JPH11315319A - Method for blowing oxygen into molten metal under reduced pressure - Google Patents
Method for blowing oxygen into molten metal under reduced pressureInfo
- Publication number
- JPH11315319A JPH11315319A JP12564598A JP12564598A JPH11315319A JP H11315319 A JPH11315319 A JP H11315319A JP 12564598 A JP12564598 A JP 12564598A JP 12564598 A JP12564598 A JP 12564598A JP H11315319 A JPH11315319 A JP H11315319A
- Authority
- JP
- Japan
- Prior art keywords
- lance
- nozzle
- reduced pressure
- sectional area
- molten metal
- 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.)
- Withdrawn
Links
Landscapes
- Manufacture And Refinement Of Metals (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は減圧下の溶融金属に
上吹きランスより酸素ガスを吹き付ける精錬方法に関す
るものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refining method for blowing oxygen gas onto a molten metal under reduced pressure from an upper blowing lance.
【0002】[0002]
【従来の技術】RH、VOD等の減圧精錬容器中での溶
鉄の脱炭精錬時に、脱炭に必要な酸素を上吹きランスよ
り吹き付ける方法が行われている。普通鋼の精錬に使用
されるRHにおいては、脱炭効率の向上、脱炭時間の短
縮、溶鋼昇熱等を目的として適宜酸素供給が行われる
が、ステンレス鋼の精錬に使用されるVODにおいて
は、溶鋼中の酸素の一部がCrの燃焼に消費されるため
酸素供給は必須である。2. Description of the Related Art During decarburization and refining of molten iron in a vacuum refining vessel such as RH and VOD, a method of blowing oxygen required for decarburization from an upper blowing lance has been used. In RH used for refining ordinary steel, oxygen is appropriately supplied for the purpose of improving decarburization efficiency, shortening the decarburization time, raising the temperature of molten steel, etc., but in VOD used for refining stainless steel, Since a part of oxygen in molten steel is consumed for burning Cr, oxygen supply is essential.
【0003】しかしながら、減圧下においては、ノズル
入り側圧と雰囲気圧の比が大きくなり、ランス吐出時の
流速が速くなるため、大気圧下に比べて溶鉄表面に衝突
する噴流の運動エネルギーが大きくなる。従って、噴流
の衝突により生じるスプラッシュやダストなどの溶鉄飛
散量が増加し、ランス、容器内壁、排ガスダクトへの地
金付着による操業性悪化、ダスト発生による歩留まり悪
化、付着地金による溶鉄の汚染などの問題が生じてい
る。[0003] However, under reduced pressure, the ratio of the pressure on the nozzle entrance side to the ambient pressure increases, and the flow velocity during discharge of the lance increases, so that the kinetic energy of the jet impinging on the surface of the molten iron increases as compared with the atmospheric pressure. . Therefore, the amount of splashing of molten iron such as splash and dust caused by the collision of the jet increases, the operability is deteriorated due to the adhesion of metal to the lance, the inner wall of the container and the exhaust gas duct, the yield is reduced due to dust generation, and the molten metal is contaminated by the adhered metal. The problem has arisen.
【0004】これらの課題を解決するために、従来より
様々な方法や装置が多数開示されている。例えば、上吹
きランスから不活性ガスを噴射し、容器内壁へのスプラ
ッシュ付着を防止する方法(特開平3−226515号
公報に記載)、ランス先端部のラバールノズル(=中細
型ノズル)のスロート部と吐出孔部の面積比より決定さ
れるノズルの圧力比に対して、真空度を変更することに
より、脱炭の効率化と二次燃焼による昇熱を別々に行う
方法(特開平5−9555号公報に記載)、酸素吹出部
の末広がり部に燃料ガス供給孔を有するランス(特開平
6−73431号公報に記載)、上吹きランスからの酸
素とは別に排ガスを二次燃焼させる酸素を溶鋼に直接当
たらないように吹き込む方法(特開平7−126737
号公報に記載)などが開示されている。[0004] In order to solve these problems, various methods and apparatuses have been conventionally disclosed. For example, a method of injecting an inert gas from an upper blowing lance to prevent splash from adhering to the inner wall of the container (described in JP-A-3-226515), a method in which a Laval nozzle (= medium-thin type nozzle) at the tip of the lance and A method of separately increasing the decarburization efficiency and increasing the heat by secondary combustion by changing the degree of vacuum with respect to the nozzle pressure ratio determined from the area ratio of the discharge holes (Japanese Patent Application Laid-Open No. 5-9555) Lance having a fuel gas supply hole at the end of the oxygen blowing section (described in JP-A-6-73431), and oxygen for secondary combustion of exhaust gas separately from oxygen from the upper blowing lance to molten steel. A method of blowing so as not to hit directly (JP-A-7-126737)
Described in Japanese Unexamined Patent Publication (KOKAI) No. 2000-214, etc.).
【0005】[0005]
【発明が解決しようとする課題】しかし、特開平3−2
26515号公報に記載の方法では、不活性ガスのガス
コストの増大、不活性ガス吹き込み分の真空排気への負
荷増加などの問題がある。一方、特開平5−9555、
特開平6−73431、特開平7−126737号各公
報に記載の方法は、いずれも積極的な二次燃焼の促進や
燃料ガスの燃焼熱により容器内壁を高温にし、スプラッ
シュの付着を防止したり、付着した地金を溶流する方法
である。これらの方法では、高温下での容器内耐火物へ
の悪影響、排ガスの高温化、酸素ガス効率の悪化、燃料
ガスコストの増大などの問題がある。However, Japanese Patent Laid-Open Publication No. Hei 3-2
The method described in Japanese Patent No. 26515 has problems such as an increase in the cost of the inert gas and an increase in the load on the vacuum exhaust due to the blowing of the inert gas. On the other hand, JP-A-5-9555,
In each of the methods described in JP-A-6-73431 and JP-A-7-126737, the inner wall of the container is heated to a high temperature by actively promoting secondary combustion and the heat of combustion of the fuel gas to prevent the adhesion of splash. This is a method in which the adhered metal is melted. These methods have problems such as adverse effects on the refractories in the container at high temperature, high temperature of exhaust gas, deterioration of oxygen gas efficiency, and increase in fuel gas cost.
【0006】本発明では、上記のような従来技術の問題
点に対し、従来技術のスプラッシュ付着を防止するとい
う考え方と一線を画し、噴流の衝突部から発生するスプ
ラッシュやダストなどの溶鉄飛散量自体を低減する方法
を提供することを目的とする。また、これにより、ガス
コストの増大や耐火物へ悪影響なしに、ランス、容器内
壁、排ガスダクトへの地金付着による操業性悪化、ダス
ト発生による歩留まり悪化、付着地金による溶鉄の汚染
などの問題を改善することを目的とする。In the present invention, the problem of the prior art described above is set apart from the concept of preventing the splash adhesion of the prior art, and the amount of molten iron scattered such as splash or dust generated from the collision portion of the jet flow. It is an object to provide a method for reducing itself. In addition, this will not only increase gas costs and adversely affect refractories, but will also degrade operability due to sticking of metal to the lance, vessel inner wall, and exhaust gas duct, reduce yield due to dust, and contaminate molten iron with the sticking metal. The aim is to improve.
【0007】[0007]
【課題を解決するための手段】本発明者らは上記問題点
を解決するために、減圧下における噴流流速に関して、
鋭意研究を重ねた結果、下記のことを見出した。Means for Solving the Problems In order to solve the above-mentioned problems, the inventors of the present invention have described a jet flow velocity under reduced pressure.
As a result of intensive research, they have found the following.
【0008】通常上吹き酸素ランスに用いられている円
型のノズルに比べ、スリット型の形状をしたノズルでは
溶鋼表面における噴流流速が低く維持できる。これは、
スリット型のノズルでは、噴流の拡がりが大きく、ノズ
ル先端からの距離が同一の位置において同一断面積の円
型ノズルに比べ、流速分布が横方向に広がってなだらか
となり、流速も低くなるためである。真空精錬容器にお
いては、上吹き酸素ノズルと溶鋼表面との距離の上限が
制約されるため、また、常圧下に比べて著しく溶鋼表面
における噴流流速が増大するため、スリット型のノズル
の効果が発揮される。[0008] Compared with a circular nozzle normally used for an upper-blown oxygen lance, a slit-shaped nozzle can maintain a low jet flow velocity on the surface of molten steel. this is,
This is because, in the slit type nozzle, the jet flow spreads greatly, and the flow velocity distribution spreads in the horizontal direction and becomes smoother and the flow velocity becomes lower than that of a circular nozzle having the same cross-sectional area at the same distance from the nozzle tip at the same position. . In vacuum refining vessels, the upper limit of the distance between the top-blown oxygen nozzle and the surface of the molten steel is restricted, and the jet flow velocity on the molten steel surface is significantly higher than under normal pressure, so the effect of the slit type nozzle is exhibited. Is done.
【0009】また、真空度や酸素ガス流量が大きく変動
する減圧下の精錬で、広範囲の真空度や酸素ガス流量の
条件にわたって噴流流速を低く維持するには、スロート
部2の断面積St と出口部3の断面積Se (図1参照)
の比Se /St が大きいノズルよりも小さいノズルが適
している。これは、Se /St が小さいノズルでは、出
口部で噴流が常に不足膨張状態で吐出するため、膨張波
が発生し、エネルギー損失があるからである。これに対
して、スロート部の断面積St と出口部の断面積Se の
比Se /St が大きいノズルを用いると、ある特定の条
件では出口部で噴流が過膨張状態で吐出するため、衝撃
波が発生し、エネルギー損失が大きくなるが、真空度や
酸素ガス流量が大きく変動する減圧下の精錬で、広範囲
の条件にわたって出口部の噴流が過膨張状態となるよう
なノズルを設計しようとすると、ノズルの出口部の断面
積が大きくなりすぎて、ランスに配置できなくなり、ラ
ンス径を拡大するなどの対策を講じなければならない。In order to maintain a low jet flow velocity over a wide range of conditions of vacuum and oxygen gas flow by refining under reduced pressure in which the degree of vacuum and oxygen gas flow greatly fluctuate, the cross-sectional area St of the throat 2 and the outlet Sectional area Se of part 3 (see FIG. 1)
Nozzles having a smaller ratio Se / St than nozzles having a larger ratio are more suitable. This is because, in a nozzle having a small Se / St, the jet flow is always discharged in an insufficiently expanded state at the outlet, so that an expansion wave is generated and energy is lost. On the other hand, if a nozzle having a large ratio Se / St between the cross-sectional area St of the throat portion and the cross-sectional area Se of the outlet portion is used, the jet flows in the outlet portion in an over-expanded state under certain conditions, so that a shock wave is generated. Although the energy loss is large, the refining under reduced pressure, where the degree of vacuum and the oxygen gas flow rate fluctuate greatly, is designed to design a nozzle in which the jet at the outlet is over-expanded over a wide range of conditions. The cross-sectional area of the outlet part becomes too large, so that it cannot be arranged on the lance, and measures such as enlarging the lance diameter must be taken.
【0010】従って、これらの知見に基づく本発明の具
体的手段は以下の通りである。 (1)減圧下の溶融金属に上吹きランスより酸素ガスを
吹き付ける精錬方法において、ランス先端部のノズルの
形状がスリット型となっている上吹きランスを用いるこ
とを特徴とする減圧下における溶融金属の酸素吹錬方
法。 (2)ランス先端部のノズルのスロート部の断面積St
と出口部の断面積Se の比Se /St が1.1以下であ
る上吹きランスを用いることを特徴とする前記(1)記
載の減圧下における溶融金属の酸素吹錬方法。Therefore, specific means of the present invention based on these findings are as follows. (1) A refining method in which oxygen gas is blown from an upper blowing lance to a molten metal under reduced pressure, wherein an upper blowing lance having a slit-shaped nozzle at the tip of the lance is used. Oxygen blowing method. (2) Cross-sectional area St of the throat of the nozzle at the tip of the lance
The method according to (1), wherein an upper blowing lance having a ratio Se / St of 1.1 or less in sectional area Se of the outlet and the outlet is used.
【0011】[0011]
【発明の実施の形態】ここで減圧下とは0.1〜600
Torrと定義する。図1および図2は本発明に用いる
上吹きランスの例を示す図である。図1は長方形型のス
リットノズルを配置した上吹きランス、図2は円環型の
スリットノズルを配置した上吹きランスである。それぞ
れ、(a) はA−A断面におけるノズル1の図、(b) はラ
ンス先端部のノズル1の平面図である。BEST MODE FOR CARRYING OUT THE INVENTION Here, the term "under reduced pressure" means 0.1 to 600.
It is defined as Torr. FIG. 1 and FIG. 2 are views showing examples of an upper blowing lance used in the present invention. FIG. 1 shows an upper blowing lance having a rectangular slit nozzle, and FIG. 2 shows an upper blowing lance having an annular slit nozzle. (A) is a view of the nozzle 1 in the AA section, and (b) is a plan view of the nozzle 1 at the tip of the lance.
【0012】本発明において、このようなノズルを配置
した上吹きランスを用いて、減圧下の溶融金属に酸素ガ
スを吹き付けることにより、溶鋼表面における酸素ガス
の噴流流速が著しく低減され、地金付着による操業性悪
化、ダスト発生による歩留まり悪化、付着地金による溶
鉄の汚染などの問題を改善することができる。また、望
ましくは、図中に示すノズルの長辺側の長さBと短辺側
の長さhの比B/hを4以上とすることにより、噴流流
速低減効果が顕著となる。In the present invention, by blowing oxygen gas onto the molten metal under reduced pressure using the upper blowing lance having such a nozzle, the jet flow velocity of the oxygen gas on the surface of the molten steel is significantly reduced, and Problems such as deterioration in operability due to the occurrence of dust, deterioration in yield due to generation of dust, and contamination of molten iron by the deposited metal can be improved. Desirably, the ratio B / h of the length B of the long side and the length h of the short side of the nozzle shown in the drawing is 4 or more, so that the effect of reducing the jet flow velocity becomes remarkable.
【0013】さらに、スロート部2の断面積St と出口
部3の断面積Se の比Se /St を1.1以下とするこ
とにより、出口部で噴流が常に不足膨張状態で吐出し、
膨張波の発生によるエネルギー損失のため、噴流流速低
減効果が向上する。Further, the ratio Se / St of the cross-sectional area St of the throat section 2 to the cross-sectional area Se of the outlet section 3 is set to 1.1 or less, so that the jet flow at the outlet section is always discharged in an insufficiently expanded state,
Due to the energy loss due to the generation of the expansion wave, the jet flow velocity reduction effect is improved.
【0014】[0014]
【実施例】真空精錬炉を用いてステンレス溶鋼の精錬試
験を行い、本発明による方法と従来の円型ノズルによる
方法の比較を行った。ノズルの設計条件を表1に、ノズ
ルの図面を図3に示す。EXAMPLE A refining test of molten stainless steel was performed using a vacuum refining furnace, and a comparison was made between the method according to the present invention and the conventional method using a circular nozzle. Table 1 shows the design conditions of the nozzle, and FIG. 3 shows a drawing of the nozzle.
【0015】本発明例、比較例ともにノズルの設計条件
のみが異なり、その他の操業条件はほぼ同様である。初
期溶鋼量は500kg、溶鋼組成は初期[C]が約0.
7%、初期[Cr]が約11%であり、[C]が約0.
01%となるまで、精錬を行った。送酸速度、ランス−
溶鋼間距離、真空度は精錬中の[C]に応じて、表2の
ように変更した。また、精錬中の地金発生量を炉内壁に
吊り下げた耐火物板への付着量を炉内壁全面に換算した
量で評価するとともに、精錬前後の溶鋼歩留まりを計算
した。ダスト発生量は排ガスダクト内に設置した濾紙の
集塵量で評価した。試験結果を表3に示す。[0015] Only the design conditions of the nozzles of the present invention and comparative examples are different, and other operating conditions are almost the same. The initial molten steel amount is 500 kg, and the molten steel composition has an initial [C] of about 0.1 kg.
7%, initial [Cr] is about 11%, and [C] is about 0.1%.
Refining was performed until the content reached 01%. Acid transfer rate, lance
The distance between molten steels and the degree of vacuum were changed as shown in Table 2 according to [C] during refining. In addition, the amount of ingots generated during refining was evaluated by converting the amount of metal adhered to the refractory plate suspended on the furnace inner wall over the entire furnace inner wall, and the yield of molten steel before and after refining was calculated. The amount of dust generated was evaluated based on the amount of dust collected on the filter paper installed in the exhaust gas duct. Table 3 shows the test results.
【0016】[0016]
【表1】 [Table 1]
【0017】[0017]
【表2】 [Table 2]
【0018】[0018]
【表3】 [Table 3]
【0019】表3に示すように、比較例に比べて本発明
例では地金付着量、ダスト発生量ともに低減し、溶鉄の
飛散が抑制されたため、溶鋼歩留が向上した。さらに、
スロート部の断面積St と出口部の断面積Se の比Se
/St を1.1以下とした場合は、さらに効果が顕著と
なっている。一方、本発明の方法で、脱炭酸素効率やC
r損失量が悪化する傾向は認められなかった。As shown in Table 3, compared to the comparative example, in the present invention example, both the amount of ingot adhesion and the amount of dust generation were reduced, and the scattering of molten iron was suppressed, so that the molten steel yield was improved. further,
The ratio Se of the cross-sectional area St of the throat to the cross-sectional area Se of the outlet
When / St is 1.1 or less, the effect is more remarkable. On the other hand, according to the method of the present invention, the decarbonation efficiency and C
There was no tendency for the amount of r loss to deteriorate.
【0020】[0020]
【発明の効果】本発明の方法で減圧下の溶融金属に酸素
ガスを吹き付けることにより、噴流流速を著しく低減す
ることが可能となった。これにより、溶鉄の飛散が抑制
され、地金付着による操業性悪化、ダスト発生による歩
留まり悪化、付着地金による溶鉄の汚染などの問題を改
善することができる。According to the method of the present invention, it is possible to remarkably reduce the jet flow velocity by blowing oxygen gas onto the molten metal under reduced pressure. Thereby, scattering of molten iron can be suppressed, and problems such as deterioration of operability due to adhesion of metal, deterioration of yield due to generation of dust, and contamination of molten iron by the adhered metal can be improved.
【図1】本発明に用いるランス先端部のノズル形状の例
を示す図である。FIG. 1 is a diagram showing an example of a nozzle shape of a lance tip used in the present invention.
【図2】本発明に用いるランス先端部のノズル形状の例
を示す図である。FIG. 2 is a view showing an example of a nozzle shape of a lance tip used in the present invention.
【図3】実施例に記載の各ランスのノズル形状を示す図
である。FIG. 3 is a view showing a nozzle shape of each lance described in the embodiment.
1 ノズル 2 スロート部 3 出口部(吐出孔部) 1 Nozzle 2 Throat 3 Exit (discharge hole)
Claims (2)
素ガスを吹き付ける精錬方法において、ランス先端部の
ノズルの形状がスリット型となっている上吹きランスを
用いることを特徴とする減圧下における溶融金属の酸素
吹錬方法。1. A refining method for blowing oxygen gas onto a molten metal under reduced pressure from an upper blowing lance, wherein an upper blowing lance having a slit-shaped nozzle at the tip of the lance is used. Oxygen blowing method for molten metal.
面積St と出口部の断面積Se の比Se /St が1.1
以下である上吹きランスを用いることを特徴とする請求
項1記載の減圧下における溶融金属の酸素吹錬方法。2. The ratio Se / St of the sectional area St of the throat part of the nozzle at the tip of the lance to the sectional area Se of the outlet part is 1.1.
2. The method for blowing oxygen under molten metal under reduced pressure according to claim 1, wherein the following blow lance is used.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP12564598A JPH11315319A (en) | 1998-05-08 | 1998-05-08 | Method for blowing oxygen into molten metal under reduced pressure |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP12564598A JPH11315319A (en) | 1998-05-08 | 1998-05-08 | Method for blowing oxygen into molten metal under reduced pressure |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH11315319A true JPH11315319A (en) | 1999-11-16 |
Family
ID=14915158
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP12564598A Withdrawn JPH11315319A (en) | 1998-05-08 | 1998-05-08 | Method for blowing oxygen into molten metal under reduced pressure |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH11315319A (en) |
-
1998
- 1998-05-08 JP JP12564598A patent/JPH11315319A/en not_active Withdrawn
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