JP3327062B2 - Melting method of ultra-low carbon / ultra low sulfur steel - Google Patents
Melting method of ultra-low carbon / ultra low sulfur steelInfo
- Publication number
- JP3327062B2 JP3327062B2 JP20967695A JP20967695A JP3327062B2 JP 3327062 B2 JP3327062 B2 JP 3327062B2 JP 20967695 A JP20967695 A JP 20967695A JP 20967695 A JP20967695 A JP 20967695A JP 3327062 B2 JP3327062 B2 JP 3327062B2
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- ultra
- slag
- ladle
- 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.)
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Treatment Of Steel In Its Molten State (AREA)
Description
【0001】[0001]
【発明の属する技術分野】本発明は、RH真空脱ガス設
備を使用した、介在物の少なく清浄性の高い極低炭かつ
極低硫鋼の溶製方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultra-low carbon and ultra-low sulfur steel having low inclusions and high cleanliness using an RH vacuum degassing system.
【0002】[0002]
【従来の技術】最近、珪素鋼板の電磁特性への品質向上
要求は厳しくなり、介在物の少なく清浄性の高い極低炭
かつ極低硫鋼(これを極低炭・極低硫鋼と記す)が要求
されている。2. Description of the Related Art In recent years, demands for improving the electromagnetic properties of silicon steel sheets have become strict, and ultra-low-carbon and ultra-low sulfur steels with few inclusions and high cleanliness (this is referred to as ultra-low carbon / ultra-low sulfur steel). ) Is required.
【0003】極低炭・極低硫鋼の溶製方法としては、生
産性増大のためRH真空脱ガス設備にて真空脱炭後、脱
ガス真空槽内の溶鋼または上昇管内の上昇環流溶鋼に向
けて粉体状の脱硫フラックスを吹き込んで脱硫する方法
(これをRH脱硫法といい、例えば、特開昭60−59
011号公報で開示されている)が一般的である。[0003] As a method for melting ultra-low carbon / ultra-low sulfur steel, in order to increase productivity, vacuum decarburization is performed using RH vacuum degassing equipment, and then molten steel in a degassing vacuum tank or rising reflux molten steel in a riser pipe. A desulfurization flux by blowing a powdery desulfurization flux (this is referred to as an RH desulfurization method.
No. 011) is common.
【0004】このRH脱硫法は、未脱酸溶鋼(過剰な溶
存酸素(フリー酸素)を含有する溶鋼)を対象に真空脱
炭処理(第1工程)した後、脱ガス真空槽内の溶鋼中に
金属Al(脱酸剤)を添加して溶鋼を脱酸処理(第2工
程)し、その後脱硫処理(第3工程)する溶製方法であ
る。In this RH desulfurization method, vacuum decarburization treatment (first step) is performed on undeoxidized molten steel (molten steel containing excess dissolved oxygen (free oxygen)), and then the molten steel in a degassing vacuum chamber is subjected to vacuum decarburization. In this method, a metal Al (a deoxidizing agent) is added to the molten steel to deoxidize the molten steel (second step), and then desulfurize (third step).
【0005】脱硫工程では、溶鋼中に溶存酸素がほとん
ど存在しない還元状態(通常1ppm以下)でないと、
脱硫反応が進行しない。このため、脱酸工程では、過剰
な溶存酸素を取り除く(溶鋼を脱酸する)だけでなく、
溶鋼中に可溶性Al(通常0.03〜0.05%程度)
を存在させるのに十分な金属Al量が添加される。[0005] In the desulfurization step, unless it is in a reduced state (usually 1 ppm or less) in which dissolved oxygen hardly exists in molten steel,
Desulfurization reaction does not proceed. Therefore, in the deoxidation process, not only remove excess dissolved oxygen (deoxidize molten steel),
Soluble Al in molten steel (usually about 0.03-0.05%)
Is added in an amount sufficient to cause the presence of Al.
【0006】[0006]
【発明が解決しようとする課題】しかしながら、脱硫処
理がこのような還元状態の溶鋼を対象に実施されても、
取鍋スラグは転炉出鋼時のFeO、MnOを含有する酸
素ポテンシャルの高い過酸化状態のままである。However, even if the desulfurization treatment is performed on such molten steel in a reduced state,
The ladle slag remains in a peroxide state with a high oxygen potential containing FeO and MnO at the time of converter steel tapping.
【0007】このため、脱硫処理中、環流用Arガスに
よって生じる取鍋内のスラグ−メタル間の揺動によっ
て、過酸化状態のスラグと溶鋼中の可溶性Alとが反応
して、多量のAl2 O3 を発生させる。[0007] Therefore, during the desulfurization process, the slag in the ladle caused by ring diverted Ar gas - by the swinging between the metal, the soluble Al in the slag and the molten steel peroxide might undergo reaction, a large amount of Al 2 the O 3 is generated.
【0008】この段階で発生するAl2 O3 は、RH処
理終了から鋳造するまでの時間が短く、浮上時間が充分
に長くとれないため、鋳造した鋳片内にAl2 O3 介在
物として残留する。The Al 2 O 3 generated at this stage remains as Al 2 O 3 inclusions in the cast slab because the time from the end of the RH treatment to the casting is short and the floating time is not long enough. I do.
【0009】従って、従来のRH脱硫法では、極低炭・
極低硫鋼の溶製は達成されても、鋳片のトータル酸素量
(トータル酸素量は、鋼中に溶解している溶存酸素量
と、鋼中にAl2 O3 等の酸化物として存在する酸素量
とを合計した酸素量で、以下T〔O〕と記す)を充分に
低減(例えば、T〔O〕≦15ppm以下)した清浄性
の高い鋼の溶製は困難であった。Therefore, in the conventional RH desulfurization method, extremely low carbon
Even if the production of extremely low sulfur steel is achieved, the total oxygen content of the slab (total oxygen content is the amount of dissolved oxygen dissolved in the steel and the amount of oxides such as Al 2 O 3 in the steel) It is difficult to smelt a highly clean steel having sufficiently reduced T [O] (for example, T [O] ≤ 15 ppm or less), which is the total amount of oxygen to be added.
【0010】本発明は、上記従来技術の問題点を解決す
るために提案されたものであり、RH脱硫法によって極
低炭・極低硫鋼を溶製する際に、介在物の少なく清浄性
の高い極低炭・極低硫鋼の溶製方法を提供することを目
的とするものである。[0010] The present invention has been proposed to solve the above-mentioned problems of the prior art, and when the ultra-low carbon / ultra-low sulfur steel is melted by the RH desulfurization method, there are few inclusions and cleanliness. It is an object of the present invention to provide a method for producing ultra-low carbon / ultra-low sulfur steel having a high melting point.
【0011】[0011]
【課題を解決するための手段】本願の第1の発明は、R
H真空脱ガス設備を用い、真空脱炭処理、脱酸処理、脱
硫処理の順に精錬して極低炭・極低硫鋼を溶製する方法
において、前記脱酸処理前までに焼石灰および金属Al
を取鍋内のスラグ上に予め添加しておき、脱酸処理終了
後、上昇管を環流する上昇環流溶鋼中に4000Nl/
min以上の流量で不活性ガスを吹き込んで溶鋼を環流
させ、この環流による溶鋼の攪拌エネルギーにより取鍋
内の溶鋼湯面およびスラグを揺動させ、この揺動によっ
て取鍋内のスラグを前記金属Alにより還元すると同時
に前記焼石灰を取鍋内のスラグに溶解させ、当該スラグ
により溶鋼を脱硫することを特徴とする極低炭・極低硫
鋼の溶製方法である。Means for Solving the Problems The first invention of the present application is an R
Using H vacuum degassing equipment, vacuum decarburization, deoxidation treatment, a method of melting the refining to very low coal-very low硫鋼in the order of the desulfurization process, burnt lime and metal before the deacidification Al
4000Nl the advance previously added on the slag in the ladle, after deacidification ends, the riser during the ascent reflux molten steel reflux /
refluxing molten steel Nde write blowing an inert gas at a higher flow rate min
Then , the molten steel surface and slag in the ladle are swung by the stirring energy of the molten steel due to the reflux , and this swing causes
Simultaneously when the slag in the ladle is reduced by the metal Al
Dissolve the calcined lime in the slag in the ladle
This is a method for producing ultra-low carbon / ultra-low sulfur steel by desulfurizing molten steel .
【0012】まず、減圧下で未脱酸溶鋼を真空脱炭し所
定の極低炭素濃度にし、この後、脱ガス真空槽内に金属
Al等の脱酸剤を添加して脱酸する。この際に、溶鋼中
に可溶性Alとして歩留らませて溶鋼中に溶存酸素(フ
リー酸素)がほとんど存在しない還元状態にする。First, the undeoxidized molten steel is vacuum decarburized under reduced pressure to a predetermined ultra-low carbon concentration, and then a deoxidizing agent such as metal Al is added to the degassing vacuum tank to deoxidize. At this time, the molten steel is made to yield as soluble Al in a reduced state in which almost no dissolved oxygen (free oxygen) is present in the molten steel.
【0013】この後、上昇管に設けた羽口から、または
上昇管の直下に配置された先端が上向いたランス等か
ら、上昇環流溶鋼中にArガス等の環流用不活性ガスを
4000Nl/min以上吹き込んで、溶鋼を脱ガス真
空槽と取鍋間で環流させると共に、脱ガス真空槽内の溶
鋼を激しく攪拌させる。この攪拌エネルギーは下降管か
ら取鍋内に環流して浮上する溶鋼に伝達され、取鍋内の
溶鋼湯面およびスラグを上下に揺動させる。Thereafter, 4000 Nl / min of an inert gas for circulation such as Ar gas is introduced into the ascending reflux molten steel from a tuyere provided on the riser or from a lance or the like disposed directly below the riser and having a tip facing upward. By blowing in the above, the molten steel is recirculated between the degassing vacuum tank and the ladle, and the molten steel in the degassing vacuum tank is vigorously stirred. This stirring energy is transmitted from the downcomer pipe to the molten steel which recirculates into the ladle and floats, and swings the molten steel surface and the slag in the ladle up and down.
【0014】この揺動により、脱酸処理前までに取鍋ス
ラグ上に添加された焼石灰は取鍋スラグに溶解して、ス
ラグ塩基度は増大すると共に、スラグ−メタル間反応が
促進して溶鋼は脱硫される。By this rocking, calcined lime added to the ladle slag before the deoxidizing treatment is dissolved in the ladle slag, the slag basicity is increased, and the reaction between the slag and metal is promoted. The molten steel is desulfurized.
【0015】同様に、揺動によって、取鍋スラグ上に添
加された金属Alは過酸化状態の取鍋スラグを還元して
脱硫処理前までに無害化させる。この結果、脱硫処理中
に生じる揺動によって溶鋼中の可溶性Alは酸化される
ことがなく、従ってAl2 O 3 を発生させることがな
い。[0015] Similarly, by swinging, the ladle slag
The added metal Al reduces the ladle slag in the peroxide state.
Detoxify before desulfurization. As a result, during desulfurization
Al in the molten steel is oxidized by the rocking that occurs
And therefore AlTwoO ThreeCan not cause
No.
【0016】また、環流用不活性ガスが4000Nl/
min以上吹き込まれて発生する揺動エネルギーは、従
来の取鍋脱硫法(取鍋内溶鋼中に吹き込みランスを浸漬
して、ランス先端から脱硫フラックスを吹き込んで脱硫
する方法)による攪拌エネルギーに比べ格段に小さいの
で、取鍋スラグは溶鋼中に巻き込まれることがない。従
って、介在物の少なく清浄性の高い極低炭・極低硫鋼の
溶製が可能となる。Further, the inert gas for reflux is 4000 Nl /
The rocking energy generated by blowing more than min is much higher than the stirring energy by the conventional ladle desulfurization method (a method in which a lance is immersed in molten steel in a ladle and a desulfurization flux is blown from the tip of the lance to desulfurize). Ladle slag does not get caught in the molten steel. Therefore, it becomes possible to produce ultra-low carbon / ultra-low sulfur steel having few inclusions and high cleanliness.
【0017】環流用不活性ガスが4000Nl/min
以下では、揺動幅が小さく揺動エネルギーが不足するた
め、焼石灰の溶解は不十分となってスラグの粘性が増加
して脱硫反応が進まない。また金属Alは取鍋スラグを
十分に還元できず、Al2 O 3 を発生させてしまうた
め、介在物が少なく清浄性の高い極低炭・極低硫鋼を溶
製できない。Inert gas for reflux is 4000 Nl / min
In the following, the swing width is small and the swing energy is insufficient.
Insufficient dissolution of calcined lime increases viscosity of slag
And the desulfurization reaction does not proceed. In addition, metal Al uses ladle slag
Al cannot be reduced sufficientlyTwoO ThreeCause
Melts ultra-low carbon / ultra low sulfur steel with low inclusions and high cleanliness.
Cannot be made.
【0018】一方、金属Alを脱酸処理後に取鍋内スラ
グ上に添加すると、脱硫開始時点で、取鍋スラグの還元
は完了していない。このため、脱硫処理中に可溶性Al
は酸化されてAl2 O3 を発生させてしまい、介在物が
少なく清浄性の高い極低炭・極低硫鋼を溶製できない。On the other hand, when metal Al is added to the slag in the ladle after the deoxidizing treatment, the reduction of the ladle slag is not completed at the start of desulfurization. Therefore, during the desulfurization treatment, the soluble Al
Is oxidized to generate Al 2 O 3 , and it is not possible to melt ultra-low carbon / ultra low sulfur steel having few inclusions and high cleanliness.
【0019】本願の第2の発明は、RH真空脱ガス設備
を用い、真空脱炭処理、脱酸処理、脱硫処理の順に精錬
して極低炭・極低硫鋼を溶製する方法において、前記脱
酸処理前までに金属Alを取鍋内のスラグ上に予め添加
しておき、脱酸処理終了後、上昇管を環流する上昇環流
溶鋼中に2000Nl/min以上の流量で不活性ガス
を吹き込むと共に50kg/min以上の速度で粉体状
のCaO−CaF2 系脱硫フラックスを吹き込んで溶鋼
を環流させ、この環流による溶鋼の攪拌エネルギーによ
り取鍋内の溶鋼湯面およびスラグを揺動させ、この揺動
によって取鍋内のスラグを前記金属Alにより還元しな
がら前記脱硫フラックスにより溶鋼を脱硫することを特
徴とする極低炭・極低硫鋼の溶製方法である。The second invention of the present application is an RH vacuum degassing facility.
Refining in the order of vacuum decarburization, deoxidation, and desulfurization
A method for melting the ultra-low carbon-very low硫鋼to the metallic Al by deacidification before possible to add beforehand on the slag in the ladle, after deacidification completed, reflux the riser It increased circulating 2000 NL / min or more flow in the molten steel Nde write blowing powdery CaO-CaF 2 based desulfurizing flux 50 kg / min or faster with blowing an inert gas into molten steel to
And the stirring energy of the molten steel by the reflux
Ri to oscillate the molten steel surface and the slag in the ladle, the swing
The slag in the ladle is not reduced by the metal Al
A method for producing ultra-low carbon / ultra-low sulfur steel, the method comprising desulfurizing molten steel with the desulfurization flux .
【0020】環流用不活性ガスを2000Nl/min
以上吹き込むと、溶鋼は環流し脱ガス真空槽内で攪拌し
て、上昇環流溶鋼中に吹き込まれた粉体状のCaO−C
aF 2 系脱硫フラックスは攪拌する溶鋼中で溶解して、
溶鋼を脱硫する。2,000 Nl / min of inert gas for reflux
With the above blowing, the molten steel is recirculated and stirred in the degassing vacuum chamber.
Powdered CaO-C blown into ascending molten steel
aF TwoThe system desulfurization flux is dissolved in the molten steel to be stirred,
Desulfurizes molten steel.
【0021】この際に、脱硫フラックス中のCaF
2 が、脱ガス真空槽内で分解して発生するガス(CaF
2 は加熱されるとフッ素ガス、SiF4 ガス、AlF3
ガス等に熱分解すると考えられる。)によっても溶鋼は
攪拌されるので、攪拌エネルギーは加算される。At this time, the CaF in the desulfurization flux
2 is a gas (CaF
2. When heated, fluorine gas, SiF 4 gas, AlF 3
It is considered to be thermally decomposed into gas and the like. ), The molten steel is also stirred, so that the stirring energy is added.
【0022】発明者等は、環流用不活性ガス流量を20
00Nl/min以上吹き込むと共に、CaO−CaF
2 系脱硫フラックスを50kg/min以上の速度で上
昇環流溶鋼中に吹き込むと、環流用不活性ガス流量を4
000Nl/min以上吹き込んだ場合と同等の揺動を
取鍋内の湯面およびスラグに与えることを実験により見
出した。The inventors set the flow rate of the inert gas for reflux at 20.
While blowing over 00Nl / min, CaO-CaF
When the system 2 desulfurization flux is blown into the ascending reflux molten steel at a speed of 50 kg / min or more, the inert gas flow rate for reflux increases by 4%.
It has been found through experiments that the same swing as in the case of blowing 000 Nl / min or more is given to the molten metal surface and slag in the ladle.
【0023】上記知見によれば、第1の発明と同様の作
用により、脱酸処理前までに添加された金属Alは、揺
動によって過酸化状態のスラグは還元されて脱硫処理前
までに無害化されるから、脱硫処理中にAl2 O3 は発
生することがなく、介在物の少なく清浄性の高い極低炭
・極低硫鋼の溶製が可能となる。According to the above findings, by the same action as in the first invention, the metal Al added before the deoxidizing treatment is reduced in the oxidized slag by the rocking and is harmless before the desulfurizing treatment. Therefore, no Al 2 O 3 is generated during the desulfurization treatment, and it is possible to produce ultra-low carbon / ultra-low sulfur steel having few inclusions and high cleanliness.
【0024】環流用不活性ガスが2000Nl/min
以上、または脱硫フラックスの吹き込み速度が50kg
/min以上の、どちらか一方の条件が満足されない
と、揺動エネルギーは不足するため、金属Alは取鍋ス
ラグを十分に還元できない。このため、脱硫処理中にA
l2 O3 を発生させてしまうため、介在物の少なく清浄
性の高い極低炭・極低硫鋼を溶製できない。2,000 Nl / min of inert gas for reflux
Above or desulfurization flux blowing speed is 50kg
If one of the conditions of / min or more is not satisfied, the swing energy is insufficient, and the metal Al cannot sufficiently reduce the ladle slag. Therefore, during the desulfurization treatment, A
Since l 2 O 3 is generated, it is not possible to melt ultra-low carbon / ultra-low sulfur steel having few inclusions and high cleanliness.
【0025】また、脱硫フラックスを吹き込んで脱硫処
理する第2の発明は、焼石灰を取鍋スラグに添加して脱
硫処理した場合に比べて、高い脱硫率が得られるから、
到達〔S〕値の低い極低硫鋼の溶製が可能となる。Further, in the second invention in which desulfurization flux is blown and the desulfurization treatment is performed, a higher desulfurization rate can be obtained as compared with a case where calcined lime is added to ladle slag and desulfurized.
It becomes possible to produce extremely low sulfur steel having a low ultimate [S] value.
【0026】[0026]
確認試験(1):図1は、スラグ上に焼石灰と金属Al
を投入された取鍋内溶鋼を、RH真空脱ガス設備におい
て、上昇管の直下に配置した先端が上向いたランスから
環流用Arガスを上昇管内に向かって吹き込み、清浄性
の高い極低炭・極低硫鋼を溶製している状況を示す。Confirmation test (1): Fig. 1 shows calcined lime and metal Al on slag
The molten steel in the ladle is charged with Ar gas for reflux into the riser from the lance with the tip facing upward located in the RH vacuum degassing facility. This shows the situation where extremely low sulfur steel is being produced.
【0027】ここで、1は取鍋、2は溶鋼、3は取鍋ス
ラグ、4は上昇管、5は下降管、6は脱ガス真空槽、7
は排気ダクト、8は合金投入口、9は環流用ガス吹き込
み管、10は副原料投入ホッパーである。Here, 1 is a ladle, 2 is molten steel, 3 is a ladle slag, 4 is an ascending pipe, 5 is a descending pipe, 6 is a degassing vacuum tank, 7
Denotes an exhaust duct, 8 denotes an alloy input port, 9 denotes a reflux gas blowing pipe, and 10 denotes an auxiliary material input hopper.
【0028】取鍋1内には、転炉精練された250トン
の未脱酸状態の溶鋼2が入っており、溶鋼2の上には、
転炉出鋼時の酸化状態の取鍋スラグ3が重量でおよそ1
〜1.5トン載っている。The ladle 1 contains 250 tons of undeoxidized molten steel 2 which has been refined by a converter.
Ladle slag 3 in the oxidized state at the time of converter tapping is approximately 1 in weight.
~ 1.5 tons.
【0029】なお、脱硫、脱珪処理した予備処理溶銑を
転炉に装入し、転炉吹錬では主に脱炭精練を行い、転炉
終点時の溶鋼成分として炭素濃度(以下〔C〕と記す)
を160〜200ppm、硫黄濃度(以下〔S〕と記
す)を30ppm前後に調整した。The pretreated hot metal subjected to desulfurization and desiliconization is charged into a converter, and in the converter blowing, decarburization smelting is mainly performed, and a carbon concentration (hereinafter referred to as [C]) as a molten steel component at the end point of the converter. Written as
Was adjusted to 160 to 200 ppm, and the sulfur concentration (hereinafter referred to as [S]) was adjusted to about 30 ppm.
【0030】環流用ガス吹き込み管9は、金属製のパイ
プの表面に耐火物を被覆した先端が上向いたランスであ
り、上昇管4の横から溶鋼2内に差し込まれている。こ
のランスの先端にはガス吐出孔があり、このガス吐出孔
は上昇管4の直下で、かつほぼ中央部に配置されてい
る。従って、このガス吐出孔より所定の環流用Arガス
流量を、上昇管4内(上昇環流溶鋼中)に向かって吹き
込み、取鍋1と脱ガス真空槽6の間で溶鋼2を環流させ
た。The recirculation gas injection pipe 9 is a lance having a metal pipe covered with a refractory on the surface thereof, the tip of which faces upward, and is inserted into the molten steel 2 from the side of the riser pipe 4. A gas discharge hole is provided at the tip of the lance, and the gas discharge hole is disposed immediately below the rising pipe 4 and substantially at the center. Accordingly, a predetermined reflux Ar gas flow rate was blown into the riser pipe 4 (in the ascending reflux molten steel) from the gas discharge holes, and the molten steel 2 was refluxed between the ladle 1 and the degassing vacuum tank 6.
【0031】副原料投入ホッパー10は、脱ガス真空槽
6横に2個(図では1個を表示)あって、各々焼石灰
粉、金属Al(粒径5〜10mm)が入っており、溶鋼
2上に投入できる。There are two auxiliary material input hoppers 10 (one is shown in the figure) beside the degassing vacuum chamber 6, each containing calcined lime powder and metallic Al (particle diameter 5 to 10 mm). 2 can be thrown.
【0032】従って、確認試験(1)では、金属Alは
取鍋スラグ3中のFeO、MnOを還元するためのスラ
グ改質剤として、焼石灰粉は取鍋スラグの塩基度を増加
させるためのスラグ成分調整剤として使用した。Therefore, in the confirmation test (1), metal Al was used as a slag modifier for reducing FeO and MnO in the ladle slag 3, and calcined lime powder was used for increasing the basicity of the ladle slag. Used as a slag component regulator.
【0033】表1は、確認試験(1)の実施例1〜実施
例8における極低炭・極低硫鋼の溶製条件と溶製結果を
示す。Table 1 shows the smelting conditions and results of ultra-low carbon / ultra-low sulfur steel in Examples 1 to 8 of the confirmation test (1).
【0034】[0034]
【表1】 [Table 1]
【0035】実施例1〜実施例5は、1トンの焼石灰粉
と200kgの金属Alを転炉出鋼直後に、取鍋1内の
スラグ上に投入した。In Examples 1 to 5, 1 ton of calcined lime powder and 200 kg of metal Al were put on the slag in the ladle 1 immediately after the start of the converter.
【0036】実施例1〜実施例5では、脱炭処理中、環
流用ガス吹き込み管9より所定の環流用Arガス流量を
吹き込み、〔C〕を15ppm以下(RH脱炭後)まで
減圧下で真空脱炭した。In Examples 1 to 5, during the decarburization treatment, a predetermined Ar gas flow rate for recirculation was blown from the recirculation gas injection pipe 9 to reduce [C] to 15 ppm or less (after RH decarburization) under reduced pressure. Vacuum decarburized.
【0037】その後、合金投入口8より真空槽6内の溶
鋼上に、金属Alを一律300kg添加して脱酸した
後、吹き込み管9より環流用Arガス流量を4000〜
5500Nl/minの範囲で、8〜10分間(これを
環流時間という)吹き込み、脱硫処理した。なお脱硫処
理中の溶鋼中の可溶性Al濃度は0.030%以上、溶
存酸素濃度は1ppm以下が確保された。Thereafter, 300 kg of metallic Al was uniformly added to the molten steel in the vacuum chamber 6 from the alloy inlet 8 to deoxidize the molten steel.
Blowing was performed at a rate of 5500 Nl / min for 8 to 10 minutes (referred to as reflux time) to perform desulfurization treatment. Note that the soluble Al concentration in the molten steel during the desulfurization treatment was 0.030% or more, and the dissolved oxygen concentration was 1 ppm or less.
【0038】上記範囲の環流用Arガスを吹き込むこと
によって、真空槽6内の溶鋼は強攪拌されて、この攪拌
エネルギーが取鍋1内に環流する溶鋼に伝わり、取鍋1
内の溶鋼2および取鍋スラグ3は上下方向におよそ5c
m揺動した。By blowing the Ar gas for reflux in the above range, the molten steel in the vacuum chamber 6 is vigorously stirred, and this stirring energy is transmitted to the molten steel circulating in the ladle 1, and the ladle 1
Molten steel 2 and ladle slag 3 in the vertical direction
m rocked.
【0039】この揺動により、1トンの焼石灰粉は取鍋
スラグ3に溶解して、脱硫反応が進行した結果、RH終
了時の〔S〕は、20ppm以下まで低減(脱硫率は3
8〜53%)できた。As a result of this rocking, 1 ton of calcined lime powder was dissolved in the ladle slag 3 and the desulfurization reaction proceeded. As a result, [S] at the end of RH was reduced to 20 ppm or less (desulfurization rate was 3%).
8-53%).
【0040】但し脱硫率は、〔(RH脱炭後〔S〕−R
H終了時〔S〕)/RH脱炭後〔S〕〕×100%で計
算した。However, the desulfurization rate is [(RH decarburized [S] -R
At the end of H [S]) / after decarburization of RH [S]] x 100%.
【0041】同様に、この揺動によって、取鍋スラグ3
はスラグ上に添加された200kgの金属Alによって
還元されて無害化されたため、脱硫処理中、溶鋼中の可
溶性Alは酸化されることなく、RH終了時のT〔O〕
は安定して15ppm以下となった。Similarly, this swing causes ladle slag 3
Was reduced and rendered harmless by 200 kg of metallic Al added to the slag, so that during the desulfurization treatment, the soluble Al in the molten steel was not oxidized, and T [O]
Stably became 15 ppm or less.
【0042】このように溶製された溶鋼を連続鋳造した
結果、鋳造後の鋳片成分は〔C〕≦20ppm、〔S〕
≦20ppmの極低炭・極低硫鋼で、かつT〔O〕≦1
5ppmの介在物の少なく清浄性の高い鋼が溶製でき
た。As a result of continuous casting of the molten steel thus produced, the slab components after casting were [C] ≦ 20 ppm and [S]
≦ 20ppm ultra low carbon / ultra low sulfur steel and T [O] ≦ 1
5 ppm of inclusions and high cleanliness steel could be melted.
【0043】実施例6〜実施例8は、焼石灰粉と金属A
lを取鍋スラグ3上に添加したタイミングをRH真空脱
ガス設備での脱酸処理前とした場合であり、その他の試
験条件を実施例1〜実施例5と同じとした場合である。In Examples 6 to 8, calcined lime powder and metal A
The case where l was added to the ladle slag 3 was before the deoxidation treatment in the RH vacuum degassing equipment, and the other test conditions were the same as in Examples 1 to 5.
【0044】この結果、実施例1〜実施例5と同じく、
RH終了時および鋳片成分は〔C〕≦20ppm、
〔S〕≦20ppm、T〔O〕≦15ppmの極低炭・
極低硫鋼かつ高清浄度鋼が安定して溶製できた。As a result, as in Examples 1 to 5,
At the end of RH and the slab components are [C] ≦ 20 ppm,
[S] ≦ 20ppm, T [O] ≦ 15ppm
Extremely low sulfur steel and high cleanliness steel could be produced stably.
【0045】比較例1〜比較例5は、脱硫工程における
環流用Arガス流量を4000Nl/min未満(20
00〜3800Nl/min範囲)とし、これ以外の試
験条件は実施例1〜実施例8と同じ条件とした場合であ
る。表2にこの試験条件および溶製結果を示す。In Comparative Examples 1 to 5, the reflux Ar gas flow rate in the desulfurization step was less than 4000 Nl / min (20
(In the range of 00 to 3800 Nl / min), and other test conditions are the same as those in Examples 1 to 8. Table 2 shows the test conditions and melting results.
【0046】[0046]
【表2】 [Table 2]
【0047】比較例1〜比較例5では、RH終了時およ
び鋳造後の鋳片成分で〔C〕≦20ppmの極低炭素鋼
が溶製できたが、鋳片成分で〔S〕≦20ppmおよび
T〔O〕≦15ppmを確保できなかった。In Comparative Examples 1 to 5, extremely low carbon steel having a content of [C] ≦ 20 ppm could be melted in the slab component at the end of RH and after casting. T [O] ≦ 15 ppm could not be secured.
【0048】この理由は、脱硫工程における環流用Ar
ガス流量が4000Nl/min未満としたため、揺動
幅が小さく焼石灰粉の滓化が不十分となって、スラグの
粘性が高くなった結果、脱硫反応が進行せず、低い脱硫
率(7〜33%)しか得られなかったためである。The reason is that Ar for reflux in the desulfurization step
Since the gas flow rate was less than 4000 Nl / min, the swing width was small and the slag of calcined lime powder was insufficient, and the viscosity of the slag was increased. As a result, the desulfurization reaction did not proceed, and the desulfurization rate was low (7 to 33%).
【0049】同時にスラグ上に添加した金属Alによる
取鍋スラグ3の還元も不十分となり、脱硫処理中に溶鋼
の一部が酸化したため、T〔O〕≦15ppmが得られ
なかったものと考えられる。At the same time, it is probable that T [O] ≦ 15 ppm could not be obtained because the ladle slag 3 was insufficiently reduced by the metal Al added on the slag and a part of the molten steel was oxidized during the desulfurization treatment. .
【0050】図2は、実施例1〜実施例8における転炉
出鋼時から鋳造鋳片までの成分推移を示す。FIG. 2 shows the transition of components from the time of tapping from the converter to the cast slab in Examples 1 to 8.
【0051】図3は、確認試験(1)における脱硫工程
における環流用Arガス流量が鋳造後の鋳片T〔O〕に
及ぼす影響を調査した結果を示す。これより、環流用A
rガス流量4000Nl/min以上が満足されない
と、鋳片T〔O〕≦15ppmを確保できないことがわ
かる。FIG. 3 shows the results of an investigation on the influence of the reflux Ar gas flow rate on the cast slab T [O] after casting in the desulfurization step in the confirmation test (1). From this, A for diversion
If the r gas flow rate of 4000 Nl / min or more is not satisfied, it can be seen that slab T [O] ≦ 15 ppm cannot be secured.
【0052】確認試験(2):本試験では、確認試験
(1)と同様に〔C〕≦15ppm以下に真空脱炭した
後、脱酸処理前までに取鍋スラグ上に200kgの金属
Alを投入して、脱酸処理した後、上昇管に設けた羽口
から環流用Arガス流量を2000Nl/min以上か
つ粉体状の脱硫フラックスを50kg/min以上の速
度で吹き込んで極低炭・極低硫鋼を溶製した。図4はこ
の状況を示す。Confirmation test (2) : In this test, 200 kg of metal Al was placed on the ladle slag before deoxidation after vacuum decarburization to [C] ≦ 15 ppm or less as in confirmation test (1). After being charged and deoxidized, an Ar gas for reflux is supplied at a flow rate of 2,000 Nl / min or more and a powdery desulfurization flux is blown at a rate of 50 kg / min or more from a tuyere provided in the riser to obtain extremely low carbon / electrode. Low sulfur steel was produced. FIG. 4 illustrates this situation.
【0053】脱硫フラックスの組成はCaO−20wt
%CaF2 を使用し、キャリアーガス(Arガス)と共
に、一律、原単位4kg/tonを吹き込んだ。The composition of the desulfurization flux is CaO-20 wt.
% CaF 2 was used, and a uniform unit of 4 kg / ton was blown together with a carrier gas (Ar gas).
【0054】図4に示すように確認試験(2)では、上
昇管羽口から脱硫フラックスおよび環流用Arガスを一
緒に吹き込んでおり、キャリアーガスも溶鋼環流用ガス
の一部として作用する。従って、本確認試験における環
流用Arガス流量には、キャリアーガスとしてのArガ
ス流量も含まれる。As shown in FIG. 4, in the confirmation test (2), the desulfurization flux and the circulating Ar gas are blown together from the riser tuyere, and the carrier gas also acts as a part of the circulating gas for the molten steel. Therefore, the flow rate of the Ar gas for recirculation in this confirmation test includes the flow rate of the Ar gas as the carrier gas.
【0055】表3に、確認試験(2)の実施例における
試験条件及び溶製結果をに示す。Table 3 shows the test conditions and the results of smelting in the example of the confirmation test (2).
【0056】[0056]
【表3】 [Table 3]
【0057】実施例9〜実施例13は、転炉出鋼直後に
取鍋スラグ上に金属Alを添加し、脱硫フラックスの吹
き込み速度を50kg/minとした場合である。また
実施例14〜実施例16はRH真空脱ガスでの脱酸処理
前に金属Alを副原料投入ホッパー10から添加し、脱
硫フラックスの吹き込み速度を70kg/minとした
場合である。いずれの場合も確認試験(1)に比べ脱硫
率は73〜88%と高かった。Examples 9 to 13 are cases in which metallic Al was added to the ladle slag immediately after the start of the converter and the blowing rate of the desulfurization flux was 50 kg / min. In Examples 14 to 16, metal Al was added from the auxiliary material input hopper 10 before the deoxidation treatment by RH vacuum degassing, and the blowing rate of the desulfurization flux was 70 kg / min. In each case, the desulfurization rate was as high as 73 to 88% as compared with the confirmation test (1).
【0058】この結果、RH終了時成分および鋳片成分
は〔C〕≦20ppm、〔S〕≦10ppm、T〔O〕
≦15ppmの極低炭・極低硫鋼かつ清浄性の高い鋼が
安定して溶製できた。As a result, the components at the end of RH and the slab components were [C] ≦ 20 ppm, [S] ≦ 10 ppm, T [O]
Ultra-low carbon / ultra-low sulfur steel of ≦ 15 ppm and highly clean steel could be stably melted.
【0059】比較例6〜比較例9は、吹き込み速度が5
0〜70kg/minであるが、環流用Arガス流量が
2000Nl/min未満である。また比較例10〜比
較例13は、環流用Arガス流量が2000Nl/mi
ni以上であるが、吹き込み速度が50kg/min未
満の場合である。In Comparative Examples 6 to 9, the blowing speed was 5
0 to 70 kg / min, but the reflux Ar gas flow rate is less than 2000 Nl / min. In Comparative Examples 10 to 13, the reflux Ar gas flow rate was 2000 Nl / mi.
ni or more, but the blowing speed is less than 50 kg / min.
【0060】これらの比較例における試験条件及び溶製
結果を表4に示す。Table 4 shows the test conditions and melting results in these comparative examples.
【0061】[0061]
【表4】 [Table 4]
【0062】これらの場合、表4に示すように80%近
くの高い脱硫率が得られ、RH終了時成分および鋳片成
分は〔C〕≦20ppm、〔S〕≦20ppmの極低炭
・極低硫鋼が得られたが、T〔O〕≦15ppmの清浄
性の高い鋼は溶製できなかった。In these cases, as shown in Table 4, a high desulfurization rate of about 80% was obtained, and the components at the end of RH and the slab components were extremely low carbon and extremely low in carbon content of [C] ≦ 20 ppm and [S] ≦ 20 ppm. Although a low sulfur steel was obtained, a highly clean steel with T [O] ≦ 15 ppm could not be melted.
【0063】[0063]
【発明の効果】本発明によれば、RH真空脱ガス設備で
の脱酸処理前までに取鍋スラグ上に焼石灰および金属A
lを添加し、RH真空脱ガス設備での環流用不活性ガス
流量を4000Nl/min以上、又は、RH真空脱ガ
ス設備での脱酸処理前までに取鍋スラグ上に金属Alを
添加し、2000Nl/min以上かつCaO−CaF
2 系脱硫フラックスを50kg/min以上の速度でR
H真空脱ガス設備の上昇環流溶鋼中に吹き込むことによ
り、取鍋スラグを無害化できT〔O〕≦15ppmの清
浄性の高い極低炭・極低硫鋼を安定して溶製できる。According to the present invention, in the RH vacuum degassing equipment,
Calcined lime and metal A on ladle slag before deoxidation
l, and inert gas for reflux in RH vacuum degassing equipment
Flow rate 4000Nl / min or more, or RH vacuum degassing
Metal Al on ladle slag before deoxidation treatment
2,000 Nl / min or more and CaO-CaF
TwoSystem desulfurization flux at a speed of 50 kg / min or more
By injecting into ascending molten steel of H vacuum degassing equipment
To make the ladle slag harmless.
Highly clean ultra-low carbon / ultra-low sulfur steel can be stably melted.
【図1】確認試験(1)における極低炭・極低硫鋼を溶
製している状況を示す図である。FIG. 1 is a view showing a state in which ultra-low carbon / ultra-low sulfur steel is melted in a confirmation test (1).
【図2】実施例1〜実施例8における転炉出鋼から鋳造
された鋳片までの成分推移を示す図である。FIG. 2 is a diagram showing a change in components from converter tapping to cast slabs in Examples 1 to 8.
【図3】確認試験(1)における脱硫工程における環流
用Arガス流量が鋳造後の鋳片T〔O〕に及ぼす影響を
示す図である。FIG. 3 is a diagram showing the effect of the reflux Ar gas flow rate on a slab T [O] after casting in a desulfurization step in confirmation test (1).
【図4】確認試験(2)における極低炭・極低硫鋼を溶
製している状況を示す図である。FIG. 4 is a view showing a situation in which ultra-low carbon / ultra-low sulfur steel is melted in confirmation test (2).
【符号の説明】 1 取鍋 2 溶鋼 3 取鍋スラグ 4 上昇管 6 脱ガス真空槽 9 環流用ガス吹き込み管 10 副原料投入ホッパー[Description of Signs] 1 Ladle 2 Molten steel 3 Ladle slag 4 Ascending pipe 6 Degassing vacuum tank 9 Recirculation gas injection pipe 10 Sub-material input hopper
フロントページの続き (72)発明者 福味 純一 東京都千代田区丸の内一丁目1番2号 日本鋼管株式会社内 (56)参考文献 特開 平6−299229(JP,A) 特開 平6−240338(JP,A) 特開 平5−214426(JP,A) 特開 昭59−208011(JP,A) 特開 昭59−56515(JP,A) 特開 昭58−113313(JP,A) 特開 昭58−37112(JP,A) 実開 平2−38458(JP,U)Continuation of the front page (72) Inventor Junichi Fukumi 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-6-299229 (JP, A) JP-A-6-240338 (JP, A) JP-A-5-214426 (JP, A) JP-A-59-208011 (JP, A) JP-A-59-56515 (JP, A) JP-A-58-113313 (JP, A) 58-37112 (JP, A) 2-38458 (JP, U)
Claims (2)
理、脱酸処理、脱硫処理の順に精錬して極低炭・極低硫
鋼を溶製する方法において、前記脱酸処理前までに焼石
灰および金属Alを取鍋内のスラグ上に予め添加してお
き、脱酸処理終了後、上昇管を環流する上昇環流溶鋼中
に4000Nl/min以上の流量で不活性ガスを吹き
込んで溶鋼を環流させ、この環流による溶鋼の攪拌エネ
ルギーにより取鍋内の溶鋼湯面およびスラグを揺動さ
せ、この揺動によって取鍋内のスラグを前記金属Alに
より還元すると同時に前記焼石灰を取鍋内のスラグに溶
解させ、当該スラグにより溶鋼を脱硫することを特徴と
する極低炭・極低硫鋼の溶製方法。1. A method for refining ultra-low carbon / ultra-low sulfur steel by refining in the order of vacuum decarburizing treatment, deoxidizing treatment, and desulfurizing treatment using an RH vacuum degassing equipment, wherein the deoxidizing treatment is performed before the deoxidizing treatment. Contact with the burnt lime and metal Al was added in advance to the slag in the ladle
Can, after deacidification ends, riser refluxed elevated circulating molten steel Nde <br/> write blowing an inert gas at a higher flow rate of 4000Nl / min in the molten steel to reflux and stirred energy of the molten steel by the recirculation
The molten steel surface and the slag in the ladle are rocked by the lug, and the slag in the ladle is changed to the metal Al by the rocking.
At the same time as reducing, the calcined lime was dissolved in the slag in the ladle.
A method for producing ultra-low carbon / ultra-low sulfur steel, wherein the molten steel is desulfurized by the slag .
理、脱酸処理、脱硫処理の順に精錬して極低炭・極低硫
鋼を溶製する方法において、前記脱酸処理前までに金属
Alを取鍋内のスラグ上に予め添加しておき、脱酸処理
終了後、上昇管を環流する上昇環流溶鋼中に2000N
l/min以上の流量で不活性ガスを吹き込むと共に5
0kg/min以上の速度で粉体状のCaO−CaF2
系脱硫フラックスを吹き込んで溶鋼を環流させ、この環
流による溶鋼の攪拌エネルギーにより取鍋内の溶鋼湯面
およびスラグを揺動させ、この揺動によって取鍋内のス
ラグを前記金属Alにより還元しながら前記脱硫フラッ
クスにより溶鋼を脱硫することを特徴とする極低炭・極
低硫鋼の溶製方法。2. A method for refining ultra-low carbon / ultra-low sulfur steel by refining in the order of vacuum decarburization treatment, deoxidation treatment, and desulfurization treatment using an RH vacuum degassing equipment, wherein the decarbonization treatment is performed until before the deoxidation treatment. 2000N in the metal Al possible to add beforehand on the slag in the ladle, after deacidification ends, the riser during the ascent reflux molten steel circulates
Inert an inert gas at a flow rate of 1 / min or more and
CaO-CaF 2 in powder form at a speed of 0 kg / min or more
Nde write blow the system desulfurization flux to reflux of molten steel, this ring
The molten steel surface and slag in the ladle are swung by the stirring energy of the molten steel by the flow, and the swing in the ladle is caused by this swing.
While reducing the lag with the metal Al, the desulfurization flash
A method for producing ultra-low carbon / ultra-low sulfur steel, which comprises desulfurizing molten steel by using heat treatment.
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JP20967695A JP3327062B2 (en) | 1995-08-17 | 1995-08-17 | Melting method of ultra-low carbon / ultra low sulfur steel |
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JP20967695A JP3327062B2 (en) | 1995-08-17 | 1995-08-17 | Melting method of ultra-low carbon / ultra low sulfur steel |
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JPH0953111A JPH0953111A (en) | 1997-02-25 |
JP3327062B2 true JP3327062B2 (en) | 2002-09-24 |
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JP20967695A Expired - Fee Related JP3327062B2 (en) | 1995-08-17 | 1995-08-17 | Melting method of ultra-low carbon / ultra low sulfur steel |
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JP4534734B2 (en) * | 2004-11-29 | 2010-09-01 | Jfeスチール株式会社 | Melting method of low carbon high manganese steel |
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JPH0953111A (en) | 1997-02-25 |
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