JPS6354045B2 - - Google Patents
Info
- Publication number
- JPS6354045B2 JPS6354045B2 JP12006981A JP12006981A JPS6354045B2 JP S6354045 B2 JPS6354045 B2 JP S6354045B2 JP 12006981 A JP12006981 A JP 12006981A JP 12006981 A JP12006981 A JP 12006981A JP S6354045 B2 JPS6354045 B2 JP S6354045B2
- Authority
- JP
- Japan
- Prior art keywords
- steel
- molten steel
- refining
- decarburization
- added
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- 229910000831 Steel Inorganic materials 0.000 claims description 39
- 239000010959 steel Substances 0.000 claims description 39
- 238000000034 method Methods 0.000 claims description 27
- 238000007670 refining Methods 0.000 claims description 21
- 239000003638 chemical reducing agent Substances 0.000 claims description 11
- 238000010079 rubber tapping Methods 0.000 claims description 11
- 239000011261 inert gas Substances 0.000 claims description 10
- 239000002904 solvent Substances 0.000 claims description 10
- 229910001220 stainless steel Inorganic materials 0.000 claims description 3
- 238000005261 decarburization Methods 0.000 description 19
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 18
- 238000006722 reduction reaction Methods 0.000 description 14
- 239000011819 refractory material Substances 0.000 description 10
- 229910052786 argon Inorganic materials 0.000 description 9
- 239000011651 chromium Substances 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- 230000009467 reduction Effects 0.000 description 8
- 238000006477 desulfuration reaction Methods 0.000 description 6
- 230000023556 desulfurization Effects 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 239000002893 slag Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 229910017082 Fe-Si Inorganic materials 0.000 description 4
- 229910017133 Fe—Si Inorganic materials 0.000 description 4
- 238000007664 blowing Methods 0.000 description 4
- 230000003628 erosive effect Effects 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 238000005978 reductive desulfurization reaction Methods 0.000 description 3
- 230000002829 reductive effect Effects 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000011017 operating method Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
- C21C7/0685—Decarburising of stainless steel
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Description
【発明の詳細な説明】
本発明は脱炭精錬終了後の溶鋼の還元精錬ある
いは脱硫精錬に関する方法である。
溶鋼の脱炭精錬法、例えばAOD（Argon
Oxygen Decaburization）法に代表される希釈
脱炭によるステンレスの精錬法に於て最大の問題
は耐火物コスト及び不活性ガスコストを如何にし
て切下げるがである。
AOD法は第１図に示す如く溶鋼１を収容した
転炉２の炉底部側壁に取付けられた羽口３から酸
素ガスと不活性ガスの混合気体を吹込むため、溶
鋼の撹拌エネルギーは極めて大きい。このため溶
鋼と接触する耐火物は高温の溶鋼により激しく表
面を洗われるのでその損耗速度は極めて大きい。
近年耐火物の品質が改善され、又AOD法の操業
方法も著しい進歩を遂げたが、普通鋼転炉の炉体
寿命レベルである1000回以上にはほど遠いレベル
である。
炉体寿命を極力延長させるにはワン・ヒートの
精錬時間を出来るだけ短くしかつワン・ヒート精
錬過程で最も耐火物を溶損する時期を省略するこ
とである。
溶損された耐火物の量を知るための極く一般的
な方法として、例えばAOD炉に於いては一般的
にはMgO―Cr2O3又はMgO―CaO系の耐火物を
使用しているので精錬の各過程に於けるスラグ中
のMgOの増加量を求めればよい。
この方法を用いて精錬の各過程におけるスラグ
中のMgOの増加量を求めたのが第２図である。
この図から明らかな如く、脱炭終了後の還元期、
脱硫期にスラグ中のMgO量の著しい増加が認め
られる。従つて耐火物の溶損は、還元脱硫期を省
略出来れば格段に少なくなることが予想され、ま
た精錬所要時間の短縮によりこの間に吹込まれる
不活性ガスの大幅な削減が期待出来る。
以上のような考えから本発明者等は種々の実験
を繰返した結果、還元脱硫期を大幅に短縮し、炉
体寿命の大幅な延長、即ち耐火物コストの大幅な
削減及び精錬時間短縮による吹込みガスの大幅な
削減を可能とする溶鋼の精錬方法を開発したもの
である。
以下本発明を詳細に説明する。
以下本発明法と通常のAOD精錬法とを比較し
て第３図を参照にして説明する。第３図ａは従来
のAOD法を示し、鋼中の炭素を効率よく脱炭す
るために鋼中炭素量の推移に応じて吹込む酸素と
アルゴンの比率を変えて、鋼中のクロムを極力酸
化しないように脱炭していく。しかし一般に鋼中
のクロムが２％前後酸化されるため脱炭終了後に
媒溶剤（CaO等）及び還元剤（Fe―Si等）を添
加し適度の時間不活性ガス吹込みにより溶鋼を撹
拌し、酸化したクロムを還元した後に還元反応に
よつて生じたスラグを除去し、引き続き媒溶剤を
添加することと同時に添加した媒溶剤によつて脱
硫を行つた後に出鋼している。
これに対して本発明では第３図ｂに示すように
脱炭終了後還元剤（Fe−Si等）を添加し、還元
剤を拡散させ溶解し易くした後出鋼する。なお還
元剤添加終了後から出鋼までの間に0.5〜１分間
前記溶鋼の撹拌を継続することが望ましい。
AOD炉耐火物の溶損は前記の通り脱炭終了から
出鋼までの還元脱硫工程において特に大である。
従つてこの工程の所要時間はできるだけ短かくし
なければならない。
本発明においては還元剤添加後から出鋼開始ま
での時間を還元反応の進度、言い換えれば還元率
との関係において限定したものである。すなわち
還元剤添加後から３分を越えた時間経過すると還
元反応が短時間のうちに急速に進行して耐火物の
溶損が特に大となることがわかつた。
本発明は特に耐火物溶損の大きい時期にスラグ
が耐火物に触れる時間を短縮するものである。す
なわち還元剤添加後３分以内に取鍋に出鋼する。
この出鋼過程において出鋼流中でスラグとメタル
間の強力な撹拌作用が得られ、還元反応が極めて
効率よく進行し、スラグ中のクロム酸の含有量は
従来法におけるAOD炉内での還元期終了時とほ
ぼ同じレベルまで低下する。すなわち還元剤添加
後３分以内に出鋼することにより耐火物溶損防止
と効率の高い還元反応を得、さらには従来還元反
応促進のため炉内に吹込んでいた不活性ガスを節
減できる。
取鍋内に収容された溶鋼に対し更に補足的な還
元と必要に応じて若干の成分調整及び温度コント
ロールを目的として出鋼後、少なくとも５分間の
不活性ガス（アルゴンガス等）吹込みを伴う処置
の後、連続鋳造又は造塊鋳込みを行う。前記出鋼
後のアルゴンガス吹込を伴う処置が５分未満では
溶鋼の均一混合が不十分である他、成分調整用の
添加した合金等が均一溶解しない。なお出鋼終了
後の取鍋内溶鋼温度は５分以上の不活性ガス吹込
みを行つても鋳込み温度が確保されるように設定
する。また取鍋内に吹込む不活性ガス量は２／
min・ｔ以上が望ましい。
本発明において脱炭終了後に還元剤とともに
CaO等の媒溶剤を添加することにより還元精錬の
他に脱硫精錬を同時に行うことができる。しかし
この媒溶剤を脱炭終了後に一括投入することは溶
鋼温度を下げることになるためその分だけ高温に
しておく必要が生じる。これは耐火物溶損の観点
から好ましくない。また低温では脱硫反応が十分
に進行しない場合がある。これを防止するために
は媒溶剤の一部又は全部を脱炭終了前に添加し予
め予熱しておくことである。またこれにより媒溶
剤によつて持ち来たされる水分を事前に除去して
おくことができる。
本発明法により、従来脱炭終了から出鋼開始ま
でに約15分を要していたものを３分以下に短縮し
たものでありこれにより従来法を100とする耐火
物溶損指数を約50に減少することができた。また
脱炭終了から鋳込み開始までに消費する不活性ガ
ス、例えばアルゴンガスの消費量指数も従来法を
100とした場合約80に減少した。
以下ステンレス鋼の脱炭精錬における実施例を
示す。
実施例 １
脱炭終了後還元に必要な量のFe―Siを添加し、
添加後３分経過後に取鍋に出鋼した。
実施例 ２
脱炭終了後アルゴンガスを溶鋼中に吹込みつつ
還元に必要な量のFe―Siを添加し、添加後１分
経過後に取鍋に出鋼した。
実施例 ３
脱炭終了前に脱硫に必要な量の媒溶剤の一部と
してCaOを添加し、脱炭終了後アルゴンガスを溶
鋼中に吹込みつつ残りのCaOと還元に必要な量の
Fe―Siを添加し、添加後１分経過後に取鍋に出
鋼した。
実施例 ４
脱炭終了前に脱硫に必要な量の媒溶剤の一部と
してCaOを添加し、脱炭終了後アルゴンガスを溶
鋼中に吹込みつつ残りのCaOと還元に必要な量の
Fe―Siを添加し、添加後１分経過後に取鍋に出
鋼した。該取鍋内溶鋼中にアルゴンガスを５分間
吹込んだ後連続鋳造した。
表１に各実施例および従来例によるCr歩留お
よび成品成分を示す。また第４図に実施例３と従
来例におけるCr歩留と溶鋼中Ｓの推移を示す。
【表】DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for reduction refining or desulfurization refining of molten steel after completion of decarburization refining. Decarburization refining methods for molten steel, such as AOD (Argon
The biggest problem in stainless steel refining methods by dilution decarburization, such as the oxygen decaburization method, is how to reduce the cost of refractories and inert gas. As shown in Figure 1, in the AOD method, a mixture of oxygen gas and inert gas is blown into the tuyere 3 attached to the bottom side wall of the converter 2 containing the molten steel 1, so the energy for stirring the molten steel is extremely large. . For this reason, the surface of the refractories that come into contact with the molten steel is violently washed by the high-temperature molten steel, so that the rate of wear and tear is extremely high.
Although the quality of refractories has improved in recent years and the operating method of the AOD method has made significant progress, it is still far from reaching the 1,000-cycle lifespan of ordinary steel converters. In order to extend the life of the furnace body as much as possible, it is necessary to shorten the one-heat refining time as much as possible and to omit the period in which refractories are most likely to be eroded during the one-heat refining process. A very common method for determining the amount of refractories that has been eroded is, for example, in AOD furnaces, MgO-Cr 2 O 3 or MgO-CaO type refractories are generally used. Therefore, it is sufficient to calculate the amount of increase in MgO in the slag during each refining process. Figure 2 shows the increase in MgO in the slag during each refining process using this method.
As is clear from this figure, the reduction period after decarburization,
A significant increase in the amount of MgO in the slag is observed during the desulfurization stage. Therefore, it is expected that the erosion of refractories will be significantly reduced if the reductive desulfurization stage can be omitted, and the amount of inert gas injected during this period can be expected to be significantly reduced by shortening the time required for refining. Based on the above considerations, the inventors of the present invention have repeatedly conducted various experiments, and as a result, they have found that the reductive desulfurization period can be significantly shortened, the life of the furnace body can be significantly extended, that is, the cost of refractories can be significantly reduced, and the refining time can be shortened. The company has developed a method for refining molten steel that makes it possible to significantly reduce the amount of mixed gas. The present invention will be explained in detail below. The method of the present invention and the conventional AOD refining method will be compared and explained below with reference to FIG. Figure 3a shows the conventional AOD method. In order to efficiently decarburize the carbon in steel, the ratio of oxygen and argon injected is changed according to the change in the amount of carbon in the steel, and the chromium in the steel is removed as much as possible. Decarburize to prevent oxidation. However, in general, around 2% of the chromium in steel is oxidized, so after decarburization is complete, a solvent (CaO, etc.) and a reducing agent (Fe-Si, etc.) are added and the molten steel is stirred by blowing inert gas for a suitable period of time. After reducing the oxidized chromium, the slag produced by the reduction reaction is removed, a solvent is subsequently added, and the steel is desulfurized using the solvent added at the same time, and then the steel is tapped. On the other hand, in the present invention, as shown in FIG. 3b, a reducing agent (Fe--Si, etc.) is added after decarburization, and the reducing agent is diffused to facilitate melting before being tapped. Note that it is desirable to continue stirring the molten steel for 0.5 to 1 minute from the end of adding the reducing agent to the time of tapping.
As mentioned above, the erosion of AOD furnace refractories is particularly large during the reductive desulfurization process from the end of decarburization to tapping.
Therefore, the time required for this step must be kept as short as possible. In the present invention, the time from the addition of the reducing agent to the start of steel tapping is limited in relation to the progress of the reduction reaction, in other words, the reduction rate. That is, it was found that when more than 3 minutes elapsed after the addition of the reducing agent, the reduction reaction rapidly progressed in a short period of time, and the melting loss of the refractory became particularly large. The present invention is intended to shorten the time that slag is in contact with refractories, especially during periods when refractory erosion is large. That is, the steel is tapped into a ladle within 3 minutes after adding the reducing agent.
In this tapping process, a strong stirring action between the slag and the metal is obtained in the tapping stream, and the reduction reaction proceeds extremely efficiently. It will drop to almost the same level as at the end of the period. That is, by tapping the steel within 3 minutes after adding the reducing agent, it is possible to prevent the melting of the refractory and obtain a highly efficient reduction reaction, and furthermore, it is possible to save the inert gas conventionally blown into the furnace to promote the reduction reaction. After tapping, inert gas (argon gas, etc.) is injected for at least 5 minutes for the purpose of further reducing the molten steel contained in the ladle and, if necessary, adjusting the composition and controlling the temperature. After treatment, continuous casting or ingot casting is performed. If the procedure involving argon gas blowing after tapping is carried out for less than 5 minutes, the molten steel will not be sufficiently mixed uniformly, and the alloy added for component adjustment will not be uniformly melted. The temperature of the molten steel in the ladle after tapping is set so that the casting temperature is maintained even if inert gas is blown for 5 minutes or more. Also, the amount of inert gas blown into the ladle is 2/
It is desirable that it is min·t or more. In the present invention, together with the reducing agent after the decarburization
By adding a solvent such as CaO, desulfurization refining can be performed simultaneously in addition to reduction refining. However, if this solvent is added all at once after the decarburization is completed, the temperature of the molten steel will be lowered, so it will be necessary to keep the temperature high. This is unfavorable from the viewpoint of corrosion of the refractory. Furthermore, the desulfurization reaction may not proceed sufficiently at low temperatures. In order to prevent this, part or all of the solvent should be added and preheated before the decarburization is completed. This also allows moisture brought in by the solvent to be removed in advance. With the method of the present invention, the conventional method of taking about 15 minutes from the end of decarburization to the start of steel tapping has been shortened to less than 3 minutes. was able to decrease to. In addition, the consumption index of inert gas, such as argon gas, consumed from the end of decarburization to the start of casting is also lower than that of the conventional method.
When set to 100, it decreased to about 80. An example of decarburization refining of stainless steel will be shown below. Example 1 After the completion of decarburization, add Fe-Si in the amount necessary for reduction,
Three minutes after the addition, the steel was tapped into a ladle. Example 2 After the completion of decarburization, while blowing argon gas into the molten steel, an amount of Fe--Si necessary for reduction was added, and 1 minute after the addition, the steel was tapped into a ladle. Example 3 Before the completion of decarburization, CaO was added as part of the solvent in the amount necessary for desulfurization, and after the completion of decarburization, argon gas was blown into the molten steel and the remaining CaO and the amount necessary for reduction were added.
Fe—Si was added, and 1 minute after addition, the steel was tapped into a ladle. Example 4 Before the completion of decarburization, CaO is added as part of the solvent in the amount required for desulfurization, and after the completion of decarburization, while argon gas is blown into the molten steel, the remaining CaO and the amount necessary for reduction are added.
Fe—Si was added, and 1 minute after addition, the steel was tapped into a ladle. After blowing argon gas into the molten steel in the ladle for 5 minutes, continuous casting was performed. Table 1 shows the Cr yield and product components of each example and conventional example. Furthermore, FIG. 4 shows the changes in Cr yield and S in molten steel in Example 3 and the conventional example. 【table】
第１図はAOD法の実施態様の説明図、第２図
は精錬の各過程における耐火物溶損量指数を示す
図、第３図ａは通常のAOD法、同じくｂは本発
明を適用したAOD法の説明図、第４図ａは従来
法のCr歩留と溶鋼中Ｓの推移を示す図、第４図
ｂは本発明実施例３のCr歩留と溶鋼中Ｓの推移
を示す図である。
Figure 1 is an explanatory diagram of the embodiment of the AOD method, Figure 2 is a diagram showing the refractory erosion amount index in each process of refining, Figure 3 a is the normal AOD method, and similarly Figure b is the case where the present invention is applied. An explanatory diagram of the AOD method. Figure 4a is a diagram showing the transition of Cr yield and S in molten steel in the conventional method. Figure 4b is a diagram showing the transition of Cr yield and S in molten steel in Example 3 of the present invention. It is.
Claims (1)
還元剤添加後３分以内に取鍋に出鋼することを特
徴とする溶鋼の精錬方法。 ２ 還元剤の添加と同時に不活性ガス吹込みを行
うことを特徴とする特許請求の範囲第１項記載の
溶鋼の精錬方法。 ３ 媒溶剤を添加することを特徴とする特許請求
の範囲第１項又は第２項記載の溶鋼の精錬方法。[Claims] 1. In refining high chromium steel by AOD method,
A method for refining molten steel characterized by tapping the steel into a ladle within 3 minutes after adding a reducing agent. 2. The method for refining molten steel according to claim 1, characterized in that inert gas is blown simultaneously with the addition of the reducing agent. 3. The method for refining molten steel according to claim 1 or 2, characterized in that a solvent is added.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12006981A JPS5822318A (en) | 1981-07-31 | 1981-07-31 | Refining process for molten steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12006981A JPS5822318A (en) | 1981-07-31 | 1981-07-31 | Refining process for molten steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5822318A JPS5822318A (en) | 1983-02-09 |
| JPS6354045B2 true JPS6354045B2 (en) | 1988-10-26 |
Family
ID=14777115
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12006981A Granted JPS5822318A (en) | 1981-07-31 | 1981-07-31 | Refining process for molten steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5822318A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59162215A (en) * | 1983-03-05 | 1984-09-13 | Nippon Steel Corp | Treatment of molten steel under pressure |
| JPS6152353U (en) * | 1984-09-10 | 1986-04-08 | ||
| JPH045217Y2 (en) * | 1984-10-29 | 1992-02-14 | ||
| US4705279A (en) * | 1986-06-25 | 1987-11-10 | Ye Data Inc. | Device for clamping a flexible disk |
| JPS63130948U (en) * | 1987-02-19 | 1988-08-26 |
-
1981
- 1981-07-31 JP JP12006981A patent/JPS5822318A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5822318A (en) | 1983-02-09 |
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