JPH07178433A - Control method of meandering in continuous hot rolling mill - Google Patents

Abstract

PURPOSE:To improve working rate and to reduce a consumption unit by executing no meandering control before starting the descent of a looper between a meandering controlling stand and a front stand and starting meandering control at the same time when an automatic gage control in the meandering controlling stand is stopped at the time of starting the descent of the looper. CONSTITUTION:Before the looper between the meandering controlling stand and the front stand is lowered, an AGC (automatic gage control) of the meandering controlling stand is operated to prevent off-gage in the thickness of material as much as possible and meandering control is not used to prevent malfunction. After this looper is lowered, the AGC of the meandering controlling stand is stopped and meandering control is started. In this way, the meandering phenomenon before the tail end of material is passed through the front stand is entirely eliminated, drawing rate due to meandering that results in unscheduled roll changing is reduced in all kind of steel and all size and these contribute to the improvement of working rate and reduction of the consumption unit of roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method which is very effective for suppressing the meandering which occurs at the time of passing a material at the tail end of a hot continuous rolling mill and for preventing the material from being narrowed down by the meandering.

[0002]

2. Description of the Related Art In a hot continuous rolling mill, a wide width (for example, 12
(00 mm or more) When rolling a thin material (for example, the finishing delivery side thickness is less than 2 mm), the rolling of the rolling mill at the next stand is not necessary, especially after the tail end of the material passes through the front stand. Easy to meander on the drive side or work side of. When the amount of meandering becomes large, the tail end of the strip S is pressed and bent by the inlet side guide SG of the meandering phenomenon occurrence stand ST _i , as shown in FIG. 6, and a narrowing accident occurs. Due to this narrowing accident, the rolls are damaged and the rolls are changed, which causes a decrease in the work rate and an increase in the roll unit. Therefore, it is essential to suppress the meandering.

Conventionally, as a method of suppressing the meandering, for example, in Japanese Patent Publication No. 58-51771, the difference between the measured values of the rolling loads on the controlled side of the work stand and the drive side (hereinafter referred to as the differential load) is the meandering amount. Therefore, a method of suppressing the meandering by the leveling operation of the rolling mill has been proposed.

However, if this meandering control system is adopted over the entire length of the material, AGC with respect to material thickness and temperature fluctuations will occur.
The rolling load fluctuates due to the movement of (automatic plate thickness control), and even if the meander does not occur due to the difference in elongation characteristics between the work side and the drive side of the rolling mill, a differential load occurs and malfunctions. That is, if the differential load fluctuation amount is ΔP _df ,

[0005]

[Equation 1]

Here, E: first-class parallel rigidity a: inter-chock distance Δy _C : meandering fluctuation amount D: second-class parallel rigidity b: strip width m: plastic coefficient per width P _C : average line load ΔS _df : Leveling fluctuation amount

When the AGC operates here, the average line load P
_C changes, and the work-drive-side gap difference ΔS _df changes due to the difference in extension between the work side and the drive side, which results in a control error when the meandering control is performed with ΔP _df instead of Δy _C. It happens.

Therefore, it is necessary to stop the AGC and start the meandering control when the material tail end passes through the front stand of the meandering control stand.

[0009]

However, as shown in FIG. 7, the front stand ST of the meandering control stand ST _i is
_When the looper device LP for controlling the tension between the meandering control stand and the front stand before the material S passes through the _i-1 is lowered from the control position, the tension may loosen to cause meandering or narrowing. However, in this case, the conventional meandering control has a problem that the control start timing is late and the meandering correction is difficult (see FIG. 5).

The problem to be solved by the present invention is to prevent a narrowing-down accident of the tail end portion of the material during rolling in the hot continuous rolling mill, to improve the work rate and to reduce the roll unit.

[0011]

In order to solve the above-mentioned problems, a meandering control method for a hot continuous rolling mill of the present invention is provided for controlling the meandering of a hot continuous rolling mill having a plurality of rolling stands and inter-stand loopers. In the meandering control method, which considers the difference between the rolling load measurement values of the work side of the meandering control stand and the drive side as the amount of meandering and suppresses the meandering by the leveling operation of the rolling mill,

When the material tail end passes through the continuous rolling mill,
Before the descent of the looper between the meandering control stand and the front stand is started, the meandering control is not performed, and the automatic plate thickness control in the meandering control stand is stopped and the meandering control is started at the time of the descent of the looper.

[0013]

In the conventional control system, as shown in FIG.
While the AGC was stopped and the meandering control was started after the tail end of the material passed through the front stand, in the present invention, as shown in FIG.
As shown in (b),

(1) Before the looper between the meandering control stand and the front stand descends, the AGC of the meandering control stand is operated to prevent the material thickness off gauge as much as possible, and the meandering control is not used to prevent malfunction.

(2) After the lowering of the looper, the AGC of the meandering control stand is turned off and the meandering control is started.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic view of a rolling control device provided with the meandering controller of the present invention. In the figure, 1 is a material to be rolled, 2 is a work roll, 3 is an intermediate roll, 4 is a backup roll, and 5 and 6 are upper backup rolls 4.
Load cells for measuring the load on the left and right bearings of the vehicle, 7 and 8 are hydraulic jacks for applying pressure to the left and right bearings of the lower backup roll 4, and 9 and 10 are hydraulic pressure commands from the hydraulic control panel 11. Servo valves for transmitting command values to the hydraulic jacks 7 and 8, and 12 are meandering controllers.

Details of the meandering controller 12 in FIG. 2 are shown in FIG.
Shown in. First, the work side rolling load actual value P measured by the work side load cell 5 at the start of the meandering control.
_The PID controller 13 calculates the difference load P _df0 between the _w and the actual rolling load value P _d on the drive side measured by the load cell 6 on the drive side 6 to _reduce the difference between the actual difference load P _df and the work side by the PID controller 13. And the drive side work roll gap difference target value ΔS _dfref . Also,
The leveling compensator 14 calculates the difference load generated regardless of the meandering due to the work roll gap difference (difference between the work side work roll gap target value S _w and the drive side work roll gap target value S _d ) operated during control. To compensate. 1/2 of the work roll gap difference target value ΔS _dfref obtained by the PID controller 13
Is distributed with positive and negative signs, and the actual value S _w0 between the work side work rolls at the start of meandering control and the actual value S between the drive side work rolls at the start of meandering control S
The hydraulic control board 1 shown in FIG. 2 _{is obtained} by adding _d0 to each other to obtain the work side work roll gap target value S _wref and the drive side work roll gap target value S _dref .
Output to 1.

Next, an example of carrying out the method of the present invention will be described below. As shown in FIG. 7, the present control is applied to the meandering occurrence phenomenon before the material tail end passes through the front stand of the meandering control stand, and as shown in FIG. 4, before the material tail end pass of the front stand. The meandering phenomenon can be completely eliminated, and the narrowing ratio due to meandering leading to irregular recombination was 0.22% for all steel types and all sizes.
This is a 20% reduction to 8%, which greatly contributes to the improvement of the work rate and the reduction of the basic unit of roll.

[0019]

By applying the present control, the meandering phenomenon before the tail end of the material passes through the front stand of the meandering control application stand is completely eliminated, and the occurrence rate of narrowing can be significantly reduced.

[Brief description of drawings]

FIG. 1A is a diagram showing a timing of a conventional meandering control method, and FIG. 1B is a diagram showing a timing of a meandering control method according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a rolling control device including a meandering controller for applying the present invention.

FIG. 3 is a block diagram showing a configuration of a meandering controller in FIG.

FIG. 4 is an explanatory diagram showing changes in meandering amount according to the present invention and the related art.

FIG. 5 is an explanatory diagram showing a problem of meandering by a conventional method.

FIG. 6 is a plan view showing a problem caused by meandering.

FIG. 7 is a perspective view illustrating meandering when the looper descends.

[Explanation of symbols]

1 material to be rolled, 2 work rolls, 3 intermediate rolls,
4 backup rolls, 5, 6 load cells, 7, 8
Hydraulic jack, 9,10 servo valve, 11 hydraulic control panel, 12 meandering controller, 13 PID controller,
14 Leveling compensator

Claims (1)

[Claims] 1. At the time of meandering control of a hot continuous rolling mill having a plurality of rolling stands and loopers between stands, the difference between the rolling load measured values of the work side and the drive side of the meandering control stand is regarded as a meandering amount, and the rolling mill is controlled. In the meandering control method that suppresses the meandering by the leveling operation, when the tail end of the material passes through the continuous rolling mill, the meandering control is not performed before the descending of the looper between the meandering control stand and the front stand, and when the looper descends. A meandering control method in a hot continuous rolling mill, characterized in that the meandering control is started at the same time as the automatic strip thickness control in the meandering control stand is stopped.