JPH05305320A - Method for controlling thickness in continuous hot rolling mill - Google Patents

Abstract

PURPOSE:To improve the accuracy of gagemeter formula by determining the amount of roll wear/expansion in each stand and executing screw down position setting of the next material and screw down position correcting control on the way of passing sheet between the stands. CONSTITUTION:The thickness control is executed in a continuous hot rolling mill having plural rolling stands 1-7 and loopers between the stands. The thicknesses on the outlet sides of the respective stands 1-7 are measured based on a mass flow fixing formula with a thickness gage 10 on the outlet side of the final stand 7, thickness gage 11 which is installed between arbitrary stands and respective looper rotation detectors 21-26 between the stands. Errors between this thickness and the estimated thickness that are determined by a formula for estimating thickness on the outlet side of an own stand itself that consists of the load and actual result of screw down position at the own stand itself are determined. The amount of roll wear/expansion of each stand is determined from them and the screw down position setting of the next material and screw down position correcting control on the way of passing sheet between the stands are executed. In this way, the reduction of off-gage length can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip thickness control method in a hot continuous rolling mill.

[0002]

2. Description of the Related Art Sheet thickness control methods in a hot continuous rolling mill are roughly classified into the following four types. Setup control that sets the reduction of each stand before the material enters the continuous rolling mill.Dynamic setup control that resets the reduction position of the post stand of the non-passing plate when the material tip is passing during the middle of the stand. Absolute value AGC h _i = MS (P _i ) + S that estimates the stand-out side plate thickness with a gauge meter formula (see the following formula) from the actual results of the own stand load and rolling position and controls it to converge to the target value. _i + ε _i However, h _i : i stand output side plate thickness P _i : i stand load S _i : i stand pressure reduction position result z _i : i stand gauge meter error Plate thickness from the plate thickness gauge placed on the final stand output side Monitor AGC, which is feedback control based on actual results. Here, in order to improve the sheet thickness accuracy in hot rolling, it is necessary to obtain the desired sheet thickness from the leading edge. In the case of applying only the monitor AGC, the rolling reduction cannot be carried out until the material tip has passed through the final stand, and improvement in the accuracy of the leading edge cannot be expected.

Therefore, it is necessary to apply setup control, dynamic setup control, and absolute value AGC. The control flow of each control method is shown in FIG. 3. In each case, it is necessary to estimate the stand-out side plate thickness by a gauge meter type consisting of a load and a rolling position, and it is essential to improve the accuracy of this gauge meter type.

In order to improve the accuracy of the gauge meter system, it is necessary to estimate the wear / expansion amount (gauge meter error) of each stand work roll for each material. Conventionally, as seen in JP-A-53-24873, the advanced rate of each stand at the leading edge is obtained from the signal rise time of the load meter or the finishing delivery side sensor, and the mass flow constant formula from the final stand delivery side thickness gauge is calculated. From this, the gauge thickness of each stand was estimated and the gauge meter error was calculated. The outline of this method is shown in FIG. In the figure, 1 is an i-stand, 2 is an i + 1 stand, 3 and 4 are load cells for measuring the rolling load of each stand, 5 is a metal-in signal detection unit for detecting that a plate is caught in a rolling roll of the stand, and 6 is Mill motor 7
Generator (PLG) 8 to detect the rotation speed of
This is a calculation unit for calculating the advanced rate f from the number of pulses n from and the metal-in signal. The advanced rate f can be obtained as follows.

First, from the i stand to the i + 1 stand (i
Is the final stand, and the feed length of the material to the final stand outlet side thickness gauge is l _R , then l _R = π · D _i N / n where D _i : work roll diameter n: work roll 1 Number of PLG output pulses per rotation N: Total number of pulses in t time, where t is the time for the material tip to move from the i stand to the i + 1 stand (when i is the last stand, the final stand outlet thickness gauge). is there.

Next, assuming that the distance between stands is l _ST (distance from the final stand to the final stand exit side plate thickness gauge when calculating the advance rate on the exit side of the final stand), the advance rate f is as follows. expressed.

F = (l _st / l _R ) −1 Therefore, f = {l _st / (π · D _i N / n)} −1 However, according to the method described in Japanese Patent Laid-Open No. 53-24873. If so, there is a difference in the passing time of each stand due to the occurrence of a loop at the tip of the material, and there is an error compared to the advanced rate at the leading edge where tension is occurring, because it is a measured value in a tensionless state. There was a drawback. As a result of actual measurement, there was an error of ± 2 to 3% with respect to the advanced rate of about 4% at the final stage of delivery.

For this reason, the accuracy of the gauge meter system is not sufficiently improved. Considering the conventional dynamic setup control as disclosed in, for example, Japanese Patent Laid-Open No. 56-71516, this control involves the i-stand biting. Based on the error ΔP _i between the predicted load and the actual load, it is assumed that all the load errors are deviations of the material plasticity coefficient, and the plasticity coefficient produces an error at the same ratio even at the i + 1 stand, and the i + 1 stand inlet side plate thickness variation ΔH _{i +1} and the modified plasticity coefficient Q ′ _{i + 1} are ΔH _{i + 1} = MS _i (ΔP _i ) (MS _i : i stand mill stretch amount) (1) Q ′ _{i + 1} = Q ′ _i / Q _i × Q _{i + 1} (Q ′ _i : corrected plasticity coefficient at i stand) (2) is a feedforward control method in which the rolling position of the i + 1 stand is corrected before the i + 1 stand is engaged.

Actually, however, the load error ΔP _i at the i-stand is, as shown in FIG. 5, (a) due to the i-stand entry side plate thickness variation, (b) due to the plastic coefficient variation,
(C) Due to a gauge meter error which is a rolling position setting error, three factors are complicatedly entangled. Therefore, if a load error occurs because the gauge meter error is a major factor and the reduction position is overtightened, it is considered that the i stand stand-out side plate thickness is smaller than the target plate thickness. Then, the cause of the error is that the plate thickness shifts in the direction opposite to the cause of the inlet side thickness and the cause of the plasticity coefficient.Therefore, when the conventional dynamic setup control is performed, there is a case where erroneous control occurs. It was

FIG. 6 shows an example of control by the conventional dynamic setup method, in which the horizontal axis represents the stand load error and the vertical axis represents the deviation of the outgoing plate thickness. Before the control shown in FIG. 6A, the inlet side plate thickness variation factor and the plasticity coefficient error factor are large,
After the control of FIG. 6 (b), these factors became smaller,
The gauge meter error factor is increasing, and the distribution of deviations does not change much before and after control. From this, it can be seen that the control is clearly overcontrolled.

[0011]

In consideration of the above, if the accuracy of the gauge meter error of each stand can be improved, the accuracy of the front stand outlet side plate thickness can be improved, and therefore the accuracy of the stand gauge meter error can be improved. The load error factor in the stand can be specified only by the plastic coefficient variation.

Also in the setup control, if the gauge meter error estimation accuracy is improved, only the control error due to the plasticity coefficient estimation error occurs, and the control accuracy can be improved.

Further, in the absolute value AGC, if the gauge meter error estimation accuracy is improved, the actual value of the stand-out side plate thickness can be obtained with high accuracy, which directly leads to improvement in control accuracy.

The problem to be solved by the present invention is to eliminate the conventional drawbacks in the calculation of the gauge meter error amount as described above.

[0015]

To solve this problem, the present invention provides a plate thickness control method for a hot continuous rolling mill having a plurality of rolling stands and inter-stand loopers,
With the final stand output side thickness gauge and the thickness gauge installed between any stands and the looper rotation detector between each stand, each stand output side thickness is measured based on the constant mass flow formula, and from the actual load and reduction position of the stand. The roll wear / expansion amount of each stand is obtained by obtaining the error from the estimated plate thickness obtained from the stand stand outlet side plate thickness estimation formula, and the rolling position setting of the next material and the rolling position correction control during the inter-stand threading are performed. Is to do.

[0016]

In the present invention, the plate thickness of each stand is measured from the constant mass flow formula by the plate thickness gauge between stands and the looper rotation detector between stands, and the gauge meter amount during the passage of the material can be accurately adjusted. Ask. As a result, the roll wear / expansion amount of each stand is obtained, the accuracy of the gauge meter system is improved, and the control accuracy of the rolling position setting of the next material and the rolling position correction control in the middle of the inter-stand passing plate are improved.

[0017]

EXAMPLES The present invention will be specifically described below based on examples.

First, as shown in FIG. 1, seven stands 1
In the hot continuous rolling mill consisting of 7 to 7, the final stand exit side plate thickness gauge 10 and the stand stand thickness gauge 11 (in this example,
(Between stands) are arranged, and the rotation detectors 21 to 26 are provided at the shaft ends of the looper rolls between the stands. Thickness gauge 10,1
1, an X-ray plate thickness gauge can be used, and rotation detectors 21 to
A pulse generator can be used for 26.

Equation (3) is obtained according to the law of constant mass flow.

H _i = h _4Xray × V ₄ / V _i (3) h ₇ = h _7Xray (3) ′ Here, h _i : i stand _output side plate thickness, V _i : i stand _output side plate speed h _4Xray : 4 -5 Measured value of thickness gauge between stands h _7Xray : Measured value of thickness gauge of exit side of final stand.

Further, since the gauge meter plate thickness is the equation (4), the gauge meter error of each stand can be obtained from the difference between the equations (3) and (4).

H _Gi = MS _i (P _i ) + S _i + ε _i (4) where h _Gi : i stand outlet side gauge meter plate thickness MS _i : i stand mill stretch amount P _i : i stand load cell actual value S _i : i stand pressure reduction position ε _i : i stand gauge meter error With this method, the gauge meter error can be measured with high accuracy over the entire length of the material, and this value can be used to set up as shown in FIG. By using control, dynamic setup control, and absolute value AGC, it is possible to improve the plate thickness accuracy of the leading edge of the next material.

Next, an example of carrying out the method of the present invention will be described below.

The plate thickness was controlled by the equipment having the structure shown in FIG. FIG. 2 shows before ((a)) and after performing the control according to the present invention.
It shows the deviation of the outlet plate thickness in ((b)). It can be seen that the distribution of the deviation is smaller after the control than that before the control, and the control accuracy is improved.

As a result of performing the rolling control of the present invention on ordinary steel with a plate thickness of 2.0 to 4.0 mm, the product yield within ± 50 μm at the tip 10 m was improved by about 10%.

[0026]

As described above, the present invention has the following effects.

Since roll wear and expansion in each stand are taken into consideration, the accuracy of the gauge meter system can be improved.

It is possible to improve the control accuracy of the rolling position setting of the next material and the rolling position correction control in the middle of the inter-stand passing plate, and to reduce the off gauge length.

[Brief description of drawings]

FIG. 1 is a schematic view showing a configuration of a rolling mill for carrying out a plate thickness control method according to the present invention.

FIG. 2 is a graph showing plate thickness deviations before (a) and after (b) control according to the present invention.

FIG. 3 is a flow chart of conventional plate thickness control, in which (a) shows a setup control, (b) shows a dynamic setup control, and (c) shows an absolute value AGC control.

FIG. 4 is an explanatory diagram showing a conventional gauge meter type plate thickness control.

FIG. 5 is an explanatory diagram showing an influence of a load error due to conventional control.

FIG. 6 is a graph showing an example of plate thickness deviation due to conventional dynamic setup control.

[Explanation of symbols]

1-7: 1st-7th stand, 10, 11: Thickness gauge, 2
1-26: Rotation speed detector

Claims (1)

[Claims] 1. A plate thickness control method for a hot continuous rolling mill having a plurality of rolling stands and a looper between stands, comprising:
With the final stand output side thickness gauge and the thickness gauge installed between any stands and the looper rotation detector between each stand, each stand output side thickness is measured based on the constant mass flow formula, and from the actual load and reduction position of the stand. The roll wear / expansion amount of each stand is obtained by obtaining the error from the estimated plate thickness obtained from the stand stand outlet side plate thickness estimation formula, and the rolling position setting of the next material and the rolling position correction control during the inter-stand threading are performed. A method for controlling plate thickness in a hot continuous rolling mill, the method comprising: