JPH0237906A - Flatness controller for sheet rolling mill - Google Patents

Abstract

PURPOSE:To improve product quality and yield by providing a load detector and bender pressure controller to the sheet rolling mill, then computing and setting the load change rate and bender pressure manipulated variable which are respectively expressed by specific conditions. CONSTITUTION:The load detector 4 and the bender pressure controller 3 are disposed to the inlet side and outlet side of the sheet rolling mill 2 having work rolls W1, W2 and back-up rolls B1, B2. The rolling load Pa of this time, when detected by the load detector 4, is inputted together with the rolling load Pb of the previous time from a memory 6 into a load change rate computing means 5 where the load change rate alpha is computed by the equation alpha=(Pa-Pb)/ Pb. Further, the bender pressure manipulated variable DELTAF is computed by the equation DELTAF=DELTAFb+g.alpha in accordance with the gain g of a gain selecting means 7. In the equation, DELTAFb is the previous bender pressure manipulated variable. The bender controller 3 suppresses a flatness fluctuation in this way even at the time of generation of disturbance, etc., during rolling. The product quality and yield are, therefore, improved.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention provides a plate provided with a bender for controlling the flatness of a rolled plate and a bender control device for controlling the bender. The present invention relates to a flatness control device for a rolling mill.

(Prior Art) When rolling a plate using a rolling mill, one of the important indicators for evaluating product quality is plate flatness. Accordingly, rolling mills with enhanced flatness control functions have been developed in recent years and are being applied to actual machines. Coupled with the fact that product quality requirements have become increasingly strict in recent years, requirements for flatness control have also become increasingly strict.

FIG. 4 shows, in the form of a flowchart, an example of vendor control performed by a conventional control device that performs feedforward control. It is known that the plate flatness after rolling tends to cause so-called "edge elongation" when the rolling load increases, and to cause so-called "belly elongation" when the rolling load decreases. Conventional control devices focus on this phenomenon, and when the rolling load increases, the bender pressure is increased to suppress edge elongation, and when the rolling load decreases, the bender pressure is reduced to suppress the belly elongation. In Figure 4, block 4
1 is a block for determining whether or not it is the timing to start control; if it is the timing to start control, the process proceeds to block 42; otherwise, the process proceeds to block 43. Block 42 is a block for inputting and storing a standard rolling load. Block 43 inputs the current rolling load and calculates the bender pressure operation amount Δ.
This is a block that calculates the bender pressure operation amount ΔF based on the rolling load Po at the rolling load P1 control start timing at the current sampling time and the control gain k, as follows: ΔF−k・(P−Po)/Po・...Calculate as (1).

Block 44 is a block that outputs the bender pressure manipulated variable ΔF determined in block 43.

Although not shown, the bender control device changes the bender pressure in accordance with the amount of bender pressure manipulation. Due to the above-mentioned effects, even when the rolling load changes rapidly and greatly due to disturbances such as acceleration and deceleration, it is possible to maintain good plate flatness.

(Problem to be solved by the invention) Generally, rolling mills have unique characteristics, and there are cases where it is easier to operate when the flatness is extended, and vice versa. The values are often different between the side where the belly is stretched and the side where the ears are stretched. Furthermore, due to product requirements, there are many cases where it is not possible to stretch the belly or the ears. With conventional control devices, it is difficult to always maintain the control gain at an optimal value in response to such operational demands.

FIG. 5 shows an example of the operation of the rolling mill when the control gain k is smaller than the optimum value. In FIG. 5, the horizontal axis is time, and the vertical axis shows flatness pattern, rolling speed, rolling load fluctuation, bender pressure operation amount ΔF1 and bender pressure manual intervention amount ΔFm. In FIG. 5, deceleration starts at timing T1, deceleration ends at timing T, acceleration starts at timing T4, and acceleration ends at timing T5. As the rolling speed decreases, the rolling load increases, and as the rolling speed increases, the rolling load decreases, and the bender pressure operation amount ΔF changes accordingly. However, since the control gain k is small, the flatness fluctuation cannot be suppressed, and the timing T2
Ear stretching occurs.

In order to correct this, the operator manually intervenes at timing T3 (manual intervention amount ΔFm occurs) to further increase the bender pressure. However, when acceleration starts at timing T4, the bender pressure operation amount ΔF does not decrease much, so that the belly stretch increases. The operator manually intervenes at time T6 to correct this, further reducing the bender pressure.

FIG. 6 shows an example of operation when the control gain k is larger than the optimum value. In this case, contrary to the case in Figure 5,
Since the amount of increase in the bender pressure operation amount ΔF from the deceleration start timing "11" to the end timing "12" is too large, a large stretch occurs. The operator manually intervenes at timing "13" to correct this and lowers the bender pressure.

However, when acceleration starts at timing T14, the bender pressure operation amount ΔF decreases significantly, causing the edge to stretch. The operator needs timing T to correct this.
Manual intervention is made at 1B to increase the bender pressure.

Assuming that it is not possible to extend the ears due to operational constraints, the fifth
The parts rolled between timing T1 and T3 in the figure and between timing T15 and TlB in FIG. 6 cannot be shipped as products.

In order to obtain a product with the desired plate flatness, the control gain must always be maintained at an optimum value, but as mentioned above, with conventional control devices, it is difficult to maintain the control gain at an optimum value. However, the desired effect could not be obtained.

The present invention has been made to solve the above problems, and it is possible to satisfy operational constraints even when the rolling load changes, and to suppress fluctuations in plate flatness.
It is an object of the present invention to provide a flatness control device for a plate rolling mill that can thereby improve product quality and further improve yield.

[Structure of the invention]

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a load detector that detects the rolling load of a plate rolling mill, and a rolling load detected by the load detector at the current control timing. The load change rate α is calculated from Pa and the rolling load Pb at the previous control timing, a= (Pa-Pb)/Pb-(2
), gain selection means for selecting the control gain g according to the operational requirements for the polarity of the load change rate α calculated by the load change rate calculation means and the plate shape, and the previous control timing. Based on the bender pressure operation amount ΔFb in , the control gain g selected by the gain selection means, and the load change rate α calculated by the load change rate calculation means, the current bender pressure operation amount ΔF is calculated as follows: ΔF=ΔFb+gaa =・(3) The present invention is characterized in that it is provided with a bender pressure manipulated variable calculating means for calculating as follows.

(Function) If the control gain g is insufficient when the load change rate α is positive, or if the control gain g becomes excessive when the load change rate α is negative, ear elongation is likely to occur, and if the load change rate α is positive When the control gain g becomes excessive, or when the control gain is insufficient when the load change rate α is negative, belly elongation tends to occur. Therefore, if it is not possible to extend the edge due to operational reasons, a larger control gain is applied when α≧0, and a smaller control gain is applied when α is less than 0. Similarly, when belly stretching is not possible, a smaller control gain is given when α≧0, and a larger control gain is given when α is less than O. In this way, by modifying the control gain of the bender control system according to the polarity of the load change rate and operational requirements, it is possible to meet the requirements for not allowing edge extension or belly extension, and to improve product quality.

(Example) FIG. 1 shows an embodiment of the present invention.

Here, the plate material 1 to be rolled is a work roll Wl.

A case is illustrated in which rolling is performed with a rolling load P by a quadruple rolling mill 2 consisting of W2 and backup rolls Bl and B2. This rolling mill is equipped with an end bender for controlling the shape of the plate, and the pressure of the bender is controlled by a bender pressure control device 3.

The rolling load P is detected by the load detector 4, and the flatness i
; It is guided by the load change rate of the rJ control device. The configuration and operation of the control device will be explained below with reference to FIG. 2 as well.

First, it is determined in block 11 whether or not it is the control start timing. As a result, if it is the control start timing, the process proceeds to block 12, and if not, the process proceeds to block 14.

In block 12, the rolling load P at the control start timing is
a is input from the load detector 4, and it is calculated as the previous rolling load Pb.
In block 13, the current and previous bender pressure operation amounts ΔF and ΔFb are cleared.

In block 14, the rolling load Pa from the load detector 4 is input manually, and it is used as the current rolling load, and in the next block 15, the load change rate calculation means 5 calculates the load change rate α according to equation (2). The polarity of the load change rate α calculated here is determined in block 16 by the gain selection means 7.

Here, if α≧0, then in block 17 g ”' g
1, and if α is 0, then in block 18 g = g
Set it to 2.

In block 19, the bender pressure operation amount ΔF is calculated by the bender pressure operation calculation means 8 based on the load change rate α from the load change rate calculation means 5 and the gain g from the gain selection means 7 according to equation (3).

The current bender pressure operation amount ΔF obtained in this way
and rolling load Pa are stored in the memory 6 as the respective previous values ΔFb and ΔPb in block 20, and in block 21, the bender pressure operation amount ΔF
is applied to the bender pressure control device 3 to control the bender pressure.

The operation of the flatness control device shown in FIGS. 1 and 2 will be explained with reference to FIG. 3.

FIG. 3 illustrates a case where an acceleration/deceleration disturbance similar to that in FIGS. 5 and 6 is applied. Assuming that selvedge extension is not possible due to operational constraints, if the load increases, the state at timing T1° in Figure 6 is allowed,
When the load decreases, the state at timing T5 in FIG. 5 is allowed. That is, when the load change rate α in the embodiments of FIGS. 1 and 2 is positive or zero, it is possible to set the control gain g1 to a value slightly larger than the optimal value, and the load change rate α When the control gain g2 is negative, it is possible to set the control gain g2 to a value slightly smaller than the optimum value.

Assuming that full extension is not possible due to operational constraints, the control gain g1 is set to a value slightly smaller than the optimal value,
It is possible to set the control gain g2 to a value slightly larger than the optimal value.

In Figure 3, it is assumed that the ears cannot be stretched. In FIG. 3, timing T21 is the deceleration start timing, T is the deceleration end timing, ``24'' is the acceleration start timing, and ``25'' is the deceleration start timing.
is the acceleration end timing. The rolling load P increases as the speed decreases from timing T to timing "22, but the bender pressure operation amount ΔF increases in accordance with the rolling load change. This increase amount is because the control gain g1 is slightly larger than the optimum value. Deceleration end timing”22
In this case, the flatness will be slightly larger than the target flatness. In response, the operator manually intervenes at timing ``23'' to reduce the bender pressure and make the flatness match the target value.Furthermore, as the rolling speed increases from timing T to timing ``25'', Although the rolling load decreases, the bender pressure operation amount ΔF decreases in accordance with the change in the rolling load. This reduction amount is due to the fact that the control gain g2 is slightly smaller than the optimal value, so the acceleration end timing is
At 25, I'm a little more belly-stretched than my goal. In response, the operator manually intervenes at timing T2B to reduce the bender pressure and bring the flatness to the target value. As described above, according to the present invention, as shown in FIG. 3, it is possible to easily realize an operation in which the selvage cannot be stretched. In particular, the present invention can achieve great effects when the target flatness is brought close to flatness.

〔Effect of the invention〕

As described above, according to the present invention, even when disturbances such as acceleration/deceleration are applied during rolling, operational or quality constraints can be satisfied, and flatness can be suppressed to suppress flatness fluctuations. A control device can be provided, which can improve product quality and further improve yield.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart for explaining the operation of the control device of the same embodiment, and FIG. 3 is an example of the operation of the control device of FIG. 1. FIG. 4 is a flowchart for explaining the operation of the conventional control device, and FIGS. 5 and 6 are time charts for explaining the operation of the conventional control device in different states. DESCRIPTION OF SYMBOLS 1... Rolled plate material, 2... Rolling machine, 3... Bender pressure control device, 4... Load detector, 5... Load change rate calculating means, 6... Memory, 7... ... gain selection means, 8... bender pressure operation amount calculation means, P... rolling load, α... load change rate, ΔF... bender pressure operation amount, g... control gain.

Claims (1)

[Scope of Claims] A flatness control device for a plate rolling mill that includes a bender for controlling the flatness of a rolled plate material and a bender control device for controlling the bender, which detects the rolling load of the plate rolling mill. Calculate the load change rate α from the rolling load Pa at the current control timing detected by this load detector and the rolling load Pb at the previous control timing as α=(Pa-Pb)/Pb. rate calculation means, gain selection means for selecting the control gain g according to the operational requirements for the plate shape and the polarity of the load change rate α calculated by the load change rate calculation means, and the bender pressure operation amount ΔFb at the previous control timing. , the bender pressure operation amount ΔF is calculated based on the control gain g selected by the gain selection means and the load change rate α calculated by the load change rate calculation means as ΔF=ΔFb+g・α. 1. A flatness control device for a plate rolling mill, characterized in that a calculation means is provided.