JPH05177227A - Method for controlling tension of cold tandem mill - Google Patents

Abstract

PURPOSE:To inhibit the variation of tension between stands and highly keep the accuracy of plate thickness when limitation of tension is controlled according to the rolling phenomenon in a low speed area when a rolling speed is reduced. CONSTITUTION:When the limitation of tension is controlled by the change of a draft position or when the limitation of tension is controlled by the change of roll speed, after the reduced rolling speed V is lowered below a fixed value Vc and the draft position is changed by a fixed amount or when the rolling speed comes below to a fixed value, the upper and lower limit values of the control of the limitation of tension are expanded. A tension set straight line is required according to rolling phenomena from an actual value of tension between stands when deceleration has been completed, rolling speed, a set value T of tension between stands when the upper and lower limit values of tension limitation control are expanded. In a low speed are the tension limitation control is carried out according to this tension set straight line thereafter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tension control method for a cold tandem rolling mill for continuously rolling a strip-shaped material to be rolled without stopping the rolling.

[0002]

2. Description of the Related Art Generally, tension control between stands in a cold tandem rolling mill is generally performed by, for example, changing tension between the i-1th stand on the upstream side and the i-th stand by changing the rolling position of the stand, or By changing the roll speed of the (i-1) th stand or the stand, the tension between the stands does not exceed the upper and lower limit values of the set value. In the low rolling speed range, the tension between stands increases due to the reduction of the amount of rolling oil entrained in the roll bite.Therefore, the tension set value between stands must be changed according to the rolling phenomenon. Limit control is performed.

[0003]

However, the tension between stands in the low speed range depends on the material of the material to be rolled, the type of rolling oil,
Since it varies depending on the amount, it is very difficult to determine an appropriate set value. When a deviation occurs between the preset tension value in the low speed range and the actual tension value between stands, the control system changes the rolling position or roll speed to eliminate the deviation. .. For example, if the set value is larger than the actual value, the rolling position is changed to the opening direction, so the plate thickness may be thicker.On the contrary, if the set value is lower than the actual value, the rolling position is changed to the closing direction. May be thin. Therefore, in the conventional control method, there is a possibility that the product may be deteriorated due to a defective plate thickness.

The object of the present invention is to solve such a problem, and when performing the tension limiting control according to the rolling phenomenon in the low speed region at the time of decelerating the rolling speed, the tension fluctuation between the stands is changed. It is an object of the present invention to provide a tension control method for a cold tandem rolling mill capable of suppressing the above-mentioned problem and sufficiently maintaining the plate thickness accuracy.

[0005]

In the method of controlling the tension of a cold tandem rolling mill according to the present invention, when the tension limiting control is performed by changing the rolling position, or the tension limiting control is changed by the roll speed. If you are
When the rolling speed is decreased, it is lowered below a certain value and a certain amount of rolling position is changed, or when the rolling speed falls below a certain value, the upper and lower limit values of the tension limiting control are expanded. After that, when the speed is further reduced, the tension between the stands increases according to the material of the material to be rolled, the type and amount of rolling oil, and the like. Then, from the actual tension value between the stands and the rolling speed when the deceleration is completed, and the tension set value between the stands and the rolling speed when the upper and lower limit values of the tension limit control are expanded, the tension setting line corresponding to the rolling phenomenon is calculated. Ask. After that, the tension limit control in the low speed region is performed based on this tension setting straight line.

[0006]

FIG. 1 is a characteristic diagram showing the relationship between rolling speed and tension in a tension control method according to an embodiment of the present invention. Here, the speed at which the rolling position is changed by a certain amount by the tension limit control after decelerating the rolling speed to a certain value Vc or less is V here.
Set to 0. Further, the tension set value at the rolling speed V0 is set to T0. When the rolling speed reaches V0, that is, when the rolling position is changed by a certain amount by the tension limiting control, the upper and lower limit values of the tension limiting control are expanded. When the rolling speed is further reduced,
The tension increases according to the material of the material to be rolled, the type and amount of rolling oil. Let V be the rolling speed at which the deceleration is completed, and T be the actual tension value at this time. If a straight line connecting (V0, T0) and (V, T) is calculated, this straight line gives T when V = 0. The value of T * is

[0007]

[Equation 1]

Therefore, if β = T * × 100 / T0 is defined,

[0009]

[Equation 2]

[0010] That is, when deceleration is completed β
Is calculated and locked on, and the tension limiting control is restarted based on the set value of the tension limiting control in the low speed range reflecting this β. Therefore, the tension set value Tr is as follows.
When accelerating the rolling mill, tension limit control is performed based on this Tr.

[0011]

[Equation 3]

When the tension limit control is performed at the roll speed, the same tension limit control may be performed with Vc = V0 in the above equation. That is, when the rolling speed becomes Vc or less, the upper and lower limit values of the tension limiting control are expanded, and the tension between stands increases as the rolling speed decreases, and the characteristic diagram in the state of Vc = V0 in FIG. 1 is obtained. Obtaining the tension setting value Tr based on this characteristic is the same as in the above-described embodiment.

FIG. 2 is a block diagram showing the construction of a rolling mill control apparatus for carrying out the tension control method of the above embodiment. The rolling mill is controlled by the control computer 1 and the line control device 2. The tension control device 3 takes in the output of the tensiometer 4 and operates the reduction position control device 5 to adjust the reduction position of the work roll 7 to control the tension between the stands to be constant. If the rolling speed is Vc or less and the amount of change in the rolling reduction position exceeds a certain value when the rolling mill is decelerated, the rolling reduction position is set at that position in order to expand the upper and lower limit values of the tension limit control. Maintained. Then, when the deceleration is completed thereafter, the line control device 2 calculates β by the above-described calculation formula, obtains the set value of the tension limit control in the low speed region, and restarts the tension limit control based on this value. Further, when the rolling mill is accelerated, the tension limit control is executed by changing the tension set value according to the rolling phenomenon based on the set value of the tension limit control.

The rolling speed can be obtained by detecting the rotation speed of the work roll 7 of the final stand or the speed of the material to be rolled. The rotation speed of the work roll 7 is controlled by the roll rotation speed control device 6 and is controlled to be constant in the above-described embodiment, but when the tension between the stands is controlled by the roll rotation speed, the rotation of the work roll 7 is controlled. The tension is controlled so that the tension characteristic of FIG. 1 can be obtained by adjusting the speed. The above-described control of the work roll (rolling position or rotation speed) is performed between the stands.

FIG. 3 shows data when the tension between the stands is controlled by controlling the rolling position of the work roll in the above embodiment and when the conventional method is used. As shown in the figure, according to the present embodiment, the plate thickness deviation is smaller than that in the conventional case.

[0016]

As described above, according to the present invention, when the rolling speed of the cold tandem rolling mill is reduced, the tension set value based on the actual tension value corresponding to the rolling phenomenon is obtained, and the tension set value is used as a reference. Since the limit control is performed, it becomes possible to suppress the tension fluctuation between the stands and also sufficiently maintain the plate thickness accuracy, thereby improving the efficiency and the yield.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between rolling speed and tension in a tension control method according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a control device for a rolling mill that implements the tension control method of the above embodiment.

FIG. 3 is a characteristic diagram showing data of the example and the conventional method.

[Explanation of symbols]

 1 control computer 2 line control device 3 tension control device 4 tensiometer 5 roll-down position control device 6 roll rotation speed control device 7 work roll

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

Claims (2)

[Claims] 1. A method for controlling the tension of a cold tandem rolling mill that continuously rolls a strip-shaped material without stopping rolling, wherein the rolling speed is changed when the tension limiting control is performed by changing the rolling position. When it is decreased, it falls below a certain value and after changing a certain amount of rolling position, the upper and lower limit values of tension limit control are expanded, and the actual tension value between stands and rolling speed when deceleration is completed. , And the tension setting line corresponding to the rolling phenomenon from the tension setting values between the stands and the rolling speed when the upper and lower limit values of the tension limit control are expanded,
Thereafter, the tension control method for the cold tandem rolling mill is characterized in that the tension limiting control in the low speed region is performed based on the tension setting straight line. 2. A method for controlling the tension of a cold tandem rolling mill, which continuously rolls a strip-shaped material to be rolled without stopping the rolling, in the case where the tension limiting control is performed by changing the roll speed. When it decreases below a certain value, the upper and lower limits of tension limit control are expanded, and
Obtain the tension setting straight line according to the rolling phenomenon from the actual tension value between the stands and the rolling speed when the deceleration is completed, and the tension set values between the stands and the rolling speed when the upper and lower limit values of the tension limit control are expanded, Thereafter, the tension control method for the cold tandem rolling mill is characterized in that the tension limiting control in the low speed region is performed based on the tension setting straight line.