JPH02263508A - Method for determining lock on timing in automatic plate thickness control of rolled steel plate - Google Patents

Abstract

PURPOSE:To improve the quality and the yield of steel plate by locking on an automatic plate thickness controller when a rolling load is measured and a differential value required from the measured value has come below the desired set value for the differential value of a preset rolling load. CONSTITUTION:A lock on timing is decided in the automatic plate thickness control of the steel plate 1 rolled by a rolling mill composed of work rolls 2 and back up rolls 3. The rolled load is measured by a load cell 6 from the time when the steel plate 1 is bitten into the rolls 2 of the rolling mill. The time when the differential value obtained from the measured value of this rolled load has come below the differential value of a preset rolling load is operated by an arithmetic and control unit 8 and the automatic plate thickness controller is locked on by this time. In this way, the controllability of the plate thickness of the steel plate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for determining lock-on timing in automatic thickness control of rolled steel plates.

<Prior art> As is well known, an automatic I roll J'5' for rolling one roll of steel:
The fftlJ control (hereinafter abbreviated as AGC) is not performed immediately after the steel plate is inserted into the rolling mill, but is started at a certain length from the tip of the steel plate. In other words, at the tip of the steel plate, there exists a portion whose thickness is not controlled for a certain length from the tip.

This uncontrolled part is unfavorable in terms of quality, so it is cut out during the finishing stage and becomes scrap.If it is longer than necessary, the yield will decrease, and if the part is of various lengths or short, it will be difficult to handle on the line. This causes problems in determining the appropriate resection location. Therefore, this uncontrolled portion must have an appropriate length.

Here, to explain the conventional AGC using a gauge meter system, as shown in Fig. 3, when a steel plate 1 is rolled by a work roll 2.2 and backup rolls 3, 3, the rolling load F+ is It is 11 flffed by the morph 4 via the reduction screw 5,
Its value is detected by the load cell 6, and the roll r
The j1 gap s i is detected by the potentiometer 7 and input to the arithmetic and control unit 8, and the thickness H of the steel plate l in the longitudinal direction is determined by the following equation (0).

H+ =S+ + (F/M)+K −・・・・・
--(1) Here, M: mill constant; constant Then, the AGC maintains an uncontrolled state for the time set by the timer 10 after the steel plate 1 is bitten by the work roll 2.2. , after the elapse of that time, the lock-on plate thickness 1 (L is the plate thickness at the AGC control start position as shown in (2) below)
Calculate and store in memory using formulas.

1(L -3L + (FL /M) +K ・-・
・・・・・・(2) Here, SL: Rolling position Fti at lock-on, rolling load at lock-on, and lock-on plate thickness HL determined by this formula (2).
and jliKrll in the longitudinal direction, which is sometimes calculated per hole according to the above equation (1), are compared using the following equation (3), and ΔH+ -1-1t HL ......--
・−・−−−(3) Calculate the reduction correction amount ΔSl based on the following formula (4) so that this plate thickness deviation ΔH1 becomes zero,
The roll gap is adjusted by controlling the roll down motor 4 via the roll down control device 9.

Here, Q: plastic constant G, AGC gain (problem to be solved by the invention) However, in the conventional technology, the size of the uncontrolled portion is set as time by the timer 10, so the steel plate The disadvantage is that the uncontrolled length changes due to fluctuations in the biting speed of the rolling mill. That is, when the biting speed is slow, the uncontrolled length becomes short, and when the biting speed is fast, the uncontrolled length becomes long.

As a means to eliminate such shortcomings, for example,
As disclosed in Japanese Patent No. 1-95965, the time t (sea) from when the steel plate is caught in the rolling mill until the AGC is locked on is the so-called lock-on timing, and the speed v (m/win ), the length of the uncontrolled portion at the tip of the steel plate 1 (=t
-v) A method has been proposed in which (rn) is kept constant.

However, since the length of unsteady parts such as the temperature drop part and the overthick part at the tip of the steel plate constantly changes depending on the rolling conditions, the method of JP-A No. 51-95965 described above There is a drawback that lock-on may start within a certain period, or conversely, lock-on may start after passing an unsteady part and entering a steady part. In other words, if lock-on is too early, shape defects such as poor flatness and poor camber spring will occur due to sudden AGC operation, and if it is delayed, problems such as an increase in board thickness defects and a decrease in yield will occur. be.

The present invention is as described above! It is an object of the present invention to provide a lock-on timing determination method in automatic thickness control of rolled steel plates that solves the problems at once.

Means for Solving the Problems> The present invention is a method for determining lock-on timing in automatic plate thickness control of a steel plate rolled by a rolling mill, and the rolling load is controlled from the time when the steel plate is bitten by the rolling mill. In automatic plate thickness control of rolled steel plates, the lock-on is performed when the differential value obtained from the rolling load measurement value becomes equal to or less than a preset target setting value of the rolling load differential value. This is a lock-on timing determination method.

<Function> According to the present invention, the behavior of the unsteady portion at the tip of the steel plate is interpreted as a change gradient by differentiating the rolling load, and when the gradient becomes less than a certain value, lock-on is performed to automatically control the plate thickness side fII. Since this starts, the thickness of the steel plate can be controlled without damaging the shape of the steel plate.

<Examples> Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an AGC control device according to the method of the present invention, and the same members as in the conventional example are given the same reference numerals.

As shown in the figure, the AGC control device of the present invention is provided with a differentiation circuit 11 in place of the timer IO in the conventional example. This differential circuit 11 receives the rolling load signal F! measured by the load cell 6! It has a function of inputting and performing differential calculation based on the amount of change ΔF and time Δt, and sending the calculated differential signal (ΔFi/Δt) to the calculation control bag W8.

On the other hand, in the arithmetic and control unit 8, the target setting value ΔF of the rolling load differential value is given in advance, and the differential signal (ΔF1/Δt) is constantly compared with the differential signal described above, and the differential signal is equal to or less than the target setting value ΔF. The time when the AGC control is started is regarded as the lock-on timing and the AGC control is started. That is, at the lock-on timing, the lock-on plate thickness HL is calculated using the above formula (2), using the rolling load signal FI from the load cell 6 as the lock-on rolling load FL, and the following (3):
AGCllillB is started based on equation (4).

In addition, regarding the size of the target set value ΔF of the rolling load differential at this time, looking at the example in Fig. 2, in order to prevent shape defects due to sudden operation of A G C', ±40 OLo is required.
A value within n/see is appropriate.

The present invention was applied to a hot strip seven-stand finishing mill. The setting value of the rolling load differential value at that time is ±40
0 ton/sec, and the differential time was 200 ns.

The results of plate thickness control at that time are shown in Table 1 along with the conventional example.As is clear from Table 1, the example of the present invention shortens the time until lock-on compared to the conventional example. It can also be seen that the length ratio within 150 μm in the coil length direction was improved.

<Effects of the Invention> As explained above, according to the present invention, the lock-on timing is determined by differentiating the rolling load from the time when the steel plate is bitten by the rolling mill, so the controllability of the plate thickness is improved. It is expected that product quality and yield will improve.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an example of the A G Cllll1ll device according to the method of the present invention, and Fig. 2 shows (a) changes in rolling load after the tip of the steel plate is bitten, and (b) differential value of the rolling load. FIG. 3 is a characteristic diagram showing an example of each change over time, and is a configuration diagram showing a conventional example of an AGCiIilJm device. Figure 1 1... Rope plate, 2... Work roll. 3...Backup roll. 4... Reduction morph, 5... Reduction screw 6.
...Load cell, 7... Potentiometer make. 8... Arithmetic control device, 9... Rolling down control device. 10...Timer, 11...Differential circuit.

Claims (1)

[Claims] A method for determining the lock-on timing in automatic plate thickness control of a steel plate rolled by a rolling mill, in which the rolling load is measured from the time the steel plate is bitten into the rolling mill, and the lock-on timing is determined from the rolling load measurement value. A method for determining lock-on timing in automatic plate thickness control of a rolled steel plate, characterized in that lock-on is performed at the timing when a differential value becomes equal to or less than a preset target value of a rolling load differential value.