JP2008183597A

JP2008183597A - Continuous casting method of steel, and method for manufacturing steel plate

Info

Publication number: JP2008183597A
Application number: JP2007020462A
Authority: JP
Inventors: Yuji Miki; 祐司三木; Yasuo Kishimoto; 康夫岸本
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2007-01-31
Filing date: 2007-01-31
Publication date: 2008-08-14

Abstract

<P>PROBLEM TO BE SOLVED: To improve the cleaning effect of AC magnetic fields by improving the flow of molten steel around an immersed nozzle. <P>SOLUTION: In a continuous casting method of steel, magnetic fields are generated by magnetic poles 30 arranged on the back surfaces of the opposed side walls of the long sides 10a of a rectangular casting mold 10 having short sides 10b and the long sides 10a, and the flow of the molten steel 8 to be supplied from the immersed nozzle 12 into the casting mold 10 is controlled by the magnetic fields. The thickness of the upper portion of the casting mold at the middle portion is thicker than the thickness at its both ends. The AC magnetic fields are applied to the molten steel existing in the portion higher than a discharge port 12a so as to agitate or move the molten steel 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、鋼の連続鋳造方法および鋼板の製造方法にかかり、特に、厳格な表面品質が要求される自動車用鋼板や、飲料缶用鋼板の素材として使用する、厚みが１００ｍｍ以上の鋳片を鋳造する際に用いるのに好適な、鋼の連続鋳造方法及び撹拌の製造方法に関する。 The present invention relates to a continuous casting method of steel and a manufacturing method of a steel plate, and in particular, a slab having a thickness of 100 mm or more used as a raw material for a steel plate for automobiles or a steel plate for beverage cans, which requires strict surface quality. The present invention relates to a steel continuous casting method and a stirring production method suitable for use in casting.

近年、自動車用鋼板を中心として、鋼製品の品質向上要求が厳しくなり、鋳片段階から清浄度の優れた高品質の鋳片の要求が高まっている。鋳片の欠陥には、介在物や気泡に起因するものや、溶鋼中の成分の偏析に起因するものがあり、溶鋼内の流動は、これらと深い関係があるため、多くの研究、発明がなされてきた。その一つとして、磁界を用いた鋳型内溶鋼流動制御方法がある。 In recent years, the demand for improving the quality of steel products has become strict, mainly for steel plates for automobiles, and the demand for high quality slabs with excellent cleanliness has increased from the slab stage. There are many slab defects due to inclusions and bubbles, and due to segregation of components in the molten steel, and the flow in the molten steel is closely related to these. Has been made. One of them is a molten steel flow control method in a mold using a magnetic field.

例えば、特許文献１（図１）には、図１に示す如く、鋳型１０内の溶鋼８のメニスカス近傍に交流（ＡＣ）の移動磁界発生装置２０を配置し、移動磁場により鋳型１０内の溶鋼８の表面に旋回流Ａを発生させ、鋳型壁面への介在物、気泡の付着を旋回流Ａの掻き出し効果で抑制することが記載されている。図において、１０ａは鋳型上の長辺、１０ｂは同じく短辺、１２は浸漬ノズル、１２ａは、その吐出孔、１４は鋳片、１４ａは、その凝固シェルである。 For example, in Patent Document 1 (FIG. 1), as shown in FIG. 1, an alternating current (AC) moving magnetic field generator 20 is disposed in the vicinity of a meniscus of molten steel 8 in a mold 10, and the molten steel in the mold 10 is moved by the moving magnetic field. It is described that a swirl flow A is generated on the surface of No. 8 and the inclusion and inclusion of bubbles on the mold wall surface are suppressed by the scraping effect of the swirl flow A. In the figure, 10a is a long side on the mold, 10b is also a short side, 12 is an immersion nozzle, 12a is a discharge hole, 14 is a cast piece, and 14a is a solidified shell.

しかしながら、浸漬ノズル１２の周辺は、鋳型長辺１０ａとの間隔が狭いので、溶鋼の旋回流Ａに淀みＢが発生し、介在物が凝固シェル１４ａに付着しやすいという問題点を有していた。 However, since the interval between the immersion nozzle 12 and the long mold side 10a is narrow, stagnation B occurs in the swirling flow A of the molten steel, and the inclusions are likely to adhere to the solidified shell 14a. .

この問題点に関し、特許文献２や特許文献３には、浸漬ノズル１２の吐出口を扁平形状とし、浸漬ノズル１２と鋳型壁面の間隔を５０ｍｍ以上確保することが提案されている。 With respect to this problem, Patent Document 2 and Patent Document 3 propose that the discharge port of the immersion nozzle 12 be flat and that the distance between the immersion nozzle 12 and the mold wall surface be 50 mm or more.

又、特許文献４には、図２に示す如く、鋳型長辺１０ａの浸漬ノズル１２周辺の厚みを、鋳型下端迄、厚くすることが記載されている。 Patent Document 4 describes that the thickness of the mold long side 10a around the immersion nozzle 12 is increased to the lower end of the mold as shown in FIG.

特開平６−２２６４０９号公報JP-A-6-226409 特開平５−２８５６１４号公報Japanese Patent Laid-Open No. 5-285614 特開２００３−１６４９４７号公報JP 2003-164947 A 特許第２９９７６８４号公報Japanese Patent No. 2999784

しかしながら、特許文献２や３に記載の技術では、特殊な形状の浸漬ノズルを用いる必要があり、浸漬ノズルから鋳型内への溶鋼流入が円滑で無くなる可能性がある。 However, in the techniques described in Patent Documents 2 and 3, it is necessary to use a specially shaped immersion nozzle, and there is a possibility that the molten steel will flow smoothly from the immersion nozzle into the mold.

一方、特許文献４に記載の技術は、主として厚みが１００ｍｍ以下の薄い鋳片の鋳造を目的としており、交流磁界の印加は考えられていなかった。 On the other hand, the technique described in Patent Document 4 is mainly intended for casting a thin slab having a thickness of 100 mm or less, and application of an alternating magnetic field has not been considered.

本発明は、前記従来の問題点を解決するべくなされたもので、交流磁界を印加した場合の溶鋼の流動を妨げないようにすることを課題とする。 The present invention has been made to solve the above-described conventional problems, and an object thereof is to prevent the molten steel from flowing when an alternating magnetic field is applied.

本発明は、短辺と長辺を有する矩形鋳型の長辺の対向側壁の背面に配設した磁極で磁界を発生させ、該磁界により浸漬ノズルから鋳型内に供給される溶鋼の流動を制御する鋼の連続鋳造方法であって、鋳型上部の幅中央部が、両端部より厚い鋳型を用いて、吐出孔より上部の溶鋼に交流磁界を印加し、溶鋼を撹拌又は移動させるようにして、前記課題を解決したものである。 In the present invention, a magnetic field is generated by a magnetic pole disposed on the back side of the opposing side wall of a long side of a rectangular mold having a short side and a long side, and the flow of molten steel supplied from the immersion nozzle into the mold is controlled by the magnetic field. In the continuous casting method of steel, the center of the width of the upper part of the mold is thicker than both ends, an alternating magnetic field is applied to the molten steel above the discharge hole, and the molten steel is stirred or moved, It solves the problem.

前記鋳型の両端部の厚みは、１００ｍｍ以上とすることができる。 The thickness of both end portions of the mold can be 100 mm or more.

本発明は、又、前記の方法で製造した鋳片を用いることを特徴とする鋼板の製造方法を提供するものである。 The present invention also provides a method for producing a steel sheet, characterized by using a slab produced by the above method.

以下、図面を参照して、本発明の実施形態を詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

本発明は、図３（Ａ）（Ｂ）（Ｃ）に示す如く、長辺１０ａと短辺１０ｂを有する矩形鋳型１０の長辺１０ａの対向側壁の背面に配置した磁極３０で磁界を発生させ、該磁界により浸漬ノズル１２から鋳型１０内に供給される溶鋼８の流動を制御する際に、図３（Ｂ）に示す如く、鋳型上部の幅中央部が、両端部より厚い鋳型を用いて、鋳型上部に磁極２０から交流磁界又は移動磁界を印加し、鋳型上部の溶鋼を移動させるようにしたものである。 In the present invention, as shown in FIGS. 3A, 3B, and 3C, a magnetic field is generated by the magnetic pole 30 disposed on the back surface of the opposing side wall of the long side 10a of the rectangular mold 10 having the long side 10a and the short side 10b. When the flow of the molten steel 8 supplied from the immersion nozzle 12 into the mold 10 is controlled by the magnetic field, as shown in FIG. An alternating magnetic field or a moving magnetic field is applied from the magnetic pole 20 to the upper part of the mold to move the molten steel on the upper part of the mold.

前記鋳型１０の下部は、図３（Ｃ）に示す如く、通常の矩形とされる。 The lower part of the mold 10 has a normal rectangular shape as shown in FIG.

このように、鋳型上部のみ浸漬ノズル１２の周辺の厚みを大とし、下部は通常の矩形とすることで、鋳型下方の設備は、従来通りとすることができる。なお、図３（Ｂ）に示す断面形状を鋳型下端まで伸ばしても良い。 Thus, the thickness of the periphery of the immersion nozzle 12 is increased only in the upper part of the mold, and the lower part is formed in a normal rectangle, so that the equipment below the mold can be made as usual. Note that the cross-sectional shape shown in FIG. 3B may be extended to the lower end of the mold.

又、前記実施形態では、上側磁極３０のみが設けられていたが、図４に示す第２実施形態の如く、浸漬ノズル１２の下側にも磁極３２を設けて、直流磁界、交流磁界、又は、これらの重畳磁界を印加してもよい。 In the above embodiment, only the upper magnetic pole 30 is provided. However, as in the second embodiment shown in FIG. 4, a magnetic pole 32 is also provided on the lower side of the immersion nozzle 12, so that a DC magnetic field, an AC magnetic field, or These superposed magnetic fields may be applied.

注(＊) 電磁撹拌強度は幅方向の平均値を示す。

Note (*) The electromagnetic stirring intensity indicates the average value in the width direction.

ここで、幅中央の流速は、鋳片のデンドライト傾角によって推定した値である。幅中央の流速は概ね０．１５ｍ／ｓ以上で気泡捕捉が抑制されることが分かった。 Here, the flow velocity at the center of the width is a value estimated by the dendrite inclination angle of the slab. It was found that the trapping of bubbles was suppressed when the flow velocity at the center of the width was approximately 0.15 m / s or more.

又、スリーパー欠陥状指数は、スラブを溶鋼亜鉛めっき鋼板に仕上げた後、コイルの外表面を目視で検査し、スリーパー状欠陥発生状況を指数化したもので、指数化は、コイルの長手方向に延びたスリーパー状の欠陥の長さを計測し、その総和を、検査したコイルの全長で割算することにより求め、比較例のＮｏ．３の値を１０として指数化した。 In addition, the sleeper defect index is obtained by visually inspecting the outer surface of the coil after finishing the slab into a molten steel galvanized steel sheet and indexing the occurrence of the sleeper defect. The indexing is performed in the longitudinal direction of the coil. The length of the extended sleeper-like defect was measured, and the total sum was divided by the total length of the inspected coil. The value of 3 was indexed as 10.

特許文献１に記載された従来技術の一例の構成を示す（Ａ）鋳型の正面から見た縦断面図及び（Ｂ）水平断面図(A) The longitudinal cross-sectional view seen from the front of a casting_mold | template and (B) horizontal sectional view which show the structure of an example of the prior art described in patent document 1 特許文献４に記載された従来技術の他の例の構成を示す斜視図The perspective view which shows the structure of the other example of the prior art described in patent document 4 本発明にかかる連続鋳造設備の第１実施形態を示す（Ａ）斜視図（Ｂ）上部の水平断面図及び（Ｃ）下部の水平断面図(A) Perspective view (B) Horizontal sectional view of the upper part and (C) Horizontal sectional view of the lower part showing the first embodiment of the continuous casting equipment according to the present invention. 同じく第２実施形態の構成を示す鋳型の縦断面図Similarly, a longitudinal sectional view of the mold showing the configuration of the second embodiment

符号の説明Explanation of symbols

８…溶鋼
１０…鋳型
１０ａ…鋳型長辺
１２…浸漬ノズル
１２ａ…突出孔
３０、３２…磁極 8 ... Molten steel 10 ... Mold 10a ... Mold long side 12 ... Immersion nozzle 12a ... Projection hole 30, 32 ... Magnetic pole

Claims

短辺と長辺を有する矩形鋳型の長辺の対向側壁の背面に配設した磁極で磁界を発生させ、該磁界により浸漬ノズルから鋳型内に供給される溶鋼の流動を制御する鋼の連続鋳造方法であって、
鋳型上部の幅中央部が、両端部より厚い鋳型を用いて、
吐出孔より上部の溶鋼に交流磁界を印加し、溶鋼を撹拌又は移動させることを特徴とする鋼の連続鋳造方法。 Continuous casting of steel that generates a magnetic field with magnetic poles arranged on the back side of a long side facing rectangular mold having a short side and a long side, and controls the flow of molten steel supplied from the immersion nozzle into the mold by the magnetic field. A method,
Using a mold where the width center part of the upper part of the mold is thicker than both ends,
A continuous casting method of steel, wherein an alternating magnetic field is applied to molten steel above the discharge hole to stir or move the molten steel.

前記鋳型の両端部の厚みが１００ｍｍ以上であることを特徴とする請求項１に記載の鋼の連続鋳造方法。 The method for continuous casting of steel according to claim 1, wherein the thickness of both ends of the mold is 100 mm or more.

請求項１又は２に記載の方法で製造した鋳片を用いることを特徴とする鋼板の製造方法。 A method for producing a steel sheet, comprising using a slab produced by the method according to claim 1 or 2.