JPH0523705A - Method for rolling steel sheet - Google Patents

Abstract

PURPOSE:To offer a method for rolling steel sheet that the sheet crown of steel sheet can be efficiently reduced without bringing an increase of the cost of equipment. CONSTITUTION:When a steel sheet is rolled with a 4 stages rolling mill which is constituted of a work roll 2 and back-up roll 1, the roll crown of the back-up roll 1 is made into a trapezoidal crown or large crown of >=0.2mm and the roll crown of the work roll 2 is made into a negative crown with a straight part in the middle part of the width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet rolling method for obtaining a steel sheet having a small sheet crown.

[0002]

2. Description of the Related Art Conventionally, various rolling methods for reducing the plate crown of a steel sheet have been studied. Examples of such methods include a method for reducing the plate crown by a rolling mechanism,
Also, there is one that reduces the plate crown depending on the shape of the roll crown.

The former method uses a six-high rolling mill, or is provided with a work roll shift mechanism, a roll cross mechanism, a bender mechanism or the like to reduce the plate crown. Although these methods are very effective, the biggest drawback is that the equipment cost rises.

On the other hand, the latter method does not have such a drawback. The latter method is disclosed in JP-A-62-27550.
As disclosed in Japanese Patent Publication No. 3, a method of rolling a work roll with a convex crown having a special shape is proposed. Also, JP-A-51-13353 and JP-A-5151
Rolling with a large backup crown as disclosed in JP-A-93766, or rolling by combining a large backup crown and a concave work roll crown as disclosed in JP-B-63-65403. The method to do is proposed. Further, JP-A-55-103201 proposes to provide a backup roll with a trapezoidal crown for rolling.

[0005]

However, according to the method disclosed in Japanese Patent Laid-Open No. 62-275503,
The method of giving the crown is not clear, and the roll profile may change due to wear, so it cannot be said that it is necessarily effective in reducing the plate crown. Also,
In Japanese Patent Publication No. 63-65403, the effect can be recognized, but the problem of spalling cannot be overcome with a backup roll having a large crown that can exert the effect. Further, in order to solve such a problem of spalling, if the concave crown shape of the work roll is made similar to the crown of the backup roll, the effect is halved. There is also a drawback that the amount of crown fluctuation is large with respect to the fluctuation of rolling load. Although the backup trapezoidal crown is also effective, there is a problem that it can not follow the change of the plate width,
Especially, it has a drawback that it becomes a minus crown for wide materials.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for rolling a steel sheet which can effectively reduce the plate crown of the steel sheet without causing a rise in equipment costs. To do.

[0007]

In order to solve the above-mentioned problems, the present invention is a method for rolling a steel sheet using a four-high rolling mill composed of work rolls and backup rolls, wherein Provided is a method for rolling a steel sheet, characterized in that the roll crown of the backup roll is a trapezoidal crown or a large crown of 0.2 mm or more, and the roll crown of the work roll is a negative crown having a straight portion at the center of the strip width. To do. Needless to say, the present invention can widen the shape control range of the steel sheet by using the bender together. Hereinafter, the present invention will be described in detail.

The inventors of the present application made various studies in order to reduce the plate crown in a four-high rolling mill (4Hi roll). FIG. 2 is a diagram showing the relationship between the width of the steel plate and the size of the plate crown in a normal 4Hi roll. As can be seen from this figure, the narrow steel plate shows a large positive crown, and the wide steel plate shows a negative crown due to the heat crown of the roll.

First, in order to reduce the crown of a narrow steel plate, a trapezoidal backup crown (backup roll chamfer) as shown in FIG. 3 was examined. When the steel plate has a narrow width and the backup roll has a trapezoidal shape as described above, the plate crown is reduced as shown in FIG. However, in the case of a wide steel plate, the negative crown increases.

In order to reduce the negative crown of a wide steel plate, as shown in Japanese Patent Publication No. 63-65403, a work roll having a normal concave crown is used.
As shown in FIG. 5, it is confirmed that the narrow crown is larger than that of the backup roll chamfer alone. Thus, it was difficult to roll a steel sheet from a narrow width to a wide width without generating a plate crown.

The inventors of the present application examined how to apply a load from the backup roll and the steel material to the work roll in order to understand the mechanism of plate crown generation when the width is narrow and the mechanism of plate crown generation when the width is wide. did.
The result is shown in FIG.

In the case of a normal roll, as shown in FIG. 6 (a), in a narrow steel material, stress is applied from the backup roll to the work roll end where no steel plate is present, and the work roll becomes convex upward. It is bent so that a plate crown is generated. In a wide steel material, such a stress from the backup roll does not exist, but a negative plate crown is generated due to the heat crown of the work roll.

When the backup roll chamfer is adopted, as shown in FIG. 6B, no detrimental stress is applied to the narrow steel plate, but stress is applied to the roll end portion from the steel plate in the wide steel plate. The work roll is bent so as to be concave upward, and a negative plate crown is generated.

When a normal concave crown is adopted for the work roll, in the narrow steel material, stress is applied from the backup roll to the work roll end portion where the steel plate does not exist, although it is reduced as compared with the case of the normal roll, After all, the work roll is bent so that it is convex upward.

As a result of such an examination, the stress applied to the work roll is such that the contact load from the backup roll does not occur in the portion where the steel material does not exist when the width is narrow, and the negative plate crown is applied to the steel material when the width is wide. It was confirmed that the adjustment should be made so that the above does not occur.

In the present invention, based on the results of such examination, rolling is carried out, for example, by combining a work roll crown and a back roll crown as shown in FIG. In FIG. 1, reference numeral 1 is a backup roll, and its roll crown is a trapezoidal crown. Further, reference numeral 2 is a work roll crown, and the roll crown is a negative crown having a straight line portion in the central portion of the plate width. The reference numerals 3 and 4 are roll axes. By defining the roll crown in this way, the contact load from the backup roll does not occur in the part where the steel material does not exist when the steel material is narrow, and when the width is wide, the negative crown at the end of the work roll causes The plate crown is prevented from occurring. Since the backup roll crown is formed for the purpose of not generating a contact load at the end of the work roll, the backup roll crown is not limited to the trapezoidal crown as shown in FIG. Is a large crown of 0.2 mm or more. Regarding the shape of the backup roll, the width A ₁ is {(roll body length-rolling minimum strip width) / 2} -100 mm, and the height B 1 is 0.1 mm, although it depends on the roll body length and the size of the material to be rolled. The above is desirable. Further, it is desirable that the width A ₂ of the work roll end portion is {(roll body length-rolling maximum strip width) / 2} -200 mm, and the height B ₂ is 0.05 mm or more.

When the roll crown is set as shown in FIG. 1, the load applied from the backup roll and the steel material to the work roll is as shown in FIG. 6 (d). That is, it can be seen that no harmful bending moment is generated regardless of whether the steel sheet is narrow or wide. Therefore, by setting such a roll crown, it becomes possible to roll a steel sheet from a narrow width to a wide width without generating a plate crown.

[0018]

Embodiments of the present invention will be described below.

Rolling was performed using a four-high rolling mill having rolls as shown in FIG. At that time, the width A ₁ (illustrated in FIG. 1) of the backup roll crown is 1200 mm and the height B is
² Is set to 0.5 mm, and the width A ² of the end shape (crown) of the work roll is set. Was 300 mm and the height was 0.2 mm. The roll length is 5500 mm, the backup roll maximum diameter is 2350 mm, and the work roll maximum diameter is 12 mm.
It was set to 00 mm.

The size is 270 mm ^t × 1720mm ^w × 51
00mm ^l Using mild steel slab, rolling temperature 900
Rolled at ℃, width 1900mm, 3400mm, 5100
A rolled material of mm was obtained. The thickness of the rolled material was fixed at 12 mm.

FIG. 7 shows the plate crown of the rolled material rolled in this way. In addition, the plate crown in the case of performing normal rolling is also shown in this figure. As is clear from FIG. 7, it was confirmed that by performing rolling according to the present invention, the plate crown can be extremely reduced from a narrow width to a wide width.

[0022]

According to the present invention, there is provided a steel sheet rolling method capable of effectively reducing the plate crown of the steel sheet. Since the present invention can be applied to existing rolling mills as it is, it has a great advantage that it is extremely low cost without causing a rise in equipment cost.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a rolling roll for carrying out the present invention.

FIG. 2 is a diagram showing a relationship between a plate width and a plate crown when a normal roll is used.

FIG. 3 is a diagram showing a rolling roll when a backup roll chamfer is adopted.

FIG. 4 is a diagram showing a relationship between a plate width and a plate crown when the roll shown in FIG. 3 is used.

FIG. 5 is a diagram showing a relationship between a plate width and a plate crown when a normal concave crown is adopted as a work roll.

FIG. 6 is a diagram showing a stress distribution exerted on a work roll at the time of rolling in the related art and the present invention.

FIG. 7 is a diagram showing a relationship between a plate width and a plate crown in the example.

[Explanation of symbols]

1; backup roll, 2; work roll, 3, 4;
Roll axis.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Satoshi Kuwahara 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A method of rolling a steel sheet using a four-high rolling mill comprising work rolls and backup rolls, wherein the roll crown of the backup roll is a trapezoidal crown or 0.2 mm. A method for rolling a steel sheet, characterized in that the above-mentioned large crown is used, and the roll crown of the work roll is a negative crown having a straight line portion in a central portion of the sheet width.