JPH07251214A - Control method for tandem mill - Google Patents

Abstract

PURPOSE:To control looper height within the allowable range from the viewpoint of operation by changing the looper height before the schedule changing point of a material to be rolled reaches a stand. CONSTITUTION:The material 1 to be rolled is led through an (i-1) th stand 2 and i-th stand 4 and brought into contact with a looper 8 on this way. The variation of looper height corresponding to the deformation-resistant difference between two stands is beforehand calculated using theoritical model of rolling and this value is preserved in a control computer 26 as table data. At the time of executing the set calculation for a finishing mill of the following material of the schedule changing point, deformation-resistant difference between two stands is determined in the control computer 26 and the variation of looper height between two stands is calculated from this value. When this value is out of the allowable range of looper height, the target value of looper height between two stands is beforehand changed before the schedule changing point reaches the rear stand of the two stands.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem rolling mill control method for rolling a metal strip on a plurality of stands.

[0002]

2. Description of the Related Art A hot strip mill is for manufacturing a hot coil by heating a slab manufactured by a continuous casting machine or the like to about 1250 ° C. and rolling it to a predetermined thickness.
Further, in order to improve productivity, the unit weight of the hot coil tends to increase, but the order of the hot coil is increasing in a large variety and in small quantities.

In order to deal with this, conventionally, a schedule change between running has been performed in which hot coils of a plurality of sizes are produced from the same slab. Also, in order to prevent off-gauges that occur in the unsteady part at the tip end of the hot coil, different sheet bars are joined in front of the finish rolling mill, and these are continuously rolled by the finish rolling mill, It is also important to manufacture hot coils, and in this case as well, it is necessary to change the running schedule.

As an example of a conventional running schedule change method, as disclosed in Japanese Examined Patent Publication No. 48-17145, when a stand reaches a certain stand, the roll schedule of the stand is changed and the pass schedule is changed. There is a method of changing the speeds of all the upstream or downstream stands including the stand while keeping the ratio constant while changing the value to the value corresponding to.

On the other hand, in a rolling mill having a looper between stands such as a finishing strip mill of a hot strip mill, the tension between the stands is controlled by the looper to a value suitable for the material to be rolled, and the height of the looper is increased. Control is performed within a range desired in operation in terms of sheet passing property and the like. In such a rolling mill, even when the running schedule is changed, the target tension value is changed from the value of the preceding material to the value of the following material in accordance with the arrival of the schedule change point, and the looper height is also desired in operation. Need to control in range.

[0006]

However, according to the conventional method described above, when the deformation resistance of the preceding material and the following material of the schedule change point is significantly different, the schedule change point reaches a certain stand. At this time, the tension suddenly changes between the previous stand and the stand. Therefore, by controlling this with the looper, the looper height may deviate from the range desired for operation, which causes inconvenience in operation. There was a problem that it would occur.

The present invention has been made to solve the above-mentioned conventional problems. When the schedule change point of the material to be rolled reaches the stand, the looper height is controlled within an allowable operating range. An object of the present invention is to provide a control method of a tandem rolling mill capable of realizing the above.

[0008]

The present invention provides a method for controlling a tandem rolling mill, which has a plurality of stands and controls the tension between two continuous stands by using a looper installed between the two stands. , The schedule change of the rolled material reaches the stand 1
The object is achieved by changing the height of the looper between the previous stand and the looper and rolling.

The present invention also achieves the above-mentioned object in the same manner by rolling by changing the roll speed so that the tension between the arbitrary stand and the immediately preceding stand does not change. is there.

[0010]

According to the present invention, in a rolling mill having a plurality of stands and controlling the tension between two continuous stands by using a looper between the two stands, a stand having a schedule change point of the material to be rolled is reached. By changing the looper height between the stand immediately before the stand and the stand before the start, when the stand having the schedule change point is reached, the stand and the stand immediately before the stand are changed. It is possible to prevent the looper height between the stand and the stand from deviating from the range desired in operation.

At this time, by changing the roll speed so that the tension in the two stands does not change, the looper height can be surely controlled within the allowable range.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an outline of two continuous stands of a tandem rolling mill to which the control method according to the present invention is applied.

In FIG. 1, 1 is the material to be rolled, 2 is the i-th
1 stand, 4 is the i-th stand, and 6 is a looper provided between the two stands. Further, 8 is a motor for driving the looper 6, 10 is a pulse generator for extracting a signal for controlling the looper from rotation of the motor, and 12 is a pulse generator.
It is a looper current control device. Reference numeral 14 is a tensiometer that detects tension from the looper angle, and 16 is a tension control device.
Further, 18 is a motor for driving the rolling stand rolls, 20 is a pulse generator for extracting a signal for controlling the roll speed from the rotation of the motor 18, and 22 is a roll speed control device. Further, 24 is a tracking device for tracking the progress of the rolled material 1, and 26 is a control computer for controlling the whole.

The rolled material 1 is composed of the (i-1) th stand 2 and the i-th stand.
It is guided through the stand 4 and contacts the looper 8 during this time. The tension of the material 1 to be rolled between the two stands is determined by the loop length determined by the difference between the rolling speeds of the adjacent two stands 2, 4 and the looper angle θ.

Further, the schedule change point of the rolled material is i-th
The amount of tension fluctuation between the two stands 2 and 4 when reaching the stand 4 mainly depends on the difference in deformation resistance between the two stands of the preceding material and the following material.

Further, since the tension between the stands is controlled by using the height of the looper 6 between the two stands, when the above-mentioned tension fluctuation amount between the two stands is large, the looper height is within an allowable range. In the present embodiment, the looper height variation amount corresponding to the two-stand deformation resistance difference is calculated in advance using the rolling theory model, and this is calculated as table data in the control computer 26. Save as.

The on-line control is performed by the control computer 26 when the finish mill setting calculation of the trailing material at the schedule change point is performed, and the difference in the two-stand deformation resistance is calculated, and from this, the looper height variation amount between the two stands θ ₁ ′ is calculated. calculated, if this is to deviate from the looper height tolerance θ ₁ L~θ ₁ U, prior to the schedule changes reaches the stand after two stands, the advance between two stands looper height target value theta ₁ ' −θ
₁ U (when it exceeds θ ₁ U) or θ ₁ ′ -θ ₁ L (θ
If it exceeds ₁ L), lower only.

More specifically, for the first and second stands of the 7-stand finishing rolling mill of the hot strip mill, low carbon steel as the preceding material and ultra low carbon steel as the following material are shown in the table of FIG. The method of changing the schedule when rolling with the pass schedule shown in is described below.

In this embodiment, the tension between 1 and 2 stands is
It is controlled by a looper between one and two stands, and the height of the looper is controlled by one stand roll speed. In the above-mentioned rolled material, the deformation resistance of the preceding material is larger, so 1
~ Change the looper height between the two stands to the lower limit of the operable range in advance. At that time, the one-stand roll speed is also changed so that the tension between the first and second stands does not change.
1 when the schedule change reaches 1 stand
The stand roll-down position is changed to the value of the trailing material, and the 1-stand roll speed is changed by the amount by which the advance rate of the 1-stand changes.

Further, when the schedule change point reaches 2 stands, the 2-stand rolling-down position is changed to the value of the trailing material, and the 2-stand roll speed is changed by the amount by which the advance ratio of 2 stands is changed. The stand roll speed is changed so that the stand speed ratio of 1 and 2 becomes the value of the pass schedule of the trailing material, and the target value of the stand tension of 1 to 2 is changed to the value of the trailing material.

The present embodiment is compared with the conventional method in which the looper height is not changed in advance. FIG. 3 shows the conventional result and FIG. 4 shows the result of the present embodiment. As is clear from the graph at the bottom of FIG. 3, it is impossible to stop the looper height within the allowable range by the conventional method, but in the method of this embodiment, the looper height is lowered in advance. Therefore, as shown in the graph at the bottom of FIG. 4, it is possible to stop within the allowable range.

[0023]

As described above, according to the present invention, in a rolling mill having a plurality of stands and controlling the tension between the stands using a looper installed between the stands, the schedule change point of the material to be rolled is Since the looper height is changed before reaching the stand, when the schedule change point reaches the stand, it is possible to control the looper height within the allowable operating range. Have. As a result, it became possible to change the running schedule of rolling materials with a large difference in deformation resistance without any problems.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a rolling mill having a plurality of stands to which a control method of the present invention is applied.

FIG. 2 is a table showing pass schedules of leading material and trailing material.

FIG. 3 is a diagram showing the results of the conventional method.

FIG. 4 is a diagram showing the results of this example.

[Explanation of symbols]

 1 ... Rolled material 2 ... i-1st stand 4 ... i-th stand 6 ... Looper

Claims (2)

[Claims] 1. A method for controlling a tandem rolling mill, comprising a plurality of stands, and controlling a tension between two continuous stands using a looper installed between the two stands, wherein a schedule change point of a material to be rolled is provided. However, the method for controlling a tandem rolling mill is characterized by changing the looper height between the stand immediately before the stand and the stand before reaching any stand. 2. The control of a tandem rolling mill according to claim 1, wherein rolling is performed by changing a roll speed so that a tension between the arbitrary stand and a stand immediately before the arbitrary stand does not change. Method.