JPH08238514A - Method for changing screw-down position in rolling mill - Google Patents

Abstract

PURPOSE: To suppress thickness/tension variations which are generated with change of rolling speed at the time of changing screw down position as roll speed is changed at a constant rate while executing screw down position control and roll speed control. CONSTITUTION: The speeds of motors 3A-3E of respective stands are changed by the rolling speed command value 12 of the sum of the command value with a process computer 10 and the command value of speed operation 11 by an operator, also screw down positions S0 , S1 at the rolling speeds V0 , V1 of respective stands are calculated with a computing element 13 for setup and the screw down positions are operated in the S0 , S1 with screw down position controllers 4A-4E at the respective stands. The thickness (h) on the outlet side of the final stand #5 is detected with a thickness gage 15 and thickness deviation Δh on which comparison calculation with the target value H that is fed from the process computor is executed is converted into the manipulated variable ΔV of speed with a computing element 16 for manipulated variables of speed and the speed at the stand #4 is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for compensating a variation in plate thickness due to a change in rolling speed by changing a rolling position in rolling a metal strip.

[0002]

2. Description of the Related Art In the strip rolling of a rolling mill, the rolling speed is varied such as deceleration for cutting the strip at the welding point, acceleration at the transition to the steady rolling section, and acceleration / deceleration by manual intervention of the operator. It depends on the factors. In such a portion where the rolling speed is changed, a non-steady rolling state occurs, and a variation in strip thickness occurs. In order to suppress this variation in strip thickness, a technique is known in which the reduction position is changed in accordance with the change in rolling speed.

In calculating the reduction position change amount, "Plate rolling theory and practice" p. 134, Japanese Patent Laid-Open No. 4-3
As disclosed in Japanese Patent No. 67309, Japanese Patent Application Laid-Open No. 6-226316, and the like, the cause of the plate thickness variation due to the change in rolling speed is the change in rolling load due to the change in the friction coefficient between the rolling roll and the material to be rolled. Then, the relationship between the rolling speed and the friction coefficient is obtained in advance, and based on this, the rolling position change amount is calculated from the rolling load change accompanying the rolling speed, and the rolling position is changed.

Also, in Japanese Unexamined Patent Publication No. 2-224810, the rolling load prediction value corresponding to the rolling speed at the time of presetting and steady rolling are provided by giving speed dependence to the expression for predicting the friction coefficient in the rolling load preliminary expression. It shows a technique of calculating two types of predicted values of a rolling load predicted value corresponding to the rolling speed during rolling, and performing rolling presetting and plate thickness control during steady rolling based on the calculated values. That is, the plate thickness control (roll-down position control) is performed during setup and during steady rolling, but with this technology, reduction is performed only for two rolling speeds: the rolling speed during setup and the rolling speed during steady rolling. The position is being calculated.

Since these rolling position change commands of the prior art are output irrespective of the time rate of change of the rolling speed, plate thickness fluctuations and tension fluctuations occur.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art.
An object of the present invention is to provide a method for changing the rolling position of a rolling mill, which can completely suppress the plate thickness / tension variation that occurs with the change of rolling speed when rolling a metal strip.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the rolling position is controlled while the rolling position is controlled at a constant ratio while performing the rolling position control for setting the rolling position and the roll speed control for setting the roll speed. At this time, the rolling position at the roll speed before the change and the rolling position at the roll speed after the change are calculated, and the rolling position within the change section of the rolling position between the roll speed before the change and the roll speed after the change is calculated. Change of the rolling position of the rolling mill characterized by outputting the rolling position change command so that the position changing speed is constant and the time required for changing the rolling position matches the time required for changing the rolling speed. Is the way.

In this case, one or more rolling-down positions at the roll speed in the process of being changed are calculated, and two or more sections divided by the rolling-down positions are sequentially changed as rolling-down position changing sections. Change the position.

[0009]

In the present invention, when the rolling mill is accelerated or decelerated, the roll-down position at two or more roll speeds of the rolling mill is calculated in advance by the setup computer, and the rolling speed of the rolling position is changed within each rolling position changing zone. Constant,
Moreover, since the rolling position command is output so that the time required for changing the rolling position matches the time required for changing the roll speed, it is possible to change the rolling position and the roll speed in synchronization. It is possible to suppress variation in thickness and variation in tension.

[0010]

1 is a block diagram showing the construction of a cold rolling apparatus and related equipment according to an embodiment of the present invention. The rolling stands # 1 to # 5 are composed of work rolls 1A to 1E and backup rolls 2A to 2E. It is assumed that the material 20 to be rolled is rolled from left to right as viewed in FIG. Here, a four-high rolling mill consisting of five stands is shown, but the number of stands is not limited to this, and
The rolling mill is not limited to four stages.

In the present invention, for example, as shown in FIG. 2, the rolling speed (roll speed) of the # 5 stand is 200 m / m.
When changing from minutes to 50 m / min, the rolling speed command values V ₀ and V ₁ of the rolling mill are obtained as the sum of the command value of the process computer 10 and the command value of the speed operation 11 by the operator. The speeds of the motors 3A to 3E of the respective stands are changed.

Further, according to the rolling speed command value 12, the setup calculator 13 previously calculates the rolling positions S ₀ and S ₁ at the rolling speeds V ₀ and V ₁ of the respective stands,
The reduction position change command values are sent to the reduction position control devices 4A to 4E of the respective stands, and the reduction position control device operates the reduction positions to S ₀ and S ₁ . Further, the outgoing side plate thickness h of the final stand # 5 is detected by the plate thickness gauge 15 and is compared and calculated with the target value H sent from the process computer to obtain a plate thickness deviation Δh, which is calculated by the speed operation amount calculator 16 as a speed operation amount. Converted to change the speed of the # 4 stand. This speed change amount ΔV is expressed by the following equation, for example.

ΔV = (Δh / H) G (1) Here, G is a control gain sent from the computer. Next, a method of calculating the rolling loads P ₀ and P ₁ and the rolling positions S ₀ and S ₁ at the rolling speeds V ₀ and V ₁ by the setup calculator 13 will be described. However, in the present embodiment, it is assumed that only the friction coefficient changes when the peripheral speed changes, and the friction coefficients at the peripheral speeds V ₀ and V ₁ are μ ₀ and μ ₁ . For the rolling loads P ₀ and P _1, the target plate thickness, the coefficient of tension and friction, etc. are substituted into the Hill rolling load equation (Equation (2)) and the Hitchcock flat roll diameter equation (Equation (3)). Then, it is obtained from the convergence calculation. That is,

[0014]

[Equation 1]

Where P is the rolling load and k is the respective load.
Deformation resistance of metal strip in tan, B is plate width, R '
Is the flat roll radius of the work roll, h_inIs each
Inlet plate thickness in tando, h_out At each stand
Output side plate thickness, μ is friction coefficient, V _R Is the work roll peripheral speed, t
_b Is the rear tension, t_f Is the forward tension, ν is the Poisson's ratio, π is
Pi and E are Young's modulus.

With respect to the respective stands thus obtained, the rolling-down positions S ₀ and S _{1 of} the respective stands are obtained from the target loads P ₀ and P ₁ . _{That, S 0 = h out - (} P 0 / M) ...... (4) S 1 = h out - (P 1 / M) ...... (5) where, M is the mill rigidity.

In the rolling mill shown in FIG. 1, when the rolling speed is reduced from 200 m / min to 50 m / min as shown in FIG. 2, simulation results of the conventional method and the present invention are shown in FIGS. 3 and 4, respectively. Shows. The conventional lower left position command value of FIG. 3A outputs a rolling position change command stepwise, while the rolling speed changes like a ramp as shown in FIG. On the other hand, in the method proposed by the present invention in FIG. 4, the rolling position change command is output like a ramp in synchronization with the rate of change of the rolling speed as shown in FIG. FIG.
The thickness of the # 5 stand on the outlet side (b) according to the present invention shown in FIG. 3 and the conventional method shown in FIG.
Comparing the figures, the method according to the invention shown in FIG.
It can be seen that fluctuations in plate thickness and tension are well suppressed.

FIGS. 5, 6 and 7 show the concept of a method for outputting a rolling position change command according to a change in rolling speed.
In the conventional method, when the rolling speed is changed from V ₀ to V ₁ as shown in FIG. 5, the rolling position change command is issued from S ₀ to S _1.
It was output to change to stepwise. In one embodiment of the present invention, as shown in FIGS. 4 (b) and 4 (c), as shown in FIGS. 6 (a) and 6 (b), the reduction position change command is output like a ramp in accordance with the rate of change of two different rolling speeds. In addition, it is possible to suppress variations in plate thickness and tension. Further, since the rolling load does not change linearly with the rolling speed, in order to further improve the accuracy, the rolling position at an intermediate speed between V ₀ and V ₁ is calculated as shown in FIG. However, in each section, the reduction position may be changed according to the change in rolling speed.

[0019]

As described above, according to the present invention, fluctuations in plate thickness and tension during acceleration / deceleration can be suppressed and stable operation can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a change in roll speed of a fifth stand.

FIG. 3 is an explanatory diagram of a rolling position command, plate thickness variation, and tension variation of a conventional method.

FIG. 4 is an explanatory diagram of a rolling position command, plate thickness fluctuation, and tension fluctuation of the method of the present invention.

FIG. 5 is a schematic diagram showing a relationship between a roll speed and a rolling position command according to a conventional method.

FIG. 6 is a schematic diagram showing a relationship between one roll speed and a rolling position command according to the present invention.

FIG. 7 is a schematic diagram showing a relationship between another roll speed and a rolling position command according to the present invention.

[Explanation of symbols]

1A to 1E Work roll 2A to 2E Backup roll 3A to 3E Morter 4A to 4E Rolling down device 15 Plate thickness gauge 20 Rolled material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Torao 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefectural Institute of Technology, Kawasaki Steel Co., Ltd. (72) Fumihiko Ichikawa 1 Kawasaki-cho, Chuo-ku, Chiba, Kawasaki Steel Engineering Co., Ltd.

Claims (2)

[Claims] 1. A roll speed before change when changing the reduction position while changing the roll speed at a constant ratio while performing the reduction position control for setting the reduction position and the roll speed control for setting the roll speed. Calculate the rolling position at the roll speed after the change, and the rolling position at the roll speed after the change, and the change speed of the rolling position within the changing section of the rolling position from the roll speed before the change to the roll speed after the change is constant. A method for changing the rolling position of a rolling mill, wherein a rolling position changing command is output so that the time required for changing the rolling position matches the time required for changing the rolling speed. 2. Further, one or more rolling-down positions at the roll speed being changed are calculated, and the rolling position is divided into two.
2. The rolling position changing method for a rolling mill according to claim 1, wherein the section is the section for changing the rolling position.