JPH07246448A - Method for preventing pin hole defect in extra low carbon steel - Google Patents
Method for preventing pin hole defect in extra low carbon steelInfo
- Publication number
- JPH07246448A JPH07246448A JP3843694A JP3843694A JPH07246448A JP H07246448 A JPH07246448 A JP H07246448A JP 3843694 A JP3843694 A JP 3843694A JP 3843694 A JP3843694 A JP 3843694A JP H07246448 A JPH07246448 A JP H07246448A
- Authority
- JP
- Japan
- Prior art keywords
- cooling water
- mold
- low carbon
- carbon steel
- cooling
- 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]
【産業上の利用分野】本発明は、連続鋳造機による極低
炭素鋼の鋳造方法に関し、さらに詳しくは、連続鋳造機
の内部水冷鋳型の冷却水流速の低減により極低炭素鋼の
ピンホール欠陥を防止する方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of casting ultra-low carbon steel by a continuous casting machine, and more particularly, to a pinhole defect of ultra-low carbon steel by reducing the flow rate of cooling water in an internal water-cooled mold of the continuous casting machine. It is about the method of preventing.
【０００２】[0002]
【従来の技術】極低炭素鋼は、溶鋼中の炭素濃度が低い
ため、他の鋼種に比較して溶鋼中の酸素濃度が高くな
り、溶鋼の脱酸時に発生する介在物の量が多いこと、そ
れと脱酸をAlで行うため、発生する介在物が高融点のAl
2O3 であることから、鋳造時に浸漬ノズル詰まりが発生
し易い。このため、極低炭素鋼の鋳造に際しては、浸漬
ノズル内壁面への介在物の付着によるノズル詰まり防止
を目的として、浸漬ノズル内へのアルゴンガスの吹き込
みを行っている。2. Description of the Related Art Ultra-low carbon steel has a low carbon concentration in the molten steel, so that the oxygen concentration in the molten steel is higher than in other steel types, and the amount of inclusions generated during deoxidation of the molten steel is large. , And since deoxidation with Al is performed, the generated inclusions are high melting point Al.
Since it is 2 O 3 , the immersion nozzle is likely to be clogged during casting. For this reason, during the casting of ultra-low carbon steel, argon gas is blown into the immersion nozzle for the purpose of preventing nozzle clogging due to adhesion of inclusions on the inner wall surface of the immersion nozzle.
【０００３】吹き込まれたアルゴンガスは図６に示すよ
うに、溶鋼流に乗って浸漬ノズル６から鋳型内へと持ち
込まれ鋳型内で浮上しきれずに凝固シェル３の内面に捕
捉されると鋳片内にピンホール欠陥として残存する。こ
のピンホール欠陥は製品での表面疵の原因となり、例え
ば、要求表面品質の厳しい冷延鋼板では、スリバー疵と
なり大きな問題となる。As shown in FIG. 6, the blown-in argon gas is carried into the mold from the dipping nozzle 6 by being carried by the molten steel flow, and when it is not fully floated in the mold and is trapped on the inner surface of the solidified shell 3, the slab is cast. Pinhole defects remain inside. This pinhole defect causes a surface flaw in the product, and for example, in a cold-rolled steel sheet having a strict required surface quality, it becomes a sliver flaw and becomes a serious problem.
【０００４】従来の極低炭素鋼のピンホール欠陥防止方
法としては、浸漬ノズルの吐出角度の制御により鋳型内
での溶鋼の上昇流速を適正化する方法、あるいは溶鋼上
に添加するモールドパウダとして発熱性パウダを使用す
ることによりメニスカスに熱を供給し、気泡捕捉の原因
となるメニスカス部の凝固シェルの倒れ込みを低減する
方法、また浸漬ノズルの吐出角度、鋳造速度の制御、あ
るいは鋳型内溶鋼への磁場の印加により溶鋼の吐出流速
を適正化し溶鋼中での気泡の浮上を促進させる方法など
がある。しかしながら、いずれの方法においてもピンホ
ール欠陥の防止方法としては十分な効果が得られていな
いのが現状である。As a conventional method for preventing pinhole defects of ultra-low carbon steel, a method of optimizing the rising velocity of molten steel in the mold by controlling the discharge angle of the immersion nozzle, or heat generation as a mold powder added on the molten steel Method to reduce the collapse of the solidified shell of the meniscus that causes bubbles to be trapped by supplying heat to the meniscus by using a conductive powder, the discharge angle of the dipping nozzle, the control of the casting speed, or the molten steel in the mold. There is a method of optimizing the flow velocity of molten steel by applying a magnetic field to promote the floating of bubbles in the molten steel. However, at present, none of the methods has been sufficiently effective as a method for preventing pinhole defects.
【０００５】[0005]
【発明が解決しようとする課題】本発明者らは、ピンホ
ール欠陥の発生メカニズムを詳細に検討した結果、鋳型
と凝固シェルとの間に発生するギャップ（主としてオッ
シレーションマーク）に起因する凝固シェルの溶鋼側表
面の凝固遅れによる凝固シェルの溶鋼側表面の凹凸部に
アルゴンガスの気泡が捕捉され、これがピンホール欠陥
となることを見出した。DISCLOSURE OF THE INVENTION The inventors of the present invention have studied in detail the generation mechanism of the pinhole defect, and as a result, the solidified shell caused by the gap (mainly oscillation mark) generated between the mold and the solidified shell. It was found that bubbles of argon gas were trapped in the irregularities of the surface of the solidified shell on the surface of molten steel due to the delay in the solidification of the surface on the surface of molten steel, and this became pinhole defects.
【０００６】本発明は、上記極低炭素鋼の連続鋳造時に
発生するピンホール欠陥を防止するためになされたもの
で、極低炭素鋼の連続鋳造時に凝固シェルを緩冷脚する
ことにより、鋳型と凝固シェルとの間に発生するギャッ
プに起因する凝固シェルの溶鋼側表面の凝固遅れを小さ
くして凝固シェルの溶鋼側表面の凹凸を小さくすること
によって、ピンホール欠陥を防止する極低炭素鋼のピン
ホール欠陥防止方法を提供することを目的とする。The present invention has been made in order to prevent pinhole defects that occur during the continuous casting of the ultra-low carbon steel described above. Ultra-low carbon steel that prevents pinhole defects by reducing the solidification delay on the surface of the solidified shell on the molten steel side due to the gap between the solidified shell and the solidified shell to reduce irregularities on the surface of the solidified shell on the molten steel side. It is an object of the present invention to provide a method for preventing the pinhole defect.
【０００７】[0007]
【課題を解決するための手段】その要旨は、連続鋳造機
による極低炭素鋼の鋳造に際し、前記連続鋳造機に付帯
する鋳型冷却水供給装置を制御することにより、連続鋳
造機の内部水冷鋳型の冷却水流速を3m/s以下、1m/s以上
の範囲にして鋳造することを特徴とする極低炭素鋼のピ
ンホール欠陥防止方法である。[Summary of the Invention] The gist of the invention is to control the mold cooling water supply device attached to the continuous casting machine during the casting of ultra-low carbon steel by the continuous casting machine so that the internal water cooling mold of the continuous casting machine is controlled. Is a method of preventing pinhole defects in ultra-low carbon steel, which comprises casting the cooling water at a flow rate of 3 m / s or less and 1 m / s or more.
【０００８】[0008]
【作用】凝固組織観察をもとに、鋳型と凝固シェルとの
間にギャップが存在するときの極低炭素鋼の凝固シェル
の溶鋼側表面の凝固遅れ度を求め、この凝固遅れ度をも
とにギャップ深さを変化させたときの鋳片表面からの距
離と凝固遅れ度との関係を図３に示す。[Operation] Based on the observation of the solidification structure, the solidification delay of the molten steel side surface of the solidification shell of ultra-low carbon steel when there is a gap between the mold and the solidification shell is determined, and this solidification delay is used as the basis. FIG. 3 shows the relationship between the distance from the slab surface and the degree of solidification delay when the gap depth is changed.
【０００９】凝固遅れ度は図４に示すように、鋳型と凝
固シェルとの間にギャップがないときの凝固シェルの溶
鋼側表面までの距離をd2とし、ギャップがあるときの凝
固シェルの溶鋼側表面までの距離をd1として、(1−d1/d
2)×100 を凝固遅れ度（％）と定義した。[0009] coagulation delay degree, as shown in FIG. 4, the distance to the molten steel surface of the solidified shell in the absence of a gap between the mold and the solidified shell and d 2, molten steel solidified shell when there are gaps If the distance to the side surface is d 1 , then (1−d 1 / d
2 ) × 100 was defined as the degree of coagulation delay (%).
【００１０】図３はギャップ深さを変化させたときの鋳
片表面からの距離と凝固遅れ度との関係を示したもので
あ。図３に示すようにギャップ深さが大きくなるとそれ
に応じた凝固遅れ度が発生し、鋳片表面に近いほど凝固
遅れ度は大きい。ここで凝固遅れ度が大きくなると、正
常（ギャップなし）な凝固部との凝固シェル厚さの差が
大きくなり、凝固シェルの溶鋼側表面の凹凸が激しくな
る。そして凝固シェルの溶鋼側表面の凹凸が激しくなる
と、凝固シェル前面を浮上していく気泡が凝固シェルの
凹凸部に捕捉されやすくなりピンホール欠陥が増加す
る。FIG. 3 shows the relationship between the distance from the surface of the slab and the degree of solidification delay when the gap depth is changed. As shown in FIG. 3, when the gap depth becomes large, a solidification delay degree corresponding to that occurs, and the solidification delay degree becomes larger as the gap depth is closer to the surface of the slab. Here, if the solidification delay becomes large, the difference in the thickness of the solidified shell from the normal (no gap) solidified portion becomes large, and the unevenness of the surface of the solidified shell on the molten steel side becomes severe. Then, when the unevenness of the surface of the solidified shell on the molten steel side becomes severe, the bubbles floating on the front surface of the solidified shell are easily captured by the uneven part of the solidified shell, and the pinhole defects increase.
【００１１】このようなメカニズムで発生するピンホー
ル欠陥を防止するには、凝固シェルの不均一凝固を改善
し凝固シェルの溶鋼側表面を平滑化することにより、浮
上する気泡の凝固シェルへの捕捉を防止する必要があ
る。In order to prevent the pinhole defect generated by such a mechanism, the uneven solidification of the solidified shell is improved and the surface of the solidified shell on the molten steel side is smoothed to trap the floating bubbles in the solidified shell. Need to be prevented.
【００１２】連続鋳造において、凝固シェルの不均一凝
固を改善するには、鋳型の冷却能を緩冷却化することが
効果的である。ここで、銅製の鋳型内には図６に示すよ
うに、冷却水路２に内部冷却水を流しているので、鋳型
１の冷却能はこの冷却水の流速により制御することが可
能である。なお、冷却水流速は鋳型冷却水供給装置のポ
ンプ回転数を変えることにより変化させる。In continuous casting, in order to improve the uneven solidification of the solidified shell, it is effective to slowly cool the cooling capacity of the mold. Here, as shown in FIG. 6, internal cooling water is flown in the cooling water passage 2 in the copper mold, so that the cooling capacity of the mold 1 can be controlled by the flow velocity of this cooling water. The cooling water flow rate is changed by changing the pump rotation speed of the mold cooling water supply device.
【００１３】冷却水と銅製の鋳型内の冷却水路表面との
間の熱伝達係数と冷却水流速との関係を図５に示す。図
５に示すように、冷却水流速が小さくなると熱伝達係数
が小さくなることが分かる。そして熱伝達係数が小さく
なると抜熱抵抗が大きくなり、鋳型の冷却能は緩冷却化
される。故に、連続鋳造においては、鋳型内部冷却水流
速を小さくして、鋳型の緩冷却化を図ることで不均一凝
固を防止可能である。The relationship between the heat transfer coefficient between the cooling water and the surface of the cooling water passage in the copper mold and the cooling water flow velocity is shown in FIG. As shown in FIG. 5, it can be seen that the heat transfer coefficient decreases as the cooling water flow velocity decreases. When the heat transfer coefficient decreases, the heat removal resistance increases, and the cooling capacity of the mold is gradually cooled. Therefore, in continuous casting, it is possible to prevent uneven solidification by reducing the cooling water flow rate inside the mold to achieve slow cooling of the mold.
【００１４】したがって、本発明者らは、連続鋳造機に
よる極低炭素鋼の鋳造時の内部水冷鋳型の冷却水流速を
3m/s以下、1m/s以上の範囲に限定した。冷却水流速の上
限を3m/sに限定した理由は、冷却水流速を3m/s以下まで
低減することで凝固遅れ度は大きく軽減され、スリバー
疵発生率は大幅に低下するからであり、下限を1m/sに限
定した理由は、冷却水流速を過度に低下させると鋳型温
度が上昇するので、鋳型表面温度が使用許容温度 350℃
以下で、鋳造を行うには冷却水流速を1m/s以上にする必
要があるからである。また、冷却水温度は鋳型表面温度
上昇の防止および冷却水の沸騰防止の観点から40℃以下
が好ましい。Therefore, the present inventors set the cooling water flow rate of the internal water-cooled mold at the time of casting ultra-low carbon steel by the continuous casting machine.
The range is limited to 3 m / s or less and 1 m / s or more. The reason for limiting the upper limit of the cooling water flow velocity to 3 m / s is that by reducing the cooling water flow velocity to 3 m / s or less, the degree of solidification delay is greatly reduced and the sliver flaw occurrence rate is significantly reduced. Is limited to 1 m / s because the mold temperature rises when the cooling water flow rate is excessively reduced, so the mold surface temperature is 350 ° C.
This is because the cooling water flow rate needs to be 1 m / s or more in order to perform casting below. Further, the cooling water temperature is preferably 40 ° C. or lower from the viewpoint of preventing the mold surface temperature from rising and preventing boiling of the cooling water.
【００１５】[0015]
【実施例】以下に、本発明の実施例について説明する。
鋳型内部冷却水流速を3m/s〜9m/sまで変化させて、炭素
量0.0020％の極低炭素鋼を鋳造した。この鋳片につい
て、凝固シェルの凝固遅れ度と、冷延鋼板におけるスリ
バー疵発生度数を調査した。図１にギャップ深さ 0.1mm
の凝固シェルの凝固遅れ度を、図２にスリバー疵発生度
数を示す。なお、鋳造条件は、鋳造速度：1.8m/min、鋳
片サイズ：1152mm×230mm 、Ar流量：15l/min 、冷却水
流速：9 、7 、5 、3m/s、鋳型振動：振幅 6mm、振動数
2.7Hzである。EXAMPLES Examples of the present invention will be described below.
Ultra-low carbon steel with a carbon content of 0.0020% was cast by changing the cooling water flow rate inside the mold from 3 m / s to 9 m / s. For this slab, the degree of solidification delay of the solidified shell and the frequency of occurrence of sliver flaws in the cold rolled steel sheet were investigated. Figure 1 shows a gap depth of 0.1mm
The coagulation delay of the coagulation shell of No. 2 is shown in FIG. 2, and the sliver flaw occurrence frequency is shown in FIG. The casting conditions are as follows: casting speed: 1.8 m / min, slab size: 1152 mm x 230 mm, Ar flow rate: 15 l / min, cooling water flow rate: 9, 7, 5, 3 m / s, mold vibration: amplitude 6 mm, vibration number
It is 2.7 Hz.
【００１６】図１に示すように、凝固シェルの凝固遅れ
度は冷却水流速を3m/s以下まで低減することで、凝固遅
れ度は大きく軽減でき、その結果、図２に示すように、
冷却水流速が3m/sではスリバー疵発生度数は極端に小さ
くなり、冷延鋼板の表面品質を大幅に改善することがで
きた。なお、スリバー疵発生度数はコイル一本の片面に
発生したスリバー疵個数である。As shown in FIG. 1, the solidification delay of the solidification shell can be greatly reduced by reducing the cooling water flow rate to 3 m / s or less. As a result, as shown in FIG.
When the cooling water flow rate was 3 m / s, the sliver flaw occurrence frequency was extremely low, and the surface quality of the cold rolled steel sheet could be greatly improved. The frequency of occurrence of sliver defects is the number of sliver defects generated on one side of one coil.
【００１７】[0017]
【発明の効果】以上述べたところから明らかなように、
本発明によれば、連続鋳造における極低炭素鋼に発生す
るピンホール欠陥を防止することができるため、鋼板の
表面品質を改善することができ、特に冷延鋼板のスリバ
ー疵防止に優れた効果を発揮する。As is apparent from the above description,
According to the present invention, since it is possible to prevent pinhole defects that occur in ultra-low carbon steel in continuous casting, it is possible to improve the surface quality of the steel sheet, and particularly excellent effects in preventing sliver flaws of cold-rolled steel sheet. Exert.
【図１】実施例の凝固シェルの凝固遅れ度を示す図であ
る。FIG. 1 is a diagram showing a coagulation delay degree of a coagulation shell of an example.
【図２】実施例のスリバー疵発生度数を示す図である。FIG. 2 is a diagram showing the frequency of occurrence of sliver defects in the example.
【図３】鋳型と凝固シェルとの間のギャップ深さを変化
させたときの鋳片表面からの距離と凝固遅れ度との関係
を示す図である。FIG. 3 is a diagram showing a relationship between a distance from a slab surface and a solidification delay degree when a gap depth between a mold and a solidified shell is changed.
【図４】凝固シェルの凝固遅れ度の定義を説明する図で
ある。FIG. 4 is a diagram illustrating the definition of a solidification delay degree of a solidified shell.
【図５】冷却水と銅製の鋳型内の冷却水路表面との間の
熱伝達係数と冷却水流速との関係を示す図である。FIG. 5: Between the cooling water and the surface of the cooling channel in the copper mold
It is a figure which shows the relationship between a heat transfer coefficient and a cooling water flow velocity.
【図６】凝固シェルへのAr気泡の捕捉状況の説明図であ
る。FIG. 6 is an explanatory diagram of a state of trapping Ar bubbles in a solidified shell.
１…鋳型、２…冷却水路、３…凝固シェル、４…凝固シ
ェルに捕捉されたArガス気泡、５…Arガス気泡、６…浸
漬ノズル、７…溶鋼、８…フラックス層。DESCRIPTION OF SYMBOLS 1 ... Mold, 2 ... Cooling channel, 3 ... Solidification shell, 4 ... Ar gas bubbles trapped in the solidification shell, 5 ... Ar gas bubbles, 6 ... Immersion nozzle, 7 ... Molten steel, 8 ... Flux layer.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 小林 高 兵庫県加古川市金沢町１番地 株式会社神 戸製鋼所加古川製鉄所内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kobayashi 1 Kanazawa-machi, Kakogawa-shi, Hyogo Prefecture Kadogawa Works Kakogawa Works
Claims (1)
し、前記連続鋳造機に付帯する鋳型冷却水供給装置を制
御することにより、連続鋳造機の内部水冷鋳型の冷却水
流速を3m/s以下、1m/s以上の範囲にして鋳造することを
特徴とする極低炭素鋼のピンホール欠陥防止方法。1. When casting ultra-low carbon steel with a continuous casting machine, the cooling water flow rate of the internal water cooling mold of the continuous casting machine is controlled to 3 m / s by controlling the mold cooling water supply device attached to the continuous casting machine. Hereinafter, a method for preventing pinhole defects in ultra-low carbon steel, which comprises casting in a range of 1 m / s or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3843694A JPH07246448A (en) | 1994-03-09 | 1994-03-09 | Method for preventing pin hole defect in extra low carbon steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3843694A JPH07246448A (en) | 1994-03-09 | 1994-03-09 | Method for preventing pin hole defect in extra low carbon steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH07246448A true JPH07246448A (en) | 1995-09-26 |
Family
ID=12525263
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3843694A Withdrawn JPH07246448A (en) | 1994-03-09 | 1994-03-09 | Method for preventing pin hole defect in extra low carbon steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07246448A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101400046B1 (en) * | 2012-04-26 | 2014-05-27 | 현대제철 주식회사 | Manufacture method for high strength casting of ultra low carbon steel |
| JP2015168000A (en) * | 2014-03-10 | 2015-09-28 | Ｊｆｅスチール株式会社 | Casting mold for continuous casting and continuous casting method of steel |
-
1994
- 1994-03-09 JP JP3843694A patent/JPH07246448A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101400046B1 (en) * | 2012-04-26 | 2014-05-27 | 현대제철 주식회사 | Manufacture method for high strength casting of ultra low carbon steel |
| JP2015168000A (en) * | 2014-03-10 | 2015-09-28 | Ｊｆｅスチール株式会社 | Casting mold for continuous casting and continuous casting method of steel |
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Legal Events
| Date | Code | Title | Description |
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| A300 | Withdrawal of application because of no request for examination |
Free format text: JAPANESE INTERMEDIATE CODE: A300 Effective date: 20010605 |