JPH0484613A - Method for controlling cold tandem rolling mill - Google Patents

Abstract

PURPOSE:To obtain a specified product thickness by maintaining the specified rolling load and backward tension of a final stand constant, controlling the draft positions of a 1st stand and the stands exclusive of the final stands to make the specified backward tension constant and controlling the number of revolution of the rolls of the final stand and the stand before this stand. CONSTITUTION:The draft position of the final stand is controlled, by which the rolling load thereof is maintained constant. The number of revolution of the rolls of the final stand is controlled, by which the backward tension thereof is maintained constant. The draft positions of the 1st stand and the stands excluding the final stand are controlled, by which the backward tension thereof is maintained constant. The numbers of revolution of the rolls of the final stand and the stand before this stand are controlled, by which the sheet thickness is maintained constant. Not only the operations are stabilized but also the shape of the rolled product is stabilized in the rolling at a high coefft. of friction and the rolling of a hard material. The sheet thickness is simultaneously kept within a permissible range and the quality of the thin plate product is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for rolling a thin plate, and particularly to a control method for cold rolling a thin plate using a cold tandem rolling mill.

[Prior Art] In a cold tandem rolling mill, the product plate thickness is controlled by manipulating the rolling position of each stand and the number of rotations of the rolls. FIG. 3 is a block diagram showing the prior art. In this example, the rolling mill consists of four stands. In the figure, 1 to 4 indicate each rolling stand. Hereinafter, equipment belonging to the first stand is designated by the symbol A, equipment belonging to the second stand is designated by the symbol B, equipment belonging to the third stand is designated by the symbol C, and the equipment belonging to the fourth stand is designated by the symbol A. The devices to which they belong are indicated by numbers, and when these devices are referred to collectively, they are indicated by numbers with these codes removed. 5 is a support roll of each stand, 6 is a work roll, 7 is a hydraulic cylinder for adjusting the rolling position, 8 is a rolling load meter, 9 is a drive motor for the work roll, and 10 is a roll rotation speed control device. 11
．． , 1-2, and 13 are tension meters for measuring the tension between the first and second stands, between the second and third stands, and between the third and fourth stands, respectively, and] 4 is the product thickness. It is a thickness gauge that measures 15 is a thickness control device, 16 and 17 are ratio setters,] 8. 1 and 20 are tensions between the first and second stands, between the second and third stands, and between the third and fourth stands, respectively. The tension control device 21 is a reduction control device.

The thickness of the product 40 measured by the thickness gauge 14 is compared with the target thickness in the thickness control device 5, and the output from the thickness control device 15 according to the deviation is sent to the roll rotation speed control device 10 of the third stand. added to C. This output is also applied to the roll rotation speed control device 10B of the second stand via the ratio setter 16, and is also applied to the roll rotation speed control device 10A of the first stand via the ratio setter 17.

This changes the mass flow within the rolling mill and controls the product thickness to the target thickness. The tension between each stand is detected by the tension meter 11.12.13 and compared with the target value by the tension control device 18.19.20. Hydraulic cylinders 7B and 7C17D are operated via 21B and 21C121D (which belong to the stand).

[Problems to be Solved by the Invention] A cold-rolled steel plate, which is a product of a cold tandem rolling mill, is annealed in the next process, such as a continuous annealing line or a batch annealing process, and then shipped through a refining process.

In the continuous annealing process, a roughness higher than a certain limit is added to the cold-rolled steel sheet in order to maintain stability through the sheet, and in batch annealing to prevent seizure. For this reason, dull work rolls are often used as the final stand rolls of recent cold tandem rolling mills. On the other hand, although cold-rolled steel sheets conventionally manufactured in cold rolling mills are mainly made of soft materials, hard materials with high deformation resistance are also often rolled. Dull-processed work rolls have a large friction coefficient (hereinafter referred to as friction coefficient) with the rolled material. When rolling using this roll, or when rolling a steel plate with high deformation resistance, the following problems occur.

FIG. 4 is a graph showing the relationship between the friction coefficient and the normalized tension change coefficient. The horizontal axis shows the friction coefficient, and the vertical axis shows the normalized tension change coefficient. The tension change coefficient means that the rolling stand position is 1. The vertical axis shows the rate at which the rear tension of the stand (the tension applied to the rolled material between the stand and the upstream stand adjacent to it) changes when the stand is changed by 0.1 mm. The value at 5 is the normalized value.

FIG. 5 is a graph showing the relationship between the average deformation resistance of the rolled material (deformation resistance of the rolled material before rolling) and the normalized tension change coefficient. The horizontal axis shows the friction coefficient, and the vertical axis shows the normalized tension change coefficient. Tension change coefficient means that when the rolling position of the rolling stand changes by
The vertical axis shows the value normalized by the value when the average deformation resistance is 1.50 kg/mnt. As shown in FIGS. 4 and 5, the value of the tension change coefficient rapidly decreases as the friction coefficient or deformation resistance increases.

For this reason, when a work roll with a large friction coefficient is used for the final stand, or when a rolled material with high deformation resistance is rolled, the change in the rolling position required to change the rear tension amount becomes large. As described above, when the rolling position is greatly changed, the rolling load fluctuates greatly. As a result, the amount of bending of the roll changes significantly, resulting in poor product shape. Furthermore, since the influence coefficient of the rolling operation on tension control has decreased, tension control becomes unstable and stable operation cannot be maintained.

An object of the present invention is to solve the above-mentioned problems and to propose a control method for a cold tandem rolling mill that can maintain stable operation without causing shape defects in products.

[Means for solving the problem] For this purpose, the following method is used instead of the conventional control method.

In a thin plate cold tandem rolling mill, by controlling the rolling position of the final stand, the rolling load of the stand is held constant, and by controlling the roll rotation speed of the final stand, the rear tension of the final stand is reduced. By keeping the tension between the stand and its preceding stand constant, and by controlling the lowering positions of the stands other than the first stand and the last stand, the rear tension of the stand can be kept constant, and the tension between the last stand and the stand can be kept constant. The product thickness is kept constant by controlling the rotation speed of the rolls in the previous stage stand. Rolling rolls with a high coefficient of friction are used in the final stand, or materials with high deformation resistance are rolled. This is a control method for a cold tandem rolling mill.

In addition, another invention maintains the rolling load of the final stand constant by controlling the rolling position of the final stand,
By controlling the roll rotation speed of the stands other than the last stand, the rear tension of the last stand (the stand I
By controlling the rolling position of the stands other than the first stand and the last stand, the rear tension of the stands is kept constant and the roll of the stands other than the last stand is kept constant. This is a method of controlling a cold tandem rolling mill for rolling materials with high deformation resistance, which is characterized by maintaining the product thickness constant after final stand rolling by controlling the rotation speed.

[Effect] With the above method, when a work roll with a large friction coefficient is used for the final stand or when rolling a rolled material with high deformation resistance, it is necessary to change the rolling position significantly to change the rear tension. disappears, and the rolling load becomes constant. Along with this, the amount of bending of the rolls can also be maintained at an optimum level, resulting in a good shape of the product. In addition, tension control is stabilized and operation is also stable. In addition, rolling load, backward tension,
and roll bending amount are maintained optimally,
The product thickness can be controlled within an acceptable range while maintaining the product shape well.

[Examples] Examples of the present invention will be described below with reference to FIGS. 1 and 2. 1 and 2 are block diagrams showing one embodiment of the present invention. In Figures 1 and 2, explanations are omitted for the same parts as in Figure 3, 2o is a tension control device between the third stand and the fourth stand, and 3] is a rolling load control device for the fourth stand. It is a device.

The signal from the fourth stand rolling load meter 8D enters the rolling load control device 31 and is compared with a target value. An output corresponding to the deviation is output from the rolling load control device 31 to the rolling position control device 21D, and the rolling force controlling device 21D is connected to the hydraulic cylinder 7.
Control D to the commanded position. Rolling load control device 31
For the control operation, those used in normal feedback control devices, such as continuous PI sub-control sampling control, etc., can be used. Furthermore, by using a dead zone of deviation, it is possible to suppress the rolling load within a certain range with an allowable width.

Next, the control of the rear tension of the fourth stand and the control of the product board thickness will be explained, but the control methods are different in FIG. 1 and FIG. 2.

In FIG. 1, the fourth stand rear tension detected by the tension meter 13 is input to the tension control device 2o. The tension control device 2o compares this value with the target value, and sends an output corresponding to the deviation to the roll rotation speed control device 1. of the fourth stand. O.D.
Enter. The roll rotation speed control device 10D changes the rotation speed of the motor 9D according to this value. As for the control operation of the tension control device 20, similar to the control operation of the rolling load control device 31, those used in normal feedback control devices, such as continuous PI sub-control sampling control, etc. can be used. Furthermore, by using a dead zone of deviation, it is possible to suppress the rolling load within a certain range within the permissible range.

The thickness of the product 40 measured by the thickness gauge 14 is compared with the target value by the thickness control device 15, and the output according to the deviation is sent to the roll rotation speed control device 10D of the fourth stand, and at the same time to the third stand. Ratio setting device 1 in roll rotation control device 10C
Added via 7. This changes the mass flow within the rolling mill and controls the product thickness to the target thickness.

In FIG. 2, the fourth stand rear tension detected by the tension meter 13 is input to the tension control device 20. The tension control device f 20 compares this value with the target value and outputs an output corresponding to the deviation to the roll rotation speed control device 10C of the third stand.
Enter. The roll rotation speed control device IOC changes the rotation speed of the motor 9C according to this value. As the control operation of the tension control device 20, the rolling load control device 31
As with the control operation, those used in conventional feedback control devices, such as continuous PI sub-control sampling control, etc., can be used. Further, by using the deviation dead zone, the rear tension of the fourth stand can be suppressed within a certain range with an allowable width.

The thickness of the product 40 measured by the thickness gauge 14 is compared with the target value in the thickness control device 15, and the output corresponding to the deviation is sent to the roll rotation speed control device of the second stand, OB, and simultaneously to the first stand. stand roll rotation control device] is added to the OA via the ratio setting device 17. This changes the mass flow within the rolling mill and controls the product thickness to the target thickness.

In the embodiment of the present invention, compared to the conventional example, the distance between the installation position of the thickness gauge 14, which is the detection end, and the rolling stand, which is the operation end, is longer, so that Since it is difficult to compensate for the resulting product thickness, the controllability of the product thickness will be somewhat poor, but since the rolling load and rear tension of the final stand are kept almost constant, the deviation in product thickness will be within the allowable range. .

The following table shows an example in which the above control method is applied to the production of cold rolled steel sheets. Methods 1 and 2 are methods according to claim 1 of the present invention, method 3 is a method according to claim 2 of the present invention,
Methods 4 and 5 are examples of conventional methods. The thickness of each product plate is 0.8 mm.

The friction coefficient of the work roll in the final stand is 0.10 in Methods 1 and 4, and 0.03 in the other methods, and the deformation resistance of the rolled material at the entry side of the final stand is 0.10 in Methods 1 and 4.
．． 3.5 is 1.30 kg/mn, and other methods are 70 kg/mn. The steepness used as an index of plate shape is the height H (mm) of waves such as medium elongation or ear waves.
The ratio H/L of the wavelength L (mm) is expressed as a percentage (%), and the better the plate shape, the lower the value.

In methods 1 to 3 according to the present invention, the load fluctuation of the final stand is drastically reduced to 1/2 to 1/3 of the conventional method,
Because the operation is stable, the steepness of the plate shape is 1/1 that of the conventional method.
2 or less, which is a significant improvement. Furthermore, variations in plate thickness that tend to occur due to shape control are sufficiently suppressed, and the plate thickness accuracy is around ±1% of the plate thickness, which is equivalent to or slightly inferior to conventional methods.

[Effects of the Invention] According to the present invention, in high friction coefficient rolling and hard material rolling, not only the operation is stabilized, but also the shape of the rolled product is stabilized, and at the same time, the plate thickness can be kept within the allowable range. It has a great effect on improving the quality of thin sheet products.

16.17...Ratio setter, 18.19.20...
Tension control device, 21 Rolling down control device, 31/4th stage

[Brief explanation of drawings]

Figures 1 and 2 are block diadems showing an embodiment of the present invention, Figure 3 is a block diagram showing the prior art, and Figure 4 is a graph showing the relationship between the friction coefficient and the normalized tension change coefficient. , FIG. 5 is a graph showing the relationship between the average deformation resistance of the rolled material (deformation resistance of the rolled material before rolling) and the normalized tension change coefficient. Note that the suffixes A and B are
1st each. Equipment belonging to the second stand, suffix C
1D represents equipment belonging to the (third) stand preceding the final stand and the final (fourth) stand, respectively. ]・1st stand, 2・2nd stand, 3・3rd stand, 4・4th stand, 5・support roll, 6・・
Work roll, 7...Hydraulic cylinder 8...Rolling load meter, 9
・・Drive motor, 10・Roll rotation speed control device, 11
．． 12.13...Tension meter, 14...Thickness gauge, 15 Thickness control device, rolling load control device for tand, 40...Product.

Claims (2)

[Claims] (1) In a thin plate cold tandem rolling mill, by controlling the rolling position of the final stand, the rolling load of the stand is kept constant, and by controlling the roll rotation speed of the final stand, the By keeping the tension constant and controlling the rolling positions of the stands other than the first stand and the last stand, the rear tension of each of the stands is kept constant, and the roll rotation speed of the last stand and the stand in front of the stand is controlled. A method for controlling a cold tandem rolling mill, characterized by: maintaining a product plate thickness constant by controlling . (2) In a thin plate cold tandem rolling mill, by controlling the rolling position of the final stand, the rolling load of the stand is kept constant, and by controlling the roll rotation speed of the stands other than the final stand, the final By keeping the rear tension of the stands constant and controlling the lowering positions of the stands other than the first stand and the last stand, the rear tension of each of the stands can be kept constant and the roll rotation speed of the stands other than the last stand can be controlled. In the cold rolling of materials with high deformation resistance, which is characterized by keeping the product plate thickness constant through control,
Control method for cold tandem rolling mill.