JPH11319925A - Manufacture of thick steel plate by camber control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably reduce the unbalance of thickness in the width direction without necessitating the installation of a straightening device and special rolling mill. SOLUTION: In the manufacturing method of a thick steel plate by camber control in which rolling is executed while suppressing the horizontal bend of the steel plate, in the case the steel plate which is divided into plural small plates after rolling is rolled, first, the allowance of camber is set about an individual plate (S2), next, the allowance of camber of the whole steel plate is calculated based on the allowance of camber obtained about all the small plates (S3). Within the range of the obtained allowance of camber of the whole steel plate and within the allowance of camber which is decided from the restriction from the viewpoint of equipment (S4), rolling is executed while controlling the camber of the steel plate (S5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thick steel plate by camber control for performing rolling while suppressing lateral bending of the steel plate.

[0002]

2. Description of the Related Art In the production of thick steel plates, during rolling, the steel plates may be displaced from the rolling direction in the width direction of the steel plate and may be bent laterally. The shape of the bent plate is called camber. When the camber occurs, not only the target plate width of the product cannot be secured, but also in a severe case, the rolling operation becomes impossible. Therefore, in order to suppress this camber,
Several measures have been proposed.

For example, Japanese Patent Application Laid-Open No. 7-60353 proposes a plate camber correction method for correcting the shape of a steel plate on which camber has occurred. In this technique, shape correction is performed by clamping both ends in the longitudinal direction of a plate and applying bending deformation in the width direction of the plate with a rolling device.
The camber amount is measured by a plurality of distance measuring devices arranged between the clamp positions.
This is to calculate and control the pushing amount of the screw-down device.

[0004] Japanese Patent Application Laid-Open No. 6-91314 discloses that
A camber control method for performing camber adjustment by adjusting the position of a roll chock has been proposed. In this technology, camber control is performed with a difference in roll interval in the roll width direction using a reversible rolling mill in which the roll chocks of upper, lower, left and right horizontal rolls are movable in the rolling direction.

[0005]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 7-60353
In the technique described in Japanese Patent Laid-Open Publication No. H11-260, it is necessary to separately install a correction device. Therefore, a space for installing this apparatus is required on the exit side of the rolling mill or the entrance side of the shear line.

[0006] As a problem of the apparatus itself of this technique, since the correction is performed by cold working, large deformation is impossible, and the amount of camber that can be corrected is limited. According to this gazette, it is stated that the purpose of the apparatus is to correct a plate camber having an arbitrary shape of about ± 10 mm. Therefore, the camber amount that can be corrected is this level, and it is considered that a camber amount larger than this cannot be corrected.

Further, since the thickness of the target thick steel plate varies widely, in this technique, it is necessary to make the clamping device and the pressing-down device movable. As a result, a driving device is required for each part of the device, and the entire device becomes complicated and maintenance is not easy. In addition, the size of the apparatus is increased and a large installation space is required.

In the technique described in Japanese Patent Application Laid-Open No. 6-91314, the roll chocks of the horizontal rolls are movable in the rolling direction, and a special rolling mill is required.

Further, this technique can avoid the interference between the unbalance setting of the roll gaps on the left and right in the width direction and the thickness control, but it is still the same as the rolling in which the wedge ratio is kept constant. Therefore, if priority is given to reducing camber,
It is inevitable that the thickness imbalance (wedge) in the width direction increases and the thickness accuracy decreases.

The present invention solves the above-mentioned problems of the prior art, and makes it possible to greatly reduce the thickness imbalance in the width direction without requiring the installation of a straightening device or a special rolling mill. It is an object of the present invention to provide a method for manufacturing a thick steel plate by camber control.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a thick steel sheet by camber control, in which rolling is performed while suppressing lateral bending of the steel sheet. Set the camber allowance for each platelet, then calculate the camber allowance for the entire steel sheet based on the camber allowance obtained for all platelets,
A method for producing a thick steel sheet by camber control, characterized in that rolling is performed while controlling the camber of the steel sheet within a camber allowable amount of the obtained entire steel sheet and within a camber allowable amount determined by facility restrictions. It is.

The present invention was made during the technical development for improving the thickness accuracy of a thick steel plate. Among them, we examined the thickness imbalance (wedge) in the width direction, which is a major factor in reducing the thickness accuracy of thick steel plates. However, when the wedge is reduced, the camber inevitably increases due to the law of constant mass flow of the rolled material, and the target plate width of the product cannot be secured. Therefore, it is impossible to reduce the wedge as long as only the rolling method is considered.

[0013] Therefore, the manufacturing process other than the rolling is reconsidered.
A method to reduce wedges was studied. In the process, we focused on the fact that some of the rolled steel sheets may become a single product after rolling, but there are quite a few steel sheets that are divided into multiple small plates.

In this case, if the divided small plates are simply arranged so that the whole outer shape is rectangular, it is no different from collecting one product from a steel plate. In this case, it is necessary to reduce the camber to secure the target plate width of the product,
As a result, the wedge cannot be reduced.

Therefore, in the present invention, instead of arranging the small plates to be divided so as to have a rectangular outer shape and determining the camber allowable amount, first, the camber allowable amount of each small plate is set for each small plate. The camber allowance of each platelet is
It is determined from the permissible limits that can be obtained from the steel sheet on which the platelets are rolled.

Next, the camber allowance of the entire steel sheet is calculated based on the camber allowance obtained for all the small plates. This is not to calculate a mere total value of the camber allowances of the individual small plates, but to calculate a geometric shape corresponding to the camber allowance assuming the entire shape connected in the longitudinal direction. The camber allowance of the entire steel sheet obtained in this way is considerably larger than the conventional camber allowance as described later.

The rolling is performed within the range of the above-mentioned upper limit of the camber allowable amount of the entire steel sheet. In the present invention, the camber allowance is greatly reduced, and in some cases, there is a possibility that the facility limit may be exceeded. Therefore, in order to avoid passing troubles, a condition that the camber is within the allowable range of the camber determined by the restriction on the equipment is provided.

The control of the camber at the time of rolling is performed by measuring the camber amount of the steel sheet during rolling. In the present invention, the camber allowance is greatly expanded, so that the wedge can be minimized within that range. Therefore, there is no factor that hinders the improvement of the plate thickness accuracy, such as an operation of keeping the wedge constant during rolling, and the plate thickness accuracy can be greatly improved.

[0019]

FIG. 1 is a flowchart showing an example of an embodiment of the present invention. First, in step S1, it is determined whether or not a steel plate to be rolled is divided into small plates in a later process, that is, whether or not there is division, based on a rolling plan or the like. If it is determined in step S1 that there is no division, the camber allowable amount of the entire steel sheet is determined, and the process proceeds to step 4.

If it is determined in step S1 that there is division, a camber allowable amount is calculated for each small plate in step S2. Here, for example, the difference between the plate width of each small plate and the plate width of the rolled steel plate is calculated, and the amount of edge truncation is subtracted therefrom to obtain the camber allowable amount.

Next, in step S3, the camber allowable amount of the entire steel plate is calculated from the camber allowable amounts of all the small plates. In this method, the geometrical shape corresponding to the camber allowance is calculated assuming the entire shape sequentially connected in the longitudinal direction, rather than calculating the simple sum of the camber allowances of the individual small plates. Here, the calculation may be performed in a plane geometrical manner. However, since the geometrical shape targets the bending of the steel plate, the shape may be represented by a radius of curvature.

For example, when the dimensions of the individual small plates are the same, the radius of curvature corresponding to the camber tolerance is also the same, so that the camber tolerance of the whole rolled steel sheet can be calculated from the radius of curvature. If the dimensions of the individual platelets are different, the radii of curvature will also be different. In this case, if the camber amount of the whole rolled steel sheet is calculated using the maximum radius of curvature among the individual small plates and set as the camber allowable amount, camber control can be performed on the safe side. As a matter of course, the camber allowance may be set to a different value in the longitudinal direction of the rolled steel sheet according to the sampling position of each small plate.

In step S4, the camber allowance of the entire rolled steel sheet is compared with a camber allowance determined by restrictions on equipment, and the smaller one is determined as the camber allowance used for camber control. This camber allowance is
For example, it is transmitted to a rolling control device of a rolling mill.

In step S5, the camber amount of the steel sheet being rolled is measured, and camber control is performed. Camber control is
It is preferable to control the camber amount with the aim of minimizing the wedge within the range of the camber allowance amount.

FIG. 2 shows an example of a rolled sheet obtained by controlling the camber amount in this manner. Here, a case where two small plates of the same size are taken in the rolling longitudinal direction will be described. FIG.
When the method of the present invention is applied, FIG. 2b shows the case of the conventional method. Assuming that the allowable value of the camber amount is c, in the conventional method (FIG. 2B), this is equal to the allowable value of the camber amount of the whole rolled plate, but in the present invention, it is the allowable value of the camber amount for each small plate. As a result, FIG.
As shown in a, it can be seen that compared to the conventional method (shown by a broken line in the figure), a considerably large camber amount can be tolerated for the rolled plate as a whole. The permissible value of the camber amount of the whole rolled sheet is c ′ in the figure, and it can be seen that the permissible value c of the conventional method (shown by a broken line in the figure) can be increased to about four times.

In the present invention, the camber allowance of the whole rolled sheet is greatly expanded, and the wedge can be minimized within the range. As a result, it is possible to greatly improve the thickness accuracy.

Since the rolled steel sheet has a relatively large camber compared to the prior art, when it is divided into small plates, it is first cut in the width direction with an end shear. After dividing the rolled steel plate into small plates, the plate is cut in the longitudinal direction with a side shear, a slitter, or the like to obtain a target product width. Even if the camber is even larger, small plates can be collected by rotating the small plates in the plane as needed and adjusting the cutting direction.

[0028]

According to the present invention, the camber allowance is set for each of the divided small plates, and the camber allowance of the entire steel sheet is calculated based on the camber allowance. As a result, the permissible amount of camber is greatly increased, and wedges can be minimized by controlling camber within that range. Therefore, the thickness accuracy can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of an embodiment.

FIG. 2 is a diagram schematically showing an allowable camber amount.

Claims (1)

[Claims] In a method of manufacturing a thick steel sheet by camber control in which rolling is performed while suppressing lateral bending of the steel sheet, when rolling a steel sheet which is divided into a plurality of small sheets after rolling, first, a permissible amount of camber for each small sheet. Then, the camber allowance of the entire steel sheet is calculated based on the camber allowance obtained for all the small plates, and the camber allowable within the range of the obtained camber allowance of the entire steel sheet and determined by the restrictions on facilities. A method for producing a thick steel sheet by camber control, characterized in that rolling is performed while controlling the camber of the steel sheet within an allowable range.