JP2002331340A - Continuous casting method - Google Patents
Continuous casting methodInfo
- Publication number
- JP2002331340A JP2002331340A JP2001135764A JP2001135764A JP2002331340A JP 2002331340 A JP2002331340 A JP 2002331340A JP 2001135764 A JP2001135764 A JP 2001135764A JP 2001135764 A JP2001135764 A JP 2001135764A JP 2002331340 A JP2002331340 A JP 2002331340A
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- Prior art keywords
- immersion nozzle
- refractory
- molten steel
- nozzle
- gas
- 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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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明はタンディッシュから
鋳型内へ溶鋼を注入するのに際して、ノズルの閉塞を防
止し、数多くの連々鋳を可能となし、かつ表面欠陥及び
内部欠陥の少ない高品質な鋳片を得ることができる連続
鋳造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality steel having a small number of surface defects and internal defects that prevents clogging of a nozzle when casting molten steel from a tundish into a mold, enables continuous casting. The present invention relates to a continuous casting method capable of obtaining a slab.
【０００２】[0002]
【従来の技術】通常、連続鋳造工程ではタンディッシュ
の整備コストを低減するため、１基のタンディッシュで
複数の鍋を交換する多連続鋳造（連々鋳）操業が行われ
ており、コスト削減を図るためにはより多くの溶鋼を１
キャストで鋳造する必要がある。2. Description of the Related Art Usually, in a continuous casting process, in order to reduce maintenance costs of a tundish, a multi-continuous casting (sequential casting) operation of replacing a plurality of pots with one tundish is performed. To get more molten steel 1
Must be cast.
【０００３】しかし、従来から浸漬ノズルの材質として
は、一般的にハイアルミナ質が使用されており、非金属
介在物（以下介在物と略称する）であるアルミナクラス
ターがノズル内孔表面に付着し、ノズル閉塞を発生しや
すい欠点を有していた。However, conventionally, a high immersion material has been generally used as a material of the immersion nozzle, and alumina clusters, which are nonmetallic inclusions (hereinafter abbreviated as inclusions), adhere to the surface of the nozzle inner hole. However, there is a disadvantage that the nozzle is easily blocked.
【０００４】浸漬ノズル材質が例え他の材質であっても
前記連々鋳、例えば数チャージ分の取鍋内溶鋼を鋳込む
ような場合には、取鍋交換前の溶鋼温度の低下もアルミ
ナ付着現象を助長する一因となり、徐々にアルミナの付
着が進行し、最終的にはノズル閉塞が発生して鋳造不可
能になってしまうケースが度々発生し、多大な損害を被
り、改善を求められていた。[0004] Even if the material of the immersion nozzle is another material, when the continuous casting is performed, for example, when the molten steel in the ladle for several charges is cast, the temperature of the molten steel before the ladle is replaced also decreases due to the alumina adhesion phenomenon. In many cases, the adhesion of alumina gradually progressed, and eventually the nozzle clogging occurred, making casting impossible, resulting in enormous damage and demand for improvement. Was.
【０００５】ノズル内にアルミナが付着することは、鋳
造中にノズルがやがて閉塞して鋳造速度を低下させなけ
ればならなくなったり、ノズル上方から閉塞部を洗浄す
る必要が生じ、鋳造スラブの品質を悪化させたり、操業
面で支障をきたすことが多発していた。[0005] The adhesion of alumina in the nozzle causes the nozzle to be blocked during casting, which requires a reduction in casting speed, and the need to clean the blocked portion from above the nozzle, resulting in poor quality of the cast slab. It often worsened or hindered operations.
【０００６】連々鋳回数を増加させて長時間の鋳造を行
う場合には、溶鋼を供給するノズル内にアルミナなどが
付着してノズルが閉塞することを防止してやらなければ
ならず、このノズル閉塞の問題に対処するためには、上
ノズルや浸漬ノズルなどからアルゴンなどの不活性ガス
を吹き込んで、ノズル内壁に異物が付着するのを防止す
ることが一般的に行われている。In the case of performing casting for a long time by continuously increasing the number of times of casting, it is necessary to prevent alumina or the like from adhering to the nozzle for supplying molten steel and to block the nozzle. In order to cope with the problem, it is common practice to blow an inert gas such as argon from an upper nozzle or an immersion nozzle to prevent foreign matter from adhering to the inner wall of the nozzle.
【０００７】しかし、ノズル内に吹き込まれた不活性ガ
スは、溶鋼と共に鋳型内に流入し、鋳型上部の溶鋼中を
通り抜け鋳型外に放散することから、溶鋼メニスカス部
にあるパウダーと溶鋼との界面を通過する際にパウダー
性欠陥の発生原因となることが知られている。また、浸
漬ノズルにアルミナ等の付着がない場合でも浸漬ノズル
の左右溶鋼吐出流には偏りがあるため、ノズル閉塞防止
を図るために吹き込んだ多量の不活性ガスは鋳型内に均
一に分散することなく、鋳型内で片沸きしてパウダー巻
き込みを益々助長していた。However, the inert gas blown into the nozzle flows into the mold together with the molten steel, passes through the molten steel at the upper part of the mold, and diffuses out of the mold, so that the interface between the powder at the molten steel meniscus and the molten steel. It is known that it causes a powder defect when passing through. Even if there is no adhesion of alumina etc. to the immersion nozzle, since the molten steel discharge flow from the left and right of the immersion nozzle is uneven, a large amount of inert gas blown to prevent nozzle clogging must be evenly dispersed in the mold. Instead, the powder boiled in the mold to promote powder entrainment.
【０００８】これに対して、鋳型内への溶鋼吐出流の偏
流抑制技術として特開平８−２９４７５７号公報が開示
されている。該公報によれば、鋳型内へ溶鋼を供給する
流量調整弁より下流側であって浸漬ノズルより上流側あ
るいは浸漬ノズルにおける溶鋼導入部分に流路絞り部を
設けると共に、該絞り部分より吐出孔に至るまでの浸漬
ノズルの部分を流速緩和部とし、上記絞り部分の流路横
断面積を上記流量調整弁全開時の流路横断面積の５０〜
９０％とし、上記流速緩和部の流路横断面積が上記絞り
部分の流路横断面積より大きく、該流速緩和部の長さを
上記絞り部分の内径の３倍以上とすることで、浸漬ノズ
ル内で溶鋼流が整流化され、浸漬ノズル左右吐出流の偏
流が抑制できると述べられている。On the other hand, Japanese Unexamined Patent Publication No. Hei 8-294747 discloses a technique for suppressing the drift of molten steel discharged into a mold. According to the publication, a flow path restricting portion is provided at a downstream side of a flow control valve for supplying molten steel into a mold and upstream of an immersion nozzle or at a molten steel introduction portion of the immersion nozzle, and a discharge port is provided from the throttle portion to a discharge hole. The portion of the immersion nozzle up to the flow rate reducing portion is set as the flow velocity reducing portion, and the flow passage cross-sectional area of the throttle portion is 50 to 50 times of the flow passage cross-sectional area when the flow control valve is fully opened.
90%, and the flow passage cross-sectional area of the flow velocity relaxation portion is larger than the flow passage cross-sectional area of the throttle portion, and the length of the flow velocity relaxation portion is at least three times the inner diameter of the throttle portion, so that the inside of the immersion nozzle is reduced. Rectifies the molten steel flow and suppresses the drift of the left and right discharge flow of the immersion nozzle.
【０００９】一方、ノズル閉塞防止のために不活性ガス
を吹き込みつつ、浸漬ノズル内壁に設けたガス吸引用の
多孔質耐火物から過剰なガスを吸引除去し、鋳型内へ流
入する不活性ガス量を最小にする技術が提案されてい
る。On the other hand, while blowing inert gas to prevent nozzle clogging, excess gas is suctioned and removed from the gas suction porous refractory provided on the inner wall of the immersion nozzle, and the amount of inert gas flowing into the mold is reduced. Techniques have been proposed to minimize.
【００１０】このような鋳型内への過剰ガス流入防止技
術として、例えば特開２０００−３０１３００号公報が
開示されている。該公報の概要ではタンディッシュから
鋳型内へ溶鋼を注入するための上ノズルに大量の不活性
ガスを吹き込みつつ、浸漬ノズル内壁に設けたガス吸引
用の多孔質耐火物から過剰なガスを吸引して、該浸漬ノ
ズルから鋳型内へ流入する不活性ガスの総流量を制御で
きると述べられている。As a technique for preventing excess gas from flowing into the mold, for example, Japanese Patent Application Laid-Open No. 2000-301300 is disclosed. In the summary of the publication, while blowing a large amount of inert gas into an upper nozzle for injecting molten steel from a tundish into a mold, excess gas is suctioned from a gas refractory porous refractory provided on the inner wall of the immersion nozzle. It is stated that the total flow rate of the inert gas flowing from the immersion nozzle into the mold can be controlled.
【００１１】[0011]
【発明が解決しようとする課題】しかし、本発明者らの
実験によると、流量調整弁より下流側であって浸漬ノズ
ルより上流側あるいは浸漬ノズルにおける溶鋼導入部分
に流路絞り部を設け、連続鋳造を行った場合でも、ノズ
ル閉塞防止のために吹き込んだ不活性ガスが原因で発生
する鋳型内の片沸きを完全に抑制できていなかった。こ
れは浸漬ノズル内に吹き込まれた不活性ガスがノズル内
を通過する際に溶鋼中より分離し、浸漬ノズル内、特に
段差下部付近に溜まり、一定量以上のガスが溜まると逃
げ場のなくなったガスが塊状で一気に鋳型内へ流入する
ためである。そのためノズル閉塞防止のために吹き込ん
だ不活性ガスを浸漬ノズル内で除去し、鋳型内へ流入す
る不活性ガス量を低減する方法が必要とされていた。However, according to the experiments conducted by the present inventors, a flow path restricting portion is provided downstream of the flow control valve and upstream of the immersion nozzle or at the molten steel introduction portion in the immersion nozzle. Even in the case of casting, one-side boiling in the mold caused by the inert gas blown to prevent nozzle clogging could not be completely suppressed. This is a gas in which the inert gas blown into the immersion nozzle separates from the molten steel when passing through the nozzle and accumulates in the immersion nozzle, especially near the lower part of the step, and there is no escape place when a certain amount of gas is accumulated. Is a lump and flows into the mold at once. Therefore, there has been a need for a method of removing the blown inert gas in the immersion nozzle in order to prevent nozzle blockage, thereby reducing the amount of the inert gas flowing into the mold.
【００１２】また、ノズル内部に吸引用多孔質耐火物を
配した浸漬ノズルを用いて連続鋳造を行い、ガス吸引を
実施したところ、従来技術の目的を達成するだけのガス
量を長時間安定的に吸引し続けることはできなかった。
これは、浸漬ノズル内部の多孔質耐火物からガス吸引を
行うためには該耐火物表面付近にガス溜まり（空隙部）
が安定的に形成されることが必要不可欠であるのに対し
て、浸漬ノズル内部の溶鋼の流れが不安定であるため、
該耐火物表面に溶鋼が度々接触し、ガス吸引が阻害され
てしまうからである。このため、浸漬ノズル内部に設け
た吸引用の多孔質耐火物を通して、長時間安定的に十分
なガス吸引量を確保する方策が必要となっていた。Further, continuous casting was performed using an immersion nozzle having a porous refractory for suction disposed inside the nozzle, and gas suction was performed. Could not continue to aspirate.
This is because, in order to perform gas suction from the porous refractory inside the immersion nozzle, gas is accumulated near the refractory surface (void).
Is indispensable to be formed stably, while the flow of molten steel inside the immersion nozzle is unstable,
This is because molten steel frequently comes into contact with the surface of the refractory and gas suction is hindered. For this reason, it has been necessary to take measures to ensure a sufficient gas suction amount stably for a long time through the suction refractory provided inside the immersion nozzle.
【００１３】本発明はこのような従来技術の問題点を解
決し、浸漬ノズルの閉塞防止を図り、多連続鋳造回数を
増加させるとともに、過剰な不活性ガスを浸漬ノズル内
で吸引除去することで、高品質な鋳片を得ることができ
る連続鋳造方法を提供することを目的とする。The present invention solves such problems of the prior art, prevents the clogging of the immersion nozzle, increases the number of times of continuous casting, and removes excess inert gas by suction in the immersion nozzle. It is an object of the present invention to provide a continuous casting method capable of obtaining high quality cast slabs.
【００１４】[0014]
【課題を解決するための手段】本発明は前記した従来方
法における問題点を解決するためになされたものであ
り、その要旨とするところは、下記手段にある。溶鋼を
鋳型内へ注入する浸漬ノズルを用いた連続鋳造方法にお
いて、浸漬ノズル内孔面に下記式（１）を満足するよう
にガス吸引用多孔質耐火物を配置し、且つ溶鋼注入方向
で該耐火物の直上部の浸漬ノズル内の流路内径ｄが該耐
火物の内径Ｄに対して０．７〜０．９倍の範囲とせしめ
た浸漬ノズルを用い、該耐火物から浸漬ノズル内からガ
ス吸引を行いながら鋳型内へ溶鋼の供給を行うことを特
徴とする連続鋳造方法。 Ｈ＞Ｈ0 ＋ｖ2 ／２ｇ ・・・・・・ （１） 但し、Ｈ：浸漬ノズル下端から吸引用多孔質耐火物下端
までの距離（ｍ） Ｈ0 ：浸漬ノズル下端から鋳造時の鋳型内制御目標メニ
スカスまでの距離（ｍ） ｖ：浸漬ノズル吐出流平均流速（ｍ／ｓ）ｇ：重力加速
度（ｍ／ｓ2 ）SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional method, and its gist lies in the following means. In a continuous casting method using an immersion nozzle for injecting molten steel into a mold, a porous refractory for gas suction is arranged on the inner surface of the immersion nozzle so as to satisfy the following expression (1), and the refractory is injected in the molten steel injection direction. Using an immersion nozzle in which the flow path inner diameter d in the immersion nozzle immediately above the refractory is 0.7 to 0.9 times the inner diameter D of the refractory, from the immersion nozzle from the refractory A continuous casting method comprising supplying molten steel into a mold while performing gas suction. H> H 0 + v 2 / 2g (1) where, H: distance from the lower end of the immersion nozzle to the lower end of the porous refractory for suction (m) H 0 : in the casting mold from the lower end of the immersion nozzle Distance to control target meniscus (m) v: Average flow velocity of immersion nozzle discharge flow (m / s) g: Gravitational acceleration (m / s 2 )
【００１５】[0015]
【発明の実施の形態】本発明者らは、前記課題を解決す
るための鍵が上記浸漬ノズル内部の吸引用多孔質耐火物
の設置位置と該耐火物の溶鋼注入方向直上部の形状にあ
ることを突き止め、該耐火物設置位置とその直上部形状
を適正化するため、数多くの実験を積み重ねた。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have found that the key to solving the above problems is the installation position of the porous refractory for suction inside the immersion nozzle and the shape of the refractory immediately above the molten steel injection direction. Numerous experiments were conducted in order to determine this and to optimize the refractory installation position and the shape immediately above the refractory.
【００１６】図１は従来技術の実施形態の１例を示した
もので、タンディッシュ１から鋳型２に注入される溶鋼
３は上ノズル４、スライディングノズル５、下ノズル
６、浸漬ノズル７を介して供給される。上ノズル４には
外部から配管が設置されており、アルゴンガスが供給さ
れる。浸漬ノズル７の下部には溶鋼メニスカスよりも低
い部分に存在する吐出孔の閉塞を防止するために、上ノ
ズルと同様に外部から配管が設置されており、ノズル内
面に設けられた多孔質耐火物１１を介して少量のアルゴ
ンガスを吹き込むとともに、上部の多孔質耐火物１０か
らはアルゴンガスの吸引を行っている。FIG. 1 shows an example of an embodiment of the prior art, in which molten steel 3 injected from a tundish 1 into a mold 2 is passed through an upper nozzle 4, a sliding nozzle 5, a lower nozzle 6, and a dipping nozzle 7. Supplied. The upper nozzle 4 is provided with a pipe from the outside, and is supplied with argon gas. At the lower part of the immersion nozzle 7, a pipe is installed from the outside similarly to the upper nozzle in order to prevent the discharge hole existing at a portion lower than the molten steel meniscus, and a porous refractory provided on the inner surface of the nozzle is provided. A small amount of argon gas is blown in through 11, and argon gas is sucked from the upper porous refractory 10.
【００１７】図２に従来のガス吸引技術を適用して鋳造
を行った場合に吸引用多孔質耐火物を介して、吸引でき
たアルゴンガスの流量を示す。このときの鋳造条件は、
スループット４．５ｔ／ｍｉｎ、上ノズルより１２リッ
トル／ｍｉｎ、浸漬ノズルより５リットル／ｍｉｎのア
ルゴンガスを吹き込んで鋳造を行った。図より明かなよ
うに従来方法では吸引できるガス量が少なく、また、鋳
造時間の経過とともに吸引量は徐々に減少していくこと
が判る。さらに吸引ガス量は、常に変動していることが
判る。FIG. 2 shows the flow rate of the argon gas that can be sucked through the suction refractory when casting is performed by applying the conventional gas suction technique. The casting conditions at this time are:
The casting was performed by blowing argon gas at a throughput of 4.5 t / min, 12 l / min from the upper nozzle, and 5 l / min from the immersion nozzle. As is clear from the figure, the amount of gas that can be sucked by the conventional method is small, and the amount of sucked gas gradually decreases as the casting time elapses. Further, it can be seen that the amount of suction gas constantly fluctuates.
【００１８】これは浸漬ノズル内部の溶鋼の流れが不安
定であるため、吸引用多孔質耐火物表面は常に吸引対象
となるガスと接触できておらず、ある頻度で繰り返し発
生する溶鋼流の変動によって、該耐火物表面は溶鋼と接
触しているからである。該耐火物表面に溶鋼が接触する
と吸引を阻害し、また溶鋼中のアルミナ等が付着するた
め、鋳造時間の経過とともに付着量が増加して、その結
果、吸引ガス量は減少していく。さらに前記浸漬ノズル
内の溶鋼流の変動に伴い、吸引ガス量が変動するため、
鋳型内へ流入するアルゴンガス量が安定せず、メニスカ
スの乱れを誘発し、鋳片におけるパウダー欠陥が発生し
ていた。[0018] This is because the flow of molten steel inside the immersion nozzle is unstable, so that the surface of the porous refractory for suction is not always in contact with the gas to be suctioned, and the fluctuation of the flow of molten steel that occurs repeatedly at a certain frequency. Thereby, the refractory surface is in contact with the molten steel. When molten steel comes into contact with the surface of the refractory, suction is hindered, and alumina or the like in the molten steel adheres, so that the amount of adhesion increases with the elapse of casting time, and as a result, the amount of suction gas decreases. Further, with the fluctuation of the molten steel flow in the immersion nozzle, the amount of suction gas fluctuates,
The amount of the argon gas flowing into the mold was not stable, which caused disturbance of the meniscus, and powder defects occurred in the slab.
【００１９】本発明者らは上記従来技術の課題を克服
し、安定的なガス吸引を実現するための様々な方策を検
討した。その結果、ノズル内部の溶鋼流の不安定性に左
右されることなく、吸引用多孔質耐火物表面が吸引対象
となるガスと常に接触するための方策として、該耐火物
の設置位置と該耐火物よりも溶鋼注入方向直上部の内径
を小さくすることが有効であることを見出した。The present inventors have studied various measures for overcoming the above-mentioned problems of the prior art and realizing stable gas suction. As a result, the installation position of the refractory and the refractory are determined as a measure to keep the surface of the porous refractory for suction constantly in contact with the gas to be suctioned without being affected by the instability of the molten steel flow inside the nozzle. It has been found that it is more effective to make the inner diameter immediately above the molten steel injection direction smaller than in the molten steel injection direction.
【００２０】図３に本発明の実施形態の１例を示した。
浸漬ノズル７にはＨ＞Ｈ0 ＋ｖ2 ／２ｇ（Ｈ：浸漬ノズ
ル下端から吸引用多孔質耐火物１０下端までの距離、Ｈ
0 ：浸漬ノズル下端から鋳造時の鋳型内制御目標メニス
カスまでの距離、ｖ：浸漬ノズル吐出流平均流速、ｇ：
重力加速度）を満足するだけ上方に吸引用多孔質耐火物
１０を配置し、該耐火物よりも溶鋼注入方向直上部の浸
漬ノズル内の流路内径ｄは該耐火物の内径Ｄに対して、
０．７〜０．９倍の範囲とするために、下ノズル６の内
径にテーパーを付与し、更に浸漬ノズル上部にリング１
２を挿入する。FIG. 3 shows an example of the embodiment of the present invention.
The immersion nozzle 7 H> H 0 + v 2 / 2g (H: Distance from the immersion nozzle lower end up to 10 lower suction porous refractory, H
0 : distance from the lower end of the immersion nozzle to the control target meniscus in the mold during casting, v: average flow velocity of the immersion nozzle discharge flow, g:
(Gravitational acceleration), the porous refractory for suction 10 is arranged above the refractory, and the inner diameter d of the flow passage in the immersion nozzle immediately above the refractory in the molten steel injection direction is smaller than the inner diameter D of the refractory.
In order to make the range of 0.7 to 0.9 times, the inner diameter of the lower nozzle 6 is tapered, and a ring 1
Insert 2.
【００２１】吸引用多孔質耐火物１０の設置位置は、該
耐火物表面が溶鋼と接触するのを防ぐため、図３にある
ように溶鋼吐出流平均流速から推定される浸漬ノズル内
のヘッド高さよりも高い位置に設置する必要がある。す
なわち、ここで浸漬ノズル内に設置される該耐火物１０
下端と浸漬ノズル下端の距離をＨとすると、Ｈは浸漬ノ
ズル内の溶鋼ヘッド高さｖ2 ／２ｇと浸漬ノズル下端か
ら鋳造時の鋳型内制御目標メニスカスまでの距離Ｈ0
（浸漬深さ）で下記のように規定できる。Ｈ＞Ｈ0 ＋ｖ
2 ／２ｇなお、ここでメニスカス位置は鋳造時に変動す
るため、実際の鋳造においては制御目標メニスカス位置
としている。The position of the porous refractory for suction 10 is determined by the head height in the immersion nozzle estimated from the average flow velocity of the molten steel discharge flow as shown in FIG. 3 in order to prevent the surface of the refractory from coming into contact with the molten steel. It must be installed at a higher position. That is, the refractory 10 installed in the immersion nozzle here.
When the distance of the lower end and the immersion nozzle lower end and H, the distance H 0 of H from the immersion nozzle lower molten steel head height v 2/2 g of the immersion nozzle to the mold in the control target meniscus during casting
(Immersion depth) can be defined as follows. H> H 0 + v
2/2 g Here, since the meniscus position which varies during casting, in the actual casting is the control target meniscus position.
【００２２】吸引用多孔質耐火物１０よりも溶鋼注入方
向直上部の浸漬ノズル内の流路内径ｄを該耐火物内径Ｄ
に対して縮小するのは該耐火物表面近傍に安定的にガス
溜まり（空隙部）を形成させるためであり、そのために
は該耐火物内径Ｄに対して該耐火物１０よりも溶鋼注入
方向直上部の浸漬ノズル内の流路内径ｄを縮小して該耐
火物上端に段差を設けることが最も有効な手段である。The inner diameter d of the flow passage in the immersion nozzle immediately above the suction refractory 10 in the molten steel injection direction is set to the inner diameter D of the refractory.
In order to form a gas reservoir (gap) in the vicinity of the surface of the refractory in a stable manner, the inner diameter D of the refractory is smaller than that of the refractory 10 in the direction in which the molten steel is injected. The most effective means is to reduce the inner diameter d of the flow passage in the upper immersion nozzle to provide a step at the upper end of the refractory.
【００２３】図３に示すように浸漬ノズル内に形成した
段差の下部にはガス溜まり（空隙部）が形成される。本
発明者らの実験によると、付与する段差の範囲は、浸漬
ノズル内の溶鋼流が不安定になっても該耐火物表面に溶
鋼が接触する機会が少なくなるように、吸引用多孔質耐
火物１０の内径Ｄに対して０．９倍以下である必要があ
り、また、あまり大きな段差を設けるとノズル閉塞防止
のために吹き込んだ不活性ガスと鋳造に見合う溶鋼流の
通過が阻害されるため、鋳造速度に対して溶鋼の供給量
が追いつかなくなることがないように０．７倍以上であ
ることが必要である。すなわち、鋳造速度を落とすこと
なく、アルミナ等が該表面に付着しないためには、形成
する段差の範囲を前記耐火物１０の内径Ｄに対して０．
７〜０．９倍の範囲とすることが最も最適であることが
判った。As shown in FIG. 3, a gas reservoir (gap) is formed below the step formed in the immersion nozzle. According to the experiments of the present inventors, the range of the step to be provided is such that even if the molten steel flow in the immersion nozzle becomes unstable, the chance of the molten steel coming into contact with the surface of the refractory is reduced, so that the porous refractory for suction is used. It is necessary to be 0.9 times or less the inner diameter D of the object 10, and if an excessively large step is provided, the passage of the inert gas blown to prevent nozzle clogging and the flow of molten steel corresponding to the casting is hindered. Therefore, it must be 0.7 times or more so that the supply amount of molten steel cannot keep up with the casting speed. That is, in order to prevent alumina or the like from adhering to the surface without lowering the casting speed, the range of the step to be formed is set to be 0.1 mm relative to the inner diameter D of the refractory 10.
It has been found that the most suitable range is 7 to 0.9 times.
【００２４】[0024]
【実施例】本発明を適用して実機鋳造を行った。このと
きの鋳造条件は、鋳片幅１６００ｍｍ、鋳片厚み２８０
ｍｍ、スループット４．５ｔ／ｍｉｎ、上ノズルより１
２リットル／ｍｉｎ、浸漬ノズル（ＩＮ）より５リット
ル／ｍｉｎのアルゴンガスを吹き込んで鋳造を行った。
また、浸漬ノズルの浸漬深さＨ0 は２００ｍｍである。
さらにまた、この鋳造条件において式（１）の第２項ｖ
2 ／２ｇは約４８ｍｍとなる。表１に鋳造条件を示す。EXAMPLES The present invention was applied to actual casting. The casting conditions at this time were: slab width 1600 mm, slab thickness 280
mm, throughput 4.5 t / min, 1 from upper nozzle
Casting was performed by blowing argon gas at 2 liter / min and 5 liter / min from the immersion nozzle (IN).
The immersion depth H 0 of the immersion nozzle is 200 mm.
Furthermore, in this casting condition, the second term v of the equation (1)
2 / 2g is about 48mm. Table 1 shows the casting conditions.
【００２５】[0025]
【表１】 [Table 1]
【００２６】本発明例１〜３では吸引用の多孔質耐火物
下端位置Ｈを浸漬ノズル下端より４００ｍｍの位置とし
た。また、前記多孔質耐火物の内径Ｄに対して該耐火物
よりも溶鋼注入方向直上部の浸漬ノズル内の流路内径ｄ
は、流路内径比ｄ／Ｄが０．８となるように段差を付与
した。In Examples 1 to 3 of the present invention, the lower end position H of the porous refractory for suction was set to a position 400 mm from the lower end of the immersion nozzle. Also, the inner diameter D of the porous refractory is larger than the inner diameter D of the flow channel in the immersion nozzle immediately above the refractory in the direction of molten steel injection.
Provided a step so that the flow path inner diameter ratio d / D became 0.8.
【００２７】比較例１〜３は、浸漬ノズル内の吸引用多
孔質耐火物位置Ｈまたは流路内径比ｄ／Ｄのどちらか一
方が本発明の範囲外となる条件でガス吸引を行いながら
鋳造した例である。一方、従来例１，２は、吸引用の多
孔質耐火物下端位置Ｈを浸漬ノズル下端より２３０ｍｍ
の位置とし、また前記多孔質耐火物の内径Ｄと該耐火物
よりも溶鋼注入方向直上部の浸漬ノズル内の流路内径ｄ
が等しく、流路に段差のない状態でガス吸引を行いなが
ら鋳造した例である。In Comparative Examples 1 to 3, casting was performed while performing gas suction under the condition that either the position H of the porous refractory for suction in the immersion nozzle or the ratio d / D of the flow path inner diameter was out of the range of the present invention. This is an example. On the other hand, in the conventional examples 1 and 2, the lower end position H of the porous refractory for suction was set at 230 mm from the lower end of the immersion nozzle.
And the inner diameter D of the porous refractory and the inner diameter d of the flow path in the immersion nozzle immediately above the refractory in the molten steel injection direction.
This is an example in which casting was performed while performing gas suction in a state where there was no step in the flow path.
【００２８】図４に本発明例２を適用してガス吸引を行
った場合の吸引ガス量を示す。図より本発明の適用で吸
引可能なガス量は増加し、また、鋳造を通して安定的に
吸引できることが判る。また、従来技術に見られたよう
な吸引量の変動もほとんど解消された。一方、比較例、
従来例では図は省略するが、吸引ガス量を安定的に確保
しながら鋳造を続行することは不可能であった。FIG. 4 shows the amount of suction gas when gas suction is performed by applying the second embodiment of the present invention. It can be seen from the figure that the amount of gas that can be sucked increases by applying the present invention, and that the gas can be stably sucked through casting. Further, the fluctuation of the suction amount as seen in the prior art was almost eliminated. On the other hand, a comparative example,
Although illustration is omitted in the conventional example, it was impossible to continue the casting while ensuring a stable suction gas amount.
【００２９】表２に本発明技術及び従来技術の鋳片品質
結果および連々鋳回数を示す。品質の指標としては、表
面欠陥については冷延工程における冷延板の目視検査に
よる表面欠陥評点、内部欠陥については熱延工程におけ
るＵＳＴ検査による内部欠陥評点を調査し、Ｎ＝２０コ
イルの平均点で評価した。Table 2 shows the slab quality results and the number of continuous castings of the present invention and the prior art. As an index of quality, surface defects were evaluated by visual inspection of a cold-rolled sheet in a cold rolling process for surface defects, and internal defect scores by a UST inspection in a hot rolling process were examined for internal defects. Was evaluated.
【００３０】[0030]
【表２】 [Table 2]
【００３１】表２より明かなように比較例１では流路内
径比ｄ／Ｄが本発明の範囲より大きかったため、十分な
ガス吸引が行えず、その結果として内部欠陥・表面欠陥
共に合格基準を満たすことはできなかった。比較例２で
は浸漬ノズル内の流路内径ｄを縮小し過ぎたため、鋳造
速度に対して溶鋼供給量が追いつかず、鋳造速度を低下
させることとなった。更に該耐火物直上部の流路が閉塞
し、鋳造の続行が不可能となった。その結果、品質基準
を満たすことはできても、高位の連々鋳回数を実現する
ことはできなかった。比較例３では吸引用多孔質耐火物
の設置位置が低かったため、鋳造の進行とともに該耐火
物表面にアルミナ等が付着・堆積し、徐々に吸引ガス量
が減少し、４鍋目で吸引が不可能となった。そのため、
４鍋以降、鋳型内へ流入するアルゴンガス量が多くな
り、内部欠陥・表面欠陥共に合格基準を満たすことはで
きなかった。As is clear from Table 2, in Comparative Example 1, since the flow path inner diameter ratio d / D was larger than the range of the present invention, sufficient gas suction could not be performed, and as a result, both internal defects and surface defects passed the acceptance criteria. Could not be met. In Comparative Example 2, since the flow path inner diameter d in the immersion nozzle was too small, the molten steel supply amount could not keep up with the casting speed, and the casting speed was reduced. Further, the flow path immediately above the refractory was blocked, making it impossible to continue casting. As a result, although the quality standard could be satisfied, a high number of continuous castings could not be realized. In Comparative Example 3, since the installation position of the porous refractory for suction was low, alumina and the like adhered and deposited on the surface of the refractory with the progress of casting, the amount of suction gas gradually decreased, and suction was not performed at the fourth pan. It has become possible. for that reason,
After 4 pans, the amount of argon gas flowing into the mold increased, and neither the internal defect nor the surface defect could meet the acceptance criteria.
【００３２】従来例１では吸引用多孔質耐火物の設置位
置が低く、更に浸漬ノズル内の溶鋼流路に段差がないた
め十分なガス吸引が行えず、鋳型内へ流入するアルゴン
ガス量が多くなり、内部欠陥・表面欠陥共に合格基準を
満たすことはできなかった。従来例２では鋳片品位を向
上させるために浸漬ノズル内に吹き込むアルゴンガス量
を絞って鋳造を行ったため、浸漬ノズルの閉塞が発生し
て鋳造を中断せざろう得ない状況に陥った。これに対し
て、本発明技術の適用によるものは高位の連々鋳回数を
実現できるとともに、表面欠陥及び内部欠陥において合
格基準を満たすことができた。In the prior art 1, the installation position of the porous refractory for suction is low, and there is no step in the molten steel flow path in the immersion nozzle, so that sufficient gas suction cannot be performed, and the amount of argon gas flowing into the mold is large. Therefore, neither the internal defect nor the surface defect could meet the acceptance criteria. In Conventional Example 2, since the casting was performed by reducing the amount of argon gas blown into the immersion nozzle in order to improve the quality of the slab, the immersion nozzle was clogged and the casting had to be interrupted. On the other hand, according to the application of the technology of the present invention, it was possible to realize a high number of consecutive castings, and to meet the acceptance criteria for surface defects and internal defects.
【００３３】図５に吸引用多孔質耐火物直上の段差付与
例を示す。該耐火物よりも溶鋼注入方向直上部の段差を
付与する方法としては、図中の（ａ）にあるように浸漬
ノズル径を拡大する方法や（ｂ）のように浸漬ノズル上
部へリングを挿入する方法などが挙げられる。FIG. 5 shows an example in which a step is provided immediately above the porous refractory for suction. As a method of providing a step just above the refractory in the molten steel injection direction, a method of increasing the diameter of the immersion nozzle as shown in (a) of the drawing, or inserting a ring into the upper part of the immersion nozzle as shown in (b) And the like.
【００３４】[0034]
【発明の効果】本発明により浸漬ノズルの閉塞を防止
し、数多くの連々鋳を可能とするとともに、ノズル閉塞
防止のために吹き込んだ過剰な不活性ガスを浸漬ノズル
内で吸引除去することで、表面欠陥及び内部欠陥の少な
い高品質な鋳片を得ることができる。According to the present invention, the immersion nozzle is prevented from being clogged, a large number of continuous castings can be performed, and excess inert gas blown for preventing the nozzle clogging is removed by suction in the immersion nozzle. A high quality cast piece with few surface defects and internal defects can be obtained.
【図１】従来技術の実施形態の１例を示す図FIG. 1 is a diagram showing an example of an embodiment of the related art.
【図２】従来技術における吸引ガス量を示す図FIG. 2 is a diagram showing a suction gas amount in a conventional technique.
【図３】本発明の実施形態の１例を示す図FIG. 3 is a diagram showing an example of an embodiment of the present invention.
【図４】本発明における吸引ガス量を示す図FIG. 4 is a diagram showing a suction gas amount in the present invention.
【図５】本発明における吸引用多孔質耐火物直上の段差
設定例を示す図FIG. 5 is a view showing an example of setting a step immediately above a porous refractory for suction in the present invention.
１ タンディッシュ ２ 鋳型 ３ 溶鋼 ４ 上ノズル ５ スライディングノズル ６ 下ノズル ７ 浸漬ノズル ８ 凝固シェル ９ パウダー １０ 不活性ガス吸引用多孔質耐火物 １１ 不活性ガス吹き込み用多孔質耐火物 １２ リング REFERENCE SIGNS LIST 1 tundish 2 mold 3 molten steel 4 upper nozzle 5 sliding nozzle 6 lower nozzle 7 immersion nozzle 8 solidified shell 9 powder 10 porous refractory for sucking inert gas 11 porous refractory for blowing inert gas 12 ring
───────────────────────────────────────────────────── フロントページの続き (72)発明者 白神 孝之 大分県大分市大字西ノ洲１番地 新日本製 鐵株式会社大分製鐵所内 Ｆターム(参考） 4E004 FB04 HA01 HA10 MB20 NC01 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayuki Shirakami 1 Nishinosu, Oita, Oita, Oita Prefecture F-term in Nippon Steel Corporation Oita Works (reference) 4E004 FB04 HA01 HA10 MB20 NC01
Claims (1)
いた連続鋳造方法において、浸漬ノズル内孔面に下記式
（１）を満足するようにガス吸引用多孔質耐火物を配置
し、且つ溶鋼注入方向で該耐火物の直上部の浸漬ノズル
内の流路内径ｄが該耐火物の内径Ｄに対して０．７〜
０．９倍の範囲とせしめた浸漬ノズルを用い、該耐火物
から浸漬ノズル内からガス吸引を行いながら鋳型内へ溶
鋼の供給を行うことを特徴とする連続鋳造方法。 Ｈ＞Ｈ0 ＋ｖ2 ／２ｇ ・・・・・・ （１） 但し、Ｈ：浸漬ノズル下端から吸引用多孔質耐火物下端
までの距離（ｍ） Ｈ0 ：浸漬ノズル下端から鋳造時の鋳型内制御目標メニ
スカスまでの距離（ｍ） ｖ：浸漬ノズル吐出流平均流速（ｍ／ｓ） ｇ：重力加速度（ｍ／ｓ2 ）In a continuous casting method using an immersion nozzle for injecting molten steel into a mold, a gas-repelling porous refractory is arranged on the inner surface of the immersion nozzle so as to satisfy the following formula (1): The flow path inner diameter d in the immersion nozzle immediately above the refractory in the direction of molten steel injection is 0.7 to 0.7 times the inner diameter D of the refractory.
A continuous casting method, characterized in that a molten steel is supplied into a mold while a gas is sucked from the inside of the immersion nozzle from the refractory using a immersion nozzle having a range of 0.9 times. H> H 0 + v 2 / 2g (1) where, H: distance from the lower end of the immersion nozzle to the lower end of the porous refractory for suction (m) H 0 : in the casting mold from the lower end of the immersion nozzle Distance to control target meniscus (m) v: Immersion nozzle discharge flow average flow velocity (m / s) g: Gravitational acceleration (m / s 2 )
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