JPS609511A - Method for controlling dimension in rolling mill - Google Patents

Abstract

PURPOSE:To roll effectively a hard and thin material by correcting the control command of a motor used for driving rolls basing on the deviation signal between target dimensions and measured dimensions, in rolling the material between a pair of rolls. CONSTITUTION:A pair of rolling rolls 2H, 2L having each a different diam. are separately driven by thyristor-Leonard devices 6H, 6L to control nonsymmetrically the speeds and torques, etc. of them. A rolling material 1 is rolled by the rolls 2H, 2L and measured by a thickness-deviation detecting device 3 to input a deviation signal to an arithmetic device 4 when the deviation in thickness is detected. The device 4 calculates the changing quantity of desired speed basing on a prescribed equation to transmit it to a speed-control arithmetic device 7 of an equipment 6L, from which the signal is outputted to a roll-driving DC motor 11 through a current-control arithmetic circuit 8, a reversible thyristor-conversion-device 9, and a current detecting device 10, to correctingly control the torque of rolling roll 2L.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention is utilized for dimensional control of general full-bending rolling equipment, particularly for automatic plate thickness control of metal plates. Among these, it is particularly effective for rolling hard and thin materials. - [Background of the Invention] In conventional rolling technology, there are two main methods for controlling the thickness of a metal plate.

As shown in Fig. 1, when a rolled material 1 is rolled by a set of rolling rolls 2, in order to control the dimension of the exit plate thickness, the roll gap, indicated by the symbol S in the figure, is added to the material. There are two methods for controlling the front and rear tension forces Tr and Tb. Another method is cold rolling using a lubricant, in which the composition of the lubricant is changed to control the coefficient of friction between the roll and the metal material. These control principles are schematically illustrated in FIG. 2 in terms of the balance between the forces of elastic deformation of the rolling mill and plastic deformation of the rolled material.

In Fig. 2, the vertical axis is the rolling load, and the horizontal axis is the entrance plate thickness H.
o, outlet side plate thickness hO+ h31 * h32 + h4
1 +h42. Roll gap SO + "1 + 52, etc. are shown on the same axis. Curves 30, 31, 32 show the elastic elongation curves of the rolling mill, and curves 40, 41, 42 show the plastic deformation curves of the rolled material. In the figure, the elastic curves When a material with an entry side thickness Ho whose plasticity curve is indicated by 40 is introduced into a state where the roll gap is set to 30 and the roll gap is set to s6, the operating point is indicated by the intersection AO of the curves 30 and 40, The plate thickness at the exit side is hol, and the rolling load at that time is P.

It is indicated by.

As a method of controlling the dimensions of the rolled material mentioned above, the method of changing the roll gap is to move SQ to SI or S2 in Fig. 2, change the operating point from Ao to A31 or tiAs*, and as a result This method controls the outlet plate thickness to h31 or h32, and is a method commonly used in all rolling equipment. Next, the method of controlling the tension of the rolled material by changing the tension is equivalent to changing the plasticity curve of the rolled material with equal constraints.If one or both of the front and rear tensions is weakened, the curve becomes 4.
It moves from 0 to 41, and conversely, if it is strengthened, it moves from 40 to 42, and the operating point moves to A41 or A42, respectively, and as a result, the exit side plate thickness is controlled to h41 or h42. Changing the slipperiness using a lubricant also results in changing the slope of the plasticity curve.

The features of each control means will be described. The method of adjusting the roll gap is the most commonly used, and in recent years hydraulic high-response roll gap adjustment devices have been put into practical use, making it the most effective method as an online control means. However, if the rolled material is hard or has become thinner and has progressed to work hardening, most of the force applied to the rolled material by narrowing the gap will be consumed by the flattening of the rolls, even if the roll gap is adjusted. Reducing the thickness of the rolled material is used as the second most effective dimensional control method after controlling the tension applied to the rolled material after the roll gap, and is especially effective when the hardness of the rolled material is ff, making it difficult to adjust the roll gap. It is a method. If I had to point out the problems, the response of the tension control method is a little slower than that of the roll gap control method, and in batch rolling, there is no tension at the leading and trailing edges, so the dimensions tend to change significantly, and this compensation is done by adjusting the roll gap. There are some limitations, such as the need to consider control and the need to roll with a constant tension depending on the rolled material. It is difficult to change lubricant control continuously online, and the reality is that once the settings are made, they are rarely changed online.

A major limitation of this is that the response is slow compared to the other two methods.

[Purpose of the invention]

It has been a long time since an asymmetric rolling method has been proposed, in which an upper and lower set of rolls are rolled with a speed difference or a torque difference. Moreover, it has been gradually demonstrated that this rolling method is particularly effective for rolling thin materials with advanced work hardening or materials that are materially hard, which could not be achieved by conventional rolling methods.

An object of the present invention is to actively utilize the asymmetric rolling method of upper and lower roll circumferential speeds as a means of dimensional control, thereby improving roll gap control, especially in automatic plate thickness control during rolling of thin plates or hard materials. The purpose is to provide an auxiliary means for controlling the plate thickness when it reaches its limit, and at the same time to restore the effective range of roll gap control.

[Summary of the invention]

FIG. 3 shows the effect on the plate thickness when the rolling speed or rolling torque of the - set of rolls is changed. Fig. 3 shows a situation in which the rolled material 1 is caught between a pair of rolling rolls 2R and 2L and rolled, but unlike normal symmetrical rolling, the neutral points 3H and 3L are asymmetrical as shown in the figure. in position. It is well known that changing the neutral point position of a set of rolls in this way can be achieved by controlling the speeds of the electric motors that drive the rolls to different values individually. (This is called true speed rolling or different torque rolling.) In such true speed or different torque rolling, the positions of the neutral points are different in the region (■) shown in the figure, so the frictional forces μFIPII and μI , Pt, are in opposite directions and cancel each other out, so that no peak of rolling load occurs. Therefore, the load distribution within the contact arc between the material and the roll is reduced compared to the case of target rolling. In other words, the vertical axis 4 in Figure 3
indicates the load, the horizontal axis 5 indicates the horizontal projection table of the contact arc, and the pressure distribution along this indicates ABC during target rolling.
In contrast to DEFG, which shows a peak at point D, in asymmetric rolling, between the positions of the neutral points of each roll (in terms of angles, φ is θ, φH1φL, and φ is each a neutral angle). # Indicates a constant load. As a result, as is well known, in asymmetric rolling, the total rolling load, which is the sum of the load distributions, is small and does not have a peak, so the degree of roll flattening is small, and the limit thickness for thin material rolling due to the load limit is also large. It will be relaxed to a wide extent.

The conventional use of true speed rolling or differential torque rolling was to set a true speed ratio or a differential torque ratio to roll a thinner plate with a small load.

The present invention focuses on the fact that the rolling load changes even with the same roll gap by changing the true speed or the degree of the different torque, and this is achieved by changing the plasticity curve shown in FIG. Take advantage of the fact that it has the same effect as adjusting.

That is, in FIG. 2, the rolling operating point at a slightly different true speed or different torque is defined as point Ao. When the degree of true speed or different torque is increased, the ■ area in Figure 3 becomes wider, and ΔCDE
It can be seen that the area of is expanded and the load is reduced.

This can be seen in Figure 2 by changing the plasticity curve from 40 to 42 while keeping the roll gap at s (1), moving the operating point from Ao to A42, and changing the load to P.

The plate thickness decreases from ho to h4w. Conversely, if the true speed or the direction of the different torque is decreased, the plasticity curve increases from 40 to 41, the operating point increases from AO to A41, the load increases from Po to P41, and the plate thickness increases from h4
It becomes thicker to 1.

It can be seen that the direction of this operation is completely opposite to the direction of roll gap operation when viewed from the rolling load. When a roll gap is used, if the plate is made thinner, the rolling load increases because the gap is narrowed. On the other hand, the direction in which the true speed or the degree of differential torque is increased is the direction in which the plate is made thinner and at the same time the rolling load is reduced. In this case, work hardening progressed by actively changing the true speed or the degree of differential torque online (actually very little), and since it is a hard material, it is easy to control the roll gap. In addition to providing an effective control method for rolled materials that cannot obtain accurate plate thickness accuracy, when the normal roll gap control reaches its limit, the rolling load is reduced by bringing it into the true speed or different torque range. However, the present invention utilizes these effects.

[Embodiments of the invention]

A first embodiment of the invention is shown in FIG. In this figure, 1 is a rolled material, and 2R and 2L are a set of rolling rolls, which basically have asymmetric diameters and whose speed, torque, etc. are controlled asymmetrically. Each rolling roll is individually and independently driven by a 61.6 t thyristor Leonard device surrounded by a dashed line, and in this figure both rolls are equipped with a speed control system (ASR).

The roll drive system does not necessarily need to be a thyristor Leonard device as long as the speed can be controlled independently. In an independent speed control system, the speed command device 51.5L independently gives speed commands, but in this embodiment, for convenience, the vertical roll speed Va is equal to or thicker than the high roll speed VL. It is assumed that the lower roll speed becomes the standard rolling speed. 3 is a thickness deviation detection device, and the output is zero when the outlet side plate thickness matches the target plate thickness. The arithmetic device 4 is the main part of the present invention implementation section,
This is a calculation device that commands the speed difference between the upper and lower rolls that should be given when a plate thickness deviation occurs.The basic calculation formula calculated by this device is as shown below.

Δ■ is the change speed difference of the upper roll selected as the control target when there is a thickness measurement difference Δh, and the direction is the speed decrease if the deviation plate thickness is thick or the speed increase if the deviation plate thickness is thin. The direction is to raise it. (1) In the formula, CaP/θML) is
This is the influence coefficient of load fluctuation when changing the speed on the low speed side, and is calculated in advance for each schedule. Since the load change divided by the rolling mill elastic modulus indicates the thickness change, (1
) The required speed change amount is calculated using the formula. In principle (1
) may be used, but to add some details regarding implementation, the control output ΔvL has a limit value ΔVIM)X +ΔVLMIN on the speed-up and speed-down sides, respectively, as shown in the calculation device 4. Δ■LMAxha■t+ΔV Lwhx riVI
I, ΔVLMtN is Vt, -ΔVLMn+≧Vt, x
ts te given, VLmtst;1. , set as the speed at which the neutral point of the upper roll reaches the entry limit of the contact arc table. As an explanation of the figure, 7 is a speed control calculation device, 8 is a current (=torque) control calculation circuit, 9 is a forward feed thyristor conversion device, 10 is a current detection device, 11 is a roll drive DC motor, and 12 is a finger chain generator. Indicates a rocky shore.

A second embodiment of the invention is shown in FIG. The difference is that the roll drive control method is not a speed command method but a torque command method. That is, as methods for asymmetrically controlling a set of upper and lower rolls, there are two possible methods: one in which a difference is given by the circumferential speed of the rolls, and the other in which a difference is given by the rolling torque. Both methods can be said to be the same in that they reduce the rolling load, but the command method that gives a difference in the output torque of the electric motor, which is directly related to the load, is more direct and accurate. . 1.2 in figure
L, 2n, and 3 are the same as in FIG. 4. The thyristor Leonard device that drives the rolls uses the F roll speed as a reference, as in the first embodiment, and sends a command based on the speed difference as a current command (-torque command) to the current control calculation circuit 8 of the thyristor Leonard devices of the upper and lower rolls, respectively. give. Furthermore, the current control calculation circuit 8 includes a torque setting device 5,
The torque is applied to the upper roll in the subtraction direction and the lower roll in the addition direction, and the torque is subtracted from the upper roll and added to the lower roll from the torque command determined at the time of target rolling, giving a torque difference.

When the sheet thickness at the exit side deviates from the target sheet thickness under rolling conditions such as this, the deviation output No. 3 is given to the control calculation circuit 4. If the plate thickness deviation is thick, a control command is given to further reduce the torque of the upper roll and further increase the torque of the lower roll, and if the deviation is thin, the control command is given in the opposite direction. The calculation formula for the control amount is given by the following formula.

Δτ is the torque change command to be given, (aP/θτ
) is calculated and given in advance for each schedule as the influence coefficient of load change when torque is changed (of course, it may be calculated online if the calculation speed is fast enough). The control range Δτ is not infinite, but has upper and lower limits as shown in 4. This is ΔτMAx<Δτ×ΔτMIN, and ΔτMAX is the torque at which the neutral point of the upper roll corresponds to the entry limit point of the contact arc table. 21M1'H corresponds to the set torque of the different torque command device. Inside the dashed line 61
The explanation of each number of 1.6L is the same as in the case of FIG.

The third embodiment is different from the first and second embodiments in its application purpose. That is, in the first and second embodiments, as plate thickness control in a state where true speed or different torque rolling is originally performed, the roll opening degree or longitudinal tension is not controlled, but the degree of true speed,
Although we have provided a method that enables plate thickness control by adjusting the degree of different torque, in this example, work hardening progressed and it became difficult to control plate thickness using the roll gap in a situation where target rolling was originally performed. In this situation, in order to continue rolling while keeping the plate thickness constant, true speed or different torque is actively used as a plate thickness control means. That is, in FIG. 6, it is assumed that the rolling rolls 2H and 2L are symmetrically driven by the same-numbered Silis-Screonard devices shown in the above-mentioned embodiment, and the automatic plate thickness control is also controlled by the thickness needle signal 3. It is assumed that the roll opening degree is adjusted using conventional hydraulic valve devices 21 and 22. In this case, when hard materials such as carbon materials and non-ferrous special alloys are being rolled, or during skin pass rolling, the deformation resistance of the material is large, so even if the roll opening is tightened and the rolling load is increased, the load is In some cases, it is consumed only for deformation and is hardly used for deforming the material. If this situation was known in advance, it would be sufficient to set the true speed or different torque rolling in advance, but even if the target rolling is started and the control is advanced, the specified thickness cannot be maintained by controlling only the roll opening degree. There are cases where it is difficult to do so. In order to solve this problem, this embodiment is proposed, and when the output of the calculation device 24 for normal automatic plate thickness control progresses unilaterally in the direction of increasing the load and reaches the limit value, the normal automatic plate thickness control A logical operation is performed to saturate and interrupt the automatic plate thickness control, and a saturated signal is provided to another arithmetic unit 25. The arithmetic device 25 performs the same calculation as that shown in the above embodiment, and executes the calculation of equation (1) or (2) according to the plate thickness deviation after saturation of the arithmetic device 24. Based on the results, plate thickness control is performed by controlling the speed of the controlled object side or the torque of both. This control lowers the rolling load so that the rolling force 24 goes out of the saturation region and returns to the controllable region, but it is necessary to take measures such as providing a slight hysteresis characteristic to prevent control hunting.

〔Effect of the invention〕

The effect of the present invention is that in true speed or different torque rolling, which has recently been put into practical use, the effect principle of true speed or different torque rolling is different from the conventional method of controlling plate thickness + til J by adjusting the roll opening or front and rear tension. We provide a new plate thickness control method using this material. The present invention is particularly effective in rolling hard materials into thin sheets.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams for explaining the rolling phenomenon, Figure 3 is a diagram for explaining the present invention in detail, and Figures 4 to 6 are diagrams showing embodiments of the present invention. . 2L, 2+1...Roll, 3...Thickness deviation detection device, 4...Arithmetic device, 5L, 5n...Speed command device,
6L. 6H...Motor open side 1 part, 5...Torque setting device,
21 and 22... Hydraulic lowering device, 23... Load detector, 24 Funeral 17

Claims (1)

[Claims] 1. In a control method for controlling the dimensions of a rolled material in a rolling mill that passes a rolled material between a set of rolls and performs rolling,
1. A method for controlling dimensions in a rolling mill, comprising modifying a control command for a motor that drives the set of rolls based on a deviation signal between a target dimension and an actual dimension.