JPS6149722A - Plate thickness controlling method of steel strip - Google Patents

Abstract

PURPOSE:To improve the plate thickness accuracy by applying a slight strain to a strip in the entry of the first stand, deriving a strain quantity and a yield stress, and deriving a deformation resistance, a frictional resistance, etc. of the strip in each stand, based on its operating value. CONSTITUTION:A tension leveler 12 is provided in front of the entry of the first stand S1, a slight strain is applied to a strip 3, and also a plate speed (v) and a tension T of the entry and the delivery of the leveler 12 are measured by a plate speed meter 5 and a tension meter 7. An operator 15 calculates a strain quantity applied by the leveler 12 from a difference of the entry and the delivery of the plate speed (v), and a computer 13 calculates a deformation resistance and a frictional resistance in each stand of the strip 3 from a difference of the tension T, an original plate thickness, etc. Subsequently, a rolling down force of each stand is derived, and a plate thickness of the strip 3 is brought to feed forward control, by which the accuracy of a plate thickness containing a discontinuous part of the strip 3 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for controlling the thickness of steel strip.

[Prior art and its problems]

Conventionally, cold tandem rolling mills that cold-roll steel strips have mainly adopted a feedback monitor system as an automatic plate thickness control system (hereinafter referred to as AGC system), which prevents sudden changes in the thickness of the steel strip. We were powerless to control the plate thickness in areas where the material changes. Therefore, in recent years, in order to deal with this problem, AGC systems with a thickness gauge installed on the entrance side of the first stand of tandem rolling mills and feedforward control added to the first stand, and AGC systems with high frequency response. A gauge meter type AGC system that utilizes a hydraulic servo system has appeared. However, these AGC systems have the following problems.

In a method in which a plate thickness gauge is installed on the entrance side of the first stand and feedforward control is added, discontinuities in plate thickness can be detected before entering the rolling mill, so changes in original plate thickness can be corrected. Since there is no ability to predict changes in deformation resistance, there is virtually no improvement in plate thickness control compared to the conventional feedback-only method.

In the gauge meter method, the hydraulic cylinder is operated in accordance with the fluctuation of the rolling blade, and in order to increase the apparent mill rigidity, a certain degree of control ability is required for changes in plate thickness and deformation resistance. The plate thickness control is considerably improved compared to the conventional feedback-only method or the method in which feedforward control is added to the first stand. However, since mill rigidity control is performed by feeding back signals from the rolling blade and rolling cylinder positions, the control loop has a time constant, and therefore, the mill rigidity cannot be made infinite in a dynamic state. However, precise thickness control at complete discontinuities (singular points), such as steel strip connections or sizing points, is not possible. In addition, this method has the disadvantage that it is not necessarily effective in improving plate thickness accuracy because it amplifies all disturbances to the rolling blade other than the material to be rolled, such as the oil film thickness of the roll bearing and roll eccentricity.

All of the above-mentioned problems are due to the fact that conventional AGC systems do not have a method of predicting the deformation resistance of the material to be rolled and controlling the sheet thickness.

From this point of view, we have attempted to improve the accuracy of thickness control by using a large digital computer to learn the friction coefficient and deformation resistance of steel strip from the rolling blade, tension, reduction rate, and advancement rate. It is being

However, this method is also effective only in the steady rolling section,
It is powerless to control the plate thickness at the joints of steel strips or at size change points with variations in deformation resistance.

[Purpose of the invention]

In view of the above-mentioned current situation, this invention has been developed to provide a method for controlling the thickness of a steel strip, which allows the thickness to be controlled with high precision even at the joints of the steel strip and the size change points that cause fluctuations in deformation resistance. The purpose is to provide

[Summary of the invention]

The steel strip thickness control method of the present invention provides the steel strip obtained by applying a slight strain to the steel strip in front of the entry side of the first stand of a rolling mill that rolls the steel strip. Determine the deformation resistance and friction coefficient of the steel strip at each stand of the rolling mill based on the yield stress and the amount of strain, and calculate the deformation resistance and friction coefficient thus obtained and the 1
The thickness of the steel strip is controlled in each stand by determining the required reduction blade in each stand based on the thickness of the steel strip measured at the front of the entrance side of the stand. Has characteristics. , [Configuration of the Invention] FIG. 1 is a configuration diagram showing one embodiment of a rolling apparatus to which the plate thickness control method of the present invention is applied. In FIG. 1, 1 is a cold tandem rolling machine, 2 is an uncoiler for supplying steel strip 3 to rolling mill 1, 14 is a tension reel for winding steel strip 3 rolled by rolling mill 1, and 5 is a tension reel for winding steel strip 3. board speed? 6 is the steel strip 3
8 is a tension meter for measuring the tension T of the steel strip 3, 8 is each stand S of the rolling mill 1, -
A rolling force detector detecting the rolling blade P at S, 9 is the roll circumferential speed of each stand 81 to S. A roll circumferential speed detection controller detects and controls 4, 10 is each stand 81 to SS
11 is a servo pulp that controls the rolling position of the rolling device; 12 is a tension for applying a slight strain r to the steel strip 3 passed through the rolling mill 1; leveler,
Reference numeral 13 denotes a process computer that processes signals such as the plate speed V obtained by the plate speed meter 5 and the like to control the plate thickness at each of the stands 81 to 8S.

In the method of the present invention, a strain is applied to the steel strip 3 in front of the entrance side of the first stand S of the rolling mill 1, and the tension T, etc. of the steel strip 3 at that time is measured. The yield stress σY and the amount of strain ε applied to the steel strip 3 are determined, and from this, each stand 8
Determine the deformation resistance σ and friction coefficient μ of the steel strip 3 at 1 to S, and based on these and the original thickness of the steel strip 3, calculate the thickness of the steel strip 3 at each stand 81 to S. 2. This is to control the feed forward.

The deformation resistance σ and friction coefficient μ of the copper strip 3 at each stand 81 to S of the rolling mill 1 are determined as follows by applying strain to the steel strip 3.

In a tension repeller, if the friction coefficient between the roll surface and the steel strip surface is set to be sufficiently large compared to the rotational resistance of the roll, the slip between the roll and the steel strip is sufficiently small and can be ignored. Therefore, the tension increment ΔT due to the repeller is given by the following equation (1).

R However, ΔT: Tension increment of steel strip, b2 Plate width, H: Plate thickness, OY: Yield stress, N: Number of rolls of repeller, R: Roll radius.

At this time, the total amount of strain ε within the repeller is 0, 5~
If the roll radius R and the steel strip thickness H are set within the range of 2.0, changes in the thickness H and yield stress σY within the repeller can be practically ignored. become able to. Therefore, the plate thickness (original plate thickness) H on the leveler entry side and the tension difference Δ between the leveler entry and exit sides
T, roll radius R, number of rolls of the repeller n1
If the plate width is given as a known value, the yield stress σY of the steel strip at that point can be found from equation (1).

Note that if changes in plate thickness H and changes in yield stress σY are corrected, it is possible to apply a strain amount of a factor of 2 or more. The amount of strain to be applied is 0.5 to 10%, preferably 0.5% to 10%.
5-5% is suitable. This is due to the fact that at ε (0.5%, it is difficult to accurately determine the strain amount ε and the tension difference ΔT between the leveler entrance and exit sides caused by applying this strain amount ε). On the other hand, when ε is 10%, it becomes difficult to accurately measure the tension difference ΔT due to mechanical loss in the repeller, and the equipment becomes larger.

Further, since the amount of distortion ε at this point is approximated by the following equation (2), the amount of distortion ε can be obtained from the equation (2).

ε=-N ・・・・・・・・・・・・・・・・・・
...(2) R Next, in the equation of deformation resistance expressed by the following equation (3), the constant α and the constant n have approximately constant values depending on the steel type, and can be given as known numbers.

σ=ru(ε+α)Q ・・・・・・・・・・・・・・・
...(3) However, σ: deformation resistance, A: constant, α, n: constants determined by the steel type.

Therefore, by substituting σY and ε determined by equations (1) and (2) into equation (3), the constants of equation (3) are determined.

Once the edge of equation (3) is determined, the deformation resistance σ at each stand can be found from equation (3) by giving the rolling reduction rate at each stand of the rolling mill, and therefore by giving the amount of strain.

In addition, the coefficient of friction μ between the steel strip and the roll at each stand can be determined by using the rolling edge P, tension T, roll radius r at each stand, and R determined from equation (3). It can be learned by solving the (Von Karman) differential equation.

Once the deformation resistance σ and friction coefficient μ of the steel strip 3 at each stand 81 to S of the rolling mill 1 have been determined as described above, the deformation resistance σ and the friction coefficient μ of the steel strip 3 From the board thickness, valley stand 81~S, on the exit side,
Since the rolling blades P at each stand S1 to S necessary to obtain the same sheet thickness as the predetermined thickness are determined, the sheet thickness may be controlled based on the rolling blades P.

The steel strip 3 is fed out from the uncoiler 2, and the plate speed V1 and plate thickness H on the repeller side are measured by the plate speed meter 5, plate thickness gauge 6, and tension gauge 7 on the entry side of the tension repeller 12.
After the (original plate thickness) and tension T support are measured, it enters the leveler 12, where a slight strain is applied. Then,
The steel strip 3 is measured by a tension meter 7 and a plate velocity meter 5 on the outlet side of the leveler 12 to measure the tension T0 and r on the outlet side of the leveler 12.
After o is measured, it enters the rolling mill 1.

On the other hand, the original plate thickness H measured at the entrance side of the leveler 12 passes through the low-pass filter 14 to the process computer 13.
is input to. The plate speeds r1 and Vo measured at the entrance and exit sides of the leveler 12 are input to the calculator 15,
Then, the amount of strain ε added by the leveler 12 is calculated, and the amount of strain ε is input to the computer 13. The tensions T1 and To measured at the inlet and outlet sides of the leveler 12 are input to the calculator 16, where the tension difference ΔT between the inlet and outlet sides of the leveler 12 is computed. is input to.

The process computer 13 calculates the yield stress σY of the copper strip 3 from the tension difference ΔT1, the original plate thickness H, etc., and calculates the yield stress σY of the copper strip 3 from the yield stress σY and the strain amount ε, etc. for each stand S, ~
The deformation resistance σ and friction coefficient μ of the steel strip 3 at S are calculated. Then, the computer 13 calculates, from the deformation resistance σ, the friction coefficient μ, and the original thickness H of the steel strip 3, the same thickness as the predetermined thickness at each stand 81 to S and the exit side. Each stand S1 required/required for
It calculates the rolling blade P at S, and outputs a control signal necessary to obtain the rolling blade P at each stand S1 to S. Rolling machine 1
In each of the stands $1 to S, the rolling position of the rolling device 10 is adjusted by a control signal outputted from the computer 13 to, for example, the servo pulp 11, and the size of the roll gap is adjusted to the required rolling blade P. It is fixed to the size that can be obtained.

The steel strip 3 is rolled at each stand S1 to S by a control signal output from the process computer 13 based on the deformation resistance σ, friction coefficient μ, and original plate thickness H at each stand S, to S of the rolling mill 1. In S5, the plate thickness is controlled by the rolling position control and/or tension control. At that time, the tracking of the steel strip 3 is performed on each stand S, ~
This is done by measuring the plate speed with a plate speed meter 5 provided between S3.

The deformation resistance when a completely discontinuous part (hereinafter referred to as a singular point) passes through the tension leveler 12, such as a connection part of the steel strip 3 or a size change point accompanied by a change in material, is as follows: The deformation resistance when the 10th rule of 12 is reached is treated as the deformation resistance before the singularity, and the deformation resistance when the singularity reaches the exit of the leveler 12 is treated as the deformation resistance after the singularity. Tracking when this singular point passes through the leveler 12 is performed, for example, by the plate thickness meter 6 on the entry side of the leveler 12.
This is done by measuring the plate thickness using a plate speed meter 5 and measuring the plate speed using a plate speed meter 5.

The steel strip 3 is controlled in the first stand S1 to the thickness determined in the first stand S1. However, corrections for changes in the thickness that could not be controlled in the first stand S1 are made using the roll circumference of the first stand. This is done by controlling the speed VKI and the lowering position of the second stand. Second
Regarding plate thickness control after stand s2, based on the theory of constant mass flow, the roll circumferential speed at each stand 82 to S is -2 to ? This is done by controlling A5 or the lowering position, or by controlling both.

In the above example, the tension repeller 12 was used to apply strain to the steel strip 3 in front of the entrance side of the rolling mill 1, but as shown in FIG. good. In addition, in FIG. 2, 18 is a torque meter for measuring the torque of the high-speed side roll and low-speed side roll of the different speed rolling mill 17, 19 is a rolling device, 2o is a rolling force detector of the different speed rolling mill 17, and 21 is a This is a roll circumferential speed detection rule for detecting the circumferential speed of a high-speed side roll and a low-speed side roll, and in FIG. 2, the same line numbers as in FIG. 1 indicate the same members.

When a different speed rolling mill is used, the yield stress σY of the IJ tube 3 is given by the following equation (4).

However, T: Torque of the high speed roll of the different speed rolling mill T2: Torque of the low speed roll, R5: Radius of the high speed roll, R2: Radius of the low speed roll, P: Reduction blade, b: Steel strip plate Width, I (': Plate thickness at the exit side of the different speed rolling mill, ε: Steel steel) Amount of strain applied to the IJ tube, T1: Tension at the entry side of the different speed rolling mill, To: Output side of the different speed rolling mill tension at.

Further, the amount of strain ε is obtained from the difference in circumferential speed between the high-speed roll and the low-speed roll.

Therefore, the yield stress σY and the amount of strain ε of the steel strip 3 can be determined by applying strain to the steel strip 3 using the different speed rolling mill 17 and measuring the tension T1, etc. at that time. 12, each stand 81 to 81 of the rolling mill 1 is
Determine the deformation resistance σ and friction coefficient μ of the strip 3 at S, and calculate these and the plate thickness measured at the entrance side of the first stand S1.
Based on this, the board thickness at each stand S, ~S, may be determined based on the feed.

As described above, in this invention, the deformation resistance and friction coefficient of the steel strip at each stand of the rolling mill can be adjusted by applying strain to the steel strip as well as the thickness of the steel strip immediately before the rolling mill. Because it predicts in real time and controls the plate thickness at each stand,
Highly accurate plate thickness can be ensured even when rolling completely discontinuous parts, such as steel strip connections or size change points that involve changes in material.

FIG. 3 shows the thickness of the steel strip in the vicinity of the connection part (exit side thickness) when the steel strip is cold rolled from the bend using the method of the present invention, together with the case using the conventional control method. In Figure 3, (a) shows the original thickness of the steel strip, and (b)
is the exit thickness of the steel strip in the case of the method of this invention,
(C) is the exit side thickness in the case of the conventional feedback monitor method, (d) is the exit side thickness in the case where the feed forward method based on plate thickness is added to the conventional feedback method to the first stand, and ( ,) shows the thickness of 109 yen by adding a gauge meter method to the conventional feedback method.

〔Effect of the invention〕

As explained above, according to the method of the present invention, the plate thickness can be controlled with high precision even at completely discontinuous parts such as steel strip connections or size change points that involve changes in material. be able to.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of a rolling apparatus to which the plate thickness control method of the present invention is applied, and FIG. 2 is a configuration diagram partially showing another embodiment of the rolling apparatus to which the plate thickness control method of the present invention is applied. figure,
FIGS. 3(a) to 3(e) are diagrams showing the exit thickness of a steel strip when the steel strip is cold-rolled without controlling its thickness by the method of the present invention and the conventional method. In the drawings: 1...Rolling mill, 2...Uncoiler-1
3...Steel strip, 4.°° tension reel, 5...Plate speed meter, 6...Plate thickness gauge, 7
...Tension meter, 8...Reduction force detector, 9
. . . Roll peripheral speed detection controller, 10. Reduction device, 11. Servo pulp, 12. Tension leveler, 13. Process computer, 14. Low pass filter, 15.
16... Arithmetic unit, 17... Different speed rolling mill, 18
...torque meter, 19...reducing device, 2
0... Rolling force detector, 21... Roll circumferential speed detector,
81~S...Stand.

Claims (1)

[Claims] The yield stress of the steel strip and the amount of strain obtained by applying a slight strain to the steel strip in front of the entry side of the first stand of a rolling mill that rolls the steel strip. Based on this, the deformation resistance and friction coefficient of the steel strip at each stand of the rolling mill are determined, and the deformation resistance and friction coefficient thus obtained and the value measured at the front of the entry side of the first stand are determined. , the thickness of the steel strip is controlled in each stand by determining the required rolling blade in each stand based on the thickness of the steel strip. Method.