JPH081205A - Plate rolling method - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a rolling method for reducing a trimming width and improving a material yield by moving a seam flaw generated during rolling of a thick plate to an end portion of the plate width. With the goal. [Structure] In the rolling of a thick plate using a rolling mill having a device capable of changing the roll interval during rolling, the reduction amount is set at the tip of the rolled material 1 in the final pass or the final passes of tenter rolling. By gradually rolling the rolling material 1 at the rear end of the rolled material 1 while gradually increasing the reduction amount, a shape 3 that becomes thinner toward the end of the rolled material is rolled, and then finish rolling is performed. How to roll a plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling method for reducing a trimming width due to a seam flaw at the end of a plate width, which occurs when rolling a metal thick plate.

[0002]

2. Description of the Related Art In the rolling of thick metal plates (thick steel plates, etc.), bulge deformation occurs in which the side surface of the rolled material is convex. The bulge deformation portion contacts the roll surface as the rolling passes are repeated, and the corner portion of the slab enters the rolling surface to form a seam flaw. FIG. 4 is a diagram showing such a bulge deformation of the rolled material, and FIG. 5 is a diagram showing that the bulge deformation of the rolled material progresses and a seam flaw is generated. 4 and 5, 1 is a rolled material, 2 is a rolling roll, 6 is a corner portion of a slab, 7 is a bulge deformation portion, and 8 is a seam flaw. Here, the arrow in FIG. 4 indicates the direction in which the material flows. When the seam flaw 8 is generated, the seam flaw generation position to the width end of the plate are trimmed to obtain a product. Therefore, in order to improve the material yield, the position where the seam flaw 8 is generated should be moved to the width end of the plate as much as possible. is necessary.

As a conventional measure against this, an edger mill having a caliber roll is used to form a groove on the side surface of the rolled material 1 to induce a double bulge deformation on the side surface of the rolled material 1 during horizontal rolling, resulting in a seam flaw. A method of moving the generation position of 8 to the plate width end is performed. FIG. 6 is a diagram showing the deformation of the plate width end portion when the groove is formed on the side surface of the rolled material 1 and the rolled material 1 is rolled. In FIG. 6, the same parts as those in FIGS. In FIG. 6, 9 is a machined groove, and 10 is a bulge portion due to double bulge deformation.

[0004]

However, the above-mentioned prior art has the following problems. In the method using the above-mentioned edger mill, as shown in FIG. 6, large swelling occurs on the side surface of the rolled material. It is difficult to properly determine the side trimming width, because the depth of the flaw cannot be judged from the appearance of the burr. Actually, to avoid re-trimming,
The trimming width must be set in consideration of the allowance, which is not a practical solution to seam defects. Furthermore, it goes without saying that the installation of the edger mill is very expensive.

It is an object of the present invention to provide a rolling method capable of moving a seam flaw to a strip width end without causing the bulging due to the double bulge deformation of the side surface of the rolled material.

[0006]

The above-mentioned problems can be solved by the following means. In the rolling of a thick plate using a rolling mill having a device capable of changing the roll interval during rolling, in the final pass or the final few passes of tenter rolling, while gradually reducing the reduction amount at the tip of the rolled material, Further, at the rear end of the rolled material, rolling is performed while gradually reducing the rolling amount, so that a shape that becomes thinner toward the end of the rolled material is rolled, and then finish rolling is performed.

[0007]

Operation: In the rolling of thick steel plates and the like, adjustment rolling, tenter rolling, and finish rolling are generally carried out in order while rolling the rolled material.
In the present invention, first, at the leading and trailing ends of the rolled material in the final pass or the final several passes of tenter rolling, using a hydraulic reduction device or the like capable of adjusting the roll gap at high speed during rolling, Roll the shape that becomes thinner toward the part.
FIG. 1 is a view showing a shape in which the rolled material becomes thinner toward the end portion after the tenter rolling. FIG. 2 is a diagram showing an example of a reduction pattern in the final pass or the final several passes of the tenter rolling. Further, FIG. 3 is a diagram showing a state where the rolled material having a shape that becomes thinner toward the end portion after the tenter rolling is finish-rolled. 1 and 3, those parts which are the same as those corresponding parts in FIG. 4 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 1, 3 is a shape portion that becomes thinner toward the end portion, 4 is a width of the shape that becomes thinner toward the end portion, and 5 is a depth of the shape that becomes thinner toward the end portion.
As seen in the rolling pattern of FIG. 2, the rolling amount of the rolled material 1 is gradually reduced to the target reduction rate at the tip of the rolled material 1.
After rolling the central portion at a target reduction ratio, the rolling material 1 is rolled at the rear end while gradually increasing the reduction amount.

Next, after the rolled material is turned, finish rolling is carried out. In this finish rolling, the surface with a shape that becomes thinner toward the end is a side surface with respect to the rolling direction, and the width end is at the plate width end. The rolled material having a reduced plate thickness is rolled toward the portion. When rolling is performed in such a state, rolling is performed with the unrolled portion left at the strip width end, or the rolling reduction at the strip width end is smaller than that at the strip width center. In such a case, the rolling elongation of the central portion of the strip width tends to be larger than the elongation of the end portion of the strip width, but the central portion of the strip width and the end portion of the strip width try to constrain the rolling elongation between them and try to stretch uniformly. In order to
A compressive residual stress in the rolling direction acts on the central portion of the strip width, and a tensile residual stress in the rolling direction acts on the end portions of the strip width.

In ordinary rolling for rolling a rolled material having no plate thickness deviation in the plate width direction, at the end of the plate width, there is elongation in the rolling direction and at the same time, there is a material as shown in FIG. However, in the rolling method of the present invention, the tensile residual stress acts on the strip width end portion, so that the transverse flow of the material is suppressed.

The above will be described below using mathematical expressions. When x is the rolling direction, y is the strip width direction, and z is the strip thickness direction, the relationship between stress and strain on the side surface of the rolled material subject to bulge deformation is as follows.

[0011]

[Equation 1]

The meanings of the symbols are as follows. dε _y : Increment of strain in sheet width direction σ _x : Stress in sheet rolling direction σ _y : Stress in sheet width direction σ _z : Stress in sheet thickness direction dσ _x : Increment of stress in sheet rolling direction dσ _y : Increment of sheet stress in sheet width direction dσ _z : Stress in sheet thickness direction Increment σ _eq : Equivalent stress d ε _eq : Equivalent plastic strain increment E: Young's modulus ν: Poisson's ratio F, G, H: Anisotropy parameter The first term in the above equation indicates the elastic strain component, and the second term is the plastic strain. Represents a component. Considering the case where an unrolled part remains at the strip width edge, the stress in the strip width direction σ _y and the stress in the strip thickness direction σ _z are 0, which is caused by the difference in elongation between the strip width center and the strip width end. There exists only the tensile stress σ _x in the rolling direction. Therefore, equation (1) becomes the following equation.

[0013]

[Equation 2]

From the equation (2), d ε _y becomes negative regardless of whether σ _x exceeds or does not exceed the yield stress, indicating that bulge deformation does not occur. Further, even when the sheet width end is in contact with the roll and the reduction ratio at the center of the plate width is larger than the reduction ratio at the end of the plate width, σ _x is larger than σ _z, dε _y becomes negative, and bulge deformation occurs. I know I won't get up.

[0015]

EXAMPLE A rolling mill capable of adjusting the roll gap at a high speed during rolling was used to perform rolling under the following conditions, and a comparison was made between cases where the present invention was applied and cases where the present invention was not applied.

The slab size is 230t × 1590w × 4169L (m
m), the rolling size is 13.6t x 3143w x 3700L (mm), and the tenter ratio is 1.95. The pass schedule is 217.6 → 190.0t (mm) for temper rolling and 190.0 for tenter rolling.
→ 172.9 → 156.4 → 140.8 → 125.5 → 111.0 → 97.6t (m
m), finish rolling is 97.6 → 75.7 → 56.5 → 40.6 → 27.9 → 2
It is 1.4 → 17.8 → 15.4 → 13.7t (mm). As a case of applying the present invention, when the shape is rolled toward the end portion in the final two passes of the tenter rolling (case 1), the thickness is reduced toward the end portion in the final pass of the tenter rolling. The case where the shape was rolled (Case 2) was carried out, and the case where the present invention was not applied was carried out (Case 3) in which the shape that became thinner toward the end was not rolled.

The results are shown in Table 1.

[0018]

[Table 1]

In the rolling of Case 3 to which the present invention was not applied, seam flaws occurred at a position 32 mm from the plate width end, whereas in Case 1 to which the present invention was applied, 12 mm from the plate width end,
In case 2, the position where the seam flaw was generated was able to be moved to the plate width end portion, which was 23 mm from the plate width end. Further, in the case to which the present invention is applied, blistering flaws do not occur, and according to the present invention,
It was confirmed that the trimming width could be greatly reduced.

[0020]

As described above, according to the present invention, it is possible to move the position where the seam flaw is generated to the end portion of the plate width without installing an effective edger mill and without causing the swelling flaw. This has the effect of improving the material yield.

[Brief description of drawings]

FIG. 1 is a diagram showing a shape that becomes thinner toward an end portion of a rolled material after tentering rolling according to the present invention.

FIG. 2 is an example of a reduction pattern in a final pass or final few passes of tenter rolling according to the present invention.

FIG. 3 is a diagram showing finish rolling of a rolled material having a shape that becomes thinner toward an end according to the present invention.

FIG. 4 is a diagram showing bulge deformation of a rolled material that occurs when rolling a thick plate.

FIG. 5 is a diagram showing that bulge deformation of the rolled material progresses and seam flaws occur.

FIG. 6 is a conventional method for forming a groove on a side surface of a rolled material,
Diagram showing the deformation of the strip width edge when the rolled material is rolled

[Explanation of symbols]

 1 Rolled material 2 Rolled roll 3 Shaped part that becomes thinner toward the end

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Yanagida 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (1)

[Claims] 1. In the rolling of a thick plate using a rolling mill having a device capable of changing the roll interval during rolling, in the final pass or final few passes of tenter rolling, the reduction amount at the tip of the rolled material. By gradually reducing the rolling amount and gradually increasing the reduction amount at the rear end of the rolled material, thereby rolling the shape that becomes thinner toward the end of the rolled material, and then performing finish rolling. Rolling method.