JPH08309401A - Working method for slab and front and rear ends of slab - Google Patents

Abstract

PURPOSE: To prevent the front end part of a slab from becoming a tongue shape and the rear end part of the slab becoming a fish tail shape owing to rolling by forming respectively the front end part into a circular-arc concave shape with its center recessed more than a side part and the rear end part in a circular-arc convex shape with its center projected more than the side part. CONSTITUTION: A continuous slab 2A obtained by a continuous casting, etc., is cut in a prescribed dimension by a torch cutter 3 before a hot rolling, and is formed to a slab 2B with prescribed dimensions. Cutting 4 by the torch cutter 3 is performed by moving the torch cutter 3 in a circular-arc shape projecting in the rear direction. The rear end part R of the preceding slab 2B with predetermined dimensions is formed in a circular-arc convex shape with its center projected more than the side part, and the front end part F of the succeeding slab 2B with predetermined dimensions is formed in a circular-arc concave shape with its center part recessed more than the side part. These are simultaneously formed by one cutting line 4, and the preceding slab 2B with predetermined dimensions and the succeeding slab 2B with predetermined dimensions are separated. The slab 2B with predetermined dimensions after cutting is rolled in the width direction by vertical rolls 5, and is rolled in the thickness direction by horizontal rolls 6 to become a rough bar 2C, then fed in a finish rolling part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab before hot rolling and a slab front and rear end processing method.

[0002]

2. Description of the Related Art Generally, a slab 2 obtained by continuous casting or the like.
As shown in FIG. 3, A is a torch cutter 3 before hot rolling.
Is cut to a desired size 4 to form a fixed-size slab 2B, which is rolled in the width direction by a rolling mill having a vertical roll 5, and rolled in a thickness direction (horizontal direction) by a rolling mill having a horizontal roll 6, It is formed to the target width and thickness.

Width-rolled and thickness-rolled rough bar 2
The cropped shape at the front and rear ends of C has a fishtail shape at the rear end R, and has a tongue shape at the front end F (which occurs more frequently than the fishtail shape in relation to the width-killing amount and the like). Conventionally, in order to suppress the fishtail shape and the tongue shape, it has been proposed to process the front and rear end shapes before hot rolling before rolling.

For example, in the technique disclosed in Japanese Patent Laid-Open No. 55-153602, the corners of the four corners of the initial rectangular slab are crushed by a vertical roll to form a cornerless slab, which is disclosed in Japanese Patent Laid-Open No. 55-48401. In the technique disclosed in Japanese Patent Laid-Open No. 53-12257, the slab is chamfered at the four corners of a rectangular cross section. are doing.

[0005]

The above-mentioned conventional techniques are all
Before rolling the slab, a special process is required to process the front and rear ends of the slab, which lowers productivity and requires the introduction of press equipment etc. before the rolling mill, and the yield for chamfering the four corners. It has the problem of lowering. Further, it is difficult to suppress the crop shape from becoming a tongue shape.

According to the present invention, the front end portion of the slab is formed into an arcuate concave shape in which the center is recessed from the side portion and the rear end portion is formed into an arcuate convex shape in which the center portion is protruded from the side portion before hot rolling. An object of the present invention is to provide a slab and a slab front-and-rear end processing method in which the front-and-rear end can be easily and easily processed without lowering productivity and yield.

[0007]

A first specific means for solving the problems in the present invention is to form an arcuate concave shape in which the front end portion is recessed in the center from the side portion and the rear end portion is protruded in the center from the side portion. That is, they are each formed in a circular arc convex shape. The second specific means for solving the problem in the present invention is to cut the slab into a rearward projecting arc shape with a torch cutter before hot rolling.

A third specific means for solving the problem in the present invention is a slab front and rear end processing method in which a continuously cast slab is cut to a required dimension before hot rolling, in a widthwise rolling in a rough rolling step. And the amount of crop shape deformation at the front and rear ends of the rough bar formed by thickness direction rolling is calculated or obtained in advance from actual results, and the front and rear ends of the slab are cut into a shape obtained by subtracting the amount of crop shape deformation from the target crop shape. .

[0009]

[Operation] The amount of crop shape deformation at the front and rear ends of the rough bar formed by the width direction rolling and the thickness direction rolling in the rough rolling process is calculated or obtained in advance from the actual results, and the obtained crop shape deformation amount is the target crop. The torch cutter 3 cuts the front and rear ends of the slab 2A before hot rolling into a shape subtracted from the shape.

Since the amount of deformation of the crop shape becomes a tongue shape at the front end of the slab and a fishtail shape at the rear end,
The front and rear end cutting shape of the slab 2B before hot rolling from which this is subtracted is an arc concave shape in which the front end portion F has a recessed center from the side portion,
The rear end R has an arcuate convex shape with the center protruding from the side,
The torch cutter 3 only moves in an arc shape, and the slab 2B
Cut the front and rear ends of the at the same time. Slab after cutting 2
When B is rolled, the uneven shape of the arc and the amount of deformation are substantially offset,
The target crop shape is approximately right angle to the front-back direction.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a continuous (long) slab 2A obtained by continuous casting or the like is cut into a required size by a torch cutter 3 before hot rolling to form a fixed size slab 2B.

The cutting 4 by the torch cutter 3 is performed by moving the torch cutter 3 in a rearward projecting arcuate shape and cutting it. The rear end portion R of the preceding slab 2B has an arcuate convex shape whose center projects from the side portion. In addition, the front end portion F of the trailing slab 2B is simultaneously formed into a circular arc concave shape with the center depressed from the side portion by one cutting line, and the leading slab 2B and trailing slab 2B having a certain dimension are formed. And separate.

The slabs 2B after cutting are supplied to a heating furnace for heating and soaking, then extracted from the heating furnace and loaded into the rough rolling section of the hot rolling mill, and then the widthwise direction is applied by the vertical rolls 5. Then, it is rolled in the thickness direction by the horizontal rolls 6 to become the rough bar 2C, and is further charged into the finish rolling section.
The front and rear ends F, R of the rough bar 2C rolled by the rough rolling section
When the front end F is deformed to become a tongue, the cropped shape is deformed from the arcuate concave shape to a fishtail shape close to a right angle to the front-rear direction, and the rear end R
Is deformed to become a fishtail shape,
The tongue shape is deformed from the arcuate convex shape to be close to a right angle with respect to the front-rear direction, and by finishing rolling, the tongue shape is further made to be closer to a right angle.

The front and rear end portions F and R of the constant-size slab 2B cut and formed by the torch cutter 3 have arc-shaped crops at the front and rear ends of the rough bar formed by width-direction rolling and thickness-direction rolling in the rough rolling step. The amount of shape deformation can be calculated or obtained in advance from actual results. That is, in the case of obtaining general mild steel from the actual data, the conventional slab 2B having the front and rear end portions at right angles to the front and rear direction shown in FIG. 3 is obtained by width-direction rolling and thickness-direction rolling in the rough rolling process. Crop shape deformation amount PF, P at the front and rear ends of the rough bar 2C
As shown in FIG. 2, R is actually measured, and the measured value is plotted in correspondence with the width reduction amount. A large number of these are plotted to create a distribution chart, and trend lines α and β are drawn.

When controlling the crop shape, the crop shape deformation amount P corresponding to the target width reduction amount ΔW is read, and the concave amount of the arcuate concave shape of the front end portion F is subtracted (cancelled). (Dimension h) is determined. At the same time, the amount of depression of the front end F becomes the amount of protrusion (dimension h) of the arcuate convex shape of the rear end R. For example, slab width W = 955 mm,
For a general mild steel material having a width reduction ΔW = 24 mm, the depth h = 140 mm can be read from FIG. Width reduction Δ
For W, (slab width W1-finishing target width W2) was used.

When calculating the crop shape deformation amount by calculation,
Assuming that the cut shape is approximated by a quadratic curve, y = a · x ² , a = 4h / W ² where depth h = 140 mm and W = 955 mm
= 6.14 · 10 ⁻⁴ .

By making the cutting shape of the front and rear ends F, R of the slab 2B before rolling into a shape obtained by subtracting the amount of deformation of the crop shape from the desired (finished) crop shape after rolling,
During rolling, the front end portion F is deformed so that the central portion projects forward rather than the side portion to fill the recessed circular arc concave shape, and the rear end portion R projects the side portion more than the central portion. Then, the arc-shaped convex portion disappears, and the front and rear ends have a substantially linear shape with very few irregularities.

From the actual data, the shape of the front end portion F of the rough bar 2C can reduce the crop loss more like fishtail than the right angle in the front-rear direction, and the shape of the rear end portion R in the front-rear direction. The tanginess is better than the right angle so that the plate passing property is better. The front and rear crop shape deformation amounts PF and PR in the actual data are not the same. Therefore, when determining the shape of the cutting line 4, the prior material and the trailing material are compared with each other in the importance of crop loss reduction and stripability. Then, if the passing property of the preceding material is emphasized, the cutting line 4 is determined as the required rear end shape for the preceding material, and if the reduction of crop loss is emphasized, the cutting line 4 is Determine the required front end shape for the row material.

[0019]

According to the present invention described in detail above, the front end portion of the slab is formed into a circular arc concave shape in which the center is recessed from the side portions, and the rear end portion is formed into a circular arc convex shape in which the center is projected from the side portions. Therefore, it is possible to reduce the tongue shape at the front end portion and the fish tail shape at the rear end portion due to rolling.

Further, since the slab is cut into a rearward projecting arc shape by a torch cutter before the hot rolling, the slab which can reduce the front end tongue shape and the rear end fishtail shape by rolling can be manufactured with high productivity and yield. The front and rear ends can be easily and easily processed without decreasing Further, the amount of crop shape deformation at the front and rear ends of the rough bar formed by width direction rolling and thickness direction rolling in the rough rolling process is calculated or obtained in advance from the actual results, and the slab front and rear ends are changed from the target crop shape to the amount of crop shape deformation. Since it is cut into a shape that subtracts, it is possible to easily and easily make the front and rear ends of the slab after rolling into the desired crop shape without lowering productivity and yield, reducing crop loss and stabilizing stripability. It will also be possible to obtain.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a distribution map of crop shape deformation amounts.

FIG. 3 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

 2 Slab 2A Continuous slab 2B Sizing slab 2C Rough bar 3 Torch cutter 4 Cutting (line) 5 Vertical roll 6 Horizontal roll F Front end R Rear end

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Hirata 1 Kanazawa-machi, Kakogawa-shi, Hyogo Prefecture Kadogawa Works Kakogawa Works

Claims (3)

[Claims] 1. A slab characterized in that a front end portion is formed in an arcuate concave shape whose center is recessed from a side portion, and a rear end portion is formed in an arcuate convex shape whose center is protruded from a side portion. 2. A method for forming front and rear edges of a slab, which comprises cutting the slab into a rearward projecting arc shape with a torch cutter before hot rolling. 3. A slab front and rear end processing method for cutting a continuously cast slab into required dimensions before hot rolling, and a crop of front and rear ends of a rough bar formed by width-direction rolling and thickness-direction rolling in a rough rolling step. A slab front-end processing method, characterized in that the amount of shape deformation is calculated or obtained in advance from an actual result, and the front and rear ends of the slab are cut into a shape obtained by subtracting the amount of deformation of the crop shape from the target crop shape.