JP2003266111A - Method for controlling gauge for tandem mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable control without dead time and also to reduce the variation in gauge by tension control. <P>SOLUTION: When controlling the gauge of a material to be rolled by using a tandem mill consisting of N stands, the output for controlling the gauge on the outlet side of the N-th stand is distributed to the roll speed in the (N-1)th stand and the set value of the gauge on the outlet side of the (N-1)th stand on the basis of tension variation between the N-th stand and the (N-1)th stand. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate thickness control method for a tandem rolling mill, and more particularly to a method for controlling the plate thickness of a thin steel sheet using a cold tandem rolling mill consisting of N stands. The present invention relates to a suitable plate thickness control method for a tandem rolling mill.

[0002]

2. Description of the Related Art Generally, in a rolling mill for cold-rolling a hot-rolled wide steel strip or the like near room temperature to produce a thin sheet such as a cold-rolled steel sheet, the sheet thickness of the thin sheet as a product is made to match a target value. ,
In addition, automatic plate thickness control (referred to as AGC) is applied in order to keep the plate thickness uniform over the whole thin plate. And
Automatic tension control (referred to as ATR) is usually applied because stable operation cannot be performed unless the tension acting on the base material to be rolled is kept within the breaking limit during cold rolling. Automatic operation of the automatic plate Two controls of thickness control and automatic tension control can be realized at the same time.

In FIG. 1, several rolling stands N, N-1,
The outline of the conventional cold rolling mill in which N-2 is arranged on a straight line is shown. In FIG. 1, the work roll 10 of each stand is
Each of them is driven by an electric motor (also referred to as a mill motor M) 20, and the electric motor 20 can freely adjust its rotational speed by a speed control device 22. Further, the space between the upper and lower work rolls 10 has a structure in which the opening can be freely adjusted by a pressure reducing device 30 driven by hydraulic pressure or an electric motor. In the figure, 12 is a reinforcing roll (also referred to as backup roll), 24 is the final N-th roll.
A plate thickness detector for detecting the plate thickness on the stand output side, 26 is a plate thickness control device for controlling the output plate thickness according to the output of the plate thickness detector 24, and 32 is a tension between the stands. The tension detector 34 for detection is a tension control device for controlling the inter-stand tension according to the output of the tension detector 32.

For the automatic thickness control, each work roll 10
Of the mass flow plate thickness by changing the number of rotations of the rolling mill and the speed difference between the rolling stands to realize the automatic plate thickness control (hereinafter, referred to as the speed AGC) by the realized speed.
There are two methods, namely, automatic plate thickness control (hereinafter referred to as rolling reduction AGC) by reducing the realized mass flow by changing the interval between the upper and lower work rolls 10 by the rolling down operation. The plate thickness control device 26 of FIG. 1 is an example in which the speed AGC is performed according to the output of the plate thickness detector 24 arranged on the exit side of the final Nth stand.

On the other hand, also in the automatic tension control, the mass flow is changed by changing the rotation speed of each work roll 10 and the speed difference between each rolling stand, and the automatic tension control according to the speed realized (hereinafter, speed control). Called ATR)
There are two methods: automatic tension control (hereinafter referred to as a reduction ATR) by reduction achieved by changing the mass flow by changing the interval between the upper and lower work rolls 10 by a reduction operation. The tension control device 34 of FIG.
This is an example in which the rolling-down ATR is performed based on the inter-stand tension between the stand and the preceding stand detected in (4).

In the case of cold rolling, the speed AGC is applied to the automatic plate thickness control, and the automatic tension control includes a reduction ATR having a dead zone (hereinafter referred to as a reduction ATL) or a speed ATR having a dead zone (hereinafter, It is common to apply the speed ATL).

In controlling the plate thickness in a conventional cold tandem rolling mill consisting of N stands, as shown in FIG. 1, the roll speed of the immediately preceding N-1 stand is manipulated to
The speed AGC for controlling the delivery side plate thickness of the Nth stand (that is, the last stand) to a target value was performed.

As described above, in the conventional plate thickness control, the rotation speed of the roll of only one stand (that is, the (N-1) th stand) is used as the operating end of the plate thickness control to control the plate thickness variation. At the same time, the tension at the front of the N-th stand is controlled by changing the rolling position of the N-th stand.

[0009]

However, in the dull rolling using the dull rolls for the N-th stand, there arises a problem that the dull transfer becomes uneven.
The fluctuation of the rolling load of the N-th stand is not preferable. Therefore, in the case of the above-mentioned dull rolling, the forward tension of the N-th stand is not usually controlled by the rolling operation of the N-th stand,
In such a situation, as the operation end of tension control,
Manipulating the roll speed of the N-1 st stand.

However, since the roll speed of the (N-1) th stand is used as the operating end of the Nth stand outlet side plate thickness control, normally, the speed ATL having a dead zone (band width) is used and the tension is If it is within a certain range, the plate thickness control is given priority, and the roll speed of the (N-1) th stand is operated.

On the other hand, when the tension fluctuation exceeds a certain threshold value, the tension control is prioritized, the output of the plate thickness control is held, and the roll speed of the (N-1) th stand is set at the operation end of the tension control. And continues until the tension settles near the set value. However, the tension control during that period becomes a disturbance for the plate thickness control, and the N-th stand output side plate thickness is
It fluctuates with respect to the target value.

In order to solve this problem, during the above-mentioned dull rolling, when controlling the N-stand stand outlet side plate thickness,
A method of changing the N-1st stand outlet side plate thickness setting value (Japanese Patent Laid-Open No. 7-68305) or a plate thickness generated when used as an operating end of the N-1st stand tension control is calculated in advance as N-th
A method of compensating on the exit side of the two stands is known.

However, since any of these methods is a method of correcting the plate thickness on the delivery side of the (N-1) th stand, a dead time corresponding to the distance between the (N-1) th stand and the Nth stand. Occurs, and there is a possibility that the plate thickness accuracy is deteriorated particularly in the low speed range.

The present invention has been made in order to solve the above-mentioned conventional problems, and performs control with no dead time to achieve the N-th time.
The object is to reduce the variation in plate thickness on the stand-out side as much as possible.

[0015]

According to the present invention, when the plate thickness of a material to be rolled is controlled using a tandem rolling mill consisting of N stands, the output for the Nth stand exit side plate thickness control is set to the Nth stand. According to the tension variation between the stand and the (N-1) th stand, the above-mentioned problem is solved by distributing the roll speed of the (N-1) th stand and the set value of the outlet side plate thickness of the (N-1) th stand.

When the tension between the Nth stand and the (N-1) th stand is close to the target tension during the distribution, the N-1st stand roll speed is mainly used as the operating end of the Nth stand exit side plate thickness control. The operating end of the Nth stand outlet side plate thickness control is shifted to the N-1th stand outlet side plate thickness set value as the tension between the stands departs from the target tension.

Conventionally, in a cold tandem rolling mill consisting of N stands, when controlling the strip thickness on the delivery side of the N stand, as shown in FIG. By controlling the tension between the stand and the (N-1) th stand, the plate thickness on the delivery side of the Nth stand is controlled, and the dead zone of tension control is limited (called a band).
When the sheet thickness control output was reached, the plate thickness control output was held and the N-1st stand roll speed was used as the operating end of the tension control. However, in the present invention, the Nth stand output is determined according to the rate of tension fluctuation. The operation end of the side plate thickness control is distributed to the N-1th stand roll speed and the N-1st stand outlet side plate thickness set value.

Specifically, for example, when the tension is close to the target tension, the N-1th stand roll speed is mainly used as the operating end of the Nth stand outlet side plate thickness control, and the inter-stand tension is separated from the target tension. Along with this, the operating end of the Nth stand outlet side plate thickness control is shifted to the N-1th stand outlet side plate thickness set value.

Therefore, the tension exceeds the band and the velocity ATL
Even when is operated, the operation end of the plate thickness control does not interfere with the N-1th stand roll speed operation by the speed ATL because it is already at the N-1st stand exit side plate thickness setting value. As a result, if the tension is near the set value, the Nth
Since the roll speed of the -1 stand is used as the operation end of the plate thickness control, it is possible to perform control without dead time.
Further, even when the deviation of the inter-stand tension from the target value is large, by smoothly shifting the operating end without disturbing the rolling conditions, it is possible to reduce the variation of the plate thickness due to the tension control, which has been a problem in the past. It becomes possible.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

In this embodiment, as shown in FIG. 2, the present invention has a low rolling reduction at the final fifth stand and a speed ATL for tension control during rolling in a cold tandem rolling mill comprising five stands. It is applied to rolling of the material used.

In the present embodiment, the control output for plate thickness control calculated by the plate thickness control device 26 similar to that of the conventional example shown in FIG.
By dividing the stand roll speed and the fourth stand outlet side plate thickness setting value, the plate thickness control on the fifth stand outlet side is performed. In this case, when the tension fluctuation is small, the fourth stand roll speed is used as the operation end of the plate thickness control, and the operation end is shifted to the fourth stand delivery side plate thickness setting value as the tension fluctuation increases.

For example, the degree of changing the fourth stand roll speed in the fifth stand exit side plate thickness control (referred to as distribution gain) is α, and is shown in FIG. 3 (detailed block of plate thickness control) and FIG. 4 (distribution gain). As described above, if the inter-stand tension between the fifth stand and the fourth stand is equal to the target value, the fifth (= N) stand exit side plate thickness control is all performed at the fourth stand.
(= N-1) It shall be performed at a stand roll speed (α
= 1), as the tension fluctuates and departs from the target tension, the ratio of the operating end of the fifth stand outlet side plate thickness control is changed to the fourth
If the tension variation between the stands reaches the upper and lower limits, the 5th stand is ejected. All the operation ends of the side plate thickness control are shifted to the fourth stand outlet side plate thickness setting value (α = 0). That is, the fifth
The output for the (= N) stand outlet side plate thickness control is based on the tension variation between the fifth stand and the fourth (= N-1) stand, and the fourth stand roll speed and the fourth stand outlet side plate thickness set value are set. If the inter-stand tension between the 5th stand and the 4th stand is equal to the target value, the 4th stand roll speed is used as the operating end of the 5th stand exit side plate thickness control. As the tension fluctuates and deviates from the target value, the fifth inter-stand tension is adjusted so that at the upper or lower limit of the tension limit, the fourth stand outlet side plate thickness setting value becomes the operating end of the fifth stand outlet side plate thickness control. The ratio of the operating end of the stand outlet side plate thickness control is shifted to the fourth stand outlet side plate thickness set value in proportion to the tension fluctuation. As a result, it is possible to eliminate the plate thickness variation due to the AGC hold or the like as much as possible, and to perform good plate thickness control.

In FIG. 3, reference numeral 40 denotes a subtracter for obtaining the difference between the Nth stand output side plate thickness target value hNref and the Nth stand output side plate thickness hN as an Nth stand output side plate thickness deviation ΔhN.
2 is the N-1st stand outlet side plate thickness target value hN-1ref and the Nth stand
Subtractors 44 and 46 for obtaining the difference of the -1 stand output side plate thickness hN-1 as the (N-1) th stand output side plate thickness deviation ΔhN-1.
Is a multiplier for multiplying the Nth stand output side plate thickness deviation ΔhN output from the subtractor 40 by a proportional coefficient α or 1−α, and 48 is an N−1th output according to the output of the multiplier 44.
A proportional-integral (PI) device for calculating the stand roll speed manipulated variable ΔVRN−1, 50 calculates an N−1th stand output side plate thickness target value correction amount Δh′N−1ref according to the output of the multiplier 46. A proportional-plus-integrator (PI) unit 52 includes the proportional-integrator 5
An adder 54 for adding the output of 0 and the output thickness deviation ΔhN−1 of the N−1th stand output side to obtain the corrected thickness deviation Δh′N−1 of the N−1th stand output, This is a proportional-integral (PI) device that calculates the N-2th stand-roll speed operation amount ΔVRN-2 according to the output of the adder 52.

[0025]

EXAMPLES The results of applying the present invention to the rolling mill are shown in FIG. Conventionally, when performing the 5th stand exit side plate thickness control,
When the tension between the stands reaches the upper and lower limits of the dead zone, the speed AT
While L operates, the output of the speed ATL to the fourth stand roll speed is a disturbance in the fifth stand outlet side plate thickness control, so that the fifth stand outlet side plate thickness variation is large, but according to the present invention. It was confirmed that by using the tension between the stands and the thickness setting in a well-balanced manner, it is possible to control the plate thickness well and to reduce the plate thickness fluctuation.

In the above description, the present invention was applied to a five-stand cold tandem rolling mill for thin steel sheets, but the present invention is not limited to this, and the number of stands is also limited to five. Not done. Further, the relationship between the distribution gain α and the tension is not limited to that shown in FIG.

[0027]

According to the present invention, when the tension is near the set value, the roll speed of the (N-1) th stand is used as the operating end of the plate thickness control, so that control without dead time becomes possible. . Further, even when the deviation of the inter-stand tension from the target value is large, it is possible to reduce the fluctuation of the plate thickness due to the tension control by smoothly shifting the operating end without disturbing the rolling conditions.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of essential parts of a rolling mill for explaining a conventional strip thickness control.

FIG. 2 is a block diagram showing a main configuration of a rolling mill to which the embodiment of the present invention is applied.

FIG. 3 is a block diagram showing an essential part of plate thickness control.

FIG. 4 is a diagram showing an example of a relationship between distribution gain α and tension.

FIG. 5 is a time chart showing changes in the thickness of the fifth stand outlet side plate and the tension between the fourth and fifth stands when the present invention is carried out, as compared with the conventional method.

[Explanation of symbols]

3, 4, 5 ... Rolling stand 10 ... Work roll 20 ... Electric motor (mill motor) 22 ... Speed control device 24 ... Plate thickness detector 26 ... Plate Thickness Control Device 30 ... Reduction device 32 ... Tension detector 34 ... Tension control device α: distribution gain

Claims (2)

[Claims] 1. When controlling the plate thickness of a material to be rolled using a tandem rolling mill consisting of N stands, the output for controlling the N-th stand output side plate thickness is output between the N-th stand and the (N-1) th stand. Based on the tension fluctuation of
A strip thickness control method for a tandem rolling mill, characterized in that the strip thickness is distributed to a 1-stand roll speed and an N-1st stand outlet-side strip thickness setting value. 2. The N-th stand and the N-th stand during the distribution.
When the tension between one stand is close to the target tension, the N-th
The 1-stand roll speed is used as the operating end of the N-th stand outlet side plate thickness control, and the operating end of the N-th stand outlet side plate thickness control is set as the N-1th stand outlet side plate thickness control as the tension between the stands deviates from the target tension. The method for controlling the plate thickness of a tandem rolling mill according to claim 1, wherein the stand-out side plate thickness setting value is shifted.