま
での時間 図１（ｂ）に示すように、炭素濃度が200ppmから20ppm
になるまでの脱炭速度定数ＫC は、脱炭処理後の溶鋼中
の活量酸素と相関関係がある。そして、脱炭処理後の溶
鋼中の活量酸素は、図１（ｂ）に示すように、脱炭処理
前（出鋼時）の溶鋼中活量酸素と関係がある。K C = ln (200/20) / t (2) However, t: Time until the carbon concentration reaches from 20 ppm to 200 ppm As shown in FIG. 1 (b), the carbon concentration is 200 ppm From 20ppm
The decarburization rate constant K C until the depletion has a correlation with the activity oxygen in the molten steel after the decarburization treatment. Then, the active oxygen in the molten steel after the decarburizing treatment is related to the active oxygen in the molten steel before the decarburizing treatment (at the time of tapping), as shown in FIG. 1 (b).
【００２３】図１（ｂ）に見られるとおり、脱炭処理後
の溶鋼中活量酸素が 400ppm 以下の領域では活量酸素の
増加とともに脱炭速度定数も増大するが、活量酸素が40
0ppm以上の領域では逆に活量酸素の増加とともに脱炭速
度定数が減少する。As shown in FIG. 1 (b), in the region where the activity oxygen in the molten steel after the decarburization treatment is 400 ppm or less, the decarburization rate constant increases as the activity oxygen increases, but the activity oxygen is 40% or less.
On the contrary, in the region of 0 ppm or more, the decarburization rate constant decreases as the activity oxygen increases.
【００２４】真空脱炭の原理は、溶鋼中の炭素と酸素と
の反応で一酸化炭素ガスを生成させ、生成した一酸化炭
素ガスを真空槽の真空排気系から排出して溶鋼中の炭素
を除去するというものである。したがって、溶鋼中には
炭素と反応するのに必要な最低限の酸素の存在が必要で
あり、一般的には酸素が多いほど下記 (3)式に示す平衡
炭素濃度Ceが低下して脱炭が進行すると考えられてい
た。The principle of vacuum decarburization is that carbon monoxide gas is generated by the reaction of carbon and oxygen in molten steel, and the generated carbon monoxide gas is discharged from the vacuum exhaust system of the vacuum tank to remove carbon in molten steel. It is to remove. Therefore, the minimum amount of oxygen necessary to react with carbon in molten steel is required. Generally, the more oxygen, the lower the equilibrium carbon concentration Ce shown in Eq. Was thought to progress.
【００２５】Ce＝k ・Pco/ａo ・・・(3) ただし、Ce：平衡炭素濃度、 k ：平衡定数、 Pco ：COガス分圧、 ａo ：溶鋼中活量酸素。Ce = k · Pco / a o (3) where Ce: equilibrium carbon concentration, k: equilibrium constant, Pco: CO gas partial pressure, a o : activity oxygen in molten steel.
【００２６】しかしながら、図１（ｂ）に示すように脱
炭反応を円滑に進行させ、脱炭速度定数ＫC を一定値以
上に維持するためには、溶鋼中活量酸素の上限値が存在
する。その理由は、溶鋼中活量酸素が必要以上に増加す
ると、真空槽内溶鋼表面に酸化物が生じ反応界面積が
減少すること、真空槽内溶鋼表面における酸素の吸着
により、界面化学反応速度が低下すること、により脱炭
速度が低下することにあると考えられる。However, as shown in FIG. 1 (b), in order to smoothly proceed the decarburization reaction and maintain the decarburization rate constant K C at a certain value or more, there is an upper limit value of the activity oxygen in the molten steel. To do. The reason is that when the active oxygen in the molten steel increases more than necessary, an oxide is generated on the surface of the molten steel in the vacuum tank to reduce the reaction interface area, and the adsorption of oxygen on the surface of the molten steel in the vacuum tank reduces the interfacial chemical reaction rate. It is considered that the decarburization rate decreases due to the decrease.
【００２７】したがって、真空脱炭処理で極低炭素溶鋼
を溶製する際の脱炭速度を安定して高く保つには、真空
脱炭処理後の溶鋼中活量酸素を一定範囲にし、そのばら
つきを小さくする必要がある。Therefore, in order to keep the decarburization rate at the time of melting ultra-low carbon molten steel by vacuum decarburizing treatment stable and high, the activity oxygen in the molten steel after vacuum decarburizing treatment should be kept within a certain range and the variation thereof should be maintained. Needs to be small.
【００２８】図１（ｂ）からわかるように、真空脱炭処
理後の溶鋼中活量酸素を 350 ppmから 500 ppmの範囲内
にあるようにすれば、ＫC を 0.25min-1以上の高い値と
することができる。更に、400ppmから450ppmの範囲内に
調整することによりＫC がおよそ 0.3 min-1以上の大き
な脱炭速度が得られる。As can be seen from FIG. 1 (b), if the active oxygen content in the molten steel after vacuum decarburization is within the range of 350 ppm to 500 ppm, the K C will be as high as 0.25 min -1 or higher. It can be a value. Furthermore, a large decarburization rate of K C of about 0.3 min −1 or more can be obtained by adjusting the content within the range of 400 ppm to 450 ppm.
【００２９】真空脱炭処理後の溶鋼中活量酸素の調整
は、例えば図１（ａ）に基づいて行うことができる。即
ち、出鋼時の溶鋼中活量酸素が約 600ppm 以上の場合
(図１（ａ）のａo 過剰域にある場合) には真空脱炭処
理前の取鍋内溶鋼中に脱酸剤を添加して予備脱酸を行
う。このときの脱酸剤添加量は下記 (4)式で計算でき
る。反対に出鋼時の溶鋼中活量酸素が約 425ppm 以下の
場合 (図１（ａ）のａo 過少域にある場合) には、後述
の(5) 、(6) 式で計算される酸素含有物質を溶鋼に添加
する。こうして脱炭処理前の溶鋼中活量酸素をおよそ 4
25〜600 ppm の範囲内に調整すれば、脱炭処理後の溶鋼
中の活量酸素を、前述の 350ppm から 500ppm の範囲内
に収めることが可能になる。The activity oxygen in the molten steel after the vacuum decarburization treatment can be adjusted, for example, based on FIG. 1 (a). That is, when the activity oxygen in molten steel at the time of tapping is about 600 ppm or more
In the case of ao excess area in Fig. 1 (a), a deoxidizer is added to the molten steel in the ladle before vacuum decarburization to perform preliminary deoxidation. The amount of deoxidizer added at this time can be calculated by the following equation (4). Oxygen molten steel Chukatsu amount of oxygen during tapping the opposite in the case of less than about 425 ppm (when in a o under-region of FIG. 1 (a)), which will be described later (5), which is calculated by the equation (6) The contained substance is added to the molten steel. In this way, the active oxygen content in the molten steel before decarburization was reduced to approximately 4
By adjusting the concentration within the range of 25 to 600 ppm, it becomes possible to keep the active oxygen in the molten steel after the decarburization treatment within the above-mentioned range of 350 to 500 ppm.
【００３０】 ＷDO＝ (0.001/η) ・｛ａo −(425〜600)｝・ (ＤＯth／Ｏth) ・・・(4) ただし、ＷDO：脱酸剤添加量(kg/t)、 ａo ：出鋼時
溶鋼中活量酸素(ppm) ＤＯth：化学量論反応脱酸剤量、 Ｏth：化学量論反応
酸素量 η：脱酸剤の種類、脱酸量に応じて変化する脱酸効率。W DO = (0.001 / η) · {a o − (425 to 600)} · (DO th / O th ) ... (4) where W DO : amount of deoxidizer added (kg / t ), A o : activity oxygen in molten steel during tapping (ppm) DO th : stoichiometric reaction deoxidizer amount, O th : stoichiometric reaction oxygen amount η: depending on deoxidizer type and deoxidation amount Deoxidizing efficiency that changes with
【００３１】真空脱炭処理中の溶鋼中活量酸素の測定に
よって、真空脱炭後の溶鋼中活量酸素が 350ppm 以下に
低下することが予測される場合には、取鍋内の溶鋼また
は真空槽内の溶鋼に酸素含有物質を供給して溶鋼中活量
酸素を高める。真空槽内溶鋼への供給は、脱ガス装置に
付属するガス吹き込み装置から真空槽内溶鋼表面または
溶鋼中に酸化性ガスを吹き込むか、または粉体吹き込み
装置または合金投入バンカーから粉状または塊状の固体
酸化物を真空槽内の溶鋼に添加して行うことができる。
このときの酸化性ガス (O2の場合) の吹き込み量または
固体酸化物(Fe2O3の場合) の添加量は、それぞれ下記
(5)、(6) 式にしたがって算出できる。When the activity oxygen in molten steel during vacuum decarburization is predicted to decrease to 350 ppm or less after vacuum decarburization, the molten steel in the ladle or vacuum An oxygen-containing substance is supplied to the molten steel in the tank to increase active oxygen in the molten steel. Supplying to the molten steel in the vacuum tank is performed by blowing an oxidizing gas from the gas blowing device attached to the degassing device into the molten steel surface in the vacuum tank or into the molten steel, or in the form of powder or lumps from the powder blowing device or the alloy charging bunker. The solid oxide can be added to the molten steel in the vacuum chamber.
At this time, the blowing amount of the oxidizing gas (in the case of O 2 ) or the addition amount of the solid oxide (in the case of Fe 2 O 3 ) was as follows.
It can be calculated according to equations (5) and (6).
【００３２】[0032]
【数１】 [Equation 1]
【００３３】以下、実施例にもとづいて本発明の効果を
説明する。The effects of the present invention will be described below based on examples.
【００３４】[0034]
【実施例１】250tonの上底吹き転炉で吹錬した炭素濃度
が0.03％〜0.07％の溶鋼を取鍋に出鋼した。出鋼時の炭
素以外の溶鋼成分は、 Si ＜0.01％、 Mn ＝0.05〜0.4
％、Ｐ ＝ 0.003〜0.02％、 Ｓ ＝ 0.003〜0.02％、
Ｎ ＝0.0008〜0.002 ％の範囲であった。Example 1 Molten steel having a carbon concentration of 0.03% to 0.07% blown in a 250 ton top-bottom blowing converter was tapped into a ladle. Molten steel components other than carbon at the time of tapping are Si <0.01%, Mn = 0.05 to 0.4
%, P = 0.003 to 0.02%, S = 0.003 to 0.02%,
N was in the range of 0.0008 to 0.002%.
【００３５】このとき、出鋼時取鍋内の溶鋼中活量酸素
は 300〜800 ppm の範囲でばらついていたので、溶鋼中
活量酸素が 600ppm 以上の場合は前記 (4)式から算出し
た量のAlを添加して、目標活量酸素 500ppm に調整した
（表１の試験No.1および2)。At this time, since the active oxygen in the molten steel in the ladle at the time of tapping varied in the range of 300 to 800 ppm, when the active oxygen in the molten steel was 600 ppm or more, it was calculated from the above formula (4). The target activity oxygen was adjusted to 500 ppm by adding an amount of Al (test Nos. 1 and 2 in Table 1).
【００３６】真空脱ガス処理には図２に示すＲＨ脱ガス
装置を使用した。The RH degassing apparatus shown in FIG. 2 was used for the vacuum degassing process.
【００３７】ＲＨ脱ガス条件としては、浸漬管４の内径
600〜750mm 、環流Arガス流量２〜３Nm3/min 、真空槽
３の到達真空度１torr以下とした。The RH degassing condition is as follows:
The flow rate was 600 to 750 mm, the flow rate of the circulating Ar gas was 2 to 3 Nm 3 / min, and the ultimate vacuum of the vacuum chamber 3 was 1 torr or less.
【００３８】先端に固体電解質型酸素センサーを取付け
た活量酸素測定用ランス７を溶鋼２中に浸漬してａ0 を
測定しつつ真空脱炭処理を行い、脱炭処理後の溶鋼中活
量酸素ａ0 が 350ppm 未満となることが予測された場合
は、ＲＨ処理初期に酸素を真空槽内に供給し脱炭処理後
の溶鋼中のａ0 が350ppm以上になるようにした。送酸速
度は 0.1〜0.2Nm3/min・溶鋼T とし、脱炭処理後の溶鋼
中のａ0 が 350〜500ppm(目標 400〜450 ppm)になるよ
うに酸素を供給して極低炭素鋼を溶製した（表１の試験
No.3〜9)。An activity oxygen measuring lance 7 having a solid electrolyte type oxygen sensor attached to its tip is immersed in the molten steel 2 and vacuum decarburization is performed while measuring a 0, and the activity in the molten steel after the decarburization treatment is carried out. When the oxygen a 0 was predicted to be less than 350 ppm, oxygen was supplied into the vacuum tank at the initial stage of the RH treatment so that the a 0 in the molten steel after the decarburizing treatment was 350 ppm or more. The acid transfer rate is 0.1 to 0.2 Nm 3 / min · Molten steel T, and oxygen is supplied so that a 0 in the molten steel after decarburization is 350 to 500 ppm (target 400 to 450 ppm). Was melted (test of Table 1
No.3 ~ 9).
【００３９】[0039]
【比較例１】出鋼時のａ0 が 600ppm 以上でも予備脱酸
を実施せず (試験No. 10〜12) 、また、真空脱炭後のａ
0 が350ppm未満になると予想される場合でも送酸を実施
せず(試験 No.13〜17) に極低炭素鋼を溶製した。[Comparative Example 1] a 0 when steel out without a preliminary deoxidation even more 600 ppm (test No. 10 to 12), also, a post-vacuum decarburization
Even when 0 was expected to be less than 350 ppm, ultra-low carbon steel was melted without carrying out acid transfer (Test Nos. 13 to 17).
【００４０】上記の実施例と比較例の操業条件と操業成
績を表１に示す。Table 1 shows the operating conditions and operating results of the above examples and comparative examples.
【００４１】比較例の脱炭速度定数ｋc が0.07〜0.24 m
in-1の低い値の範囲内でばらついているのに対し、実施
例ではばらつきが小さく、0.29〜0.34 min-1と値も大き
い。The decarburization rate constant kc of the comparative example was 0.07 to 0.24 m.
While being distributed in a range of low values of in -1, small variations in the embodiment, even larger .29-.34 min -1 and values.
【００４２】その結果、炭素濃度200ppmから 20ppmへの
脱炭時間は、比較例で 9.6〜32.9minであるものが、本
発明方法では 6.8〜7.9minに短縮され、しかも脱炭時間
のばらつきも小さくなる。As a result, the decarburization time from the carbon concentration of 200 ppm to 20 ppm was 9.6 to 32.9 min in the comparative example, but was shortened to 6.8 to 7.9 min in the method of the present invention, and the variation of the decarburization time was small. Become.
【００４３】[0043]
【表１】 [Table 1]
【００４４】[0044]
【実施例２】真空脱ガス装置として、図３に示す真空脱
ガス装置を使用した。Example 2 The vacuum degassing apparatus shown in FIG. 3 was used as the vacuum degassing apparatus.
【００４５】脱ガス条件を、浸漬管４の内径2000mm、溶
鋼攪拌用Arガス流量２〜３Nm3/min、到達真空度１torr
以下とした以外は実施例１と同様の条件で極低炭素鋼を
溶製した。表２の試験No.1〜3 は出鋼時の溶鋼中のａ0
が 600ppm 以上でAl予備脱酸を実施した場合、試験No.5
〜7 は真空脱炭処理中に送酸を実施した場合である。The degassing conditions are as follows: the inner diameter of the immersion pipe 4 is 2000 mm, the flow rate of Ar gas for stirring molten steel is 2 to 3 Nm 3 / min, and the ultimate vacuum is 1 torr.
Ultra-low carbon steel was melted under the same conditions as in Example 1 except for the following. Test Nos. 1 to 3 in Table 2 are a 0 in the molten steel at the time of tapping.
When Al pre-deoxidation is carried out at a concentration of 600 ppm or more, test No. 5
~ 7 is the case where the acid transfer was carried out during the vacuum decarburization treatment.
【００４６】[0046]
【比較例２】出鋼時の溶鋼中のａ0 が600ppm以上でも予
備脱酸を実施せず（表２の試験No.8〜10）あるいは真空
脱炭後のａ0 が350ppm以下でも送酸を実施せず（表２の
試験No.11〜13）に極低炭素鋼を溶製した場合である。
表２に操業条件と操業成績を示す。[Comparative Example 2] Even if a 0 in molten steel at the time of tapping is 600 ppm or more, preliminary deoxidation is not carried out (test Nos. 8 to 10 in Table 2) or even if a 0 after vacuum decarburization is 350 ppm or less, acid transfer Is carried out (Test Nos. 11 to 13 in Table 2) without performing the above process.
Table 2 shows the operating conditions and operating results.
【００４７】比較例２の脱炭速度定数ｋC ＝0.11〜0.23
min-1に対し、実施例２ではｋC ＝0.31〜0.34 min-1に
改善された。この脱炭速度改善効果により炭素濃度200p
pmから20ppm までの脱炭時間は10.9〜20.9min から 6.8
〜7.4 min に短縮され、ばらつきもごく小さい範囲にす
ることができた。Decarburization rate constant k C of Comparative Example 2 = 0.11 to 0.23
to min -1, it was improved k C = 0.31~0.34 min -1 in Example 2. Due to this decarburization rate improvement effect, carbon concentration of 200p
Decarburization time from pm to 20ppm is from 10.9 to 20.9min to 6.8
It was shortened to ~ 7.4 min, and the variation could be kept within a very small range.
【００４８】[0048]
【表２】 [Table 2]
【００４９】[0049]
【発明の効果】本発明方法によれば、前述のように真空
脱炭処理時間が短縮でき、しかも処理時間のばらつきも
小さくなる。それによって、極低炭素鋼の高速溶製が可
能となり、生産計画に沿って安定した操業が可能とな
る。As described above, according to the method of the present invention, the vacuum decarburization processing time can be shortened and the processing time variation can be reduced. This enables high-speed smelting of ultra-low carbon steel and enables stable operation according to the production plan.
【図１】（ａ）は出鋼時の低炭素溶鋼中の活量酸素と真
空脱炭処理後の極低炭素溶鋼中の活量酸素との関係を示
す図、（ｂ）は極低炭素溶鋼中の活量酸素と脱炭速度定
数との関係を示す図、である。FIG. 1 (a) is a diagram showing a relationship between active oxygen in low carbon molten steel at the time of tapping and active oxygen in extremely low carbon molten steel after vacuum decarburization treatment, and (b) is extremely low carbon. It is a figure which shows the relationship between the activity oxygen in molten steel, and a decarburization rate constant.
【図２】本発明の実施例で使用したＲＨ真空脱ガス装置
の概略縦断面図である。FIG. 2 is a schematic vertical sectional view of an RH vacuum degassing apparatus used in an example of the present invention.
【図３】本発明の他の実施例で使用したＤＨ真空脱ガス
装置の概略縦断面図である。FIG. 3 is a schematic vertical sectional view of a DH vacuum degassing apparatus used in another embodiment of the present invention.
１: 取鍋、２: 溶鋼、３: 真空槽、４: 浸漬管、５: ガ
ス・粉体吹込装置 ６: 合金投入バンカー、７: 活量酸素測定ランス1: Ladle, 2: Molten steel, 3: Vacuum tank, 4: Immersion pipe, 5: Gas / powder injection device, 6: Alloy injection bunker, 7: Lance for measuring oxygen activity
Claims (3)
〜500 ppm となるように脱炭処理前の溶鋼または脱炭処
理中の溶鋼の酸素含有量を調整して脱炭処理を行うこと
を特徴とする極低炭素鋼の製造方法。1. The activity oxygen in molten steel after vacuum decarburization is 350
A method for producing an ultra-low carbon steel, which comprises performing decarburization treatment by adjusting the oxygen content of the molten steel before the decarburization treatment or the molten steel during the decarburization treatment so as to be up to 500 ppm.
な場合にはその溶鋼に脱酸剤を添加し、過少な場合には
脱炭処理前または脱炭処理中の溶鋼に酸素含有物質を添
加することによって、真空脱炭処理後の溶鋼中の活量酸
素が 350〜500 ppm となるように調整して脱炭処理を行
うことを特徴とする極低炭素鋼の製造方法。2. When the activity oxygen in the molten steel before vacuum decarburization treatment is excessive, a deoxidizing agent is added to the molten steel, and when it is too small, it is added to the molten steel before decarburization treatment or during decarburization treatment. A method for producing ultra-low carbon steel characterized by performing decarburization treatment by adjusting the active oxygen in molten steel after vacuum decarburization treatment to be 350 to 500 ppm by adding an oxygen-containing substance. .
して、取鍋内の溶鋼中活量酸素を定期的または連続的に
測定し、脱炭処理後の溶鋼中活量酸素が350ppm未満に低
下することが予測される場合には、真空槽内の溶鋼に酸
化性ガスを吹き込むか、または固体酸化物を添加して、
真空脱炭処理後の溶鋼中の活量酸素が 350〜500ppmにな
るように調整しつつ脱炭処理を行うことを特徴とする極
低炭素鋼の製造方法。3. When performing vacuum decarburization with a vacuum degasser, the active oxygen in molten steel in the ladle is measured regularly or continuously, and the active oxygen in molten steel after decarburization is less than 350 ppm. If it is expected to decrease to, the oxidizing gas is blown into the molten steel in the vacuum tank, or solid oxide is added,
A method for producing ultra-low carbon steel, which comprises performing decarburization while adjusting the activity oxygen in molten steel after vacuum decarburization to be 350 to 500 ppm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18920792A JPH0633133A (en) | 1992-07-16 | 1992-07-16 | Production of ultralow carbon steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18920792A JPH0633133A (en) | 1992-07-16 | 1992-07-16 | Production of ultralow carbon steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0633133A true JPH0633133A (en) | 1994-02-08 |
Family
ID=16237333
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18920792A Pending JPH0633133A (en) | 1992-07-16 | 1992-07-16 | Production of ultralow carbon steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0633133A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08291319A (en) * | 1995-04-20 | 1996-11-05 | Nippon Steel Corp | Method for smelting dead-soft steel |
| US6992737B2 (en) | 2002-03-08 | 2006-01-31 | Seiko Epson Corporation | Color filter substrate, electrooptic device and electronic apparatus, and methods for manufacturing color filter substrate and electrooptic device |
| CN112646954A (en) * | 2020-11-23 | 2021-04-13 | 首钢集团有限公司 | RH refining method for improving removal rate of ultra-low carbon steel inclusions |
-
1992
- 1992-07-16 JP JP18920792A patent/JPH0633133A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08291319A (en) * | 1995-04-20 | 1996-11-05 | Nippon Steel Corp | Method for smelting dead-soft steel |
| US6992737B2 (en) | 2002-03-08 | 2006-01-31 | Seiko Epson Corporation | Color filter substrate, electrooptic device and electronic apparatus, and methods for manufacturing color filter substrate and electrooptic device |
| CN112646954A (en) * | 2020-11-23 | 2021-04-13 | 首钢集团有限公司 | RH refining method for improving removal rate of ultra-low carbon steel inclusions |
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