JPS6027450A - Continuous casting method of steel plate - Google Patents

Abstract

PURPOSE:To prevent segregation and shrinkage with a casting method in which a molten steel is supplied between a pair of cooling rolls by varying the circumferential speeds of the cooling rolls thereby decreasing the unsolidified melt interposed between the dendrite crystals as far as possible. CONSTITUTION:Cooling rolls 1, 1 are spaced adequately from each other and are provided freely rotatably in parallel with each other. A molten metal 2 is supplied onto said rolls to form a solidified shell 3, thereby casting continuously a steel plate 4. The rolls 1, 1 in this stage are rotated respectively at different circumferential speeds (v1), (v2) in an arrow direction. Dendrite crystals 5 are then formed at the solidification boundary of the layer 3. When the solidification boundary comes to the superposed part, the crystals 5 facing each other collide vigorously against each other at a relative speed (v1-v2) and the tips thereof are broken and are meshed densely with each other. The broken tips 5a intrude into the gap 6 formed between the crystals 5 to close the gap 6. The gap 6 is therefore considerably decreased and the unsolidified melt 7 remains therein and the amt. thereof is considerably decreased, by which segregation and shirinkage are effectively prevented.

Description

【発明の詳細な説明】 本発明は鋼板の連続鋳造法に係り、特に溶鋼′ｆ、凝固
１−て鋼板を鋳造する２つの冷却ロールの周速を異なら
せ、凝固層界面に生成さｎる樹枝状結晶を積極的に衝突
させて相互に破壊し、結晶間に取り残さ几る未凝固溶鋼
の割合を低減することにより、鋼板の偏析と内部側ｎの
発生を有効に防止し得るようにした鋼板の連続鋳造法に
係る。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuous casting of steel sheets, and in particular, the peripheral speeds of two cooling rolls for casting molten steel and solidified steel sheets are made to differ, so that molten steel is produced at the interface of the solidified layer. By actively colliding the dendrites to destroy each other and reducing the proportion of unsolidified molten steel remaining between the crystals, it is possible to effectively prevent segregation of the steel plate and the occurrence of internal n. Concerning the continuous casting method of steel plates.

従来、連続鋳造法として第１図に示すような方法が卸ら
ｎている。すなわち、互いに並行に水平方向に回転駆動
自在に配設さｆした二本の冷却ロール１，１上に溶鋼２
ｔ−供給する。供給さｎた溶鋼２は同一速度ｖ１で回転
する冷却ロール１と接触して冷却さ几凝固し、冷却ロー
ル１面に凝固層３を形成する。そして、冷却ロール１に
よる冷却速度は速く凝固層３は、わずかな時間に成長し
、ロール１，１間でやや圧延さｎてロール１，１間より
下方に板状の鋳物を連続鋳造する方法である。Conventionally, a method as shown in FIG. 1 has been used as a continuous casting method. That is, molten steel 2 is placed on two cooling rolls 1, 1 which are arranged parallel to each other so as to be freely rotatable in the horizontal direction.
t-supply. The supplied molten steel 2 comes into contact with the cooling roll 1 rotating at the same speed v1, is cooled and solidified, and forms a solidified layer 3 on the surface of the cooling roll 1. The cooling rate by the cooling roll 1 is fast, and the solidified layer 3 grows in a short period of time, and is rolled slightly between the rolls 1 and 1 to continuously cast a plate-shaped casting below the space between the rolls 1 and 1. It is.

ところで、溶鋼は鉄の中にＣ，Ｓｔ、Ｍｎ、Ｐ。By the way, molten steel contains C, St, Mn, and P in the iron.

Ｓその他の元素を少量ずつ溶かした合金である故、その
凝固過程において凝固界面に樹枝状結晶の成長がみらｎ
る。Because it is an alloy in which S and other elements are dissolved in small amounts, dendrite growth is observed at the solidification interface during the solidification process.
Ru.

第２図に示す如く、最終凝固位置である鋼板４の厚み中
央部は粗大な樹枝状結晶５の積み重ねで、この結晶５間
に多数の間［６が形成さｎる。そして、この間隙６に未
凝固溶鋼１が残存して樹枝状結晶５とで固液共存域を作
っている。As shown in FIG. 2, the center of the thickness of the steel plate 4, which is the final solidification position, is a stack of coarse dendrites 5, and a large number of dendritic crystals 5 are formed between the crystals 5. The unsolidified molten steel 1 remains in this gap 6 and forms a solid-liquid coexistence region with the dendrites 5.

未凝固溶鋼Ｔも最終的には凝固するが、ある区域の未凝
固溶鋼Ｔが凝固しはじめると、その収縮により当該区域
内に周辺刀）ら濃化さｎた未凝固部Ａを吸引する。そう
すると、未凝固溶鋼が吸引さｎた周辺区域には真空部が
できる。この真空部が、いわゆるひけといわ几ているも
のでｓ、ｐ、ｈ部割几の原因にもなる。第３図及び第４
図は、このひけ８０発生状況を示した鋼板４の断面図で
ある。The unsolidified molten steel T will also solidify eventually, but when the unsolidified molten steel T in a certain area begins to solidify, the unsolidified portion A that has thickened from the surrounding area will be sucked into the area due to its contraction. This creates a vacuum in the area around which the unsolidified molten steel is sucked. This vacuum area is so-called sink and is also the cause of the shrinkage in the s, p, and h parts. Figures 3 and 4
The figure is a cross-sectional view of the steel plate 4 showing how this sink mark 80 occurs.

このひけ、ないし内部割ルはスラブと異なり、特に薄い
鋼板を鋳造する場合にあっては、成品の機械的強度に影
響するところ大である。Unlike slabs, these sink marks or internal cracks greatly affect the mechanical strength of the finished product, especially when casting thin steel plates.

また、凝固過程において溶鋼中成分より低い成分値の固
体が析出し、未凝固部の成分は濃化されて液体状態を維
持する。このようにして鋼板厚み方向での最終凝固位置
、すなわち鋼板軸心部は他の部分に比べて極端に高い成
分値となり、こｎが偏析とよは几るものである。この偏
析は、上述のように未凝固部が多いほど、すなわち樹枝
状結晶５が形成する間隙が多いほどその度合が高く、中
心割ｆＬまたは・ぐイゾとよば九る品質欠陥の原因とな
る。In addition, during the solidification process, solids with lower component values than those in the molten steel precipitate, and the components in the unsolidified portion are concentrated and maintain a liquid state. In this way, the final solidification position in the thickness direction of the steel plate, that is, the axial center of the steel plate, has an extremely high component value compared to other parts, and this is more likely to be called segregation. As mentioned above, the greater the number of unsolidified parts, that is, the greater the number of gaps formed by the dendrites 5, the higher the degree of this segregation, which causes a quality defect called central cracking. .

このように、凝固層３の凝固界面に生成される樹枝状結
晶５の存在は、冷却条件に起因するひけ及び偏析から成
る品質欠陥を誘発するという欠点があった。As described above, the presence of dendrites 5 generated at the solidification interface of the solidified layer 3 has the drawback of inducing quality defects consisting of sink marks and segregation due to cooling conditions.

本発明は、上記事情に鑑みてなさ几、その目的とすると
ころは、樹枝状結晶間に介在する未凝固溶鋼を可及的に
少なくして偏析とひけの発生を防止し、もって良質な鋼
板を得ることができる鋼板の連続鋳造法を提供するにあ
る。The present invention was developed in view of the above circumstances, and its purpose is to reduce as much as possible the amount of unsolidified molten steel interposed between dendrites to prevent segregation and sink marks, thereby producing high-quality steel sheets. The objective is to provide a continuous casting method for steel sheets that can obtain.

上記目的は、本発明によ九ば次のようにして達成さ几る
。即ち、適宜離間しつつ互に並行に回転自在に設けた冷
却ロール間へ溶鋼を供給し、こ几ら冷却ロールを同方向
に回転させて溶鋼を冷却しつつ冷却ロール間より鋼板を
鋳造するに際して、前記冷却ロールの周速を異ならせる
ことにより、冷却ロール面に形成さｎる凝固層同士に重
合方向に開力・う相対速度を与えて凝固界面に生成さ九
ている樹枝状結晶を相互に破壊し、鋼板の最終凝固位置
である厚み中央部における樹枝状結晶間に形成される間
Ｉ！Ｊを減少し、この間隙内に残存する未凝固溶鋼の全
体量を低減させるようにしたことを特徴とする。こ几に
より、未凝固溶鋼の存在により発生する偏析やひけを防
止し、冷却条件に起因する品質欠陥を可及的に低減する
ようにしたものである。The above object is achieved in the following manner according to the present invention. In other words, molten steel is supplied between cooling rolls that are freely rotatable in parallel with each other while being appropriately spaced apart, and the cooling rolls are rotated in the same direction to cool the molten steel while casting a steel plate from between the cooling rolls. By varying the circumferential speed of the cooling roll, an opening force and a relative velocity are applied to the solidified layers formed on the surface of the cooling roll in the direction of polymerization, thereby causing the dendrites formed at the solidified interface to mutually interact. The I! J is reduced to reduce the total amount of unsolidified molten steel remaining in the gap. This method prevents segregation and sink marks caused by the presence of unsolidified molten steel, and reduces quality defects caused by cooling conditions as much as possible.

以下、本発明に係る鋼板の連続鋳造法の好適〜実施例を
添付図面に従って説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the continuous casting method for steel sheets according to the present invention will be described below with reference to the accompanying drawings.

第５図に示す如く、２つの冷却ロール１，１は、図示し
ないモータによって周速を異ならせる（ｖＩ笑ｖ２）よ
うに設けら扛ている。いず九のロール１全速くするよう
にしてもよいが、その比率はｏ、　ｉ　−ｉ％が望まし
い。As shown in FIG. 5, the two cooling rolls 1, 1 are provided so as to have different circumferential speeds (vI (v2)) by a motor (not shown). It is also possible to make the roll 1 of 9th speed all the way, but it is desirable that the ratio is o, i -i%.

さらに、二つのロールの速度差の大きさを周期的にかえ
てもよい。Furthermore, the magnitude of the speed difference between the two rolls may be changed periodically.

次に、このように両ロール１，１を異速にしたことによ
る作用について述べる。Next, the effect of setting both rolls 1, 1 at different speeds will be described.

冷却ロール１，１はモータの駆動により同方向ではある
けｎども異なる周速度で回転駆動され、冷却ロール１，
１上には溶鋼２が供給さｎる。供給さｆ′Ｌｆｃ溶鋼２
は冷却ロール１と接触して冷却さ几凝固し、冷却ロール
１面に凝固層３が形成さｎるとともに、その凝固界面に
は樹枝状結晶５が生成さ几る。この凝固層３は冷却ロー
ル１１Ｃそれぞｎ付与さｎた周速度（ｖＩ＋Ｖ２）と同
一の速度を与えら扛重合方向に同かつて進行する。凝固
界面が重合部に差し掛たると相対向する樹枝状結晶５は
相対速度（ｖｌ−ｖ２）で激しく衝突する。この衝突に
より樹枝状結晶５の先端は折ｎて壊さｎる。この様子を
示したのが第６図であり、先端の折九た樹枝状結晶５同
士は相互に密に噛み合い、また樹枝状結晶５間に形成さ
ｎる間隙６内に折損した先端５ａが入り込み間隙６を塞
ぐことになる。このため、重合後の樹枝状結晶５間に形
成さｎる間隙６は、樹枝状結晶５が破壊さルない場合と
比べて著しく少なくなり、この少なくなった間隙６のみ
に未凝固溶鋼１が残存することになる。こｎにより、鋼
板４の最終凝固位置である厚み中央部における樹枝状結
晶５間に介在する未凝固溶鋼７が大幅に減少することに
なる。The cooling rolls 1, 1 are driven by a motor to rotate in the same direction but at different circumferential speeds.
Molten steel 2 is supplied onto the molten steel 1. Supplied f'Lfc molten steel 2
is cooled and solidified in contact with the cooling roll 1, and a solidified layer 3 is formed on the surface of the cooling roll 1, and dendrites 5 are generated at the solidified interface. The solidified layer 3 is given the same circumferential speed (vI+V2) as the cooling roll 11C, and advances in the same direction in the polymerization direction. When the solidification interface approaches the polymerization part, the opposing dendrites 5 collide violently at a relative velocity (vl-v2). This collision breaks the tips of the dendrites 5. This situation is shown in FIG. 6, where the broken dendrites 5 at the tips are closely interlocked with each other, and the broken tips 5a are in the gaps 6 formed between the dendrites 5. This will close the entry gap 6. Therefore, the gaps 6 formed between the dendrites 5 after polymerization are significantly smaller than in the case where the dendrites 5 are not destroyed, and the unsolidified molten steel 1 is present only in the reduced gaps 6. It will remain. As a result, the amount of unsolidified molten steel 7 interposed between the dendrites 5 at the center of the thickness, which is the final solidification position of the steel plate 4, is significantly reduced.

このように、２つの冷却ロール１，１の周速を異ならせ
、樹枝状結晶５を積極的ＶＣ破壊するようにしたので、
結晶間に介在する凝固完了前の未凝固溶鋼の絶対量が激
減し、未凝固溶鋼の製出あるいは吸引に基づく偏析やひ
け全有効に防止することができる。In this way, since the circumferential speeds of the two cooling rolls 1, 1 are made different and the dendrites 5 are actively destroyed by VC,
The absolute amount of unsolidified molten steel interposed between crystals before completion of solidification is drastically reduced, and segregation and sinkage due to production or suction of unsolidified molten steel can be completely prevented.

なお、本発明方法の特徴でおる冷却ロールの周速を異な
らせるという手段は、鋳造後の圧延工程において常用さ
扛るに至った真速ロールによる圧延と外見上共通すると
ころがるるようにみえるが、圧延ロールを異速にするの
は剪断力を与えて圧力が籠もるの７防止し、さらに大き
な圧延加重をかけること、すなわち圧下刃を弱めること
にあるに対し、本発明方法のそｆＬは凝固界面に生成さ
ルる樹枝状結晶を破壊することにおり、特に未凝固溶鋼
全減少させて偏析及びひけの防止を目的としている点で
本質的に異なるものである。Note that the method of varying the circumferential speed of the cooling roll, which is a feature of the method of the present invention, appears to be similar in appearance to rolling with true speed rolls, which has come to be commonly used in the rolling process after casting. The purpose of setting the rolling rolls at different speeds is to apply a shearing force to prevent pressure from building up, and to apply a larger rolling load, that is, to weaken the rolling blades. They are essentially different in that their purpose is to destroy the dendrites formed at the solidification interface, and in particular to prevent segregation and sink marks by reducing the total amount of unsolidified molten steel.

以上、要するに本発明によｎば次のような優れた効果を
発揮する。In short, the present invention exhibits the following excellent effects.

（１）　樹枝状結晶間に介在する未凝固溶＠を可及的に
減少させて、偏析とひけの発生を有効に防止し、もって
良質な鋼板を得ることができる。(1) It is possible to reduce as much as possible the unsolidified melt interposed between dendrites, effectively prevent segregation and sink marks, and thereby obtain high-quality steel sheets.

（２）冷却ロールの周速を異ならせるという簡単な方法
によって冷却条件に起因する品質欠陥を有効に防止でき
経済性の向上かはか九る。(2) A simple method of varying the circumferential speed of the cooling roll can effectively prevent quality defects caused by cooling conditions and improve economic efficiency.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は従来の連続鋳造装置を示す概略断面図、第２図
は同装置による場合の問題点を説明する凝固層の重合拡
大断面図、第３図、第４図は同じく同装置により得ら几
た鋼板の中央縦断面図、第５図は本発明方法に係る連続
鋳造装置の好適一実施例を示す概略断面図、第６図は同
じく同装置による場合の凝固層の重合部を示す拡大断面
図である。 尚、図中１は冷却ロール、２は溶鋼、３は凝固層、４は
鋼板、５は樹枝状結晶、１は未凝固溶鋼である。 特許出願人　石川島播磨重工業株式会社代理人　弁理士
　絹　谷　信　雄Fig. 1 is a schematic sectional view showing a conventional continuous casting device, Fig. 2 is an enlarged sectional view of the solidified layer of the solidified layer to explain the problems with the same device, and Figs. 3 and 4 are the same. Fig. 5 is a schematic sectional view showing a preferred embodiment of the continuous casting apparatus according to the method of the present invention, and Fig. 6 shows the overlapping part of the solidified layer when using the same apparatus. It is an enlarged sectional view. In the figure, 1 is a cooling roll, 2 is molten steel, 3 is a solidified layer, 4 is a steel plate, 5 is a dendrite, and 1 is unsolidified molten steel. Patent applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Agent: Nobuo Kinuya, patent attorney

Claims (1)

【特許請求の範囲】[Claims] 適宜離間しつつ互に並行に回転自在に設けた冷却ロール
間へ溶鋼を供給し、こ几ら冷却ロールを同方向に回転さ
せて溶鋼を冷却しつつ冷却ロール間より鋼板ｔ″鋳造す
るに際して、前記冷却ロールの周速を異ならせることに
より、冷却ロール面に形成さルる凝固層同士に重合方向
に向かう相対速度を与えて凝固界面に生成さ九ている樹
枝状結晶を相互に破壊し、鋼板の最終凝固位置である厚
み中央部における樹枝状結晶間に介在する未凝固溶４を
減少させるようにしたことを特徴とする鋼板の連続鋳造
法。When molten steel is supplied between cooling rolls that are freely rotatable in parallel with each other and spaced apart from each other, and the molten steel is cooled by rotating the cooling rolls in the same direction, a steel plate t'' is cast from between the cooling rolls. By varying the circumferential speed of the cooling roll, a relative speed in the direction of polymerization is imparted to the solidified layers formed on the surface of the cooling roll, thereby mutually destroying dendrites formed at the solidification interface, A continuous casting method for a steel plate, characterized in that unsolidified melt 4 interposed between dendrites in the center of the thickness, which is the final solidification position of the steel plate, is reduced.