JP3052076B2 - Decompression refining method excellent for decarburization - Google Patents
Decompression refining method excellent for decarburizationInfo
- Publication number
- JP3052076B2 JP3052076B2 JP10181547A JP18154798A JP3052076B2 JP 3052076 B2 JP3052076 B2 JP 3052076B2 JP 10181547 A JP10181547 A JP 10181547A JP 18154798 A JP18154798 A JP 18154798A JP 3052076 B2 JP3052076 B2 JP 3052076B2
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- decarburization
- vacuum
- gas
- area
- 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 - Fee Related
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- 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、溶鋼の真空脱ガス
処理において、地金の飛散、付着を抑制した状態で、短
時間での極低炭素濃度域までの脱炭や脱ガスを可能とす
る減圧精錬方法に関する。The present invention relates to a vacuum degassing process for molten steel, which makes it possible to decarburize or degas to a very low carbon concentration range in a short time while suppressing scattering and adhesion of metal. To a vacuum refining method.
【０００２】[0002]
【従来の技術】本発明者らは、すでに真空脱ガス装置を
用いた脱炭においては、ＣＯガスが溶鋼内部から発生す
る内部脱炭と、真空雰囲気に暴露されている自由表面で
ＣＯガスが発生する表面脱炭があり、炭素濃度が約３０
ｐｐｍよりも高い領域では内部脱炭が、それ以下の低炭
素領域では表面脱炭が主として起こり、極低炭素鋼を効
率的に溶製するには表面脱炭の促進が必要であることを
明らかにしてきた（鉄と鋼、第８０年（１９９４）、第
３巻、２１３ページ以降）。また、表面脱炭を活性化さ
せるためには、溶鋼内に吹き込まれた不活性ガスの気泡
が表面に浮上し破泡する領域である気泡広がり面を広く
とる必要があることも示し、特開平６−１１６６２４号
公報には、この気泡広がり面を極限まで広くとり、７ｐ
ｐｍ以下という炭素濃度まで効率的に脱炭する方法とし
て直胴型で大径の浸漬管を取鍋内溶鋼に浸漬し、該浸漬
管内部を減圧する真空脱ガス方法を開示した。この真空
脱ガス方法は、浸漬管内の溶鋼面における気泡広がり面
積が、取鍋内の溶鋼面の面積の１０％以上、浸漬管の内
側平断面積の１０〜９５％になるように調整し、更に、
供給するＡｒガス流量を０．６〜１５ＮＬ／ｍｉｎ・ｔ
ｏｎの範囲に調整している。また、特開平６−４９５２
７号公報では、初期に浸漬管内を３００ｔｏｒｒ以下の
高真空にすると共に浸漬管内の溶鋼面における気泡広が
り面の泡立ち高さを高くし、末期に低真空で浸漬管内の
溶鋼面における気泡広がり面の泡立ち高さを低くすると
いった調整が行われている。（以下、０ｔｏｒｒに近い
方を高真空とし、圧力が高い方を低真空とする。）2. Description of the Related Art The present inventors have found that in decarburization using a vacuum degassing device, CO gas is generated from inside molten steel and CO gas is generated on a free surface exposed to a vacuum atmosphere. There is surface decarburization that occurs and the carbon concentration is about 30
Internal decarburization occurs mainly in the region higher than ppm, and surface decarburization occurs mainly in the low carbon region below that, and it is clear that promotion of surface decarburization is necessary to efficiently melt ultra-low carbon steel. (Iron and Steel, 80 (1994), Vol. 3, pp. 213 et seq.). In addition, it has been shown that in order to activate surface decarburization, it is necessary to widen the bubble spreading surface, which is a region where bubbles of the inert gas blown into the molten steel float on the surface and break. In Japanese Patent Application Laid-Open No. 6-116624, this bubble spreading surface is taken as wide as possible and
As a method for efficiently decarburizing to a carbon concentration of pm or less, a vacuum degassing method in which a straight-body type large-diameter immersion pipe is immersed in molten steel in a ladle and the inside of the immersion pipe is depressurized is disclosed. In this vacuum degassing method, the bubble spreading area on the molten steel surface in the immersion tube is adjusted so as to be 10% or more of the area of the molten steel surface in the ladle and 10 to 95% of the inner cross-sectional area of the immersion tube, Furthermore,
Ar gas flow rate to be supplied is 0.6 to 15 NL / min.t
Adjusted to the on range. Also, Japanese Patent Application Laid-Open No. 6-4952
No. 7, in the early stage, the inside of the immersion tube was made to have a high vacuum of 300 torr or less and the height of the bubble spreading surface on the molten steel surface in the immersion tube was increased. Adjustments have been made to lower the foaming height. (Hereinafter, the one closer to 0 torr is high vacuum, and the one with higher pressure is low vacuum.)
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、溶鋼の
脱炭反応を効率的に進めるためには、気泡広がり面の面
積や浸漬管形状だけでなく、吹き込む不活性ガスの流
量、浸漬管内の真空度、ガス吹き込み位置（方法）につ
いても総合的に組み合わせて制御する必要があることが
分かった。ところが、以上の公報で示されていた技術だ
けでは、最適条件が充分に開示されておらず、例えば、
１５分以内に１０ｐｐｍ以下の炭素濃度に到達させ、か
つ、地金飛散をほぼ完全に抑制して効率的精錬を実施す
るための条件については、全く明確に示されていなかっ
た。そして、特開平６−１１６６２４号公報に示す方法
においては、供給するＡｒガス流量を０．６〜１５ＮＬ
／ｍｉｎ・ｔｏｎにしているが、精錬における脱炭速度
の向上や耐火物の損耗等を考慮した適正供給量を示すも
のではなく、Ａｒガス量が過剰あるいは不足して、有効
な脱炭が行えず、未だ解決すべき以下のような問題があ
る。過剰な場合、 浸漬管内の溶鋼面においてスピッティングが発生す
る。 過剰な溶鋼の循環及びガスアタックにより耐火物の損
耗が大きい。 浸漬管内壁に地金付きが発生し、地金が再び溶鋼内に
溶解することに伴い炭素濃度が上昇し、溶鋼の脱炭速度
が相対的に低下する。 Ａｒガスの排気量に応じた真空度を確保するための装
置等の設備投資が大きくなる。不足の場合、 炭素と酸素の接触が不足することにより脱炭が進み難
くなり、精錬に長時間を要する。 極低炭素の溶製が困難となる。また、特開平６−４９
５２７号公報に示す方法においては、以下のような問題
があった。 末期過程では、初期過程よりも低真空で脱炭を行わな
ければならないため、Ａｒガスの気泡膨張を活用した脱
炭反応を積極的に現出できず、脱炭精錬時間の延長とな
る。 脱炭精錬時間の延長に伴い耐火物の損耗が大きくな
る。本発明はかかる事情に鑑みてなされたもので、前記
公報で開示した後の引き続く研究によって、地金の飛散
や付着を抑制した状態で、極低炭素濃度域までの脱炭や
脱ガスを、短時間に且つ確実に安定的に処理するという
減圧精錬方法の工業的確立に発展させる高効率減圧精錬
方法を提供することを目的とする。However, in order to efficiently promote the decarburization reaction of molten steel, not only the area of the bubble expansion surface and the shape of the immersion tube, but also the flow rate of the inert gas to be blown and the degree of vacuum in the immersion tube are required. It was also found that the gas blowing position (method) also needs to be comprehensively controlled in combination. However, only the techniques disclosed in the above publications do not sufficiently disclose the optimum conditions.
The conditions for achieving a carbon concentration of 10 ppm or less within 15 minutes, and for suppressing metal splattering almost completely and performing efficient refining have not been disclosed at all. In the method disclosed in JP-A-6-116624, the supplied Ar gas flow rate is set to 0.6 to 15 NL.
/ Min · ton, but does not indicate the appropriate supply amount in consideration of the improvement of the decarburization rate in refining and the wear of refractories, etc., and the amount of Ar gas is excessive or insufficient, and effective decarburization can be performed. However, there are still the following problems to be solved. If it is excessive, spitting occurs on the molten steel surface in the immersion tube. Excessive molten steel circulation and gas attack cause large wear of refractories. Metal ingot occurs on the inner wall of the immersion pipe, and the metal is melted into the molten steel again, so that the carbon concentration increases and the decarburization rate of the molten steel relatively decreases. Equipment investment such as a device for securing a degree of vacuum corresponding to the exhaust amount of the Ar gas increases. In the case of shortage, decarburization becomes difficult due to insufficient contact between carbon and oxygen, and refining takes a long time. It becomes difficult to produce extremely low carbon. Also, Japanese Patent Application Laid-Open No. 6-49
The method disclosed in Japanese Patent No. 527 has the following problems. In the final stage, decarburization must be performed at a lower vacuum than in the initial stage, so that a decarburization reaction utilizing bubble expansion of Ar gas cannot be actively exhibited, and the decarburization refining time is extended. As the decarburization refining time is prolonged, the wear of refractories increases. The present invention has been made in view of such circumstances, and by a subsequent study disclosed in the above-mentioned publication, in a state in which scattering and adhesion of metal are suppressed, decarburization and degassing to an extremely low carbon concentration region, It is an object of the present invention to provide a high-efficiency vacuum refining method that can be developed for industrial establishment of a vacuum refining method for performing stable processing in a short time and surely.
【０００４】[0004]
【課題を解決するための手段】前記目的に沿う請求項１
記載の脱炭に優れた減圧精錬方法は、取鍋内の溶鋼に浸
漬管を浸漬し、該浸漬管内を減圧すると共に該浸漬管の
直下位置にある前記溶鋼の下部（例えば、前記取鍋の底
部）から、前記溶鋼中に不活性ガスを吹き込んで前記溶
鋼を精錬する減圧精錬方法において、前記不活性ガスの
流量をＱ（ＮＬ／ｍｉｎ）、前記浸漬管内の溶鋼面にお
ける気泡の広がり面積をＳ（ｍ2 ）、前記浸漬管内の真
空度をＰ（ｔｏｒｒ）、前記溶鋼の全重量をＷ（ｔｏｎ
／ｃｈ）とした場合、以下の式を満足する。 ０．０２≦（Ｑ1/3 ・Ｓ2/3 ）／（Ｗ・Ｐ2/3 ）≦０．
１０ また、請求項２記載の脱炭に優れた減圧精錬方法は、請
求項１記載の脱炭に優れた減圧精錬方法において、前記
不活性ガスの流量Ｑ、気泡の広がり面積Ｓ、又は真空度
Ｐの少なくとも一つを調整することにより前記式を満足
させる。請求項３記載の脱炭に優れた減圧精錬方法は請
求項１又は２記載の脱炭に優れた減圧精錬方法におい
て、前記取鍋内の溶鋼内に浸漬する浸漬管は、内側平断
面積が、前記取鍋内の溶鋼面の面積の１０％以上、８０
％以下とする。ここで、前記式において、（Ｑ1/3 ・Ｓ
2/3 ）／（Ｗ・Ｐ2/3 ）が０．０２以上とするのは、
０．０２未満では、不活性ガス量の絶対量が不足、及び
／又は、不活性ガスの膨張効果が減少するので、脱炭速
度が低下し、更には、到達炭素濃度が高くなるからであ
る。また、０．１０を超えると、不活性ガスの膨張が小
さくなり、脱炭速度も不活性ガス供給量の増加の割合に
比較して向上しなくなる。この理由から極低炭素鋼を溶
製する際には、０．０２以上０．１以下とし、より好ま
しくは０．０４〜０．１以下とする。また、浸漬管の内
側平断面積を、取鍋内の溶鋼面の面積の１０％以上とし
たのは、１０％未満では脱炭を効率よく行うための浸漬
管内の溶鋼面における気泡広がり面が確保できないと共
にガスリフトによる溶鋼の循環が十分に行われないから
であり、また、８０％を超えると、溶鋼のサンプリング
が困難となり操業の支障となる等の制約上の問題が生じ
るからである。この理由から、浸漬管の内側平断面積
は、取鍋内の溶鋼面の面積の１５〜６５％にするとより
好ましい。According to the present invention, there is provided a semiconductor device comprising:
The vacuum refining method excellent in decarburization described is a method of immersing a dip tube in molten steel in a ladle, reducing the pressure in the dip tube, and lowering the molten steel immediately below the dip tube (for example, in the ladle). In the vacuum refining method of refining the molten steel by blowing an inert gas into the molten steel from the bottom), the flow rate of the inert gas is set to Q (NL / min), and the spread area of bubbles on the molten steel surface in the immersion tube is determined. S (m 2 ), the degree of vacuum in the dip tube is P (torr), and the total weight of the molten steel is W (ton
/ Ch), the following expression is satisfied. 0.02 ≦ (Q 1/3 · S 2/3 ) / (W · P 2/3 ) ≦ 0.
10. The reduced pressure refining method excellent in decarburization according to claim 2 is the same as the reduced pressure refining method excellent in decarburization according to claim 1, wherein the flow rate Q of the inert gas, the spread area S of the bubbles, or the degree of vacuum By adjusting at least one of P, the above expression is satisfied. The decompression refining method excellent in decarburization according to claim 3 is the decompression refining method excellent in decarburization according to claim 1 or 2, wherein the immersion pipe immersed in the molten steel in the ladle has an inner flat cross-sectional area. , 80% or more of the area of the molten steel surface in the ladle, 80
% Or less. Here, in the above equation, (Q 1/3 · S
2/3 ) / (W · P 2/3 ) is 0.02 or more because
If it is less than 0.02, the absolute amount of the inert gas is insufficient and / or the expansion effect of the inert gas is reduced, so that the decarburization rate is reduced and the ultimate carbon concentration is increased. . On the other hand, if it exceeds 0.10, the expansion of the inert gas becomes small, and the decarburization rate does not improve as compared with the rate of increase of the inert gas supply amount. For this reason, when the ultra-low carbon steel is melted, it is set to 0.02 or more and 0.1 or less, more preferably 0.04 to 0.1 or less. In addition, the inner flat cross-sectional area of the immersion pipe is set to 10% or more of the area of the molten steel surface in the ladle. If it is less than 10%, the bubble expansion surface in the molten steel surface in the immersion pipe for efficient decarburization is reduced. This is because the molten steel cannot be secured and circulation of the molten steel by the gas lift is not sufficiently performed, and if it exceeds 80%, sampling of the molten steel becomes difficult, which causes a problem in restriction such as hindering operation. For this reason, the inner cross-sectional area of the immersion tube is more preferably set to 15 to 65% of the area of the molten steel surface in the ladle.
【０００５】請求項１〜３記載の脱炭に優れた減圧精錬
方法は、まず、取鍋内の溶鋼に浸漬管を浸漬し、該浸漬
管内を減圧するので、浸漬管内で溶鋼が上昇する。そし
て、浸漬管の直下に位置する溶鋼の下部から浸漬管に不
活性ガスを吹き込む。吹き込まれた不活性ガスは高圧域
から低圧域に移動、即ち、上昇すると共にその気泡を膨
張させる。その過程において気泡表面では、溶鋼中に存
在する炭素及び酸素がＣＯガスとなり、気泡内に取り込
まれると考えられる。また、溶鋼中に存在する水素、窒
素等の気体も同様に気泡中に取り込まれると考えられ
る。最後にこれらの気体が浸漬管内の溶鋼面から溶鋼外
部に排出されることにより、脱炭は行われる。なお、気
泡は浸漬管内の溶鋼面付近で最も膨張することから、こ
のＣＯガスの取り込みは、浸漬管内の溶鋼面付近で最も
行われると考えられ、この面での気泡の広がり、即ち、
浸漬管内の溶鋼面における気泡広がり面を拡大すること
が重要と考えられる。したがって、浸漬管内の溶鋼面か
ら離脱するときに気泡が破泡して生じる気体と液体の界
面積を大きくすることにより、溶鋼中の炭素がＣＯガス
となって気体側に積極的に移行して脱炭を促進する。一
方、不活性ガスを多量に流入することにより気泡の前表
面積を大きくしようとしても、気泡の広がりが、不活性
ガスの流入量に対応して大きくならないため、気泡一つ
一つの膨張が充分に起こらず、脱炭の効果は不活性ガス
供給量の増加の割に得られない。これらを考慮して、最
適に脱炭が行えるよう、前記不活性ガスの流量をＱ（Ｎ
Ｌ／ｍｉｎ）、前記浸漬管内の溶鋼面における気泡の広
がり面積をＳ（ｍ2 ）、前記浸漬管内の真空度をＰ（ｔ
ｏｒｒ）、前記溶鋼の全重量をＷ（ｔｏｎ／ｃｈ）とし
た場合に、以下の式を満足する範囲で精錬を行う。 ０．０２≦（Ｑ1/3 ・Ｓ2/3 ）／（Ｗ・Ｐ2/3 ）≦０．
１０ 前記式を満足する範囲で精錬を行うことにより、溶鋼中
に吹き込んだ不活性ガスの気泡膨張を適切に促進して、
脱炭容量係数（脱炭効率）を高めて極低炭素鋼を溶製す
ることができる。また、不活性ガスの過剰供給よって、
浸漬管内壁に地金付着が発生し、付着地金が溶鋼中に再
溶解することに伴い炭素濃度が上昇する結果、相対的に
脱炭速度が低下することや到達炭素濃度が高くなること
を防止でき、更には、不活性ガスのアタック及び溶鋼の
循環による耐火物の損傷等の発生を抑制することができ
る。また、請求項２記載の脱炭に優れた減圧精錬方法で
は、不活性ガスの流量Ｑ、浸漬管内の溶鋼面における気
泡の広がり面積Ｓ、又は浸漬管内の真空度Ｐの少なくと
も一つを調整して前記式を満足する範囲で精錬を行うこ
とにより、不活性ガスの膨張を最適化し、脱炭速度の向
上や到達炭素濃度を低下させることができる。In the vacuum refining method excellent in decarburization according to claims 1 to 3, first, the immersion pipe is immersed in the molten steel in the ladle and the pressure in the immersion pipe is reduced, so that the molten steel rises in the immersion pipe. Then, an inert gas is blown into the immersion tube from below the molten steel located immediately below the immersion tube. The injected inert gas moves from the high-pressure region to the low-pressure region, that is, rises and expands the bubbles. In the process, it is considered that carbon and oxygen existing in the molten steel become CO gas on the bubble surface and are taken into the bubbles. It is also considered that gases such as hydrogen and nitrogen existing in the molten steel are similarly taken into the bubbles. Finally, degassing is performed by discharging these gases from the molten steel surface in the immersion tube to the outside of the molten steel. Since the bubbles expand most near the molten steel surface in the immersion tube, it is considered that the capture of the CO gas is most performed near the molten steel surface in the immersion tube, and the expansion of the bubbles on this surface, that is,
It is considered important to enlarge the bubble spreading surface on the molten steel surface in the immersion tube. Therefore, by increasing the interfacial area between gas and liquid generated when air bubbles break off when leaving the molten steel surface in the immersion tube, carbon in the molten steel becomes CO gas and positively moves to the gas side. Promote decarburization. On the other hand, even if an attempt is made to increase the front surface area of the bubbles by flowing a large amount of the inert gas, the expansion of the bubbles does not become large in accordance with the amount of the inert gas flowing, so that the expansion of each bubble is sufficient. It does not occur, and the effect of decarburization cannot be obtained for the increase of the inert gas supply. In consideration of these, the flow rate of the inert gas is set to Q (N
L / min), the spread area of bubbles on the molten steel surface in the immersion tube is S (m 2 ), and the degree of vacuum in the immersion tube is P (t).
orr), when the total weight of the molten steel is W (ton / ch), refining is performed within a range satisfying the following expression. 0.02 ≦ (Q 1/3 · S 2/3 ) / (W · P 2/3 ) ≦ 0.
10 By performing refining in the range satisfying the above formula, appropriately promote the bubble expansion of the inert gas blown into the molten steel,
Ultra-low carbon steel can be melted by increasing the decarburization capacity coefficient (decarburization efficiency). Also, due to the excessive supply of inert gas,
Metal deposition on the inner wall of the immersion pipe, and the carbon concentration rises as the metal deposit re-melts in the molten steel, resulting in a relatively lower decarburization rate and a higher carbon concentration reached. In addition, it is possible to prevent the refractory from being damaged due to the inert gas attack and the circulation of the molten steel. In the vacuum refining method excellent in decarburization according to claim 2, at least one of the flow rate Q of the inert gas, the spread area S of bubbles in the molten steel surface in the immersion pipe, or the degree of vacuum P in the immersion pipe is adjusted. By performing refining within the range satisfying the above expression, the expansion of the inert gas can be optimized, the decarburization rate can be improved, and the attained carbon concentration can be reduced.
【０００６】[0006]
【発明の実施の形態】続いて、添付した図面を参照しつ
つ、本発明を具体化した実施の形態につき説明し、本発
明の理解に供する。ここに、図１は本発明の一実施の形
態に係る脱炭に優れた減圧精錬方法を適用する減圧精錬
装置の説明図、図２は（Ｑ1/3 ・Ｓ2/3 ）／（Ｗ・Ｐ
2/3 ）の値（以下、指数という）と脱炭容量係数の関係
を表すグラフ、図３は浸漬管径と浸漬管の内側平断面積
及び浸漬管内の溶鋼面における気泡広がり面積の関係を
表すグラフ、図４は真空度と標準大気圧７６０ｔｏｒｒ
を基準とした気泡の表面積の拡大率の関係を表すグラフ
である。DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is an explanatory diagram of a vacuum refining apparatus to which a vacuum refining method excellent in decarburization according to an embodiment of the present invention is applied, and FIG. 2 is (Q 1/3 · S 2/3 ) / (W・ P
2/3 ) is a graph showing the relationship between the value (hereinafter referred to as an index) and the decarburization capacity coefficient. 4 is a graph showing the degree of vacuum and the standard atmospheric pressure of 760 torr.
6 is a graph showing the relationship between the enlargement ratio of the surface area of the bubble with reference to FIG.
【０００７】図１に示すように、本発明の一実施の形態
に係る脱炭に優れた減圧精錬方法を適用する減圧精錬装
置１０は、取鍋１１と浸漬管１２を有しており、取鍋１
１底面には、ガス吹き込み孔１３が設けられている。浸
漬管１２は、取鍋１１内の溶鋼１４内に、浸漬した状態
で設けられていると共に浸漬管１２内は減圧（１〜１０
ｔｏｒｒ程度）されている。ここで、浸漬管１２は、内
側の平断面積が、取鍋１１内の溶鋼面の面積の２５％程
度のものを用いた。以下、これらについて詳しく説明す
る。まず、浸漬管１２の真下位置にある取鍋１１底面の
ガス吹き込み孔１３から、溶鋼１４中に浸漬管１２内に
向けて不活性ガスの一例であるＡｒガスを流入する。こ
のＡｒガスは、溶鋼を循環させる役割も果たすので、浸
漬管１２内の溶鋼面における気泡広がり面１５の中心が
浸漬管１２の中心からずれるように流入する。このＡｒ
ガスは、図４から分かるように、上昇するにつれその気
泡を大きくし、浸漬管１２内の溶鋼面に気泡広がり面１
５を形成する。なお、この広がり方は、Ａｒガスの流量
を極端に少量に、又はＡｒガスの上昇距離を極端に長く
しないかぎり一定と考えることができ、本発明の実施に
おいては一定と考えることができる。また、脱炭は、Ａ
ｒガス上昇中のＡｒガス気泡内に炭素をＣＯガスとして
取り込むことによって行われるが、この取り込みは、Ａ
ｒガスが最も膨張する浸漬管１２内の溶鋼面に達する付
近で最も多いと考えられ、気泡広がり面積を大きくする
ことが重要となる。一方、Ａｒガスを多量に流入するこ
とにより気泡の全表面積を大きくしようとしても、気泡
の広がりが、Ａｒガスの流入量に対応して大きくならな
いため、気泡一つ一つの膨張が充分に起こらず、脱炭の
効果はＡｒガス供給量の増加の割に得られない。As shown in FIG. 1, a vacuum refining apparatus 10 to which a vacuum refining method excellent in decarburization according to one embodiment of the present invention is applied has a ladle 11 and a dip tube 12. Pot 1
On one bottom surface, a gas blowing hole 13 is provided. The immersion tube 12 is provided in the molten steel 14 in the ladle 11 in a state of being immersed, and the pressure in the immersion tube 12 is reduced (1 to 10).
torr). Here, the immersion tube 12 used had an inner flat sectional area of about 25% of the area of the molten steel surface in the ladle 11. Hereinafter, these will be described in detail. First, Ar gas, which is an example of an inert gas, flows into the molten steel 14 from the gas injection hole 13 on the bottom surface of the ladle 11 located directly below the dip tube 12. Since the Ar gas also plays a role in circulating the molten steel, the Ar gas flows in such a manner that the center of the bubble spreading surface 15 on the molten steel surface in the immersion pipe 12 is shifted from the center of the immersion pipe 12. This Ar
As can be seen from FIG. 4, the gas enlarges its bubbles as it rises, and the gas spreads on the molten steel surface in the immersion pipe 12.
5 is formed. This spread can be considered to be constant unless the flow rate of the Ar gas is extremely small or the rising distance of the Ar gas is extremely long, and can be considered to be constant in the embodiment of the present invention. Decarburization is A
This is performed by capturing carbon as CO gas in the Ar gas bubbles during the rise of the r gas.
It is considered that there is most r gas near the molten steel surface in the immersion pipe 12 where the gas expands most, and it is important to increase the bubble spreading area. On the other hand, even if an attempt is made to increase the total surface area of the bubbles by flowing a large amount of Ar gas, the expansion of each bubble does not sufficiently occur because the expansion of the bubbles does not increase in accordance with the inflow amount of the Ar gas. However, the effect of decarburization cannot be obtained for the increase in the supply amount of Ar gas.
【０００８】そこで、Ａｒガスの流量Ｑ（ＮＬ／ｍｉ
ｎ）、浸漬管１２内の溶鋼面における気泡の広がり面積
Ｓ（ｍ2 ）、浸漬管１２内の真空度Ｐ（ｔｏｒｒ）、前
記溶鋼１４の全重量Ｗ（ｔｏｎ／ｃｈ）を以下の式を満
足する範囲で精錬を行う。０．０２≦（Ｑ1/3 ・Ｓ
2/3 ）／（Ｗ・Ｐ2/3 ）≦０．１０まず例えば、図３か
ら浸漬管径及び気泡広がり面積Ｓを決定する。ここで、
図３に示すグラフは、溶鋼の全重量Ｗが１７５ｔｏｎ／
ｃｈ、取鍋内の溶鋼の溶鋼面の直径が３．３ｍ、溶鋼の
取鍋底面からの高さが２．８ｍであり、厚さ３０ｃｍの
浸漬管を溶鋼に４０ｃｍ浸漬し、浸漬管内の真空度Ｐを
１ｔｏｒｒとする測定条件にて、浸漬管径と気泡広がり
面積との関係を表したものである。なお、グラフに示す
領域Ａがこの条件において可能かつ適切な気泡広がり面
積となる。この可能かつ適切な気泡広がり面積は、浸漬
管径を大きくするにつれ大きくなるが、浸漬管径が約
１．７ｍに達した後は浸漬管径を大きくしても大きくな
らない。これは、気泡の広がり方が一定であるのに対
し、浸漬管内の溶鋼面の取鍋底面からの高さが、浸漬管
径を大きくすることにより低くなるためである。また、
浸漬管径及び気泡広がり面積の決定は、気泡広がり面が
浸漬管内の溶鋼面をすべて覆うように決定すると溶鋼の
循環が行われなくなるので、浸漬管内の溶鋼面に対して
気泡広がり面が小さくなるようにする。Ａｒガスの吹き
込み位置を、浸漬管の下端からＡｒガスが洩れない範囲
で偏心させることにより気泡広がり面を調整して、溶鋼
の攪拌を阻害することなく精錬ができるようにして、領
域Ａから決定する。そこで例えば、浸漬管径を１．７ｍ
にして、気泡の広がり面積Ｓを１．７ｍ2 とすれば、溶
鋼の全重量Ｗは１７５ｔｏｎ／ｃｈは決まっているの
で、次に真空度Ｐ及びＡｒガスの流量Ｑを決定する。こ
こで、気泡の広がり面積Ｓは、真空度Ｐを１〜１０ｔｏ
ｒｒ程度の間で変化させても、浸漬管内の溶鋼面の高さ
はほぼ変化しないため誤差範囲と考えることができ、ま
た、Ａｒガスの流量Ｑを変えることによっても、気泡の
広がり方はほぼ変化しないため誤差範囲と考えることが
できる。そこで、真空度Ｐを１ｔｏｒｒ、Ａｒガスの流
量Ｑを４００ＮＬ／ｍｉｎとすることにより、（Ｑ1/3
・Ｓ2/3 ）／（Ｗ・Ｐ2/3 ）の値は０．０６となる。こ
れは、前記式を満足し、脱炭反応を一次反応で仮定した
ときの脱炭容量係数は、０．２８（１／ｍｉｎ）とな
り、脱炭を効率良く行うことができる。なお、気泡広が
り面積Ｓの値は、Ａｒガスの流量Ｑによる浸漬管内の溶
鋼面の盛り上がり高さ分の気泡の広がりは考慮せず、溶
鋼の静止面での気泡広がり面の面積とする。Therefore, the flow rate Q of the Ar gas (NL / mi
n), the spread area S (m 2 ) of bubbles on the molten steel surface in the immersion pipe 12, the degree of vacuum P (torr) in the immersion pipe 12, and the total weight W (ton / ch) of the molten steel 14 are represented by the following equations. Refining to the extent satisfied. 0.02 ≦ (Q 1/3 · S
2/3 ) / (W · P 2/3 ) ≦ 0.10 First, for example, the diameter of the immersion pipe and the bubble spreading area S are determined from FIG. here,
The graph shown in FIG. 3 shows that the total weight W of the molten steel is 175 ton /
ch, the diameter of the molten steel surface of the molten steel in the ladle is 3.3 m, the height from the bottom of the molten steel is 2.8 m, and a 30 cm thick immersion tube is immersed in the molten steel by 40 cm, and the vacuum in the immersion tube is set. It shows the relationship between the immersion tube diameter and the bubble spreading area under the measurement condition where the degree P is 1 torr. The region A shown in the graph is a possible and appropriate bubble spreading area under this condition. This possible and appropriate bubble spreading area increases as the dip tube diameter increases, but does not increase after the dip tube diameter reaches approximately 1.7 m, even if the dip tube diameter increases. This is because the expansion of the bubbles is constant, while the height of the molten steel surface in the immersion tube from the bottom of the ladle is reduced by increasing the diameter of the immersion tube. Also,
In the determination of the dip tube diameter and the bubble spreading area, if the bubble spreading surface is determined so as to cover all the molten steel surface in the dip tube, the circulation of the molten steel will not be performed, so the bubble spread surface will be smaller than the molten steel surface in the dip tube. To do . Ar gas blowing
The immersion position is eccentric within a range where Ar gas does not leak from the lower end of the immersion tube to adjust the bubble spreading surface so that refining can be performed without hindering the stirring of the molten steel, and is determined from the region A. Therefore, for example, the dip tube diameter is set to 1.7 m.
Assuming that the spread area S of the bubbles is 1.7 m 2 , the total weight W of the molten steel is determined to be 175 ton / ch, so the degree of vacuum P and the flow rate Q of Ar gas are determined next. Here, the spreading area S of the bubble is determined by setting the degree of vacuum P to 1 to 10 to.
Even if it is changed between rr and rr, the height of the molten steel surface in the immersion tube hardly changes, so it can be considered as an error range. Since it does not change, it can be considered as an error range. Therefore, by setting the degree of vacuum P to 1 torr and the flow rate Q of Ar gas to 400 NL / min, (Q 1/3
The value of (S 2/3 ) / (W · P 2/3 ) is 0.06. This satisfies the above formula, decarburization capacity factor, assuming the decarburization reaction in the primary reaction can be carried out 0.28 (1 / min), and the decarburization efficiency. Note that the value of the bubble spreading area S is the area of the bubble spreading surface on the stationary surface of the molten steel without taking into account the spread of bubbles by the rising height of the molten steel surface in the immersion pipe due to the flow rate Q of the Ar gas.
【０００９】[0009]
【実施例】前記脱炭に優れた減圧精錬方法を用いて、炭
素濃度が３０ｐｐｍから１０ｐｐｍ以下になるまでの脱
炭容量係数の測定実験（ＮＯ．１〜２０）を行った。こ
こでは、溶鋼の全重量Ｗ、Ａｒガスの流量Ｑ、浸漬管内
の溶鋼面における気泡の広がり面積Ｓ、浸漬管内の真空
度Ｐをそれぞれ調整し実験を行った。なお、溶鋼の全重
量Ｗが３５０ｔｏｎ／ｃｈのときには、取鍋内の溶鋼の
溶鋼面の直径が４．４ｍ、溶鋼の取鍋底面からの高さが
３．３ｍであり、厚さが５０ｃｍ、内径が２．２ｍの浸
漬管を溶鋼に５０ｃｍ浸漬しており、また、溶鋼の全重
量が１７５ｔｏｎ／ｃｈのときには、取鍋内の溶鋼の溶
鋼面の直径が３．３ｍ、溶鋼の取鍋底面からの高さが
２．８ｍであり、厚さが３０ｃｍ、内径が１．７ｍの浸
漬管を溶鋼に４０ｃｍ浸漬している。EXAMPLES Using the above-described vacuum refining method excellent in decarburization, measurement experiments (NO. 1 to 20) of the decarburization capacity coefficient until the carbon concentration was reduced from 30 ppm to 10 ppm or less were performed. Here, the experiment was performed by adjusting the total weight W of the molten steel, the flow rate Q of the Ar gas, the area S of the bubbles spread on the molten steel surface in the dip tube, and the degree of vacuum P in the dip tube. When the total weight W of the molten steel is 350 ton / ch, the diameter of the molten steel surface of the molten steel in the ladle is 4.4 m, the height of the molten steel from the bottom of the ladle is 3.3 m, and the thickness is 50 cm. When an immersion pipe with an inner diameter of 2.2 m is immersed in molten steel by 50 cm and the total weight of the molten steel is 175 ton / ch, the diameter of the molten steel surface of the molten steel in the ladle is 3.3 m, and the bottom surface of the molten steel ladle is The height of the immersion pipe is 2.8 m, the thickness is 30 cm, and the inner diameter is 1.7 m.
【００１０】[0010]
【表１】 [Table 1]
【００１１】表１及び図２に示すように、溶鋼の全重量
Ｗ、Ａｒガスの流量Ｑ、気泡の広がり面積Ｓ、及び真空
度Ｐの調整により、指数が０．０２以上０．１０以下を
示せば、脱炭容量係数は０．１０（１／ｍｉｎ）以上を
示し、効率よく脱炭が行われることがわかる。すなわ
ち、１０ｐｐｍ以下の極低炭素鋼が短時間で溶製でき
る。また、溶鋼の全重量Ｗを３５０ｔｏｎ／ｃｈ、取鍋
内の溶鋼面の直径を４．４ｍとし、取鍋内の溶鋼面積の
１５％と６５％に相当する内側の平断面積を有する浸漬
管を用いて、溶鋼の全重量Ｗ、Ａｒガスの流量Ｑ、気泡
広がり面積Ｓ、及び真空度Ｐを調整して指数が０．０２
〜０．１０となるようにした場合についても実施した結
果、地金付着や耐火物の損傷等の操業の支障がなく、効
率よく脱炭を行うことができた。一方、ＮＯ．５、Ｎ
Ｏ．７、ＮＯ．９、ＮＯ．１０、ＮＯ．２０について
は、指数が前記範囲を満足していない。ＮＯ．５、Ｎ
Ｏ．７、ＮＯ．９及びＮＯ．１０は、指数が０．０２未
満を示し、脱炭容量係数が小さく、精錬に長時間を要
し、その結果として耐火物の損耗をも招く。また、Ｎ
Ｏ．２０は指数が０．１０を超え、脱炭容量係数は大き
いものの、スピッティングや耐火物の損耗が非常に大き
いため、工業的方法としては妥当でない。As shown in Table 1 and FIG. 2, by adjusting the total weight W of the molten steel, the flow rate Q of the Ar gas, the spread area S of the bubbles, and the degree of vacuum P, the index becomes 0.02 or more and 0.10 or less. If shown, the decarburization capacity coefficient is 0.10 (1 / min) or more, which indicates that decarburization is performed efficiently. That is, extremely low carbon steel of 10 ppm or less can be melted in a short time. Also, the total weight W of the molten steel is 350 ton / ch, the diameter of the molten steel surface in the ladle is 4.4 m, and the inner flat cross-sectional area corresponds to 15% and 65% of the molten steel area in the ladle. To adjust the total weight W of the molten steel, the flow rate Q of the Ar gas, the bubble spreading area S, and the degree of vacuum P to obtain an index of 0.02.
As a result of carrying out also in the case where it was set to ０．１0.10, decarburization was able to be performed efficiently without any trouble in operation such as adhesion of ingot and damage of refractory. On the other hand, NO. 5, N
O. 7, NO. 9, NO. 10, NO. With regard to 20, the index does not satisfy the above range. NO. 5, N
O. 7, NO. 9 and NO. No. 10 has an index of less than 0.02, has a small decarburization capacity coefficient, requires a long time for refining, and as a result, wears the refractory. Also, N
O. Although 20 has an index exceeding 0.10 and has a large decarburization capacity coefficient, it is not appropriate as an industrial method because spitting and wear of refractories are very large.
【００１２】[0012]
【発明の効果】請求項１〜３記載の脱炭に優れた減圧精
錬方法においては、不活性ガスの流量をＱ（ＮＬ／ｍｉ
ｎ）、前記浸漬管内の溶鋼面における気泡の広がり面積
をＳ（ｍ2 ）、前記浸漬管内の真空度をＰ（ｔｏｒ
ｒ）、前記溶鋼の全重量をＷ（ｔｏｎ／ｃｈ）とした場
合、 ０．０２≦（Ｑ1/3 ・Ｓ2/3 ）／（Ｗ・Ｐ2/3 ）≦０．
１０ を満足する範囲で精錬を行うので、不活性ガスを最適量
流入して、不活性ガスの膨張を最適化でき、それによっ
て、安定且つ確実に、更には、効率的に脱炭や脱ガスを
行うことができる。また、それに伴い以下の効果があ
る。 脱炭容量係数が向上し、精錬時間の短縮、到達炭素濃
度の低下が可能となりる。 浸漬管内壁に地金付着が発生するのを抑制し、付着地
金が溶鋼中に再溶解することによって生じる炭素濃度の
上昇を防止できる。 前記炭素濃度の上昇によって生じる相対的な脱炭容量
係数の低下を防止することができる。 不活性ガスを有効に脱炭に寄与せしめるので、不活性
ガスの流量を最小限に抑えることができる。 不活性ガスの流量を最小限に抑えることにより、真空
度を確保するための装置等の設備にかかる必要コスト及
びエネルギーが低減でき、工業的方法として妥当とな
る。特に、請求項２記載の脱炭に優れた減圧精錬方法に
おいては、前記不活性ガスの流量Ｑ、気泡の広がり面積
Ｓ、又は真空度Ｐの少なくとも一つを調整することによ
り前記式を満足させるので、脱炭に寄与する不活性ガス
量を精度良く制御することができる。請求項３記載の脱
炭に優れた減圧精錬方法においては、前記取鍋内の溶鋼
内に浸漬する浸漬管は、内側平断面積が、前記取鍋内の
溶鋼面の面積の１０％以上、８０％以下とするので、浸
漬管内の溶鋼面における気泡広がり面が十分に確保でき
ると共にガスリフトによる溶鋼の循環が十分に行われ
る。According to the vacuum refining method excellent in decarburization according to claims 1 to 3, the flow rate of the inert gas is set to Q (NL / mi).
n), the spread area of bubbles on the molten steel surface in the dip tube is S (m 2 ), and the degree of vacuum in the dip tube is P (torn).
r), when the total weight of the molten steel is W (ton / ch), 0.02 ≦ (Q 1/3 · S 2/3 ) / (W · P 2/3 ) ≦ 0.
Since the refining is performed within the range satisfying the condition 10, the optimum amount of the inert gas can be introduced to optimize the expansion of the inert gas, thereby stably and surely and efficiently decarburizing or degassing. It can be performed. In addition, there are the following effects. The decarburization capacity coefficient is improved, so that the refining time can be shortened and the ultimate carbon concentration can be reduced. It is possible to suppress the occurrence of adhesion of the metal on the inner wall of the immersion tube, and to prevent an increase in the carbon concentration caused by the metal being redissolved in the molten steel. It is possible to prevent a decrease in the relative decarburization capacity coefficient caused by the increase in the carbon concentration. Since the inert gas effectively contributes to decarburization, the flow rate of the inert gas can be minimized. By minimizing the flow rate of the inert gas, the required cost and energy required for equipment such as a device for securing a vacuum degree can be reduced, which is appropriate as an industrial method. In particular, in the vacuum refining method excellent in decarburization according to the second aspect, the above expression is satisfied by adjusting at least one of the flow rate Q of the inert gas, the area S of expanding the bubbles, or the degree of vacuum P. Therefore, the amount of inert gas contributing to decarburization can be controlled with high accuracy. In the vacuum refining method excellent in decarburization according to claim 3, the immersion pipe immersed in the molten steel in the ladle has an inner flat cross-sectional area of 10% or more of the area of the molten steel surface in the ladle, Since it is 80% or less, a bubble expansion surface on the molten steel surface in the immersion tube can be sufficiently ensured, and the molten steel is sufficiently circulated by the gas lift.
【図１】本発明の一実施の形態に係る脱炭に優れた減圧
精錬方法を適用する減圧精錬装置の説明図である。FIG. 1 is an explanatory diagram of a vacuum refining apparatus to which a vacuum refining method excellent in decarburization according to an embodiment of the present invention is applied.
【図２】（Ｑ1/3 ・Ｓ2/3 ）／（Ｗ・Ｐ2/3 ）の値と脱
炭容量係数の関係を表すグラフである。FIG. 2 is a graph showing a relationship between a value of (Q 1/3 · S 2/3 ) / (W · P 2/3 ) and a decarburization capacity coefficient.
【図３】浸漬管径と浸漬管の内側平断面積及び浸漬管内
の溶鋼面における気泡広がり面積の関係を表すグラフで
ある。FIG. 3 is a graph showing a relationship between a diameter of a submerged pipe, a plane cross-sectional area inside the submerged pipe, and a bubble spreading area on a molten steel surface in the submerged pipe.
【図４】真空度と標準大気圧７６０ｔｏｒｒを基準とし
た気泡の表面積の拡大率の関係を表すグラフである。FIG. 4 is a graph showing a relationship between a degree of vacuum and an enlargement ratio of a surface area of a bubble based on a standard atmospheric pressure of 760 torr.
１０ 減圧精錬装置 １１ 取鍋 １２ 浸漬管 １３ ガス吹き
込み孔 １４ 溶鋼 １５ 気泡広が
り面DESCRIPTION OF SYMBOLS 10 Decompression refining apparatus 11 Ladle 12 Immersion pipe 13 Gas injection hole 14 Molten steel 15 Bubble spreading surface
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) C21C 7/10 C21C 7/068 ──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. 7 , DB name) C21C 7/10 C21C 7/068
Claims (3)
管内を減圧すると共に該浸漬管の直下位置にある前記溶
鋼の下部から、前記溶鋼中に不活性ガスを吹き込んで前
記溶鋼を精錬する減圧精錬方法において、 前記不活性ガスの流量をＱ（ＮＬ／ｍｉｎ）、前記浸漬
管内の溶鋼面における気泡の広がり面積をＳ（ｍ2 ）、
前記浸漬管内の真空度をＰ（ｔｏｒｒ）、前記溶鋼の全
重量をＷ（ｔｏｎ／ｃｈ）とした場合、以下の式を満足
する範囲で精錬を行うことを特徴とする脱炭に優れた減
圧精錬方法。 ０．０２≦（Ｑ1/3 ・Ｓ2/3 ）／（Ｗ・Ｐ2/3 ）≦０．
１０1. An immersion pipe is immersed in molten steel in a ladle, the interior of the immersion pipe is depressurized, and an inert gas is blown into the molten steel from a lower portion of the molten steel located immediately below the immersion pipe. In the vacuum refining method for refining, the flow rate of the inert gas is Q (NL / min), the spread area of bubbles on the molten steel surface in the dip tube is S (m 2 ),
When the degree of vacuum in the immersion tube is P (torr) and the total weight of the molten steel is W (ton / ch), refining is performed within a range satisfying the following expression, and reduced pressure excellent in decarburization is provided. Refining method. 0.02 ≦ (Q 1/3 · S 2/3 ) / (W · P 2/3 ) ≦ 0.
10
面積Ｓ、又は真空度Ｐの少なくとも一つを調整すること
により前記式を満足させることを特徴とする請求項１記
載の脱炭に優れた減圧精錬方法。2. The decarburization method according to claim 1, wherein the above expression is satisfied by adjusting at least one of the flow rate Q of the inert gas, the area S of the bubble expansion, and the degree of vacuum P. Excellent vacuum refining method.
は、内側平断面積が、前記取鍋内の溶鋼面の面積の１０
％以上、８０％以下とすることを特徴とする請求項１又
は２記載の脱炭に優れた減圧精錬方法。3. An immersion pipe immersed in molten steel in the ladle has an inner flat cross-sectional area of 10 mm of the area of the molten steel surface in the ladle.
%. The vacuum refining method excellent in decarburization according to claim 1, wherein the concentration is not less than 80% and not more than 80%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10181547A JP3052076B2 (en) | 1998-06-11 | 1998-06-11 | Decompression refining method excellent for decarburization |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10181547A JP3052076B2 (en) | 1998-06-11 | 1998-06-11 | Decompression refining method excellent for decarburization |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11350021A JPH11350021A (en) | 1999-12-21 |
| JP3052076B2 true JP3052076B2 (en) | 2000-06-12 |
Family
ID=16102702
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10181547A Expired - Fee Related JP3052076B2 (en) | 1998-06-11 | 1998-06-11 | Decompression refining method excellent for decarburization |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3052076B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014042495A (en) * | 2012-08-28 | 2014-03-13 | Toto Kogyo Co Ltd | Lower rail traveling type sliding door device of vinyl house |
-
1998
- 1998-06-11 JP JP10181547A patent/JP3052076B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014042495A (en) * | 2012-08-28 | 2014-03-13 | Toto Kogyo Co Ltd | Lower rail traveling type sliding door device of vinyl house |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11350021A (en) | 1999-12-21 |
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