JP3246372B2 - Continuous casting of steel - Google Patents
Continuous casting of steelInfo
- Publication number
- JP3246372B2 JP3246372B2 JP34940596A JP34940596A JP3246372B2 JP 3246372 B2 JP3246372 B2 JP 3246372B2 JP 34940596 A JP34940596 A JP 34940596A JP 34940596 A JP34940596 A JP 34940596A JP 3246372 B2 JP3246372 B2 JP 3246372B2
- Authority
- JP
- Japan
- Prior art keywords
- slab
- thickness
- width
- mold
- casting
- 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.)
- Expired - Fee Related
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Description
【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【0001】[0001]
【発明の属する技術分野】本発明は、鋳片の中心偏析を
低減する鋼の連続鋳造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 continuously casting steel to reduce the segregation of cast slabs.
【0002】[0002]
【従来の技術】鋼の連続鋳造法において、鋳片は内部に
鋳造方向に伸長した未凝固相を有して多数のロール間を
引き抜かれるので、溶鋼静圧によるロール間における鋳
片の膨らみ(以下、「バルジング」と記す)や凝固収縮
のために溶鋼体積の変化が生じ、この溶鋼体積の変化分
を補うために溶質元素の濃化した濃化溶鋼が鋳片中心に
集積し、中心偏析が生成する。2. Description of the Related Art In a continuous casting method of steel, a slab has an unsolidified phase elongated in a casting direction and is drawn out between a number of rolls. The volume of molten steel changes due to solidification and shrinkage. To compensate for the change in the volume of molten steel, concentrated molten steel containing solute elements accumulates at the center of the slab, and the center segregates. Is generated.
【0003】そのために、中心偏析の低減を意図して、
低温鋳造や電磁攪拌による鋳造組織の改善等、数多くの
技術が提案実施されており、今日、これらの多くの技術
のなかから有効な手段として未凝固鋳片に軽圧下を施す
ことが実用化されている。[0003] Therefore, in order to reduce the center segregation,
Numerous technologies have been proposed and implemented, such as low-temperature casting and improvement of the casting structure by electromagnetic stirring, and among these many technologies, it has been put to practical use to apply light reduction to unsolidified slabs as an effective means. ing.
【0004】特公平3−6855号公報(以下、「先行
技術1」と記す)には、鋳片の中心が液相線温度となる
時点から流動限界固相率(固相率0.6ないし0.8)
となる時点までの領域で0.5mm/minないし2.
0mm/minの割合で未凝固鋳片を連続的に圧下する
ことが開示されている。先行技術1によれば、この圧下
により凝固収縮量を補償することができ、中心偏析のみ
ならずV偏析や逆V偏析の発生を防止することが可能と
している。[0004] Japanese Patent Publication No. Hei 3-6855 (hereinafter referred to as "prior art 1") discloses a flow limit solid fraction (solid fraction of 0.6 to 0.6) from the time when the center of a slab reaches a liquidus temperature. 0.8)
0.5 mm / min to 2.
It is disclosed that the unsolidified slab is continuously reduced at a rate of 0 mm / min. According to Prior Art 1, the amount of solidification shrinkage can be compensated for by this reduction, and not only the center segregation but also the occurrence of V segregation and reverse V segregation can be prevented.
【0005】特公昭62−34461号公報(以下、
「先行技術2」と記す)には、鋳型と鋳片の液相線クレ
ータエンドとの間の凝固シェルを積極的にバルジングさ
せて鋳片中央側の未凝固層の厚さを増大させ、次いで液
相線クレータエンドと固相線クレータエンドとの間の鋳
片に圧下を加えることが開示されている。先行技術2に
よれば、中心偏析の発生原因とならない領域で鋳片を積
極的にバルジングさせ、未凝固層を厚くしてその後圧下
するので、未凝固層の閉塞を防止でき、中心偏析を大幅
に低減することが可能としている。[0005] Japanese Patent Publication No. 62-34461
According to "prior art 2"), the solidified shell between the mold and the liquidus crater end of the slab is actively bulged to increase the thickness of the unsolidified layer on the slab center side, It is disclosed to apply a reduction to the slab between the liquidus crater end and the solidus crater end. According to Prior Art 2, since the slab is positively bulged in a region where the center segregation does not occur, the unsolidified layer is thickened and then reduced, so that the blockage of the unsolidified layer can be prevented, and the center segregation is greatly reduced. It is possible to reduce it.
【0006】[0006]
【発明が解決しようとする課題】しかし先行技術1で
は、鋳片幅が1800mmを超える広幅の場合には、鋳
片幅方向の凝固の不均一性に起因して、未凝固層が鋳片
幅方向で閉塞されるため、鋳片の全幅に渡って中心偏析
を大きく改善することが不可能である。更に、凝固の完
了した鋳片両短辺側も圧下されるために、大きな圧下力
を必要とする。However, according to the prior art 1, when the slab width is more than 1800 mm, the unsolidified layer has a large slab width due to non-uniform solidification in the slab width direction. Because of the blockage in the direction, it is not possible to greatly improve center segregation over the entire width of the slab. Further, since both short sides of the slab after solidification are also reduced, a large rolling force is required.
【0007】又、先行技術2では、鋳片短辺側は圧下さ
れず、且つ鋳片幅中央側の未凝固層が厚いため、先行技
術1における上記の2つの問題点は解決されるが、積極
的にバルジングさせることによる鋳造の不安定性と、バ
ルジングに伴う鋳片内部割れの発生とが懸念されるた
め、大きなバルジングを生じさせること、即ち大きな圧
下量を確保することが困難であり、必ずしも中心偏析の
改善が十分でない。In the prior art 2, since the short side of the slab is not reduced and the unsolidified layer at the center of the slab width is thick, the above two problems in the prior art 1 are solved. It is difficult to generate large bulging, that is, it is difficult to secure a large rolling reduction, because the instability of casting due to active bulging and the occurrence of slab internal cracks due to bulging are concerned. Center segregation is not sufficiently improved.
【0008】本願発明は上記事情に鑑みなされたもの
で、その目的とするところは鋳型出口での鋳片幅中央側
の未凝固層厚みを厚くすることで、最終凝固部近傍に未
凝固層の閉塞の発生を防止するとともに濃化溶鋼の流動
を可能な限り抑制し、鋳片の中心偏析を大幅に改善する
ことができる鋼の連続鋳造法を提供するものである。The present invention has been made in view of the above circumstances, and its purpose is to increase the thickness of the unsolidified layer at the center of the slab width at the exit of the mold so that the unsolidified layer is formed near the final solidified portion. It is an object of the present invention to provide a continuous casting method of steel capable of preventing occurrence of blockage, suppressing flow of concentrated molten steel as much as possible, and greatly improving center segregation of a slab.
【0009】[0009]
【課題を解決するための手段】第1の発明に係る鋼の連
続鋳造法は、鋳型出口における鋳片形状を、鋳片幅中央
側の鋳片厚みが鋳片短辺側に比較して拡大した形状と
し、二次冷却帯における凝固完了までの期間に鋳片厚み
の拡大部にロール圧下を加えて鋳片を鋳造する鋼の連続
鋳造法であって、鋳片幅をW、鋳片短辺での鋳片厚みを
D、メニスカスから固相線クレータエンドまでの距離を
Lとしたときに、鋳型出口における鋳片幅中央位置の鋳
片厚みの拡大量dを下記の(1)式の範囲内とすること
を特徴とするものである。d>D(W−2.4D)/2L ……(1) Means for Solving the Problems] continuous casting of steel according to the first invention, the slab shape in cast-type outlet, slab width central portion of the slab thickness as compared to the slab short side and enlarged shape, continuous steel casting the slab by adding roll reduction to the enlarged portion of the slab thickness in the period leading up to completion of solidification in the secondary cooling zone
In the casting method, the slab width is W and the slab thickness at the short side of the slab is
D, distance from meniscus to solidus crater end
L, the casting at the center of the slab width at the mold exit
The expansion amount d of Kataatsumi is characterized in range and be Rukoto of (1) below. d> D (W-2.4D) / 2L (1)
【0010】本発明では、鋳片幅方向中央側の鋳片厚み
が厚くなる鋳型を用いて鋳型内凝固を進行させ、鋳型出
口での鋳片形状を鋳片中央側の鋳片厚みの厚い形状、即
ち、鋳片中央側の未凝固層の厚い形状としているので、
鋳型直下で更にバルジングさせる必要はなく、そのた
め、鋳型直下にてバルジングさせることによる鋳造の不
安定性と、バルジングに伴う鋳片内部割れの発生とを解
消することができる。又、鋳型の形状を変更するだけ
で、鋳片厚み拡大量を任意に且つ大きくすることができ
るため、最終凝固部近傍での未凝固層の閉塞の発生を防
止すると共に、鋳片の圧下を十分に行なうことが可能と
なり、中心偏析の改善効果が大きい。そして中心偏析を
防止するためには鋳片厚みの拡大部のみを圧下すればよ
く、従って溶鋼静圧よりわずかに大きい圧下力で圧下可
能となる。In the present invention, solidification in the mold is advanced by using a mold having a thicker slab thickness on the center side in the slab width direction, and the slab shape at the mold outlet is changed to a shape with a thicker slab thickness on the slab center side. That is, since the unsolidified layer at the center of the slab has a thick shape,
It is not necessary to further perform bulging immediately below the mold, so that instability of casting caused by bulging immediately below the mold and occurrence of internal cracks in the slab due to bulging can be eliminated. Also, by simply changing the shape of the mold, the slab thickness expansion amount can be arbitrarily and increased, so that the occurrence of blockage of the unsolidified layer near the final solidified portion is prevented, and the reduction of the slab is reduced. This can be performed sufficiently, and the effect of improving center segregation is great. Then, in order to prevent the center segregation, it is sufficient to reduce only the enlarged portion of the slab thickness, so that it is possible to reduce with a reduction force slightly larger than the molten steel static pressure.
【0011】その際の鋳片厚みの拡大量は、最終凝固位
置近傍での濃化溶鋼の流動が可能な限り定常状態に近い
状況を実現させることを意図して、その値を決定する必
要がある。 At this time, the amount of increase in the thickness of the slab is determined by the final solidification level.
Flow of concentrated molten steel in the vicinity of
Its value must be determined with the intention of realizing the situation.
It is necessary.
【0012】図5に示すように、鋳片幅をW、鋳片短辺
での鋳片厚みをD、鋳片幅方向の鋳片厚みの拡大部の範
囲をW−2.4D、鋳型出口における鋳片幅中央位置の
鋳片厚みの拡大量をdとすると、鋳片幅方向の未凝固層
角度φ(ラジアン)は下記の(3)式で近似される。 φ≒2d/(W−2.4D) ……(3) As shown in FIG . 5, the slab width is W, and the short side of the slab is
Is the slab thickness at D, and the range of the enlarged slab thickness in the slab width direction.
W-2.4D at the center of the slab width at the mold exit
Assuming that the expansion of the slab thickness is d, the unsolidified layer in the slab width direction
The angle φ (radian) is approximated by the following equation (3). φ ≒ 2d / (W-2.4D) (3)
【0013】又、図6に示すように、鋳片短辺での鋳片
厚みをD、メニスカスから固相線クレータエンドまでの
距離をLとすると、鋳造方向の未凝固層角度θ(ラジア
ン)は下記の(4)式で近似される。 θ≒D/L ……(4) As shown in FIG. 6, the slab at the short side of the slab
Thickness D, from meniscus to solidus crater end
Assuming that the distance is L, the unsolidified layer angle θ in the casting direction (radius
Is approximated by the following equation (4). θ ≒ D / L (4)
【0014】最終凝固位置近傍での鋳片幅方向の濃化溶
鋼の流動を定常状態に近い流れとするため、即ち、凝固
収縮等による溶鋼体積の変化が生じた場合にも、濃化溶
鋼は流動せずに、固相率が低く濃化されていない溶鋼が
流動して溶鋼体積の不足分を補充するためには、鋳片幅
方向の未凝固層角度φを鋳造方向の未凝固層角度θより
大きくすることが望ましい。 Concentration melting in the slab width direction near the final solidification position
In order to make the flow of steel near steady state, that is, solidification
Even when the volume of molten steel changes due to shrinkage, etc.
The steel does not flow and the molten steel with low solid fraction and unconcentrated
In order to replenish the shortage of molten steel volume by flowing, the slab width
The unsolidified layer angle φ in the casting direction from the unsolidified layer angle θ in the casting direction.
It is desirable to make it larger.
【0015】鋳片幅方向の未凝固層角度φを鋳造方向の
未凝固層角度θより大きくする条件として、(3)式及
び(4)式から鋳型出口における鋳片幅中央位置の鋳片
厚みの拡大量dが前述した(1)式として導かれる。 The angle φ of the unsolidified layer in the slab width direction is
As a condition for making the angle larger than the unsolidified layer angle θ, the equation (3) and
From equation (4), the slab at the center of the slab width at the exit of the mold
The enlargement amount d of the thickness is derived as the aforementioned equation (1).
【0016】第2の発明に係る鋼の連続鋳造法は、第1
の発明において、鋳片幅をW、鋳片短辺での鋳片厚みを
Dとしたときに、鋳片幅中央側の少なくともW−2.4
Dの範囲の鋳片厚みを拡大させることを特徴とするもの
である。 The continuous casting method for steel according to the second invention is characterized in that
In the invention, the slab width is W and the slab thickness at the short side of the slab is
D, at least W-2.4 on the slab width center side
Characterized by increasing the slab thickness in the range of D
It is.
【0017】連続鋳造法では次工程の要求により、種々
の鋳片幅を鋳造する必要がある。本発明では鋳片の幅中
央側の鋳片厚みが厚くなる鋳型を用いて鋳造するが、鋳
型幅全体に渡って鋳片厚みを拡大すると、鋳造する鋳片
幅の変更毎に鋳型を交換しなければならず、極めて非効
率である。そこで本発明では、鋳片短辺側に鋳片厚みの
平坦な範囲を設け、この平坦部で鋳片幅の変更を行な
い、同一鋳型で種々の幅の鋳片の鋳造を可能とすること
を検討した。しかしこの平坦部が広くなると未凝固層が
閉塞し、ロール圧下による中心偏析の改善効果が低下す
る。そこで鋳片厚みの拡大部の範囲を鋳片幅方向で種々
に変更して中心偏析改善効果と対比して調査した結果、
鋳片幅をW、鋳片短辺での鋳片厚みをDとしたときに、
鋳片厚みの拡大部が少なくともW−2.4Dの範囲確保
されれば、中心偏析の改善効果を損なわないことが判明
した。即ち、その外側の鋳片厚みは平坦としてもよいこ
とが分かった。鋳片厚みの拡大部の範囲がW−2.4D
未満となると、鋳片短辺側に未凝固層の閉塞が発生して
圧下効果が少なくなり、鋳片短辺側の中心偏析の改善が
十分にできず、望ましくない。 In the continuous casting method, various types of
It is necessary to cast the slab width. In the present invention,
Casting is performed using a mold with a thicker slab on the center side.
When the slab thickness is increased over the entire mold width,
The mold must be changed every time the width is changed, which is extremely ineffective
Rate. Therefore, in the present invention, the slab thickness
Provide a flat area and change the slab width in this flat area.
The ability to cast slabs of various widths with the same mold
It was investigated. However, when this flat part becomes wider, the unsolidified layer
Blockage reduces the effect of reducing center segregation due to roll pressure
You. Therefore, the range of the enlarged part of the slab thickness is varied in the slab width direction.
As a result of conducting a survey in comparison with the effect of improving center segregation
When the slab width is W and the slab thickness at the short side of the slab is D,
Enlarged part of slab thickness secures at least W-2.4D range
If it is done, it turns out that the effect of improving center segregation is not impaired
did. That is, the thickness of the slab on the outside may be flat.
I understood. The range of the enlarged part of the slab thickness is W-2.4D
When it is less than, the clogging of the unsolidified layer occurs on the short side of the slab
Reduction of rolling reduction effect and improvement of center segregation on short side of slab
Not enough and not desirable.
【0018】このように、鋳片短辺側の片側当たり、最
大で鋳片短辺での鋳片厚みの1.2倍分の長さを平坦部
とすることが可能となり、この平坦部で鋳片幅の変更を
行なうことができる。例えば短辺での鋳片厚みが230
mmの鋳片において、2150mm幅を最大幅とする鋳
型であれば、鋳片厚みの拡大部は幅中央側の1598m
mとなり、片側276mmの範囲が平坦部となり、従っ
て、この鋳型で2150mmから1600mmの幅の鋳
片まで鋳造することができる。 In this manner, the shortest side of the cast slab is
Large, flat 1.2 mm length of slab thickness on short side of slab
It is possible to change the slab width in this flat part
Can do it. For example, the slab thickness on the short side is 230
mm with a maximum width of 2150 mm
If it is a mold, the enlarged part of the slab thickness is 1598m on the width center side
m, and a range of 276 mm on one side becomes a flat portion.
The casting with a width of 2150 mm to 1600 mm
Pieces can be cast.
【0019】第3の発明に係る鋼の連続鋳造法は、第1
の発明又は第2の発明において、鋳型出口における鋳片
厚みの鋳片幅方向の形状を、下記の(2)式に従い定め
ることを特徴するものである。 y=K〔(x/lo)2 −2(x/lo)3 +(x/lo)4 〕 ……(2)The continuous casting of steel according to the third invention, first
In the invention of the second aspect, the shape of the thickness of the slab at the outlet of the mold in the slab width direction is determined according to the following equation (2). y = K [(x / lo) 2 -2 ( x / lo) 3 + (x / lo) 4 ] ... (2)
【0020】但し、(2)式においてyは、鋳片厚みの
平坦な面を基準とした鋳片厚みの拡大方向への変位量
で、鋳片厚みの拡大量の1/2に等しく、xは、鋳片厚
みが拡大を開始した位置を起点とした鋳片幅方向への距
離、及び、loは、鋳片厚みの拡大部の鋳片幅方向の長さ
であり、又、Kは定数で、鋳型幅の1/2における鋳片
厚みの拡大量をdとしたとき、鋳型幅の1/2、即ちx
=lo/2における変位量yが、鋳片厚みの拡大量dの1
/2に等しいとしてKを決定する。In the equation (2), y is the displacement of the slab thickness in the direction of enlargement with respect to the flat surface of the slab thickness, and is equal to 1/2 of the slab thickness enlargement. Is the distance in the slab width direction starting from the position at which the slab thickness started to expand, and lo is the length of the slab thickness expansion portion in the slab width direction, and K is a constant. Then, when the amount of expansion of the slab thickness at 1/2 of the mold width is d, 1/2 of the mold width, ie, x
= Lo / 2, the displacement amount y is 1 of the expansion amount d of the slab thickness.
K is determined as equal to / 2.
【0021】本発明では鋳片厚みが幅方向で一定でない
ために、鋳型直下において溶鋼静圧によるバルジングで
鋳片に局所的な変形を発生させる懸念がある。局所的な
変形を発生させると、鋳片に割れを生じ、ブレークアウ
ト等の操業異常が発生するので、鋳型出口での鋳片の形
状は、バルジングによる変形が発生しても局所的な変形
の発生しない形状とすることが望ましい。そこで、鋳型
直下においてバルジングしたときの形状を予め与えてお
くと、バルジングによる変形は鋳片幅方向で均等にな
り、局所的な変形を防止することができる。鋳片のバル
ジング形状と最も近い曲線は、両端固定の梁に均等荷重
が作用したときの梁の変形曲線であるので、両端固定の
梁に均等荷重が作用したときの梁の変形曲線、即ち、
(2)式を採用して鋳型出口での鋳片の形状と定めるこ
ととする。In the present invention, since the slab thickness is not constant in the width direction, there is a concern that the slab may be locally deformed by bulging due to the molten steel static pressure immediately below the mold. If local deformation occurs, the slab cracks and operation errors such as breakouts occur.Therefore, the shape of the slab at the exit of the mold will not change even if deformation due to bulging occurs. It is desirable that the shape does not occur. Therefore, if the shape at the time of bulging immediately below the mold is given in advance, the deformation due to bulging becomes uniform in the slab width direction, and local deformation can be prevented. The curve closest to the bulging shape of the slab is the deformation curve of the beam when an equal load is applied to the beam fixed at both ends, so the deformation curve of the beam when the equal load is applied to the beam fixed at both ends, that is,
Equation (2) is adopted to determine the shape of the slab at the exit of the mold.
【0022】[0022]
【発明の実施の形態】本発明を適用した鋳片断面が矩形
型の連続鋳造機の鋳片幅中央位置の側断面の概要図を図
2に、又、鋳型の平断面の概要図を図3に示す。DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a schematic view of a side section at the center position of a slab width of a continuous caster having a rectangular slab section to which the present invention is applied, and FIG. 3 is shown.
【0023】図3に示すように本発明で用いる鋳型1
は、銅製で水冷構造の対向する一対の鋳型長辺15と、
鋳型長辺15に挟まれた銅製で水冷構造の対向する一対
の鋳型短辺16とから構成されている。そして、対向す
る鋳型長辺15間の間隔は、幅の中央側が鋳型短辺16
側に比較して広くなり、鋳片厚みの拡大部17を形成
し、その外側は対向する鋳型長辺15間の間隔は一定の
平坦部18、18aとなっている。鋳型短辺16は、こ
の平坦部18、18aでのみ鋳型長辺15内を摺動し、
鋳片幅(W)の変更が可能となっている。鋳片厚みは、
鋳型短辺16側の鋳片厚み(D)から徐々に拡大し、鋳
型長辺15の中央位置で最も拡大して鋳片厚み(D+
d)となり、鋳片厚みは鋳型長辺15の中心線で実質的
に左右対称の形状となっている。As shown in FIG. 3, the mold 1 used in the present invention
Is a pair of opposed mold long sides 15 of copper and water-cooled structure,
It is composed of a pair of opposed short sides 16 of a water cooling structure made of copper sandwiched between the long sides 15 of the mold. The distance between the opposed mold long sides 15 is such that the center of the width is the mold short side 16.
It is wider than the side, and forms an enlarged portion 17 of the slab thickness, and the outside is a flat portion 18, 18a in which the distance between the opposing mold long sides 15 is constant. The mold short side 16 slides in the mold long side 15 only at the flat portions 18 and 18a,
The slab width (W) can be changed. The slab thickness is
The slab thickness gradually increases from the slab thickness (D) on the short side 16 of the mold, and the slab thickness (D +
d), and the slab thickness is substantially symmetrical with respect to the center line of the long side 15 of the mold.
【0024】そして図2に示すように、タンディッシュ
12内の溶鋼11は、タンディッシュ12の底部に設け
られ、先端がメニスカス14に浸漬する浸漬ノズル13
を介して鋳型1内に連続的に注入される。鋳型1内に注
入された溶鋼11は鋳型1に接触して冷却され外周に凝
固層7を形成し、次いで凝固層7は鋳型1下方の二次冷
却帯2に設けたサポートロール3、ガイドロール4、及
び圧下ロール5を通り、下方に連続的に引き抜かれる。
二次冷却帯2は水スプレー又はエアーミストスプレーに
よる冷却帯となっており、鋳型1より引き抜かれた凝固
層7の表面は冷却され、凝固相7の内部の未凝固層8の
厚みを減少させ、固相線クレータエンド10にて凝固を
完了して、鋳片6となる。尚、図2に示す破線は液相線
温度であり、液相線温度の先端位置、即ち液相線クレー
タエンド9より引き抜き方向下方で、鋳片厚み中心にお
いて固相が出現して、固液共存層となる。As shown in FIG. 2, the molten steel 11 in the tundish 12 is provided at the bottom of the tundish 12 and has a tip dipped in a meniscus 14.
Through the mold 1. The molten steel 11 injected into the mold 1 is cooled by contacting the mold 1 to form a solidified layer 7 on the outer periphery. Then, the solidified layer 7 is provided on the support roll 3 and the guide roll provided in the secondary cooling zone 2 below the mold 1. 4, and is continuously pulled downward through the reduction roll 5.
The secondary cooling zone 2 is a cooling zone by water spray or air mist spray. The surface of the solidified layer 7 drawn from the mold 1 is cooled, and the thickness of the unsolidified layer 8 inside the solidified phase 7 is reduced. The solidification is completed at the solidus crater end 10 to form a slab 6. The dashed line shown in FIG. 2 is the liquidus temperature, and the solid phase appears at the center of the slab thickness at the tip position of the liquidus temperature, that is, below the liquidus crater end 9 in the drawing direction. It becomes a coexistence layer.
【0025】この二次冷却帯2での引き抜き中の凝固完
了までの期間に、鋳片厚みの拡大部17に圧下ロール5
にてロール圧下を加える。その際に、鋳片中央側と鋳片
短辺側との鋳片厚みが実質的に同一になるまで圧下する
と、鋳片6の次工程へのハンドリングが容易になるので
望ましい。図4は、鋳片6の二次冷却帯2におけるロー
ル圧下による形状変化を模式的に示したもので、図4の
(a)、(b)、(c)、(d)は、それぞれ図2にお
けるI−I断面、II−II断面、III−III断面、及びIV−
IV断面に対応する。During the period until the solidification during the drawing in the secondary cooling zone 2 is completed, the reduction roll 5
Roll pressure is applied with. At this time, it is preferable to reduce the slab thickness until the slab thickness on the slab center side and the slab short side side becomes substantially the same, because handling of the slab 6 to the next step becomes easy. FIG. 4 schematically shows a shape change of the slab 6 in the secondary cooling zone 2 due to a roll reduction, and FIGS. 4 (a), (b), (c) and (d) are diagrams respectively. II, II-II, III-III, and IV-
Corresponds to IV section.
【0026】ロール圧下は、鋳片幅中央位置における鋳
片厚み中心の固相率が0.01から0.75の範囲を、
0.5mm/minないし2.5mm/minの割合で
連続的に行なうことが望ましい。The roll reduction is such that the solid phase ratio at the center of the slab thickness at the center position of the slab width is in the range of 0.01 to 0.75,
It is desirable to carry out continuously at a rate of 0.5 mm / min to 2.5 mm / min.
【0027】鋳片幅中央位置における鋳片厚み中心の固
相率が0.01未満では溶鋼11が容易に流動して、中
心偏析が発生しないため圧下する効果なく、又、鋳片幅
中央位置における鋳片厚み中心の固相率が0.75を超
えると固液共存層中の未凝固層8の流動が不可能とな
り、ロール圧下しても未凝固層8が移動しないために、
圧下する効果がないためである。If the solid phase ratio at the center of the slab thickness at the center of the slab width is less than 0.01, the molten steel 11 flows easily, and the center segregation does not occur. If the solid phase ratio at the center of the slab thickness exceeds 0.75, the flow of the unsolidified layer 8 in the solid-liquid coexisting layer becomes impossible, and the unsolidified layer 8 does not move even if the roll is rolled down.
This is because there is no effect of rolling down.
【0028】ロール圧下の速度が、0.5mm/min
未満では圧下量が不足して中心偏析の改善効果が十分に
得られず、又、2.5mm/minを超えると、凝固層
7の変形が大きくなり内部割れが発生するためである。The speed under roll pressure is 0.5 mm / min.
If it is less than 30 mm, the effect of reducing center segregation cannot be sufficiently obtained because the amount of reduction is insufficient, and if it exceeds 2.5 mm / min, the deformation of the solidified layer 7 becomes large and internal cracks occur.
【0029】図1は、上記の本発明を適用したときの、
鋳片厚みの拡大部17と鋳片短辺側の平坦部18、18
aとにおける鋳片厚みの推移の例をメニスカス14から
の距離に対して示したものである。鋳片厚みの拡大部1
7は固相率が0.01から0.75の範囲で連続的にロ
ール圧下され、固相率0.75の位置では鋳片6は幅全
体に渡り実質的に平坦な形状となる。尚、図1において
鋳片短辺側の鋳片厚みも連続的に減少しているが、これ
は凝固後の温度低下に伴う体積収縮により鋳片厚みが収
縮するためである。FIG. 1 shows the case where the present invention is applied.
An enlarged portion 17 of the slab thickness and flat portions 18 and 18 on the short side of the slab.
3A shows an example of the transition of the slab thickness at a distance from the meniscus 14. Expanded part 1 of slab thickness
Rolls 7 are continuously rolled down in the solid phase ratio of 0.01 to 0.75, and at the position of the solid phase ratio of 0.75, the slab 6 has a substantially flat shape over the entire width. In FIG. 1, the thickness of the slab on the short side of the slab also decreases continuously, because the thickness of the slab shrinks due to the volume shrinkage accompanying the temperature decrease after solidification.
【0030】鋳片厚みの拡大部17の幅方向長さ(lo)
は、鋳片幅をW、鋳片短辺での鋳片厚みをDとしたとき
に、鋳片幅中央側の少なくともW−2.4Dの範囲を確
保することが望ましい。従って鋳型1において、鋳造可
能な最大幅に対して、(最大幅−2.4×鋳片厚み)の
範囲を鋳片厚みの拡大部17とすれば、鋳型1にて鋳片
幅が最大幅から(最大幅−2.4×鋳片厚み)の幅まで
鋳造可能となる。鋳造する幅の格差が大きく、一つの鋳
型1では全ての鋳造幅に対応できない場合には、上記に
従って最大幅の異なる鋳型1を複数個準備すればよい。The length (lo) in the width direction of the enlarged portion 17 of the slab thickness
It is preferable that, when the slab width is W and the slab thickness at the short side of the slab is D, at least the range of W-2.4D at the center of the slab width is secured. Therefore, in the mold 1, if the range of (maximum width-2.4 x slab thickness) is defined as the enlarged portion 17 of the slab thickness with respect to the maximum width that can be cast, the slab width in the mold 1 is the maximum width. From (maximum width-2.4 x slab thickness). If there is a large difference in casting width and one casting mold 1 cannot handle all casting widths, a plurality of casting molds 1 having different maximum widths may be prepared as described above.
【0031】鋳片6の幅中央位置における鋳片厚みの拡
大量(d)は、鋳片幅(W)、鋳片短辺での鋳片厚み
(D)、及び、メニスカス14から固相線クレータエン
ド10までの距離(L)から(1)式の右辺を算出し、
算出された値より大きな値とすることが望ましい。ここ
でメニスカス14から固相線クレータエンド10までの
距離(L)は、二次冷却帯2の冷却強度によりその都度
凝固係数を測定して算出すれば正確に求めることができ
るが、鋳造方向の未凝固層角度θは、二次冷却強度が高
い時の方が大きくて二次冷却強度の低い範囲をカバーす
るので、二次冷却強度が高い時の凝固係数(約30mm
/min1/2 )を用いればよい。The expansion amount (d) of the slab thickness at the width center position of the slab 6 is determined by the slab width (W), the slab thickness (D) at the short side of the slab, and the solidus line from the meniscus 14. From the distance (L) to the crater end 10, the right side of the equation (1) is calculated,
It is desirable that the value be larger than the calculated value. Here, the distance (L) from the meniscus 14 to the solidus crater end 10 can be accurately obtained by calculating and calculating the solidification coefficient each time based on the cooling strength of the secondary cooling zone 2. The unsolidified layer angle θ is larger when the secondary cooling strength is high and covers the range where the secondary cooling strength is low, so that the solidification coefficient when the secondary cooling strength is high (about 30 mm
/ Min 1/2 ) may be used.
【0032】尚、鋳片厚みの拡大量(d)の上限は、そ
の後のロール圧下に伴う内部割れが発生しない範囲にお
いて、経済性を考慮した実用的な範囲で決定すればよ
い。The upper limit of the amount of increase (d) in the thickness of the slab may be determined within a practical range in consideration of economy, as long as no internal cracking occurs due to the subsequent roll reduction.
【0033】鋳型出口における鋳片厚みの鋳片幅方向の
形状は、(2)式に従い定めることが望ましい。この場
合、予め鋳片幅の中央位置における鋳片厚みの拡大量
(d)と、鋳片厚みの拡大部17の鋳造幅方向の長さ
(lo)とを決めておき、(2)式にy=d/2、x=lo
/2を代入して、定数Kを定め、その後、任意の位置
(x)における変位量(y)を算出すれば、鋳片幅方向
の形状が決定する。The shape of the slab thickness in the slab width direction at the mold outlet is desirably determined according to the equation (2). In this case, the slab thickness expansion amount (d) at the center position of the slab width and the length (lo) of the slab thickness expansion portion 17 in the casting width direction are determined in advance, and the equation (2) is used. y = d / 2, x = lo
/ 2 is substituted to determine a constant K, and then the displacement (y) at an arbitrary position (x) is calculated to determine the shape in the slab width direction.
【0034】尚、鋳型1を出た後、圧下を開始する前に
更にバルジングさせてから圧下してもよい。After leaving the mold 1, it may be further bulged before starting the reduction, and then reduced.
【0035】[0035]
【実施例】図2に示す連続鋳造機と図3に示す鋳型とを
用いて本発明を実施した。対象鋼種はC:0.15wt
%、Si:0.2wt%、Mn:0.5wt%の40キ
ロ級Alキルド鋼で、鋳造速度が1.8m/min、タ
ンディッシュ内での溶鋼過熱度は25〜35℃であっ
た。EXAMPLE The present invention was carried out using a continuous casting machine shown in FIG. 2 and a mold shown in FIG. The target steel type is C: 0.15wt
%, Si: 0.2 wt%, and Mn: 0.5 wt%, a 40 kg class Al-killed steel, the casting speed was 1.8 m / min, and the degree of superheat of the molten steel in the tundish was 25 to 35 ° C.
【0036】本発明で用いた鋳型は、短辺側の鋳片厚み
が230mmで、鋳造可能な最大幅は2150mmであ
る。そこで(5)式により鋳片厚みの拡大部の最小幅を
算出して、その結果から鋳型の幅中央位置を挟んで16
00mmの範囲を鋳片厚みの拡大部と定め、2150m
m幅と1600mm幅の鋳片を鋳造した。 2150−2.4×230=1598(mm) ……(5)The mold used in the present invention has a slab thickness of 230 mm on the short side and a maximum castable width of 2150 mm. Then, the minimum width of the enlarged portion of the slab thickness is calculated by the equation (5), and from the result, the minimum width of the slab 16
The area of 00 mm is defined as an enlarged part of the slab thickness, and 2150 m
Cast pieces of m width and 1600 mm width were cast. 2150−2.4 × 230 = 1598 (mm) …… (5)
【0037】次に、メニスカスから固相線クレータエン
ドまでの距離(L)を、凝固係数=30mm/min
1/2 を用いて(6)式により算出し、算出した距離
(L)から(1)式の右辺を(7)式により算出して鋳
片厚みの拡大量(d)を20mmと決めた。 L=[(230/(2×30)]2×1800=26450(mm) ……(6) d>[230×(2150−2.4×230)]/(2×26450)=6.9(mm) ……(7)Next, the distance (L) from the meniscus to the solidus crater end was determined by the solidification coefficient = 30 mm / min.
Using 1/2 , it was calculated by equation (6), and from the calculated distance (L), the right side of equation (1) was calculated by equation (7), and the enlargement amount (d) of the slab thickness was determined to be 20 mm. . L = [(230 / (2 x 30)] 2 x 1800 = 26450 (mm) ... (6) d> [230 x (2150-2.4 x 230)] / (2 x 26450) = 6.9 (mm) ... … (7)
【0038】そして(2)式において、lo=1600m
m、x=800mmにおける変位量(y)が10mmと
して定数K=160mmを求め、任意の位置(x)にお
ける変位量(y)を算出して鋳片厚みの形状を定め、そ
の形状に沿って鋳型長辺を加工した。In the equation (2), lo = 1600 m
Assuming that the displacement amount (y) at m, x = 800 mm is 10 mm, a constant K = 160 mm is obtained, the displacement amount (y) at an arbitrary position (x) is calculated, the shape of the slab thickness is determined, and along the shape, The long side of the mold was processed.
【0039】鋳片厚みの拡大部へのロール圧下は、幅中
央位置の鋳片厚み中心の固相率が0.05と推定される
場所から開始し、固相率が0.75と推定される場所ま
で行い、そしてこの間の圧下速度が1.8mm/min
の一定速度となるように、一定割合で圧下ロールのロー
ル間隔を減少させて設定し、この間で鋳片厚みは実質的
に平坦な形状となる。この時の圧下ロールの圧下荷重は
圧下ロール一対当たり62トン、97トン、及び123
トンの三水準で行い、圧下荷重の影響も調査した。尚、
設定値以上のロール反力が作用した場合は、その圧下ロ
ールはバランス位置まで後退する構造となっている。Rolling down to the portion where the slab thickness is increased starts from the position where the solid fraction at the center of the slab thickness at the center of the width is estimated to be 0.05, and the solid fraction is estimated to be 0.75. And the rolling speed during this time is 1.8 mm / min
Is set so as to reduce the roll interval of the reduction roll at a fixed rate so that the thickness of the slab becomes substantially flat. The rolling load of the rolling roll at this time was 62 tons, 97 tons, and 123 tons per rolling roll.
The test was conducted at three levels of tons, and the effect of the rolling load was also investigated. still,
When a roll reaction force equal to or greater than the set value is applied, the rolling roll retreats to the balance position.
【0040】鋳造された鋳片は1600mm幅及び21
50mm幅のいずれも、凝固完了近くまで鋳片幅方向に
液相が開放されるので、溶鋼の定常流れが確保されて濃
化溶鋼の集積が発生しないため、中心偏析及びセンター
ポロシティの発生程度が鋳片幅全体に渡って大幅に改善
された。尚、中心偏析とセンターポロシティの発生状況
に及ぼす圧下荷重の影響は、圧下ロール一対当たり62
トンで十分効果が認められており、123トンの場合に
は若干の鋳片厚みの減少が認められ、完全に鋳片が平坦
になった後も圧下されていたと推定される。このように
圧下ロール一対当たりの圧下荷重を最適値に制御するこ
とにより、所望する固相率範囲を的確に圧下することが
可能で、最終凝固直前の不要圧下を避けることができ
る。The cast slab is 1600 mm wide and 21 mm wide.
In any of the 50 mm widths, the liquid phase is released in the slab width direction until near the completion of solidification, so that steady flow of molten steel is ensured and accumulation of concentrated molten steel does not occur, so that the degree of occurrence of center segregation and center porosity is reduced. Significant improvement over the entire slab width. The effect of the rolling load on the occurrence of center segregation and center porosity is as follows:
A sufficient effect was recognized at tons, and in the case of 123 tons, a slight decrease in the slab thickness was recognized, and it is estimated that the slab was reduced even after the slab was completely flattened. By controlling the rolling load per pair of rolling rolls to the optimum value in this way, it is possible to accurately reduce the desired solid phase ratio range, and to avoid unnecessary reduction immediately before final solidification.
【0041】[0041]
【発明の効果】本発明によれば、鋳造の不安定性やバル
ジングに伴う鋳片内部割れの発生を懸念することなく鋳
片中央側の鋳片厚みを拡大することが可能となり、その
ため、鋳片幅中央側の未凝固層厚みを厚くすることで、
最終凝固部近傍に未凝固層の閉塞の発生を防止するとと
もに定常的な溶鋼流動を発生させて濃化溶鋼の流動を可
能な限り抑制するので、鋳片の中心偏析を大幅に改善す
ることができる。According to the present invention, it is possible to increase the thickness of the slab at the center of the slab without having to worry about instability of casting or the occurrence of internal cracks in the slab due to bulging. By increasing the thickness of the unsolidified layer at the center of the width,
Prevents clogging of the unsolidified layer in the vicinity of the final solidification zone and generates a steady flow of molten steel to suppress the flow of concentrated molten steel as much as possible. it can.
【図1】本発明を適用したときの鋳片幅中央側の鋳片厚
みの拡大部と鋳片短辺側の平坦部とにおける鋳片厚みの
推移の例を示した図である。FIG. 1 is a diagram showing an example of transition of a slab thickness in an enlarged portion of a slab thickness on a slab width center side and a flat portion on a short side of a slab when the present invention is applied.
【図2】本発明を適用した鋳片断面が矩形型の連続鋳造
機の鋳片幅中央位置の側断面の概要図である。FIG. 2 is a schematic view of a side cross section at a center position of a slab width of a continuous casting machine having a rectangular slab section to which the present invention is applied.
【図3】本発明を適用した鋳型の平断面の概要図であ
る。FIG. 3 is a schematic view of a plane cross section of a mold to which the present invention is applied.
【図4】本発明を適用した際の、二次冷却帯におけるロ
ール圧下による鋳片の形状変化を模式的に示した図であ
り、(a)、(b)、(c)、(d)はそれぞれ図2に
おけるI−I断面、II−II断面、III−III断面、及びIV
−IV断面に対応する。FIG. 4 is a view schematically showing a change in the shape of a slab due to roll reduction in a secondary cooling zone when the present invention is applied, and (a), (b), (c), and (d). Are respectively II section, II-II section, III-III section, and IV section in FIG.
-Corresponds to section IV.
【図5】鋳片幅方向の未凝固層角度φを模式的に示す図
である。FIG. 5 is a diagram schematically showing an unsolidified layer angle φ in a slab width direction.
【図6】鋳造方向の未凝固層角度θを模式的に示す図で
ある。FIG. 6 is a view schematically showing an unsolidified layer angle θ in a casting direction.
1 鋳型 2 二次冷却帯 3 サポートロール 4 ガイドロール 5 圧下ロール 6 鋳片 7 凝固層 8 未凝固層 9 液相線クレータエンド 10 固相線クレータエンド 11 溶鋼 REFERENCE SIGNS LIST 1 mold 2 secondary cooling zone 3 support roll 4 guide roll 5 reduction roll 6 cast piece 7 solidified layer 8 unsolidified layer 9 liquidus crater end 10 solidus crater end 11 molten steel
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平5−185186(JP,A) 特開 平3−32455(JP,A) 特開 平6−262318(JP,A) 特開 平6−154979(JP,A) 特開 平6−154980(JP,A) 特開 昭62−33048(JP,A) 特開 昭60−6254(JP,A) 特開 平9−1292(JP,A) 特開 平8−215815(JP,A) 特開 平2−15858(JP,A) 特表 平2−500501(JP,A) (58)調査した分野(Int.Cl.7,DB名) B22D 11/04 311 B22D 11/128 350 B22D 11/20 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-185186 (JP, A) JP-A-3-32455 (JP, A) JP-A-6-262318 (JP, A) JP-A-6-262318 154979 (JP, A) JP-A-6-154980 (JP, A) JP-A-62-233048 (JP, A) JP-A-60-6254 (JP, A) JP-A 9-1292 (JP, A) JP-A-8-215815 (JP, A) JP-A-2-15858 (JP, A) JP-A-2-500501 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) B22D 11/04 311 B22D 11/128 350 B22D 11/20
Claims (3)
央側の鋳片厚みが鋳片短辺側に比較して拡大した形状と
し、二次冷却帯における凝固完了までの期間に鋳片厚み
の拡大部にロール圧下を加えて鋳片を鋳造する鋼の連続
鋳造法であって、鋳片幅をW、鋳片短辺での鋳片厚みを
D、メニスカスから固相線クレータエンドまでの距離を
Lとしたときに、鋳型出口における鋳片幅中央位置の鋳
片厚みの拡大量dを下記の(1)式の範囲内とすること
を特徴とする鋼の連続鋳造法。d>D(W−2.4D)/2L ……(1) The method according to claim 1] billet in cast-type outlet shape, a shape slab width central portion of the slab thickness is enlarged compared to the slab short side, it casts the period until completion of solidification in the secondary cooling zone Continuous casting of steel by casting a slab by applying roll reduction to the enlarged part of the piece thickness
In the casting method, the slab width is W and the slab thickness at the short side of the slab is
D, distance from meniscus to solidus crater end
L, the casting at the center of the slab width at the mold exit
Continuous casting of steel characterized by larger amounts d the range and be Rukoto of (1) below the Kataatsumi. d> D (W-2.4D) / 2L (1)
としたときに、鋳片幅中央側の少なくともW−2.4D
の範囲の鋳片厚みを拡大させることを特徴とする請求項
1に記載の鋼の連続鋳造法。2. The slab width is W and the slab thickness at the short side of the slab is D.
And at least W-2.4D at the center of the slab width
The method for continuously casting steel according to claim 1, wherein the thickness of the slab is increased in the range of (1).
の形状を、下記の(2)式に従い定めることを特徴とす
る請求項1又は請求項2に記載の鋼の連続鋳造法。 y=K〔(x/lo) 2 −2(x/lo) 3 +(x/lo) 4 〕 ……(2) 但し、(2)式においてyは、鋳片厚みの平坦な面を基
準とした鋳片厚みの拡大方向への変位量で、鋳片厚みの
拡大量の1/2に等しく、xは、鋳片厚みが拡大を開始
した位置を起点とした鋳片幅方向への距離、及び、lo
は、鋳片厚みの拡大部の鋳片幅方向の長さであり、又、
Kは定数で、鋳型幅の1/2における鋳片厚みの拡大量
をdとしたとき、鋳型幅の1/2、即ちx=lo/2にお
ける変位量yが、鋳片厚みの拡大量dの1/2に等しい
としてKを決定する。 3. A slab width direction of a slab thickness at a mold outlet.
Is determined in accordance with the following equation (2).
The method for continuously casting steel according to claim 1 or 2. y = K [(x / lo) 2 -2 ( x / lo) 3 + (x / lo) 4 ] ... (2) However, y in equation (2), based on the flat surface of the slab thickness
The displacement of the slab thickness in the direction of enlargement
X is equal to 1/2 of the expansion amount, x is the slab thickness start expanding
Distance in the slab width direction from the starting position, and lo
Is the length in the slab width direction of the enlarged portion of the slab thickness, and
K is a constant, the amount of increase in slab thickness at half the mold width
Where d is half of the mold width, ie, x = lo / 2.
The displacement y is equal to 1/2 of the expansion d of the slab thickness.
Is determined as K.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP34940596A JP3246372B2 (en) | 1996-12-27 | 1996-12-27 | Continuous casting of steel |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP34940596A JP3246372B2 (en) | 1996-12-27 | 1996-12-27 | Continuous casting of steel |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH10193067A JPH10193067A (en) | 1998-07-28 |
JP3246372B2 true JP3246372B2 (en) | 2002-01-15 |
Family
ID=18403533
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JP34940596A Expired - Fee Related JP3246372B2 (en) | 1996-12-27 | 1996-12-27 | Continuous casting of steel |
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JP (1) | JP3246372B2 (en) |
Cited By (1)
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CN101992282B (en) * | 2009-08-17 | 2012-06-06 | 攀钢集团攀枝花钢铁研究院有限公司 | Continuous casting method |
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---|---|---|---|---|
JP2008183597A (en) * | 2007-01-31 | 2008-08-14 | Jfe Steel Kk | Continuous casting method of steel, and method for manufacturing steel plate |
JP4505530B2 (en) * | 2008-11-04 | 2010-07-21 | 新日本製鐵株式会社 | Equipment for continuous casting of steel |
JP5476959B2 (en) * | 2009-12-08 | 2014-04-23 | Jfeスチール株式会社 | Continuous casting method under light pressure |
JPWO2013069121A1 (en) * | 2011-11-09 | 2015-04-02 | 新日鐵住金株式会社 | Steel continuous casting equipment |
US20140190655A1 (en) * | 2011-11-09 | 2014-07-10 | Nippon Steel & Sumitomo Metal Corporation | Continuous casting apparatus for steel |
JP5870966B2 (en) * | 2013-05-31 | 2016-03-01 | Jfeスチール株式会社 | Manufacturing method of continuous cast slab |
-
1996
- 1996-12-27 JP JP34940596A patent/JP3246372B2/en not_active Expired - Fee Related
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101992282B (en) * | 2009-08-17 | 2012-06-06 | 攀钢集团攀枝花钢铁研究院有限公司 | Continuous casting method |
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JPH10193067A (en) | 1998-07-28 |
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