JP2004243384A - Method of manufacturing hot steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a hot steel strip by which a variation in width and a variation in thickness in the longitudinal direction of the steel strip are corrected in high accuracy. <P>SOLUTION: In the method of manufacturing the hot strip, edging is performed by setting the opening degree of the rolls of a vertical rolling mill (7) on the basis of the rate of a change in width which is a change in width per unit length in the longitudinal direction of a hot slab (11) or a rough bar (12). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

ここで、Ｗ０：板幅圧下前の板幅、Ｗｈ：水平圧延後の板幅、
Ｗ０ｍｉｎ：板幅圧下前の最小板幅
ΔＷｍｉｎ：最小板幅圧下量、ｔ０：板幅圧下前の板厚、
ｔｈ：水平圧延後の板厚、Ｄｅ：竪圧延機ロール径、
Ｄｈ：水平圧延機ロール径、Ｔ：粗バー温度、
Ｓ：板幅変化率、Ｖ：圧下速度比、ｘ：粗バーの長手方向位置
式（２）より板幅変化率および圧下速度比を考慮した水平圧延後の板幅が予測可能である。ここで、式（２）において、従来の板幅予測式と異なる諸量を用いている点について説明する。
【００４０】
板幅圧下前の板幅をＷ０、板幅圧下後の板幅をＷ１とすると、板幅変動がない場合は、Ｗ０、Ｗ１は長手方向によらず一定であるが、板幅変動が存在する場合には、粗バーの長手方向位置をｘとすると、Ｗ０、Ｗ１はｘの関数として表わされる。そこで、Ｗ０、Ｗ１を板幅変化率Ｓ、圧下速度比Ｖ、板幅圧下前の最小板幅Ｗ０ｍｉｎ、最小板幅圧下量をΔＷｍｉｎで表わす。
【００４１】
図５は、各諸量の関係を示す図である。
Ｗ０、Ｗ１は式（３）、（４）で表わされる。
【００４２】
Ｗ０＝Ｓｘ ＋ Ｗ０ｍｉｎ …（３）
Ｗ１＝Ｖｘ ＋ （Ｗ０ｍｉｎ−ΔＷｍｉｎ） …（４）
ここで、板幅変化率Ｓ、圧下速度比Ｖは図５に示すように形状の変化をｘの一次関数として近似している。
【００４３】
すると、板幅圧下量ΔＷは式（５）で表わされる。
ΔＷ＝Ｗ０−Ｗ１＝（Ｓ−Ｖ）ｘ ＋ΔＷｍｉｎ …（５）
従来は板幅に影響する因子として板幅圧下量ΔＷが用いられていたが、本発明においては以上の考察から導かれる式（５）に基き、目標板幅を調整することとした。
【００４４】
式（２）に基づいて、板幅変動を修正して長手方向の位置ｘによらず水平圧延後に一定の板幅Ｗｈを得るための最小板幅圧下量△Ｗｍｉｎと竪圧延機の圧下速度比Ｖを求める方法について説明する。
【００４５】
図４に示すように、幅戻り量Ｗｒは板幅圧下量ΔＷに比例し、式（６）で表わされる。
Ｗｒ ＝ａΔＷ ＋ｂ …（６）
ここで係数ａ、ｂに影響を及ぼす因子は発明者らの研究によれば以下のとおりである。
ａ：ｔ、Ｗ０、Ｄｅ、Ｔ、Ｓ、Ｖ
ｂ：ｔ、Δｔ、Ｗ１、Ｄｅ、Ｔ、Ｓ、Ｖ
式（５）と式（６）を、式（１）に代入すると式（７）を得る。
【００４６】

尚、式（７）を変形して得られる式（８）は、上述の式（２）に対応するものである。
【００４７】

そこで、式（７）において、水平圧延後の板幅Ｗｈが長手方向位置ｘによらず一定となるためには式（９）、（１０）が成立することが条件である。
【００４８】
｛Ｓ−（１−ａ）（Ｓ−Ｖ）｝＝ ０ …（９）
Ｗｈ−｛Ｗ０ｍｉｎ−（１−ａ）ΔＷｍｉｎ＋ｂ｝＝０ …（１０）
この式（９）、（１０）を変形して一般的な関数の形式で表現するとそれぞれ式（１１）、（１２）を得る。
【００４９】

このようにして求めた、最小板幅圧下量△Ｗｍｉｎによって竪圧延機の開度の最大値が決定され、竪圧延機の圧下速度比Ｖによって竪圧延機の開度変更方法が決定される。従って、これらによって板幅変動を修正するための竪圧延機の開度設定方法が決定される。
【００５０】
次に、板幅変動を修正する場合の手順を説明する。
本板幅変動修正方法では、熱間スラブ、粗バーあるいは板厚圧下プレス後の粗バーの板幅を板幅計測器で計測し、計測した板幅に基づいて長手方向の板幅変化率を算出する。そして、板幅変化率、スラブ寸法、スラブ温度、板厚圧下プレスの圧下条件、板幅圧下後の水平圧延条件に基づいて、竪圧延機のロール開度および板幅圧下速度を決定する。
【００５１】
まず板厚圧下プレスにより減厚された粗バーの板幅を、板厚圧下プレスの下流側に配置された板幅計測器により長手方向に連続的に測定する。そして、この測定結果に基づいて、板幅圧下前の板幅Ｗ０と板幅変化率Ｓを算出する。
【００５２】
次に板厚圧下プレスの圧下条件から、板厚圧下プレス後すなわち板幅圧下前の板厚ｔ０を得る。また加熱炉でのスラブの加熱条件および板厚圧下プレスの圧下条件等から板厚圧下プレス後の粗バーの温度Ｔ、水平圧延後の板厚ｔｈを得る。さらに操業データから竪圧延機および水平圧延機のロール径Ｄｅ、Ｄｈを得る。
【００５３】
そして、これらの情報と式（１１）より板幅変動を修正するための圧下速度比Ｖを計算し、圧下速度比Ｖと粗バーの搬送速度から竪圧延機の竪圧延機の圧下速度を計算する。また式（１１）で計算された圧下速度比Ｖと式（１１）の計算に使用した情報から式（１２）により最小板幅圧下量△Ｗｍｉｎを計算する。
【００５４】
以上の手順により、最小板幅圧下量から竪圧延機の初期開度が計算でき、また圧下速度比から竪圧延機の開閉圧下速度を決定することができる。即ち、圧下速度比Ｖにより振幅変動を修正し、ΔＷｍｉｎにより目標幅に合せ込み板幅の絶対値を決定することができる。
【００５５】
続いて、板幅予測式をもとに板厚圧下プレス後の板幅変動を修正する実験を行った。板幅変動量約２０ｍｍ、板幅変動長さ約３００ｍｍの板幅変動がある板厚９０ｍｍの熱間鋼を板幅予測式に基づいて水平圧延によって板幅変動が修正されるように最大圧下量４０ｍｍの竪圧延を行い、圧下量３０ｍｍの水平圧延を行った。
【００５６】
図６は、粗バーの長手方向のある一部分における竪圧延前、竪圧延後、水平圧延後の長手方向板幅プロファイルを示す図である。水平圧延後は板厚減少分長さが長くなるが、図６では比較しやすいように板厚減少分を計算で割り戻し、竪圧延前後と並べて表示した。竪圧延前に約２０ｍｍあった板幅変動は水平圧延後１ｍｍ以下に修正され、この予測式により歩留まりが大きく向上することが確認された。
【００５７】
本実施の形態では、板幅圧下条件と水平圧延条件から水平圧延後の板幅を予測し、この予測に基づいて水平圧延後に板幅変動が修正されるように板幅変動に応じて竪圧延機のロール開度を変更している。
【００５８】
修正すべき板幅変動形状を予め板幅計測器により測定しているため、プレスサイクルやプレスピッチなどの板厚圧下プレスの圧下条件の変化、スラブあるいは板厚圧下プレス後の粗バーの温度変化によって長手方向の板幅変動の周期が変化した場合であっても、高い精度で板幅変動を修正することができる。
【００５９】
尚、本実施の形態では、粗バーの板幅変動を修正するための竪圧延機のロール開度の設定方法について述べたが、本発明はこの実施形態に限定されず、熱間スラブの長手方向の板幅変動を修正する場合においても同様に適用することができる。
【００６０】
続いて、本発明の板幅変動修正方法の実施例について説明する。
図７は、本発明の板幅変動修正方法が適用される設備構成を示す図である。
【００６１】
連続鋳造設備１あるいは加熱炉２から搬送された板厚３００ｍｍ以下、板幅５００〜２５００ｍｍのスラブ１１は板幅圧下プレス３により板幅方向に圧下調整された後、板厚圧下プレス４により板厚方向に圧下されて板厚１００ｍｍ以下の粗バー１２に成形される。
【００６２】
粗バー１２の幅端部には波形の板幅変動が生ずるが、この板幅変動は板厚圧下プレスの下流側に配置された板幅計測器５により計測される。板幅計測器５の計測（サンプリング）周期は、例えば板幅変動長さが５００ｍｍ、粗バーの搬送速度を３０ｍ／ｍｉｎとすると最低でも０、５秒以下、好ましくは０．１秒以下である。計測された板幅情報は制御装置６に送られ板幅変化率が計算され、さらに上述した板幅予測式にもとづき竪圧延機７の初期開度および開閉圧下速度が設定される。
【００６３】
竪圧延機７により板幅圧下された粗バー１２はその後水平圧延機８によって板厚８０ｍｍ以下に減厚され、さらに次工程で種々の加工および冷却が行われ熱間鋼帯として巻き取られる。
【００６４】
なお図７では板厚圧下プレス４の前の板幅調整手段を板幅圧下プレス３としたが、この実施形態に限定されずＶＳＢ（バーティカルスケールブレーカー）等の竪圧延機を用いて構成しても良い。
【００６５】
なお水平圧延機８の下流側に板幅計測器５を設置し、水平圧延後の長手方向の板幅を制御装置６にフィードバックし、竪圧延機７のロール開度および圧下速度を修正することにより、さらに板幅精度を向上させることができる。
【００６６】
また板厚圧下プレス４の下流側に配置され、粗バーの幅圧下を行う竪圧延機７のロールにカリバーとよばれる孔型を有するロールを用いても良い。
【００６７】
本実施の形態によれば熱間スラブや粗バーの板幅変動の修正が効果的に行え、熱間鋼帯の製造を歩留り良く行うことが可能になる。
【００６８】
【発明の効果】
以上説明したように、本発明によれば鋼帯の長手方向の板幅変動や板厚変動が高い精度で修正された熱間鋼帯を製造することができる。
【図面の簡単な説明】
【図１】板幅変動修正方法が適用される粗バーの板幅変動を示す図。
【図２】板幅変化率の定義を示す図。
【図３】板幅変動及び圧下パターンによる接触弧長を示す模式図。
【図４】板幅圧下量と幅戻り量の関係を示す図。
【図５】各諸量の関係を示す図。
【図６】本発明に係る板幅予測式を用いて板幅変動を修正した結果を示す図。
【図７】本発明の板幅変動修正方法が適用される設備構成を示す図。
【符号の説明】
１…連続鋳造設備
２…加熱炉
３…板幅圧下プレス
４…板厚圧下プレス
５…板幅計測器
６…制御装置
７…竪圧延機
８…水平圧延機
１１…スラブ
１２…粗バー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a hot steel strip, and more particularly, to a method of manufacturing a hot steel strip with a corrected width variation.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a hot strip manufacturing technology has been devised in which a strip thickness reduction press is arranged in a row of hot steel strip manufacturing equipment, and a slab is reduced in pressure in the strip thickness direction to manufacture a hot strip.
[0003]
In the thickness reduction press used in the present technology, a large reduction amount can be obtained in one pass as compared with a conventional roll rolling mill, and one press has a capability of a plurality of rough rolling mills. For this reason, there is an advantage that the equipment cost can be reduced, and the equipment row is shortened to apply a large pressure reduction, so that the temperature drop of the slab, the rough bar and the hot steel strip is small.
[0004]
In addition, the die used in the thickness reduction press repeats contact and separation with the slab, so the contact time with the slab is short, and the roll is not exposed to high temperature and high load for as long as a roll, so the die has less fatigue. There are benefits too.
[0005]
However, in the thickness reduction press, the reduction of the slab is not continuous as in a rolling mill, but is intermittent. Therefore, depending on the press cycle, the “plate width variation length” as shown in FIG. A vertically symmetrical sheet width fluctuation of the width fluctuation amount of 1 to 25 mm with respect to the sheet center line in the rolling direction as a symmetric axis is generated. The “plate width variation length” refers to one unit length of the plate width variation that periodically fluctuates in the longitudinal direction.
[0006]
If the strip width is not constant in the longitudinal direction, the strip width end is usually trimmed in a later step to obtain a steel strip having a constant strip width. However, in this trimming, trimming is performed in the longitudinal direction in accordance with the minimum plate width. Therefore, when the plate width variation, which is the amount of change in the plate width, is large, the trim margin becomes large and the yield decreases. Therefore, it is desired to make a correction so as to minimize the amount of the periodic plate width fluctuation in the longitudinal direction.
[0007]
Conventionally, with respect to such a plate width fluctuation in the longitudinal direction, in the disclosed technology, a vertical rolling mill and a horizontal rolling mill are provided on the downstream side of the plate thickness reduction press to correct the plate width fluctuation. (For example, see Patent Document 1).
[0008]
In addition, there is also a method in which a width reduction press and a horizontal rolling mill are provided downstream of the thickness reduction press to correct variations in width (for example, see Patent Document 2).
[0009]
The method of correcting the plate width fluctuation shown in Patent Document 2 will be described below. First, the opening of the sheet width reduction press is set so that the sheet width after horizontal rolling becomes a desired sheet width (step 1). However, even if the sheet width reduction press is performed with the opening set to a desired sheet width, the desired sheet width cannot be obtained because of the width return that occurs during horizontal rolling, which is a subsequent step. The width return is affected by the material, dimensions, and temperature of the slab, the amount of reduction in the thickness reduction press, the feed speed of the slab, and the target width of the slab. Conditions that affect this width return are referred to as initial conditions.
[0010]
The controller calculates the opening degree of the plate width reduction press from these input initial conditions (step 2). Then, the opening degree is instructed to the plate width reduction press (step 3).
[0011]
The sheet width reduction press performs the sheet width reduction at this opening, and thereafter, rolling is performed by a horizontal rolling mill. The width of the slab rolled by the horizontal rolling mill is measured by a strip width measuring instrument installed downstream of the horizontal rolling mill. The board width measurement value is sent to the control device (step 4). The controller calculates the difference between the desired plate width and the measured plate width (step 5), and calculates the correct opening of the plate width reduction press from this difference and the initial conditions (step 6). By repeating steps 3 to 6, a desired target plate width is obtained.
[0012]
In addition to this, a method of correcting a sheet width variation which cancels a sheet width variation caused by a thickness reduction by a thickness reduction press by performing a preforming in which a slab is subjected to a sheet width variation by a vertical rolling mill or a sheet width reduction press in advance. (See, for example, Patent Document 3).
[0013]
[Patent Document 1]
JP-A-61-235002
[Patent Document 2]
JP 2001-9502 A
[Patent Document 3]
JP 2000-254708 A
[Problems to be solved by the invention]
By the way, when correcting the fluctuation of the strip width in the longitudinal direction, if the rolling is performed while the roll opening of the vertical rolling mill is constant, a dog bone is formed at the end of the strip width of the rough bar which is the steel strip after the vertical rolling. A locally thickened portion called a plate thickness is formed. The reduction amount of the wide part is large and the reduction amount of the narrow part is small, but the larger the reduction amount of the width is, the larger the dog bone becomes. The dogbone in the wide part becomes large, and conversely, the dogbone in the narrow part becomes small. As a result, thickness variations occur in both the width direction and the longitudinal direction.
[0017]
Horizontal rolling must be performed to flatten the dog bone and produce a hot steel strip with no thickness variation.However, if horizontal rolling is performed on a portion where a large dog bone is present, the width of the strip after horizontal rolling will return. Conversely, when horizontal rolling is performed in a portion where a small dog bone is present, the amount of return of the sheet width after horizontal rolling becomes small, and a sheet width fluctuation occurs. That is, even if the width reduction press and the horizontal rolling mill are provided on the downstream side of the thickness reduction press, if the horizontal rolling is performed while the roll opening degree of the vertical rolling mill is kept constant, the width variation of the width may occur. Is not modified.
[0018]
However, Patent Document 1 does not clearly describe a method of measuring a sheet width variation generated by a sheet thickness reduction press or a method of setting a roll opening of a vertical rolling mill. For this reason, it is possible that the sheet width reduction is performed by setting the roll opening of the vertical rolling mill so as to promote the sheet width fluctuation, and conversely, the sheet width fluctuation may be increased.
[0019]
Further, Patent Document 2 does not clarify how to change the opening degree of the die of the plate width reduction press with respect to the plate width fluctuation that periodically exists in the longitudinal direction. Further, since a method of obtaining a desired plate width by repeating Steps 3 to 6 is employed, a target plate width may not be obtained for a predetermined length from the leading end of the coarse bar.
[0020]
In the technology described in Patent Document 3, the sheet width is reduced before the sheet thickness reduction press. Here, when examining this preforming, assuming that the slab having a thickness of 250 mm is reduced to 90 mm by a thickness reduction press and the length of the width variation of the slab is 200 mm, the length of the width variation to be preformed is: 72 mm. If the rolling width is reduced by a rolling mill, if the rolling width is reduced to 20 mm and the width of the rolling width is changed to 72 mm, the roll radius used for rolling is reduced to 70 mm or less from a geometrical relationship. Has a very small roll diameter. When a roll having a small diameter is used, high-precision rolling cannot be performed because the roll is bent by the rolling load. For this reason, a backup roll is required to reinforce the roll that performs the reduction, which causes a problem that the rolling equipment becomes large and the equipment cost increases.
[0021]
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a method for manufacturing a hot steel strip in which a width variation and a thickness variation in a longitudinal direction of a steel strip are corrected with high accuracy. I do.
[0022]
[Means for Solving the Problems]
The present invention for solving the above problems, the hot slab or coarse bar, by setting the roll opening degree of the vertical rolling mill based on the sheet width change rate which is the sheet width change per unit length in the longitudinal direction. This is a method for producing a hot steel strip in which the sheet width is reduced.
[0023]
Further, the present invention provides the method for manufacturing a hot steel strip according to the above-described invention, wherein the hot slab or the rough bar has a sheet width change rate, which is a sheet width change per unit length in a longitudinal direction, and a sheet width reduction. A method of manufacturing a hot steel strip in which a roll opening of the vertical rolling mill is set based on a rolling speed ratio which is a ratio of a rolling speed of the vertical rolling mill to a conveying speed in a process to reduce a sheet width. .
[0024]
Further, the present invention provides the method for manufacturing a hot steel strip according to the above-described invention, wherein the sheet width of the hot slab or the rough bar is measured in advance by a sheet width measuring unit, and the sheet width change rate is calculated from the measured sheet width. Is a method for manufacturing a hot steel strip.
[0025]
Further, the present invention is the method for producing a hot steel strip according to the above-described invention, wherein the coarse bar is a coarse bar after a thickness reduction by a group of rough rolling mills.
[0026]
Further, the present invention is the method for manufacturing a hot steel strip according to the above-described invention, wherein the rough bar is a rough bar after reducing the thickness by a thickness reduction press.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
A description will be given of a method of correcting a width variation of a sheet used in the method of manufacturing a hot steel strip according to the present invention.
FIG. 1 is a diagram showing a plate width variation of a rough bar to which the plate width variation correction method is applied. Assumed plate width fluctuations are a plate width fluctuation length of 100 mm to 20 m and a plate width fluctuation amount of 1 to 25 mm, and the coarse bar has a symmetrical shape with respect to the center line. It should be noted that the plate width change rate is defined as a change in the plate width per unit length in the longitudinal direction as shown in FIG.
[0028]
As described above, in order to correct the variation in the sheet width, it is necessary to predict the sheet width after the horizontal rolling from the sheet width reduction conditions and the horizontal rolling conditions. Then, based on this prediction method, it is possible to change the roll opening of the vertical rolling mill so that the sheet width fluctuation is corrected after horizontal rolling.
[0029]
The following factors are known as factors affecting the sheet width after the sheet width reduction and subsequent horizontal rolling are performed. That is, sheet thickness: t, sheet width: W, sheet width reduction: ΔW, sheet thickness reduction: Δt, vertical rolling mill roll diameter: De, horizontal rolling mill roll diameter: Dh, coarse bar temperature: T It is.
[0030]
The reason why the roll diameter of the vertical rolling mill affects the sheet width is that the length of contact between the roll of the vertical rolling mill and the rough bar during rolling (hereinafter referred to as the contact arc length) affects the shape of the dog bone. is there. That is, the larger the roll diameter is, the larger the contact arc length is. However, as the contact arc length is larger, the thickest part of the dog bone is closer to the center in the plate width direction and the height is also smaller. In addition, the range in which the dog bone exists is also widened. When the rough bar on which such a dog bone is formed is horizontally rolled, the width spread during the horizontal rolling is relatively small.
[0031]
Until now, in the method of predicting the sheet width after performing the sheet width reduction and the subsequent horizontal rolling, the sheet width fluctuation shape of the rough bar before the sheet width reduction and the process of the sheet width reduction have not been considered.
[0032]
The inventors of the present invention have conducted extensive studies on the deformation of the sheet width and their relationship, and as a result, the rate of change in the sheet width in the longitudinal direction representing the sheet width fluctuation shape of the rough bar before the sheet width reduction, and the longitudinal direction representing the process of the sheet width reduction. It has been found that the rolling speed of the vertical rolling mill with respect to the transport speed of the rough bar (hereinafter, referred to as “rolling speed ratio”) affects the width of the sheet after horizontal rolling. The details are shown below.
[0033]
FIG. 3 is a schematic diagram showing a contact arc length based on a plate width variation and a rolling-down pattern. FIG. 3A shows the contact arc length when the plate width change rate and the reduction speed ratio are zero. As shown in FIG. 3 (B), the sheet width increases toward the rear end in the longitudinal direction (the sheet width change rate is assumed to be positive), and the roll opening of the vertical rolling mill decreases (when the rolling speed is positive). In this case, the contact arc length increases. Conversely, as shown in FIG. 3 (C), when the sheet width increases toward the rear end in the longitudinal direction and the roll opening of the vertical rolling mill increases, the contact arc length decreases. Therefore, as described above, it was concluded that since the contact arc length affects the shape of the dog bone, the rate of change in the strip width in the longitudinal direction and the reduction speed ratio affect the strip width after horizontal rolling.
[0034]
Therefore, the inventors conducted experiments to verify this theory. In the experiment, using a vertical rolling model tester and a horizontal rolling model tester, pure lead having a thickness of 11 mm, a width of 140 to 160 mm, and a length of 400 mm was reduced by 0.1 to 10 mm with a vertical rolling model tester. And horizontal rolling was performed with a rolling reduction of 3.5 mm using a horizontal rolling model tester. At that time, the effect of the sheet width change rate and the reduction speed ratio on the relationship between the sheet width reduction amount and the width return amount was investigated by conducting experiments with variously changing the sheet width change rate and the reduction speed ratio.
[0035]
FIG. 4 is a diagram showing the relationship between the sheet width reduction amount and the width return amount obtained from the experiment. Note that the width return amount is a value obtained by subtracting the sheet width after the sheet width reduction from the sheet width after the horizontal rolling.
[0036]
The plate width after the horizontal rolling is in a relationship represented by the formula (1) from the plate width before the plate width reduction, the plate width reduction amount, and the width return amount.
Wh = W0− △ W + Wr (1)
Here, Wh: strip width after horizontal rolling, W0: strip width before strip width reduction ΔW: strip width reduction amount, Wr: width return amount Note that the above-described factors and strip width affecting strip width after horizontal rolling. The rate of change and the reduction speed ratio relate to the Wr term in the above equation.
[0037]
It is clear from the experimental results shown in FIG. 4 that the width change rate and the reduction speed ratio influence the width return amount. Therefore, it has been proved that it is necessary to consider the sheet width change rate and the rolling reduction ratio in order to predict the sheet width after horizontal rolling.
[0038]
The present inventors further studied in detail the effects of the sheet width before vertical rolling, the sheet thickness before vertical rolling, the roll diameter of the vertical rolling mill, the roll diameter of the horizontal rolling mill, and the coarse bar temperature on the width return amount. As a result, the plate width prediction formula after horizontal rolling represented by the formula (2) was completed.
[0039]

Here, W0: the sheet width before the sheet width reduction, Wh: the sheet width after the horizontal rolling,
W0min: minimum width before reduction of width ΔWmin: minimum reduction amount of width, t0: thickness before reduction of width,
th: thickness after horizontal rolling, De: vertical rolling mill roll diameter,
Dh: roll diameter of horizontal rolling mill, T: coarse bar temperature,
S: Strip width change rate, V: Rolling speed ratio, x: Coarse bar longitudinal position position From formula (2), the strip width after horizontal rolling in consideration of the strip width change rate and the rolling speed ratio can be predicted. Here, a description will be given of the fact that various quantities different from those of the conventional sheet width prediction equation are used in equation (2).
[0040]
Assuming that the sheet width before the sheet width reduction is W0 and the sheet width after the sheet width reduction is W1, if there is no sheet width fluctuation, W0 and W1 are constant regardless of the longitudinal direction, but there is sheet width fluctuation. In this case, if the longitudinal position of the coarse bar is x, W0 and W1 are represented as functions of x. Therefore, W0 and W1 are represented by the sheet width change rate S, the reduction speed ratio V, the minimum sheet width W0min before the sheet width reduction, and the minimum sheet width reduction amount by ΔWmin.
[0041]
FIG. 5 is a diagram showing the relationship between various quantities.
W0 and W1 are represented by equations (3) and (4).
[0042]
W0 = Sx + W0min (3)
W1 = Vx + (W0min−ΔWmin) (4)
Here, the plate width change rate S and the reduction speed ratio V approximate the shape change as a linear function of x as shown in FIG.
[0043]
Then, the sheet width reduction amount ΔW is expressed by Expression (5).
ΔW = W0−W1 = (S−V) x + ΔWmin (5)
Conventionally, the sheet width reduction amount ΔW has been used as a factor affecting the sheet width. However, in the present invention, the target sheet width is adjusted based on Expression (5) derived from the above considerations.
[0044]
Based on equation (2), the minimum sheet width reduction amount △ Wmin and the reduction speed ratio of the vertical rolling mill for correcting the sheet width fluctuation and obtaining a constant sheet width Wh after horizontal rolling regardless of the position x in the longitudinal direction. A method for obtaining V will be described.
[0045]
As shown in FIG. 4, the width return amount Wr is proportional to the plate width reduction amount ΔW and is expressed by equation (6).
Wr = aΔW + b (6)
Here, the factors affecting the coefficients a and b are as follows according to the study of the inventors.
a: t, W0, De, T, S, V
b: t, Δt, W1, De, T, S, V
By substituting Equations (5) and (6) into Equation (1), Equation (7) is obtained.
[0046]

Equation (8) obtained by modifying equation (7) corresponds to equation (2) described above.
[0047]

Therefore, in the equation (7), it is a condition that the equations (9) and (10) are satisfied in order for the plate width Wh after the horizontal rolling to be constant regardless of the longitudinal position x.
[0048]
{S- (1-a) (SV)} = 0 (9)
Wh− {W0min− (1−a) ΔWmin + b} = 0 (10)
When Expressions (9) and (10) are modified and expressed in the form of a general function, Expressions (11) and (12) are obtained, respectively.
[0049]

The maximum value of the opening of the vertical rolling mill is determined by the minimum sheet width reduction amount △ Wmin thus determined, and the method of changing the opening of the vertical rolling mill is determined by the rolling speed ratio V of the vertical rolling mill. Accordingly, a method for setting the opening of the vertical rolling mill for correcting the variation in the sheet width is determined based on these.
[0050]
Next, a description will be given of a procedure for correcting a plate width variation.
In this method, the width of a hot slab, a rough bar or a rough bar after a thickness reduction press is measured with a width measuring instrument, and the longitudinal width change rate is determined based on the measured width. calculate. Then, the roll opening degree and the sheet width reduction speed of the vertical rolling mill are determined based on the sheet width change rate, the slab size, the slab temperature, the rolling conditions of the sheet thickness reduction press, and the horizontal rolling conditions after the reduction of the sheet width.
[0051]
First, the width of the coarse bar reduced in thickness by the thickness reduction press is continuously measured in the longitudinal direction by a width measuring instrument arranged downstream of the thickness reduction press. Then, based on the measurement results, the sheet width W0 and the sheet width change rate S before the sheet width reduction are calculated.
[0052]
Next, the sheet thickness t0 after the sheet thickness reduction press, that is, before the sheet width reduction is obtained from the reduction conditions of the sheet thickness reduction press. Further, the temperature T of the rough bar after the thickness reduction press and the thickness th after the horizontal rolling are obtained from the heating conditions of the slab in the heating furnace and the reduction conditions of the thickness reduction press. Further, roll diameters De and Dh of the vertical rolling mill and the horizontal rolling mill are obtained from the operation data.
[0053]
Then, the reduction speed ratio V for correcting the sheet width variation is calculated from the information and the equation (11), and the reduction speed of the vertical rolling mill of the vertical rolling mill is calculated from the reduction speed ratio V and the conveying speed of the rough bar. I do. Further, the minimum sheet width reduction amount で Wmin is calculated by the equation (12) from the reduction speed ratio V calculated by the equation (11) and the information used in the calculation of the equation (11).
[0054]
By the above procedure, the initial opening of the vertical rolling mill can be calculated from the minimum sheet width reduction amount, and the opening / closing reduction speed of the vertical rolling mill can be determined from the reduction speed ratio. That is, the amplitude fluctuation can be corrected by the reduction speed ratio V, and the absolute value of the plate width can be determined to match the target width by ΔWmin.
[0055]
Subsequently, an experiment was performed to correct the sheet width fluctuation after the sheet thickness reduction press based on the sheet width prediction formula. The maximum rolling amount of hot steel with a thickness of 90 mm, which has a width variation of about 20 mm and a width variation of about 300 mm, is corrected by horizontal rolling of a 90 mm thick steel sheet based on the strip width prediction formula. A vertical rolling of 40 mm was performed, and a horizontal rolling of a rolling reduction of 30 mm was performed.
[0056]
FIG. 6 is a view showing a longitudinal plate width profile before vertical rolling, after vertical rolling, and after horizontal rolling in a part of the coarse bar in the longitudinal direction. After the horizontal rolling, the length of the sheet thickness decrease becomes longer, but in FIG. 6, the sheet thickness decrease is divided back by calculation and displayed side by side before and after the vertical rolling for easy comparison. The fluctuation of the sheet width, which was about 20 mm before the vertical rolling, was corrected to 1 mm or less after the horizontal rolling, and it was confirmed that the yield was greatly improved by this prediction formula.
[0057]
In the present embodiment, the strip width after horizontal rolling is predicted from the strip width reduction conditions and the horizontal rolling conditions, and the vertical rolling is performed according to the strip width variation so that the strip width variation is corrected after the horizontal rolling based on the prediction. The roll opening of the machine has been changed.
[0058]
Since the width variation shape to be corrected is measured in advance by a width measurement device, changes in the rolling conditions of the thickness reduction press, such as the press cycle and press pitch, and the temperature change of the slab or the coarse bar after the thickness reduction press Thus, even if the period of the plate width fluctuation in the longitudinal direction changes, the plate width fluctuation can be corrected with high accuracy.
[0059]
In this embodiment, the method of setting the roll opening of the vertical rolling mill to correct the variation in the width of the coarse bar has been described. However, the present invention is not limited to this embodiment, and the length of the hot slab may be reduced. The same can be applied to the case of correcting the plate width variation in the direction.
[0060]
Next, an embodiment of the method of correcting a width variation of the present invention will be described.
FIG. 7 is a diagram showing a facility configuration to which the method for correcting a plate width variation according to the present invention is applied.
[0061]
The slab 11 having a thickness of 300 mm or less and a width of 500 to 2500 mm conveyed from the continuous casting equipment 1 or the heating furnace 2 is adjusted in the sheet width direction by the sheet width reduction press 3, and then the thickness is reduced by the thickness reduction press 4. It is pressed down in the direction and is formed into a rough bar 12 having a plate thickness of 100 mm or less.
[0062]
A corrugated plate width variation occurs at the width end of the rough bar 12, and the plate width variation is measured by the plate width measuring device 5 arranged downstream of the plate thickness reduction press. The measurement (sampling) cycle of the sheet width measuring device 5 is, for example, at least 0, 5 seconds or less, and preferably 0.1 seconds or less when the sheet width fluctuation length is 500 mm and the conveying speed of the coarse bar is 30 m / min. . The measured strip width information is sent to the controller 6 to calculate the strip width change rate, and based on the above-described strip width prediction formula, the initial opening degree and the opening / closing reduction speed of the vertical rolling mill 7 are set.
[0063]
The coarse bar 12 whose width has been reduced by the vertical rolling mill 7 is then reduced to a thickness of 80 mm or less by the horizontal rolling mill 8, and further processed and cooled in the next step to be wound as a hot steel strip.
[0064]
In FIG. 7, the width adjusting means before the thickness reduction press 4 is the width reduction press 3. However, the invention is not limited to this embodiment, and is configured using a vertical rolling mill such as a VSB (vertical scale breaker). Is also good.
[0065]
It is to be noted that the strip width measuring device 5 is installed downstream of the horizontal rolling mill 8 and the strip width in the longitudinal direction after the horizontal rolling is fed back to the control device 6 to correct the roll opening and the rolling speed of the vertical rolling mill 7. Thereby, the plate width accuracy can be further improved.
[0066]
Further, a roll having a hole type called a caliber may be used as a roll of the vertical rolling mill 7 which is disposed on the downstream side of the thickness reduction press 4 and reduces the width of the coarse bar.
[0067]
According to the present embodiment, it is possible to effectively correct the variation of the plate width of the hot slab and the rough bar, and it is possible to manufacture the hot steel strip with a high yield.
[0068]
【The invention's effect】
As described above, according to the present invention, it is possible to manufacture a hot steel strip in which the variation in the width and thickness of the steel strip in the longitudinal direction is corrected with high accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram showing a plate width variation of a rough bar to which a plate width variation correction method is applied.
FIG. 2 is a diagram showing a definition of a sheet width change rate.
FIG. 3 is a schematic diagram showing a contact arc length based on a plate width variation and a rolling-down pattern.
FIG. 4 is a diagram showing a relationship between a sheet width reduction amount and a width return amount.
FIG. 5 is a diagram showing the relationship between various quantities.
FIG. 6 is a view showing a result of correcting a sheet width fluctuation using the sheet width prediction formula according to the present invention.
FIG. 7 is a diagram showing an equipment configuration to which a sheet width variation correction method according to the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Continuous casting equipment 2 ... Heating furnace 3 ... Strip width reduction press 4 ... Strip thickness reduction press 5 ... Strip width measuring device 6 ... Control device 7 ... Vertical rolling mill 8 ... Horizontal rolling mill 11 ... Slab 12 ... Coarse bar

Claims (5)

Production of hot steel slabs cast by continuous casting equipment, or hot strips in which the rough bars after the slabs are reduced in thickness are reduced in the sheet width direction by a vertical rolling mill and then reduced in the sheet thickness direction by a horizontal rolling mill. In the method,
The hot slab or the coarse bar is characterized in that the width of the vertical rolling mill is set based on a plate width change rate, which is a plate width change per unit length in a longitudinal direction, and the plate width is reduced. Method of manufacturing hot steel strip. Production of hot steel slabs cast by continuous casting equipment, or hot strips in which the rough bars after the slabs are reduced in thickness are reduced in the sheet width direction by a vertical rolling mill and then reduced in the sheet thickness direction by a horizontal rolling mill. In the method,
The hot slab or the rough bar, a sheet width change rate which is a sheet width change per unit length in a longitudinal direction, and a reduction which is a ratio of a reduction speed of the vertical rolling mill to a conveyance speed in a width reduction process. A method for producing a hot steel strip, comprising setting a roll opening of the vertical rolling mill based on a speed ratio and reducing a sheet width. The plate width of the hot slab or the coarse bar is measured in advance by a plate width measuring unit,
The method for manufacturing a hot steel strip according to claim 1, wherein the plate width change rate is calculated from the measured plate width. The method for manufacturing a hot steel strip according to any one of claims 1 to 3, wherein the rough bar is a rough bar after a thickness reduction by a rough rolling mill group. The method for manufacturing a hot steel strip according to any one of claims 1 to 3, wherein the rough bar is a rough bar that has been reduced in thickness by a thickness reduction press.

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