JP2000096128A - Method for vacuum-refining low nitrogen molten steel - Google Patents
Method for vacuum-refining low nitrogen molten steelInfo
- Publication number
- JP2000096128A JP2000096128A JP10288909A JP28890998A JP2000096128A JP 2000096128 A JP2000096128 A JP 2000096128A JP 10288909 A JP10288909 A JP 10288909A JP 28890998 A JP28890998 A JP 28890998A JP 2000096128 A JP2000096128 A JP 2000096128A
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- nitrogen
- refining
- ladle
- immersion
- 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- Withdrawn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
- 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、脱炭及び脱ガス等
の減圧精錬における吸窒素を防止する溶鋼の減圧精錬方
法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for vacuum refining molten steel for preventing nitrogen absorption in vacuum refining such as decarburization and degassing.
【０００２】[0002]
【従来の技術】溶鋼の炭素、水素あるいは窒素濃度を低
下させる方法として、真空（減圧）を利用したＲＨ、Ｄ
ＨやＶＯＤ等が広く用いられている。しかし、これ等の
方法では、溶鋼の炭素や窒素をある程度にまで低減でき
るが、十分に炭素や窒素等を低減した溶鋼の溶製が困難
である。従って、減圧下における精錬効率を高めて極低
炭素、低窒素等の溶鋼の溶製を行う方法として、例え
ば、特開平１−９２３１４号公報では、取鍋内径の０．
５以下に相当する内径を有する浸漬管を用い、この浸漬
管内を減圧すると共に、取鍋の底部から不活性ガスを吹
き込んで溶鋼を攪拌しながら、脱炭及び脱ガス（脱窒素
及び脱水素）精錬を行なう取鍋精錬方法が提案されてい
る。また、特開平７−２７８６３９号公報では、取鍋内
径Ｄ／浸漬管内径Ｄ1 が０．５〜０．８である浸漬管を
浸漬し、この浸漬管内を減圧して取鍋の底部から不活性
ガスを吹き込んで溶鋼を攪拌しながら、ＡｌあるいはＡ
ｌ合金鉄を添加して吹酸によって昇温し、次いで、減圧
した状態で浸漬管内に脱硫用のフラックスの添加するこ
とにより脱硫精錬を行ない、引き続き浸漬管内を大気圧
に複圧して浸漬管の浸漬深さを０．５ｍ未満にして不活
性ガスによる攪拌を行う精錬方法が提案されている。こ
の精錬は、溶鋼を吹酸昇温できるので、脱硫精錬等の時
間の経過に伴う溶鋼の温度の低下や脱硫反応の低下、あ
るいは精錬炉（転炉）等に配合する冷鉄源（スクラッ
プ）の使用量の低減等の問題を解決できる等の利点があ
る。2. Description of the Related Art As a method for lowering the concentration of carbon, hydrogen or nitrogen in molten steel, RH and D using vacuum (reduced pressure) are used.
H and VOD are widely used. However, these methods can reduce the carbon and nitrogen of the molten steel to a certain extent, but it is difficult to produce molten steel with sufficiently reduced carbon and nitrogen. Therefore, as a method for increasing the refining efficiency under reduced pressure to produce molten steel with extremely low carbon, low nitrogen, etc., for example, Japanese Patent Application Laid-Open No. 1-92314 discloses a method of producing a molten steel having a ladle inner diameter of 0.1 mm.
Using a dip tube having an inner diameter equivalent to 5 or less, decompression and degassing (denitrification and dehydrogenation) while reducing the pressure inside the dip tube and blowing molten gas from the bottom of the ladle to stir the molten steel. Ladle refining methods for refining have been proposed. Further, in JP-A 7-278639 and JP-ladle inner diameter D / dip tube inner diameter D 1 is immersed a dip tube is 0.5 to 0.8, from the bottom of the ladle to the immersion tube by vacuum not While stirring the molten steel by blowing active gas, Al or A
(1) Add ferrous iron, raise the temperature by blowing acid, then perform desulfurization refining by adding flux for desulfurization into the immersion tube under reduced pressure, and subsequently double-pressurize the immersion tube to atmospheric pressure to A refining method has been proposed in which the immersion depth is set to less than 0.5 m and stirring is performed with an inert gas. In this refining, the molten steel can be heated with a blowing acid, so that the temperature of the molten steel decreases and the desulfurization reaction decreases with the lapse of time such as desulfurization refining, or a cold iron source (scrap) mixed in a refining furnace (converter) or the like. There is an advantage that problems such as reduction of the amount of used can be solved.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、特開平
１−９２３１４号公報に記載された精錬方法では、脱炭
及び脱ガス精錬を行った後、浸漬管内を大気圧に複圧し
てから、取鍋内の溶鋼中から浸漬管を上昇するために、
外気が浸入し、この外気中の窒素により溶鋼の吸窒素
（窒素のピックアップ）が生じて溶鋼の窒素（Ｎ）濃度
が高くなる。更に、浸漬管内を大気圧に複圧した後にお
いても、溶鋼の表面を覆うスラグが少ないために、溶鋼
が外気と接触して吸窒素が起こり溶鋼中の窒素濃度がよ
り高くなる等の問題がある。また、特開平７−２７８６
３９号公報に記載された精錬方法も、脱炭及び脱ガス精
錬を行った後に、浸漬管内を大気圧に複圧するので、浸
漬管や排気系から浸入した外気により溶鋼の吸窒素（窒
素のピックアップ）が生じて溶鋼中の窒素濃度が高くな
る。また、この脱硫精錬を終了して大気圧に複圧した
後、浸漬管の浸漬深さを０．５ｍ未満にして不活性ガス
により溶鋼の攪拌を行うために、浸漬管や排気系から浸
入した外気中の窒素と溶鋼との接触や溶鋼中への窒素の
巻き込みが生じて、溶鋼への吸窒素（窒素ピックアッ
プ）が増加する。更に、脱硫精錬を終了してから溶鋼の
攪拌を行うために、脱硫精錬時に形成されたスラグによ
り浸漬管等の耐火物が損耗する等の問題がある。However, in the refining method described in JP-A-1-92314, after performing decarburization and degassing refining, the inside of the immersion pipe is double-pressurized to atmospheric pressure, and then the ladle is heated. To raise the immersion pipe from inside the molten steel in
The outside air enters, and the nitrogen in the outside air causes nitrogen absorption (nitrogen pickup) of the molten steel, thereby increasing the nitrogen (N) concentration of the molten steel. Furthermore, even after the inside of the immersion pipe is double-pressurized to atmospheric pressure, there is little slag covering the surface of the molten steel, so that the molten steel comes into contact with the outside air, causing nitrogen absorption and increasing the nitrogen concentration in the molten steel. is there. Also, Japanese Patent Application Laid-Open No. 7-2786
In the refining method described in Japanese Patent Publication No. 39, since decarburization and degassing refining are performed, the inside of the immersion pipe is double-pressurized to the atmospheric pressure. ) Occurs and the nitrogen concentration in the molten steel increases. Further, after the desulfurization refining was completed and the pressure was doubled to the atmospheric pressure, in order to stir the molten steel with an inert gas with the immersion depth of the immersion tube being less than 0.5 m, the immersion tube or the exhaust system was introduced. The contact between the nitrogen in the outside air and the molten steel and the entrainment of nitrogen into the molten steel occur, so that nitrogen absorption (nitrogen pickup) into the molten steel increases. Further, since the molten steel is stirred after the desulfurization refining is completed, there is a problem that slag formed during the desulfurization refining causes refractories such as immersion pipes to be worn.
【０００４】本発明はかかる事情に鑑みてなされたもの
で、脱炭及び脱ガス等の減圧精錬における吸窒素を防止
し、耐火物等の損耗を抑制することができる低窒素溶鋼
の減圧精錬方法を提供することを目的とする。[0004] The present invention has been made in view of the above circumstances, and a method for reducing the pressure of low-nitrogen molten steel under reduced pressure refining such as decarburization and degassing, thereby suppressing wear of refractories and the like. The purpose is to provide.
【０００５】[0005]
【課題を解決するための手段】前記目的に沿う本発明の
低窒素溶鋼の減圧精錬方法は、一本の浸漬管を取鍋内の
溶鋼に浸漬して、前記取鍋の底部から不活性ガスを吹き
込みながら、前記浸漬管内を減圧して前記溶鋼の脱炭及
び脱ガス精錬を行った後、前記浸漬管内を複圧し、前記
取鍋の底部からの不活性ガスの吹き込み量を０．１〜
０．５ＮＬ／分・溶鋼トンに減らし、前記浸漬管内にフ
ラックスを添加して前記浸漬管内の溶鋼面を覆ってい
る。この方法により、複圧した後、不活性ガスにより溶
鋼を緩慢に攪拌して、フラックスに溶鋼の熱を積極的に
伝達して溶解を促進し、この溶解あるいは軟化したフラ
ックスにより浸漬管内の溶鋼表面を覆って外気を遮断し
て溶鋼への吸窒素を抑制する。そして、取鍋の底部から
の不活性ガスの吹き込み量が０．１ＮＬ／分・溶鋼トン
未満では、浸漬管内に添加したフラックスへの熱の伝達
が不足してフラックスの溶解あるいは軟化によるスラグ
化が困難となり、空隙が形成されて吸窒素を防止できな
い。一方、不活性ガスの吹き込み量が０．５ＮＬ／分・
溶鋼トンを超えると、溶鋼の攪拌が強くなり過ぎて溶鋼
の露出が生じて外気と接触し、吸窒素が生じる。According to the present invention, there is provided a vacuum refining method for low-nitrogen molten steel according to the present invention, in which one dipping tube is immersed in molten steel in a ladle and an inert gas is introduced from the bottom of the ladle. While performing the decarburization and degassing and refining of the molten steel by depressurizing the inside of the immersion tube while blowing, the inside of the immersion tube is double-pressurized, and the amount of inert gas blown from the bottom of the ladle is 0.1 to
The flux is reduced to 0.5 NL / min. Tons of molten steel, and flux is added to the dip tube to cover the molten steel surface in the dip tube. According to this method, the molten steel is gently stirred with an inert gas after the double pressure, and the heat of the molten steel is actively transmitted to the flux to promote the melting. And shut off the outside air to suppress nitrogen absorption into the molten steel. If the flow rate of the inert gas from the bottom of the ladle is less than 0.1 NL / min. / Ton of molten steel, heat transfer to the flux added into the immersion tube is insufficient, and slag is formed by melting or softening of the flux. It becomes difficult and voids are formed, preventing nitrogen absorption. On the other hand, the flow rate of the inert gas is 0.5 NL / min.
When the molten steel exceeds the ton, the agitation of the molten steel becomes too strong, and the molten steel is exposed and comes into contact with the outside air to generate nitrogen absorption.
【０００６】ここで、前記浸漬管内に添加するフラック
スのＣａＯの含有量を２０〜７０重量％とすることがで
きる。これにより、添加したフラックスを速やかに軟化
あるいは溶解して溶鋼の表面を覆うことができる。な
お、浸漬管内に添加するフラックスのＣａＯ含有量が２
０重量％未満では、フラックス中のＣａＯの含有量が不
足するのでスラグの塩基度が低下して、浸漬管等の耐火
物の損耗が増加する。一方、ＣａＯの含有量が７０重量
％を超えると、フラックスの融点が高くなってスラグ化
し難く、溶鋼と外気の遮断が悪くなり吸窒素が発生する
と共に、フラックスの価格も高くなりコストが増大す
る。Here, the CaO content of the flux added to the dip tube may be 20 to 70% by weight. Thereby, the added flux can be quickly softened or dissolved to cover the surface of the molten steel. The CaO content of the flux added into the immersion tube was 2
If the content is less than 0% by weight, the content of CaO in the flux is insufficient, so that the basicity of the slag is reduced and the wear of refractories such as a dip tube is increased. On the other hand, when the content of CaO exceeds 70% by weight, the melting point of the flux becomes high, making it difficult to form slag, the interception of the molten steel and the outside air becomes poor, nitrogen absorption occurs, and the price of the flux also increases, increasing the cost. .
【０００７】更に、前記浸漬管の浸漬の内表面積を前記
取鍋内の溶鋼の全表面積の０．１〜０．７とすることも
できる。これは、浸漬管内の浸漬部の内表面積／取鍋の
全溶鋼表面積が０．１より小さいと、浸漬管内に吹き込
む不活性ガスにより形成される気泡活性面（不活性ガス
気泡の放出面）が狭くなり脱炭とその後に行う脱硫精錬
等の反応が阻害され、一方、０．７より大きくなるとサ
ンプリング等の作業性が阻害されるからである。Further, the inner surface area of the immersion tube may be 0.1 to 0.7 of the total surface area of the molten steel in the ladle. This is because, when the ratio of the inner surface area of the immersion part in the immersion tube / the total molten steel surface area of the ladle is smaller than 0.1, the bubble activated surface formed by the inert gas blown into the immersion tube (inert gas bubble emission surface). This is because the reaction becomes narrower and the reaction of decarburization and the subsequent desulfurization refining or the like is hindered.
【０００８】[0008]
【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。図１は本発明の一実施の形態に係る
低窒素溶鋼の減圧精錬方法に適用する減圧精錬装置の正
断面図である。まず、本発明の一実施の形態に係る低窒
素溶鋼の減圧精錬方法に用いる減圧精錬装置１０は、鋼
製で耐火物（図示せず）を内張りした取鍋１１と、取鍋
１１内の溶鋼１２に浸漬する浸漬管１３及び浸漬管１３
と連通する真空槽１４と、浸漬管１３及び真空槽１４の
内部を排気して減圧するためのエゼクターに連接した排
気ダクト１５と、浸漬管１３内に合金鉄等を添加するた
めの貯蔵ホッパー１６、添加シュート１７を備えてい
る。更に、取鍋１１の底部１８には、取鍋１１内に不活
性ガスを吹き込むためのポーラスプラグ１９を設けてお
り、矢印で示す流れを形成することにより溶鋼１２の攪
拌を行う。なお、１２ａは浸漬管１３内の溶鋼１２の湯
面（溶鋼面）であり、１３ａと１４ａは浸漬管１３と真
空槽１４をボルト・ナット等の締結手段により接合する
ためのフランジである。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. FIG. 1 is a front sectional view of a vacuum refining apparatus applied to a vacuum refining method for low nitrogen molten steel according to one embodiment of the present invention. First, a vacuum refining apparatus 10 used for a vacuum refining method of low nitrogen molten steel according to an embodiment of the present invention includes a ladle 11 made of steel and lined with a refractory (not shown), and a molten steel in the ladle 11. Immersion tube 13 and immersion tube 13
Tank 14, which communicates with the immersion pipe 13, an exhaust duct 15 connected to an ejector for evacuating and depressurizing the inside of the immersion pipe 13, and a storage hopper 16 for adding alloy iron or the like into the immersion pipe 13. , An addition chute 17. Further, a porous plug 19 for blowing an inert gas into the ladle 11 is provided at the bottom 18 of the ladle 11, and the molten steel 12 is stirred by forming a flow indicated by an arrow. Reference numeral 12a denotes a molten metal surface (a molten steel surface) of the molten steel 12 in the immersion tube 13, and 13a and 14a denote flanges for joining the immersion tube 13 and the vacuum chamber 14 by fastening means such as bolts and nuts.
【０００９】次に、前記減圧精錬装置１０を用いた低窒
素溶鋼の減圧精錬方法について説明する。取鍋１１に図
示しない精錬炉の一例である転炉を用いて、炭素濃度を
１００〜６００ｐｐｍに脱炭精錬した１５０トンの溶鋼
１２を受鋼し、ポーラスプラグ１９から不活性ガスの一
例であるアルゴンガスを溶鋼１２中に０．６〜１５ＮＬ
／（分・溶鋼トン）吹き込みながら、この溶鋼１２内に
一本の浸漬管１３を浸漬して、浸漬管１３及び真空槽１
４内を０．１〜１００ｔｏｒｒに減圧して脱炭及び脱ガ
ス精錬を行った。また、この取鍋１１と浸漬管１３の条
件としては、浸漬管の浸漬部の内表面積Ｓ1 ／取鍋内の
溶鋼の全表面積Ｓの比Ｓ1 ／Ｓを０．１〜０．７の範囲
にした。これは、比Ｓ1 ／Ｓが０．１より小さいと、浸
漬管１３内に吹き込むアルゴンガスにより形成される気
泡活性面（アルゴンガス気泡の放出面）が狭くなり脱炭
とその後に行う脱硫精錬等の反応が阻害され、比Ｓ1 ／
Ｓが０．７より大きくなるとサンプリング等の作業性が
阻害されるからである。この理由から比Ｓ1 ／Ｓを０．
１５〜０．６５にするとより好ましい結果が得られる。
そして、ポーラスプラグ１９から供給されるアルゴンガ
スによって、取鍋１１内の溶鋼１２が図１中の矢印で示
す流れにより攪拌され、浸漬管１３内の溶鋼１２の湯面
１２ａで膨張したアルゴンガスの気泡活性面により、脱
炭反応が促進されて脱炭と減圧雰囲気による脱ガス（脱
窒素及び脱水素）が行われる。この脱炭及び脱ガス精錬
は、溶鋼１２中の炭素濃度が３〜１０ｐｐｍ、水素濃度
が１〜５ｐｐｍに到達した時点で終了した。Next, a method for vacuum refining of low nitrogen molten steel using the vacuum refining apparatus 10 will be described. Using a converter as an example of a smelting furnace (not shown) in the ladle 11, a 150-ton molten steel 12 decarbonized and refined to a carbon concentration of 100 to 600 ppm is received, and is an example of an inert gas from the porous plug 19. 0.6 to 15 NL of argon gas in molten steel 12
/ (Min / ton of molten steel) while immersing one immersion pipe 13 in the molten steel 12 while blowing,
4 was decompressed to 0.1 to 100 torr to perform decarburization and degas refining. The conditions of the ladle 11 and the dip tube 13 are such that the ratio S 1 / S of the inner surface area S 1 of the dip portion of the dip tube to the total surface area S of the molten steel in the ladle is 0.1 to 0.7. Range. This is because if the ratio S 1 / S is smaller than 0.1, the bubble active surface (the discharge surface of argon gas bubbles) formed by the argon gas blown into the immersion tube 13 becomes narrow, and the decarburization and the subsequent desulfurization refining are performed. Are inhibited, and the ratio S 1 /
This is because when S is larger than 0.7, workability such as sampling is impaired. For this reason, the ratio S 1 / S is set to 0.
A more preferable result is obtained when the ratio is 15 to 0.65.
Then, the molten steel 12 in the ladle 11 is agitated by the flow indicated by the arrow in FIG. 1 by the argon gas supplied from the porous plug 19, and the argon gas expanded on the molten metal surface 12 a of the molten steel 12 in the immersion pipe 13. The decarburization reaction is promoted by the bubble activated surface, and decarburization and degassing (denitrification and dehydrogenation) in a reduced pressure atmosphere are performed. The decarburization and degassing refining were completed when the carbon concentration in the molten steel 12 reached 3 to 10 ppm and the hydrogen concentration reached 1 to 5 ppm.
【００１０】脱炭及び脱ガス精錬を終了した後、浸漬管
１３及び真空槽１４内を大気圧に複圧する。複圧によ
り、浸漬管、真空槽及び排気ダクトを含めた排気系等の
隙間から外気が浸入し、この外気中の窒素が溶鋼に吸窒
素されるいわゆる窒素ピックアップが発生する。この窒
素ピックアップを防止するために、浸漬管１３及び真空
槽１４内を複圧した後、直ちにポーラスプラグ１９から
のアルゴンガス量を０．１〜０．５ＮＬ／（分・溶鋼ト
ン）に減少して、貯蔵ホッパー１６からフラックスを切
り出して添加シュート１７から浸漬管１３内に添加す
る。添加されたフラックスは、図１中の矢印で示す溶鋼
１２の緩慢になった流れによって、浸漬管１３内に保持
され、この流れよって伝達される溶鋼１２の熱により軟
化あるいは溶解されスラグ化して溶鋼１２の湯面１２ａ
を覆うことができる。After the decarburization and the degassing refining are completed, the inside of the immersion tube 13 and the vacuum chamber 14 are double-pressurized to atmospheric pressure. Due to the double pressure, outside air enters through gaps in an exhaust system including a dip tube, a vacuum tank, and an exhaust duct, and a so-called nitrogen pickup occurs in which nitrogen in the outside air is absorbed by molten steel. In order to prevent this nitrogen pickup, the pressure of the argon gas from the porous plug 19 is immediately reduced to 0.1 to 0.5 NL / (min. Then, the flux is cut out from the storage hopper 16 and added into the immersion tube 13 from the addition chute 17. The added flux is held in the immersion tube 13 by the slow flow of the molten steel 12 indicated by the arrow in FIG. 1, and is softened or melted by the heat of the molten steel 12 transmitted by this flow to form slag, thereby forming molten steel. 12 hot water surfaces 12a
Can be covered.
【００１１】このフラックスの代表的な例として、Ｃａ
Ｏを５０重量％、ＳｉＯ2 を３０重量％、ＭｇＯを１０
重量％、ＣａＦ2 を１０重量％を含有した０．５〜１０
ｍｍの粒度を構成する物を用い、その添加量も０．５〜
１５ｋｇ／（溶鋼トン）とした。このフラックスの粒度
が０．５ｍｍ未満では、添加した際にフラックスの一部
が飛散して全てをスラグ化することができず、場合によ
っては排気ダクト等へ付着する等の問題がある。一方、
フラックスの粒度が１０ｍｍを超えると、添加した際
に、粒の間に隙間が発生して湯面１２ａに外気が導通し
て吸窒素の原因となったり、スラグ化するのに時間を要
する。また、フラックスの添加量が０．５ｋｇ／（溶鋼
トン）未満では、浸漬管１３内の溶鋼１２の湯面１２
ａ、又は取鍋１１内の溶鋼１２の全表面を覆うことがで
きないので外気からの吸窒素を招く。一方、フラックス
の添加量が１５ｋｇ／（溶鋼トン）を超えると、フラッ
クスの過剰添加となり副材料のコストが上昇する。更
に、アルゴンガスの供給量を０．１〜０．５ＮＬ／（分
・溶鋼トン）に減少しているので、フラックスを浸漬管
１３内に保持した状態でスラグ化することができ、湯面
１２ａを外気から確実に遮断して吸窒素を防止できる。
そして、浸漬管１３を溶鋼１２中から上昇して精錬を終
了した後は、連続鋳造等の後工程に搬送されて鋳片等に
加工される。A typical example of this flux is Ca
O 50% by weight, SiO 2 30% by weight, MgO 10
Wt%, and contained a CaF 2 10 wt% 0.5 to 10
mm, and the amount of addition is 0.5 to
15 kg / (ton of molten steel). When the particle size of the flux is less than 0.5 mm, when the flux is added, a part of the flux is scattered and cannot be entirely turned into slag, and in some cases, there is a problem that the flux adheres to an exhaust duct or the like. on the other hand,
When the particle size of the flux exceeds 10 mm, a gap is generated between the particles when the flux is added, and the outside air is conducted to the molten metal surface 12a to cause nitrogen absorption, or it takes time to form slag. If the amount of the added flux is less than 0.5 kg / (ton of molten steel), the molten steel 12
a, or the entire surface of the molten steel 12 in the ladle 11 cannot be covered, so that nitrogen absorption from outside air is caused. On the other hand, if the added amount of the flux exceeds 15 kg / (ton of molten steel), the flux is excessively added, and the cost of the auxiliary material increases. Further, since the supply amount of the argon gas is reduced to 0.1 to 0.5 NL / (minute / ton of molten steel), the slag can be formed while the flux is held in the immersion tube 13, and the molten metal surface 12 a Can be reliably shut off from outside air to prevent nitrogen absorption.
Then, after the immersion pipe 13 is raised from the molten steel 12 and the refining is completed, the immersion pipe 13 is conveyed to a post-process such as continuous casting to be processed into a slab or the like.
【００１２】[0012]
【実施例】次に、低窒素溶鋼の減圧精錬方法の実施例に
ついて説明する。転炉を用いて、炭素濃度を３００ｐｐ
ｍに脱炭した１５０トンの溶鋼１２を入れた取鍋１１内
に、ポーラスプラグ１９から５ＮＬ／（分・溶鋼トン）
のアルゴンガスを吹き込みながら、浸漬管１３及び真空
槽１４内を減圧して脱炭及び脱ガス精錬を行った後、浸
漬管１３及び真空槽１４内を大気圧に複圧すると共に、
ポーラスプラグ１９からのアルゴンガス量を減少して、
ＣａＯを５０重量％、ＳｉＯ2 を３０重量％、ＭｇＯを
１０重量％、ＣａＦ2 を１０重量％を含有した０．５〜
１０ｍｍの粒度のフラックスを添加して、吸窒素、耐火
物の損耗等を調査した。EXAMPLE Next, an example of a method for vacuum refining of low-nitrogen molten steel will be described. Using a converter, carbon concentration is 300pp
5 NL / (min / ton of molten steel) from the porous plug 19 into the ladle 11 containing 150 tons of molten steel 12 decarburized to m
While blowing the argon gas, the inside of the immersion tube 13 and the vacuum chamber 14 is decompressed to perform decarburization and degassing and refining, and then the inside of the immersion tube 13 and the vacuum chamber 14 is double-pressurized to atmospheric pressure.
By reducing the amount of argon gas from the porous plug 19,
The CaO 50 wt%, a SiO 2 30 wt%, 10 wt% of MgO, 0.5 to containing the the CaF 2 10 wt%
A flux having a particle size of 10 mm was added, and nitrogen absorption, wear of refractories, and the like were investigated.
【００１３】表１に示すように、まず、実施例１は、取
鍋１１内の溶鋼の全表面積に対する浸漬管１３の浸漬部
の内表面積すなわち浸漬管内面積比Ｓ1 ／Ｓが０．６と
なる浸漬管１３を用いて脱炭及び脱ガス精錬を行った
後、浸漬管１３及び真空槽１４内を大気圧に複圧すると
同時にアルゴンガス量を０．１ＮＬ／（分・溶鋼トン）
に減少して、前記のフラックスを０．６ｋｇ／溶鋼トン
添加してから３分後に浸漬管１３を上昇して精錬を終了
した。その結果、フラックスのスラグ化が十分に行われ
ており、耐火物の損耗がなく、溶鋼１２の窒素ピックア
ップも全く無く窒素濃度１０ｐｐｍの低窒素の溶鋼が得
られ、総合評価としては優れた結果（○）であった。ま
た、実施例２は、浸漬管内面積比Ｓ1 ／Ｓが０．３とな
る浸漬管１３を用いて脱炭及び脱ガス精錬を行ってか
ら、浸漬管１３及び真空槽１４内を大気圧に複圧すると
同時にアルゴンガス量を０．４ＮＬ／（分・溶鋼トン）
に減少して、実施例１と同じ組成のフラックスを３．０
ｋｇ／溶鋼トン添加してから２分後に浸漬管１３を上昇
して精錬を終了した。その結果、フラックスのスラグ化
が十分に行われており、耐火物の損耗がなく、溶鋼１２
の窒素ピックアップも全く無く窒素濃度１２ｐｐｍの低
窒素の溶鋼が得られ、総合評価としては優れた結果
（○）であった。As shown in Table 1, first, in Example 1, the ratio S 1 / S of the inner surface area of the immersion portion of the immersion tube 13 to the total surface area of the molten steel in the ladle 11, that is, S 1 / S is 0.6. After performing decarburization and degassing and refining using the immersion tube 13, the inside of the immersion tube 13 and the vacuum chamber 14 is double-pressurized to atmospheric pressure, and at the same time, the amount of argon gas is 0.1 NL / (minute / ton of molten steel).
3 minutes after the above flux was added at 0.6 kg / ton of molten steel, the immersion pipe 13 was raised to finish the refining. As a result, the slag of the flux was sufficiently performed, the refractory was not worn away, and there was no nitrogen pickup of the molten steel 12 at all. Thus, a low-nitrogen molten steel having a nitrogen concentration of 10 ppm was obtained. ○). In Example 2, decarburization and degassing and refining were performed using the immersion tube 13 having an immersion tube area ratio S 1 / S of 0.3, and then the immersion tube 13 and the inside of the vacuum chamber 14 were brought to atmospheric pressure. At the same time as double pressure, the argon gas amount is 0.4 NL / (min / ton of molten steel)
And the flux having the same composition as in Example 1 was changed to 3.0.
Two minutes after the addition of kg / ton of molten steel, the immersion tube 13 was raised to finish the refining. As a result, the slag of the flux is sufficiently performed, the refractory is not worn, and the molten steel 12
, A low-nitrogen molten steel having a nitrogen concentration of 12 ppm was obtained without any nitrogen pickup, and the overall evaluation was excellent (○).
【００１４】[0014]
【表１】 [Table 1]
【００１５】これに対して、比較例は、浸漬管内面積比
Ｓ1 ／Ｓが０．３となる浸漬管１３を用いて脱炭及び脱
ガス精錬を行ってから、浸漬管１３及び真空槽１４内を
大気圧に複圧し、アルゴンガス量は変化させず、２分後
に浸漬管１３上昇して精錬を終了した。その結果、耐火
物の損耗は無かったが、溶鋼１２に窒素ピックアップを
生じて窒素濃度が２０ｐｐｍと高く、低窒素の溶鋼を得
ることができず、総合評価としては悪い（×）結果とな
った。On the other hand, in the comparative example, after the decarburization and degassing and refining were performed using the immersion tube 13 having an area ratio S 1 / S of 0.3 in the immersion tube, the immersion tube 13 and the vacuum tank 14 were used. The inside was double-pressurized to atmospheric pressure, the amount of argon gas was not changed, and the immersion pipe 13 was raised after 2 minutes to complete the refining. As a result, although there was no wear of the refractory, nitrogen pickup occurred in the molten steel 12 and the nitrogen concentration was as high as 20 ppm, so that low-nitrogen molten steel could not be obtained. .
【００１６】以上、本発明の一実施の形態を説明した
が、本発明は、上記した形態に限定されるものでなく、
要旨を逸脱しない条件の変更等は全て本発明の適用範囲
である。例えば、ポーラスプラグからの不活性ガスの吹
き込みの方法について、前記のように脱炭及び脱ガス精
錬を行って浸漬管及び真空槽内を大気圧に複圧してから
減量する他に、大気圧に複圧する直前に減量することも
でる。また、浸漬管内に添加したフラックスが溶解ある
いは軟化した状態になってからポーラスプラグからの不
活性ガスの吹き込みを停止することもできる。更に、極
低炭素（炭素濃度１０ｐｐｍ以下）に到るまで脱炭して
いない低炭素の溶鋼を用いて、フラックス添加を行って
窒素の少ない溶鋼を得ることもできる。Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.
All changes in conditions that do not depart from the gist are within the scope of the present invention. For example, as for the method of blowing the inert gas from the porous plug, in addition to performing decarburization and degassing and refining the inside of the immersion tube and the vacuum tank to the atmospheric pressure as described above, and then reducing the pressure, the pressure is reduced to the atmospheric pressure. You can also reduce the weight just before double pressure. Further, the blowing of the inert gas from the porous plug can be stopped after the flux added into the immersion tube is dissolved or softened. Furthermore, flux addition is performed using a low-carbon molten steel that has not been decarburized until it reaches an extremely low carbon (carbon concentration of 10 ppm or less) to obtain a molten steel with a small amount of nitrogen.
【００１７】[0017]
【発明の効果】請求項１〜３記載の低窒素溶鋼の減圧精
錬方法は、一本の浸漬管を取鍋内の溶鋼に浸漬して、取
鍋の底部から不活性ガスを吹き込みながら、浸漬管内を
減圧し溶鋼の脱炭及び脱ガス精錬を行った後、浸漬管内
を複圧し、取鍋の底部からの不活性ガスの吹き込み量を
０．１〜０．５ＮＬ／分・溶鋼トンに減らし、浸漬管内
にフラックスを添加して浸漬管内の溶鋼面を覆うので、
脱炭及び脱ガス等の減圧精錬における吸窒素を効率良く
防止し、耐火物等の損耗を抑制した低窒素の溶鋼を得る
ことのできる。According to the vacuum refining method for low-nitrogen molten steel according to the first to third aspects of the present invention, one dipping tube is dipped in molten steel in a ladle and immersed while blowing an inert gas from the bottom of the ladle. After decompressing the inside of the pipe and decarburizing the molten steel and degassing and refining, the inside of the immersion pipe is double-pressed to reduce the amount of inert gas blown from the bottom of the ladle to 0.1 to 0.5 NL / min. Since flux is added to the immersion tube to cover the molten steel surface in the immersion tube,
Nitrogen absorption in decompression refining such as decarburization and degassing can be efficiently prevented, and a low-nitrogen molten steel with reduced wear of refractories can be obtained.
【００１８】特に、請求項２記載の低窒素溶鋼の減圧精
錬方法は、浸漬管内に添加するフラックスのＣａＯ含有
量を２０〜７０重量％にするので、フラックスの溶解あ
るいは軟化を迅速に行うことができ低窒素の溶鋼を溶製
することができる。In particular, in the vacuum refining method for low-nitrogen molten steel according to the second aspect, the CaO content of the flux added into the immersion tube is set to 20 to 70% by weight, so that the flux can be rapidly dissolved or softened. As a result, molten steel with low nitrogen can be produced.
【００１９】請求項３記載の低窒素溶鋼の減圧精錬方法
は、浸漬管の浸漬部の内表面積を取鍋内の溶鋼の全表面
積の０．１〜０．７にしているので、フラックスの溶解
あるいは軟化を促進でき、低窒素の溶鋼を安定して溶製
することができる。In the vacuum refining method for low-nitrogen molten steel according to claim 3, since the inner surface area of the immersion portion of the immersion tube is set to 0.1 to 0.7 of the total surface area of the molten steel in the ladle, the melting of the flux is performed. Alternatively, softening can be promoted and low nitrogen molten steel can be stably produced.
【図１】本発明の一実施の形態に係る低窒素溶鋼の減圧
精錬方法に適用する減圧精錬装置の断面図である。FIG. 1 is a cross-sectional view of a vacuum refining apparatus applied to a vacuum refining method for low nitrogen molten steel according to an embodiment of the present invention.
１０ 減圧精錬装置 １１ 取鍋 １２ 溶鋼 １２ａ 湯面 １３ 浸漬管 １３ａ フラン
ジ １４ 真空槽 １４ａ フラン
ジ １５ 排気ダクト １６ 貯蔵ホッ
パー １７ 添加ジュート １８ 底部 １９ ポーラスプラグDESCRIPTION OF SYMBOLS 10 Decompression refining apparatus 11 Ladle 12 Molten steel 12a Metal surface 13 Immersion pipe 13a Flange 14 Vacuum tank 14a Flange 15 Exhaust duct 16 Storage hopper 17 Addition jute 18 Bottom part 19 Porous plug
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 4K013 AA00 BA02 BA07 BA12 CA01 CA11 CB09 CE00 CE02 CE05 CE07 CE09 CF13 DA05 DA10 DA12 FA05 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K013 AA00 BA02 BA07 BA12 CA01 CA11 CB09 CE00 CE02 CE05 CE07 CE09 CF13 DA05 DA10 DA12 FA05
Claims (3)
て、前記取鍋の底部から不活性ガスを吹き込みながら、
前記浸漬管内を減圧して前記溶鋼の脱炭及び脱ガス精錬
を行った後、前記浸漬管内を複圧し、前記取鍋の底部か
らの不活性ガスの吹き込み量を０．１〜０．５ＮＬ／分
・溶鋼トンに減らし、前記浸漬管内にフラックスを添加
して前記浸漬管内の溶鋼面を覆うことを特徴とする低窒
素溶鋼の減圧精錬方法。1. Dipping one dipping tube into molten steel in a ladle and blowing an inert gas from the bottom of the ladle,
After decompressing the molten steel and degassing and refining the molten steel by depressurizing the inside of the immersion pipe, the inside of the immersion pipe is double-pressurized, and the blowing amount of the inert gas from the bottom of the ladle is 0.1 to 0.5 NL /. The method for reducing and refining low-nitrogen molten steel, comprising reducing the amount of molten steel to tons and adding flux to the dip tube to cover the molten steel surface in the dip tube.
法において、前記浸漬管内に添加するフラックスのＣａ
Ｏ含有量を２０〜７０重量％とする低窒素溶鋼の減圧精
錬方法。2. The vacuum refining method for low-nitrogen molten steel according to claim 1, wherein the flux of Ca added to the immersion tube is Ca.
A vacuum refining method for low nitrogen molten steel having an O content of 20 to 70% by weight.
精錬方法において、前記浸漬管の浸漬部の内表面積を前
記取鍋内の溶鋼の全表面積の０．１〜０．７とする低窒
素溶鋼の減圧精錬方法。3. The vacuum refining method for low-nitrogen molten steel according to claim 1 or 2, wherein the inner surface area of the immersion portion of the immersion tube is 0.1 to 0.7 of the total surface area of the molten steel in the ladle. Vacuum refining method for low nitrogen molten steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10288909A JP2000096128A (en) | 1998-09-25 | 1998-09-25 | Method for vacuum-refining low nitrogen molten steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10288909A JP2000096128A (en) | 1998-09-25 | 1998-09-25 | Method for vacuum-refining low nitrogen molten steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000096128A true JP2000096128A (en) | 2000-04-04 |
Family
ID=17736369
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10288909A Withdrawn JP2000096128A (en) | 1998-09-25 | 1998-09-25 | Method for vacuum-refining low nitrogen molten steel |
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| Country | Link |
|---|---|
| JP (1) | JP2000096128A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114959187A (en) * | 2022-06-15 | 2022-08-30 | 包头钢铁（集团）有限责任公司 | Thermal protection method for RH dip pipe argon hose |
-
1998
- 1998-09-25 JP JP10288909A patent/JP2000096128A/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114959187A (en) * | 2022-06-15 | 2022-08-30 | 包头钢铁（集团）有限责任公司 | Thermal protection method for RH dip pipe argon hose |
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