JPH08267113A - Method for controlling plate camber in plate rolling - Google Patents

Abstract

PURPOSE: To suppress the generation of plate camber by providing a quantity measuring type plate camber sensor on at least one side of the inlet and outlet sides of a rolling mill and executing light reduction rolling at the final pass when the measured plate camber exceeds the allowable critical value. CONSTITUTION: The signals from the fixed quantity type camver sensors 5 provided on the inlet and outlet sides of the rolling mill for rolling a material 1 to be rolled are fed through a a signal converter 7 to an arithmetic unit 8 with which rolling reduction of the next pass is calculated and control is executed with a screw-down controller 9. The curvature 1/δ of camber is set to 0±0.0002 (mm<-1> ) as the allowable critical value and light reduction rolling is executed in the final pass at the draft of <=5%, preferably, <=3% to only the pass at which the camber over this allowable critical value is indicated. In this way, the generation of camber is effectively suppressed and deterioration of quality due to decrease of straightening and ununiform cooling in a succeeding process is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling plate warpage in thick plate rolling, and in particular, it suppresses plate warpage occurring at the rolling end portion of a thick plate, which is suitable for thick plate rolling by a reverse rolling mill. I will suggest a method to do so.

[0002]

2. Description of the Related Art Upward / downward warpage at the leading and trailing edges of a thick plate in reverse rolling causes residual strain and an increase in load during straightening work, as well as quality due to uneven cooling in the cooling process. It causes deterioration, and has been regarded as a major problem to be solved in plate rolling technology. The upward and downward warpage of such thick plate rolling is
Many factors such as temperature difference between upper and lower surfaces of the material to be rolled, difference in friction state, difference in upper and lower work roll diameters, fluctuation of plate thickness and reduction rate, etc. occur. Therefore, the control of the plate warpage during the rolling of the thick plate has been one of the extremely difficult problems to be solved.

On the other hand, conventionally, for example, Japanese Patent Laid-Open No. 57-57
Japanese Patent No. 88909 proposes a method of detecting the temperatures of the upper and lower surfaces of the thick plate and correcting the warp of the thick plate based on the temperature difference. However, with this method, the warpage caused by the temperature difference is extremely effective and controllable,
There was no effect on the warpage caused by the other factors mentioned above. Moreover, in order to eliminate this temperature difference, for example, in the case where extra water is applied to the material to be rolled, not only is the rolling load increased due to the temperature decrease, but in particular, controlled rolling (CR material) is performed. In this case, since the rolling temperature is strictly controlled, there is a problem that the material quality is adversely affected.

In addition, Japanese Patent Laid-Open No. 63-132708 proposes a method for controlling the plate warp by controlling the rotation speeds of upper and lower work rolls utilizing different peripheral speed rolling. Certainly, this method is effective for thin materials, but for thick materials, the impact drop when biting the rolled material is large, so it is difficult to make a difference in the rotation speed of the upper and lower work rolls. , Or the rotation speed control itself is difficult,
The reality is that a sufficient warpage control effect is not obtained.

[0005]

SUMMARY OF THE INVENTION The present invention proposes a control technique capable of effectively suppressing the occurrence of warpage at the edge of a thick plate in view of the above-mentioned problems of the conventional technique. With the goal.

[0006]

In order to achieve the above object, the inventors first tried to quantitatively clarify the influence of the warpage of the thick plate on the warpage of the thick plate. As a result, it has been found that even if various types of plate warpage occur, if the rolling with a small reduction rate, that is, the light reduction rolling is performed, the influence of the factor causing the warpage is almost eliminated, and it is effective in suppressing the plate warpage.

That is, the present invention is a method developed based on such knowledge and has the following constitution. (1) When controlling the plate warpage that occurs when hot rolling a thick steel plate with a plate rolling mill, the amount of plate warping is controlled by a quantitative warpage sensor installed on at least one of the inlet and outlet sides of this rolling mill. A method for controlling plate warpage in thick plate rolling, which comprises measuring and performing light reduction rolling in the final pass when the amount of plate warp exceeds an allowable limit value. (2) When controlling the plate warpage that occurs when hot rolling a thick steel plate with a plate rolling mill, the amount of plate warping is controlled by a quantitative warpage sensor installed on at least one of the inlet and outlet sides of this rolling mill. If the amount of warpage is measured and the amount of warpage exceeds the allowable limit value, the rolling schedule for the next pass and subsequent rolling schedules is set so that the rolling rate is such that the warpage can be kept small even if the final pass is lightly rolled. A method for controlling plate warpage in thick plate rolling, which comprises changing the rolling temperature. The allowable limit value of the plate warp amount requiring the change of the pass schedule is when the warp curvature 1 / ρ is 0 ± 0.0002 (mm ⁻¹ ) or more. In addition, the light reduction rolling performed in the final pass is
The rolling reduction is performed under the condition of 5% or less.

[0008]

The present invention is basically constructed on the basis of the idea of lightly reducing the final pass and establishing an effective control technique capable of preventing the reduction in rolling efficiency due to the light reduction. This idea is based on the following findings.

That is, FIG. 1 shows two typical examples of the cause of plate warpage; (a) When there is a difference in the vertical friction coefficient between the work roll and the material, (b) the upper and lower surfaces of the rolled material. It shows the results of an investigation of the relationship between the rolling reduction and the generated warp curvature when there is a temperature difference. As shown in this figure, even if the difference in friction coefficient or the temperature difference that causes the plate warpage is the same, the smaller the reduction rate, the smaller the warp curvature 1 / ρ (mm ^-1 ). It can be seen that light reduction rolling is effective in suppressing the above. Further, as shown in this figure, if the plate thickness is determined, it is possible to calculate the reduction rate for suppressing the warp to a certain level or less. Therefore, in the final pass, if light reduction rolling with an appropriate reduction ratio according to the plate thickness is performed, it is convenient to suppress the occurrence of plate warpage.

The reason why the plate warp can be suppressed by performing such a light reduction rolling in the final pass has not been completely clarified, but the inventors have only processed the surface layer of the material by the light reduction. It is presumed that this is because the effect of the difference in elongation between the upper and lower materials due to the asymmetry factor is small because it does not exist.

However, if the final pass light reduction rolling as described above is applied to all rollings, that is, to all rolled materials, the number of rolling passes unnecessarily increases and the rolling efficiency decreases. Occurs. Actually, such a plate warp may or may not occur depending on the heating state of the material, the cooling difference between the upper and lower surfaces of the material during rolling, the characteristics of the upper and lower work rolls, and the like. Therefore,
In order to eliminate the above-mentioned inconvenience (decrease in efficiency), it can be said that it is effective to perform the final pass light reduction rolling only when warpage occurs during rolling. This is because if extreme warpage occurs during rolling, there is a high possibility that plate warpage will occur even in the final pass.

Therefore, in the present invention, in order to quantitatively detect the warpage during rolling, a quantitative warpage sensor is installed on at least one of the inlet side and the outlet side of the rolling mill, and this sensor is used for rolling. Detect and measure the amount of plate warp in the middle, and only in the pass where the measured value shows the amount of warp exceeding the predetermined allowable value of warp curvature, the final pass is subjected to light reduction rolling with a reduction rate of 5% or less. By doing so, the occurrence of warpage was suppressed and the reduction in rolling efficiency was minimized.

That is, when a certain amount of plate warp is detected during rolling, the pass schedule from the next pass is changed,
By controlling the final pass for obtaining the target plate thickness so that it can be performed even in the light reduction rolling, the plate warp is surely suppressed. For that purpose, it is necessary to accurately measure the amount of plate warpage during rolling, and it is also necessary to perform feed front control.

In the present invention, the warp curvature 1 / ρ is set to 0 ± 0.0002 (mm ^-1 ) as an allowable limit value in order to change the pass schedule to meet the above demand. This value means that as the rolling progresses, that is, as the plate becomes thinner, the warpage increases to a certain level, so it is necessary to keep this value around this value in the initial stage of rolling. If it exceeds, there is a possibility of causing a large warp in the final pass, so the allowable limit value 1 / ρ of the control reference value is limited to 0 ± 0.0002 (mm ⁻¹ ).

Further, in the present invention, the light reduction rolling performed in the final pass is performed at a reduction rate of 5% or less. This is because if the rolling reduction is 5% or more, a large warp may occur when the plate thickness is thin. It is preferably 3% or less.

[0016]

EXAMPLE An example of the control method according to the present invention will be described below. FIG. 2 shows a thick plate rolling facility and a system configuration suitable for applying the control method of the present invention.
In the figure, 1 is a material to be rolled, 2, 2'is upper and lower work rolls, 3, 3'is upper and lower backup rolls, and 4 is a reduction device. For such a rolling mill, quantitative warpage sensors 5 are installed on both the input side and the output side of the rolling mill, and the signal from the warpage sensor 5 is output as a warpage amount via a signal converter 7. As configured. In the figure, 6 is a table roll, 8 is an arithmetic unit, and 9 is a rolling down control unit.

A method for controlling the plate warpage when performing reverse rolling of a thick plate using the above rolling equipment will be described. First, since a warp occurred at the tip of the material 1 to be rolled in a certain rolling pass, the warp sensor 5 measured the warp, and the warp amount was 0.0002 (mm
^-1 ) was exceeded and 0.00025 (mm ^-1 ) was exhibited. Therefore, it is determined that there is a high possibility that the warp will occur even in the final pass due to some cause of the warp, and the arithmetic unit 8 changes the rolling-down schedule after the pass. At the time of the change, even if there was a warpage factor from the final plate thickness, a reduction rate was calculated so that the occurrence of warpage would be small in the final pass, and the reduction schedule was changed so that the final pass would have this reduction rate.

Table 1 shows the details of the plate warpage control method at this time. The table shows the rolling schedule and the warp curvature after entering the thickening pass, but since the warp curvature exceeded the allowable limit value (0.0002 (mm ^-1 )) at the 13th pass, the warp was within the allowable limit in the final pass. The rolling schedule after the next pass was changed as shown in the same table in order to reduce the rolling reduction to 3% so as to be less than the value. As a result, although the number of passes increased by one pass, the final warp curvature was significantly reduced to 0.00008 (mm ⁻¹ ), confirming that the control method of the present invention is effective.

[0019]

[Table 1]

[0020]

As described above, according to the present invention, even if a warp occurs due to various causes of the warp, the occurrence of the warp can be effectively suppressed by lightly rolling the final pass. As a result, there is a ripple effect that the correction load in the subsequent process can be reduced and quality deterioration due to uneven cooling can be prevented. Further, since it is a method of performing final pass light reduction rolling only when necessary, it is possible to suppress the reduction of rolling efficiency as much as possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a rolling reduction and a bending curvature when a warp occurs due to a warp generation factor.

FIG. 2 is an explanatory diagram showing a plate rolling equipment and a system configuration to which the present invention is applied.

[Explanation of symbols]

 1 Rolled material 2, 2'Upper / lower work rolls 3, 3'Upper / lower backup rolls 4 Rolling down device 5 Warp sensor 6 Table roll 7 Signal conversion device 8 Computing device 9 Rolling down control device

Claims (4)

[Claims] 1. When controlling a plate warpage that occurs when a thick steel plate is hot-rolled by a plate rolling machine, a plate type warp sensor is installed on at least one of the inlet side and the outlet side of the rolling machine. A method for controlling plate warpage in thick plate rolling, which comprises measuring the amount and rolling the final pass in a light reduction when the amount of plate warp exceeds an allowable limit value. 2. When controlling a plate warpage that occurs when a thick steel plate is hot-rolled by a plate rolling machine, a plate type warp sensor is installed on at least one of the inlet side and the outlet side of the rolling machine. If the amount of warpage exceeds the allowable limit value, the rolling schedule after the next pass is adjusted to the final pass so that the rolling rate can be suppressed even if the final pass is lightly reduced. Warping control method in thick plate rolling, characterized in that the rolling schedule is changed to perform rolling. 3. The permissible limit value of the plate warp amount requiring a change in the pass schedule is 0 ± 0.00 in the warp curvature 1 / ρ.
02 (mm ^-1 ) or more, The control method of Claim 1 or 2 characterized by the above-mentioned. 4. The reduction ratio of light reduction rolling performed in the final pass is 5
The control method according to claim 1 or 2, wherein the control is performed at a rate of not more than%.