JPH0615321A - Shape control method in thick plate rolling - Google Patents

Abstract

PURPOSE:To prevent the deterioration of flatness caused by the lower temp. in both edge parts than the temp. in the middle part in the breadthwise direction of a material to be rolled during rolling stage. CONSTITUTION:Using devices 5 for measuring breadthwise temp. distribution and devices 6 for measuring sheet crown which are arranged on one side or both sides of the inlet and outlet sides of a rolling mill with which the final pass of thick plate rolling is executed, the breadthwise temp. distribution and sheet crown of the material 1 to be rolled are measured before the final rolling pass. Based on the obtained breadthwise temp. distribution and the data of the thickness and width of the material 1 to be rolled, the amount of cooling strain of the material 1 to be rolled is calculated and, based on this amount of cooling strain and the data of sheet crown, the material 1 to be rolled is finished into a shape by which cooling strain is concelled using a shape controlling means which is arranged in the rolling mill in the final rolling pass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for advantageously improving the shape, especially the flatness, of a thick plate obtained by rolling a thick plate.

[0002]

2. Description of the Related Art In thick plate rolling, a flatness defect is likely to occur in the latter half pass when the thickness of the plate to be rolled becomes thin. Therefore, in the pass after the thickness is reduced to a predetermined plate thickness, it is referred to as a shape control pass, and rolling is performed according to a predetermined rolling schedule in accordance with the constant crown ratio control so that the flatness defect does not occur. Is common.
However, in actual rolling, due to rolling load prediction error, roll profile prediction error, plate crown prediction error, etc., the plate crown of the material to be rolled is different from the prediction, which often results in poor flatness. It was happening.

As a countermeasure, there is a method of using a shape control means such as work roll bending to prevent flatness defects by feedback control or feedforward control based on the data of the plate profile and rolling load. 55-42167, 55-109510, 60-213
No. 304 is proposed in each publication.

[0004]

Thus, the conventional flatness control in the rolling of thick plates is aimed at rolling the thick plate as flat as possible in order to suppress the flatness of the product. Had been However, in the hot rolling of thick plates, the temperature distribution in the width direction of the material to be rolled becomes a distribution in which the temperature at both ends is lower than the temperature at the central part, so no matter how much the rolling finishes into a flat plate, Strain often occurred during the subsequent cooling process. That is, since the temperature distribution of the material to be rolled has a low distribution at the end portions, the material to be rolled has a difference in the amount of heat shrinkage in the width direction after cooling, which causes an edge-stretched shape. Such a tendency becomes more remarkable as the plate thickness is smaller.

In order to prevent such an ear extension phenomenon,
It was considered that the temperature distribution in the width direction of the material to be rolled during rolling was made uniform by performing cooling control using a shower cooling device, etc. However, there is a problem in that the rolling efficiency decreases because the rolling load increases and the rolling load increases.
In addition, in a normal process, after rolling, it is straightened with a straightening machine such as a roller leveler, but with this straightening machine,
The cooling distortion cannot be corrected. This is because the material to be rolled after straightening is still at a high temperature and becomes a flat plate with the temperature distribution in the width direction still generated, and the subsequent cooling also causes distortion. In addition, some of the recent roller levelers have a bending mechanism, and a method of applying a pre-strain to a thick plate by using the bending mechanism during straightening so that the plate becomes flat after cooling is also considered. However, the bending in such a roller leveler basically does not have a large strain imparting effect to give a pre-strain because the plate is bent, so that it cannot be actually utilized.

It is an object of the present invention to propose a shape control method capable of advantageously solving the above-mentioned problems and improving the final flatness of a thick plate that has been rolled and cooled.

[0007]

In order to solve the above problems, the inventors of the present invention estimate the amount of strain that occurs after cooling from the temperature distribution in the width direction of the material to be rolled during rolling, and cancel out the amount of strain. It was found that the flatness of the product can be remarkably improved after cooling by preliminarily imparting such distortion by rolling. The present invention is based on the above findings.

That is, the present invention uses a width direction temperature distribution measuring device and a plate crown measuring device which are arranged on one or both of an inlet side and an outlet side of a rolling mill which controls a final rolling pass in thick plate rolling. Prior to the pass, the temperature distribution in the width direction and the plate crown of the material to be rolled are measured, and the cooling strain amount of the material to be rolled is calculated based on the obtained temperature distribution in the width direction and the thickness and width data of the material to be rolled. Then, based on the cooling strain amount and the data of the plate crown, in the final rolling pass, the shape control means arranged in the rolling mill is used to finish the material to be rolled into a shape that cancels the cooling strain. It is a shape control method in plate rolling.

[0009]

In the present invention, the cooling strain amount of the material to be rolled is estimated based on the temperature distribution in the width direction of the rolled material and the control is performed to perform rolling in a shape in which this cooling strain is offset. Almost all cooling distortion after cooling is eliminated, and the flatness can be effectively improved. Further, since the strain is introduced by the finish rolling, a large strain can be easily given.

The present invention will be described in more detail below. FIG. 1 schematically shows the temperature distribution in the width direction of the thick plate after the final rolling pass. In this way, compared with the widthwise central portion, the temperature of the material to be rolled is decreased in a predetermined range (Δw) near the end portion, and is decreased by ΔT at the end portion. Since the widthwise central portion is different from the end portion, the flatness defect represented by the following equation is caused.

[0011]

[Equation 1]

In order to prevent the flatness defect (λ) represented by the above formula (1) from occurring after cooling, the thick plate before cooling has a shape that cancels the cooling distortion, that is, the steepness is the same as the above λ. In addition, rolling may be performed so as to have a shape that cancels λ. Therefore, in the final rolling pass, shape control means such as work roll bending is used to control the final rolling steepness so as to cancel the cooling strain (hereinafter referred to as -λ).

The widthwise temperature distribution and strip crown of the material to be rolled prior to such final rolling pass are most preferably measured immediately before this final rolling pass, but are measured several passes before. May be. This is because the rolling pass is a constant crown ratio control and the temperature drop amount can be estimated, so that the width direction temperature distribution and the value of the plate crown immediately before the final rolling pass can be predicted without much error. Further, the width direction temperature distribution measuring device and the plate crown measuring device used for the above-mentioned measurement may be arranged on one or both of the inlet side and the outlet side of the reverse rolling machine mainly used for rolling the thick plate. Further, rolling for imparting −λ is not limited to the final one pass, and may be a plurality of passes including the final pass.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a system configuration diagram for carrying out the shape control of the present invention when a work roll bending device is used as the shape control means, as one embodiment of the present invention.
In the figure, 1 is a material to be rolled, 2 is a work roll, 3 is a backup roll, and 4 is a working cylinder of a work roll bender.

Before biting into the final pass, a thermometer 5 for measuring the temperature distribution in the width direction of the material 1 to be rolled and a plate crown measuring sensor 6 respectively provide a temperature distribution in the width direction of the material 1 to be rolled and a plate profile (plate). Thickness, board width, crown) are measured. Based on the measured temperature distribution, temperature drop (ΔT), final plate thickness (w), and material of the material to be rolled (coefficient of linear expansion),
The process computer 7 predicts the flatness defect (steepness λ) after cooling by using the equation (1) described above. Next, the bending force at which the steepness becomes −λ in the final pass is calculated by the process computer 7 using the plate crown of the rolled material 1 on the entry side of the final pass measured by the plate crown measuring sensor 6. In this calculation, the relation between the steepness and the change in plate crown ratio is shown by the following equation.

[0016]

[Equation 2]

Further, the plate crown is expressed by the following formula from the plate crown model by bending force, plate thickness, plate width and the like.

[0018]

[Equation 3] Cr = f (F _w , F, t, w ...) (3) Here, Cr: plate crown, F _w : bending force, F: rolling load.

Using the above equations (2) and (3), since the target steepness of the final pass is −λ, the bending force of the final pass is obtained, and this bending force data is input to the control panel 8. The work roll bender vent amount is adjusted by controlling the valve stands 9 and 10 upstream of the working cylinder 4.

The present invention has been described above by using the work roll bending device as the shape control means. However, the present invention is not limited to the work roll bending device. For example, a roll shift device, a roll cross device, etc. It goes without saying that the shape control means may be used.

Next, the present invention will be described based on the results of a specific actual machine test. Fig. 3 shows the conventional case (Fig. (A)) and
The occurrence rate of edge extension with a steepness of 0.5% or more is shown for each plate thickness when the flatness control is performed by applying the method of the present invention ((a) in the same figure). As is clear from the figure, it is understood that the ear extension can be significantly reduced by executing the control according to the present invention.

[0022]

The shape control method for thick plate rolling of the present invention estimates the cooling strain amount of the material to be rolled based on the temperature distribution in the width direction of the rolled material, and rolls it into a shape that cancels this cooling strain. By controlling so that not only the ear extension that has been generated after cooling is significantly reduced, but not only a great effect can be obtained in improving the quality of the product, but also the load of the adjustment process such as cold correction and heat retention correction. It can be reduced.

[Brief description of drawings]

FIG. 1 is a graph schematically showing the temperature distribution in the width direction of a thick plate after the end of the final rolling pass.

FIG. 2 is a system configuration diagram in the case where a work roll bending device is used as the shape control means as one embodiment of the present invention.

FIG. 3 shows a case in which the incidence of ear extension with a steepness of 0.5% or more in the conventional case (FIG. 3 (a)) and a case in which flatness control is performed by applying the method of the present invention (FIG. 3). (a)) is a graph comparing and showing.

[Explanation of symbols]

 1 rolled material 2 work roll 3 backup roll 4 roll bender working cylinder 5 thermometer 6 plate crown measurement sensor 7 process computer 8 control panel 9 valve stand 10 valve stand

Claims (1)

[Claims] 1. Prior to the final rolling pass, a width direction temperature distribution measuring device and a strip crown measuring device are arranged on one or both of an inlet side and an outlet side of a rolling mill that controls the final rolling pass in thick plate rolling. The temperature distribution in the width direction and the plate crown of the material to be rolled are measured, and the cooling strain amount of the material to be rolled is calculated based on the obtained temperature distribution in the width direction and the plate thickness and width data of the material to be rolled. In the final rolling pass based on the cooling strain amount and the data of the plate crown, the shape control means arranged in the rolling mill is used to finish the material to be rolled into a shape that cancels the cooling strain. Shape control method in.