KR20030054637A - Device and method for flatness control for reversing mill - Google Patents

Abstract

PURPOSE: A feedback control system and a feedback control method for controlling flatness of strip in reversing rolling mill are provided to improve shape of top and end parts of the strip where the strip is decelerated or accelerated by installing thickness profile meter in front and rear of the reversing rolling mill. CONSTITUTION: In a feedback control system for performing flatness control by measuring longitudinal tension distribution at the output side in each proceeding direction of the strip in a reversing rolling mill for obtaining desired thickness of the strip by rolling strip forwardly and reversely for several times, the feedback control system for controlling flatness of the strip in the reversing rolling mill comprises thickness profile meters(728,729) for measuring widthwise thickness distribution of the strip; reference thickness operation parts(734,735) for minimizing wave; optimum work roll bending force calculation parts(736,737) for calculating optimum bending force by receiving information on the rolling mill, rolling conditions and values measured at the thickness profile meters(728,729); and optimum work roll bending force storage parts(738,739) for storing the optimum bending force calculated at the optimum work roll bending force calculation parts(736,737) to apply the stored optimum bending force during subsequent passes.

Description

Feedback control device and method for performing flatness control {Device and method for flatness control for reversing mill}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback control apparatus and method for performing flatness control, and more particularly, by installing a thickness profile meter before and after a lobe rolling mill, to reduce the shape of a strip top / end part as a deceleration period. A feedback control device and method for performing flatness control to improve.

1 is a schematic view for explaining the cause of shape defects.

The shape defect in cold rolling does not occur when the thickness profile of the roll gap and the side material coincide, as shown in FIG. 1 (b), but the shape defect does not occur uniformly as shown in FIG. It is a phenomenon in which a wave is formed by forming a plate in a long plate direction as compared to a place where rolling is less.

2 is a view showing the type of flatness failure and the stress distribution accordingly.

As shown in FIG. 2, the shape defect includes a center buckle in which the length of the center portion is long, and an edge wave phenomenon in which the lengths of both ends are long.

Figure 3 is a schematic diagram showing the type of the actuator, Figure 4 is a schematic view showing the configuration of a feedback control system of a general reversible rolling mill applied to the present invention, Figure 5 is a view showing a conventional shape measuring device.

The reversible rolling mill rolls the plate several times in the forward and reverse directions as shown in Figure 4 to obtain the desired thickness. And the shape meter (Shape Meter) before and after the rolling mill is used to control the shape by measuring the unit tension distribution in the plate width direction.

However, the flatness of the acceleration / deceleration section, that is, the Top and End sections, is poor compared to the normal section even when the shape feedback control is performed. This is because the thickness profile of the top and end portions of the material is not uniform compared to the middle portion. Therefore, there is a need in the related art for a method of improving the flatness of the top and end portions as well as the flatness of the middle portion by providing a thickness profile meter before and after the reversible rolling mill.

In addition, in the conventional shape control method, only the feedback control was performed by measuring the flatness of the plate rolled through the rolling mill in the exit shape measuring instrument. In the shape control, the feedback control removes the flatness defect due to the mismatch between the roll gap and the side thickness profile, and removes the shape disturbance existing in the side plate when it is transmitted to the exit side. For this reason, feedback control must be included in shape control. However, the feedback control using the shape measuring device has a problem in that it cannot effectively cope with other flatness disturbances in response to the sudden change of the material profile of the top and end portions.

On the other hand, the configuration and function of the conventional flatness feedback controller, as follows.

As shown in FIG. 4, the conventional flatness feedback controller performs flatness control using the stresso meta 403 capable of measuring the tension distribution in the longitudinal direction as shown in FIG. 5.

FIG. 6 is a diagram illustrating a control logic process in the feedback control system 409 and 410 shown in FIG. 4.

The plate flatness signal measured by the shape measuring device sets the target shape by calculating the deviation value of the signal measured in each zone of the shape measuring device and correction according to the measurement conditions by the shape error signal calculation and correction unit 617. The flatness error which is the difference with the target flatness set by the part 615 is calculated. The flatness error F (i) may be expressed as a function of each shape control actuator model as shown in Equation 1 below. Here, the shape control actuator model is obtained by experimenting with a function measured by the stressor when applying the asymmetrical reduction to the work roll bender and the back-up roll.

Here, F (i) is the flatness error value of the i-th region, Is an asymmetrical rolling control model, Is the work roll bender control model, and i is the partition number in the stressometer.

In Equation 1, the problem solving method of flatness error control is to find the coefficient value C of each control model. The least-squares method is used as a mathematical method to find the coefficients. When Equation 1 is expressed as a determinant, Equation 2 is shown below.

F = AC

Where F = [f (1) f (2) ... f (n)] ^T , C = [C1, C2], to be.

In Equation 2, the coefficient value C of each control model may be obtained by matrix calculation as shown in Equation 3 below.

The coefficient values C ₁ , C ₂ (619, 620) of each control model obtained by the least-squares calculation unit 618 are input to the proportional-integral control units 622, 623, respectively, so that C ₁ , C ₂ converges to zero. The integral control is performed to output the output values 625 and 626 of the respective shape actuators.

Here, the meaning of the coefficient value C of the control model is as follows. A large value of C means a large difference between the target flatness and the measured flatness, and a small value of C means that the target flatness and the measured flatness are similar. In addition, an error value that cannot be separated by the workload vendor model and the asymmetrical reduction model is obtained as shown in Equation 4 below, and the cooling control operation unit 624 uses the cooling control operation unit 624 to compensate for the error value. Determine On / Off so that the error value of the area is zero.

However, the feedback control using the shape measuring device having the configuration and function as described above has a problem in that it cannot effectively cope with other flatness disturbances in response to the sudden change of the material profile of the top and end portions.

An object of the present invention for solving the problems of the prior art as described above is to install a thickness profile meter before and after the loaf rolling mill, to perform the flatness control to improve the shape of the strip top / end portion of the deceleration acceleration section It is to provide a feedback control apparatus and method.

1 is a schematic view for explaining the cause of the shape defect,

2 is a view showing the type of flatness failure and the stress distribution accordingly,

Figure 3 is a schematic diagram showing the type of actuator,

Figure 4 is a schematic view showing the configuration of a feedback control system of a general reversible rolling mill applied to the present invention,

5 is a view showing a conventional shape measuring device,

FIG. 6 is a diagram illustrating a control logic process in the feedback control system 409 and 410 shown in FIG. 4.

7 is a configuration diagram schematically showing the configuration of a shape control system according to an embodiment of the present invention,

8 is a configuration diagram of a thickness profile meta device according to an embodiment of the present invention;

9 is a flowchart illustrating a process of a flatness feed forward controller according to an embodiment of the present invention;

10 is a view showing the geometric relationship of sheet rolling.

※ Explanation of code about main part of drawing ※

305, 401: Back-up Roll 306, 402: Work Roll

307: Work Roll Bender 308: Asymmetric Skewer

403: shape measuring device

404: Coiler / Uncoiler

409, 410: Flatness feedback controller in forward / reverse rolling

411, 413, 614: width distribution signal

615: target shape setting unit 616: target stress distribution signal

617: Shape error signal calculation and correction unit 618: Least squares calculation unit

619: Skewing Error 620: WR bending error

621: residual error

622: reduction force proportional to integral controller

623: WR Bending Proportional-Integral Controller

624: cooling control calculation unit

625: reduction force control output

626: WR bending control output

627: nozzle on / off signal output

728, 729: thickness profile meter

730, 731: thickness profile signal

732, 733: thickness profile storage

734, 735: target thickness profile calculator

736, 737: optimum work roll bending force calculation unit

738, 739: feed forward bending force storage unit

740, 741: feed pack, feed forward weight setting unit

742, 743: Flatness Feedback Controller

744: central information processing unit

745 signal switching unit

746, 747: Crown Feed Forward Controller

In order to achieve the above object, according to the present invention, in the reversible rolling mill to obtain a desired thickness of the steel sheet by rolling the steel sheet in the forward / reverse direction a number of times, by measuring the tension distribution in the longitudinal direction of the exit direction of the steel sheet, A feedback control apparatus for performing control, comprising: a thickness profile meta for measuring a width distribution in a thickness direction of a steel sheet; A target thickness calculator for minimizing waves; An optimal work roll bending force calculation unit configured to calculate an optimal bending force by receiving mill information, rolling conditions, and values measured in the thickness profile meta; And an optimum work roll bending force storage unit for storing an optimum bending force value from the optimum work roll bending force calculation unit to be applied at a later pass. It provides a flatness feedback control device, characterized in that made.

In addition, a feedback control method for performing flatness control by measuring the tension distribution in the lengthwise exit direction of the steel sheet in a reversible rolling mill in which a steel sheet is rolled a number of times in the forward / reverse direction to obtain a desired thickness of the steel sheet. In the step, measuring the width distribution of the thickness of the steel sheet; Calculating a target thickness to minimize the wave; Calculating an optimal bending force by receiving mill information, rolling conditions, and the thickness distribution value; Storing the optimal bending force value for application at a later pass; And performing shape control of the steel sheet using the stored optimal bending force value. It provides a flatness feedback control method comprising a.

Hereinafter, a feedback control apparatus and method for performing flatness control according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1) Reversible Rolling Mill Configuration and Shape Actuator

The reversible rolling mill to which the present invention is applied is shown in FIGS. 3 and 4 for the 4Hi rolls 401 and 402, the shape measuring machine 403 and the winding machine 404 provided before and after the rolling mill, and the shape control of FIG. It is composed of a work roll bender 307 that applies bending to the rolls shown in Fig. 2 and a reduction cylinder that can apply an asymmetrical reduction force 308 to the back-up roll.

2) Flatness Feed Forward Controller Configuration

7 is a schematic view showing the configuration of a shape control system according to an embodiment of the present invention, Figure 8 is a configuration diagram of a thickness profile meta device according to an embodiment of the present invention, Figure 9 is a view of the present invention 10 is a flowchart illustrating a process of a flatness feed forward controller according to an embodiment, and FIG. 10 is a diagram illustrating a geometric relationship of sheet rolling.

The present invention proposes that the thickness profile meta (728, 729), the flatness feed forward controller (746, 747) and the central information processing unit 744 for managing the mill information and rolling information in the existing shape control system of FIG. Added improved shape control system.

Mill information and rolling information include the following.

Mill info: Crown of work roll, backup roll, diameter, width, roll choke length

Rolling information: entry and exit tension, roll speed, total rolling load, friction coefficient, material width, friction coefficient, material strain resistance coefficient, material elastic modulus

The thickness profile meta is a measuring instrument for measuring the thickness distribution in the plate width direction, as shown in FIG. 8.

The flatness feed forward controllers 746 and 747 may include a thickness profile storage unit 732 and 733 for measuring and storing the exit width direction thickness distribution from the exit thickness profile meta, a exit target thickness calculator 734 and 735 for minimizing waves, The optimum work roll bending force calculation unit 736 and 737 and the optimum work roll bending force for receiving the mill information, the rolling conditions, and the thickness profile storage unit 732 and 734 from the entry and exit side thickness profiles. The optimal work roll bending force storage units 738 and 739 for storing the calculated values of the calculation units 736 and 737 for the next pass are provided.

The calculation logic of the optimum bending force calculation units 736 and 737 among the feed forward controllers 746 and 747 shown in FIG. 7 is the same as that described in FIG. 9.

First, the width direction from the entrance thickness profile 732 measured in the exit target thickness profile 734, the Mill information 744, and the profile meta 729 (which becomes the entrance thickness profile of the next pass) to minimize the wave. The rolling load distribution calculation for each section is performed (946).

At this time, the rolling load distribution formula is as follows.

First, a point where the speed between the plate and the roll coincides between the roll gaps in which rolling is performed is called a neutral point, and the output side is called an advanced station and an entrance side is called a reverse station. At this time, the load of the advanced station and the reverse station is calculated by [Equation 5] below, the load means a vertical load acting in the x position in FIG.

Where p ⁺ is the load in the advanced region, p ^- is the load in the reverse region, h is the plate thickness at any point, k is the average yield stress, h ₀ is the exit plate thickness, and h ₁ is the entry side Plate thickness Is the exit unit tension, Is the entry unit tension, Is the exit yield stress, Is the entry yield stress, Is the contact angle.

In addition, the neutral angle may be expressed as Equation 6 below.

Therefore, the load acting on each divided section in the work roll width direction is linear, and the load in the reverse area is roll contact section 0 to By integrating Equation 7 below.

Where C ₀ is a hitchcock constant, R is a work roll radius, R 'is a deformation work roll radius, Is a rolling reduction, v ₀ is Poisson's ratio, and E ₀ is an elastic modulus.

The following is the calculation process to find the contact pressure between rolls. At this time, a division model divided in the width direction at a predetermined interval is used to obtain the width direction pressure distribution.

The rolling load distribution (p (j)) acting on the work roll calculated earlier to find the contact pressure between the work roll and the backup roll, the bender force (J / 2) of the work roll initially set by the operator, and the backup roll The repulsive force q (j) between the back-up roll and the work roll is obtained by using the equilibrium equation of the force showing the equilibrium relationship and the suitable conditional equation between the roll and the roll during rolling. . This is shown in Equations 8 and 9 below.

Where p (j) is the section-specific load acting between the workpiece and the work roll, q (j) is the contact pressure acting between the work roll and the backup roll, Δz is the division interval, and Y _B (i) is Backup roll axis displacement, Y _W (i) is the work roll axis displacement, ΔY _BW is the relative displacement of the axis between the rolls, K ₁ is the contact elastic modulus between the work roll, backup roll, R _CW (i) is the interval It is a work roll crown value for each, and R _CB (i) is a backup roll crown value for each section.

On the other hand, the axial displacement of the work roll and the backup roll can be represented by the following [Equation 10] and [Equation 11].

Here, α _B (i, j), α _W (i, j) are axial displacement influence coefficients of the backup roll and the work roll, and are coefficients representing the roll deflection at the i position when a unit load acts on the j position of the roll. , This is determined by Equation 12 and Equation 13 below by the geometrical structure of the roll.

Contact pressure distribution between the work roll and the backup roll by using the equations [10] and [11], which are the axial displacement calculation equations, into [9], which is a suitable conditional equation, and [8], which is the equilibrium equation. Can be obtained.

And the roll flat deformation amount is calculated | required from following formula (14) from the rolling load p (j) received from a strip.

In addition, the flexural deformation (Y _B , Y _W ) of each roll is obtained from the contact pressure between the rolls, _{and the} roll flat deformation amount is obtained from the rolling load distribution of the work roll. do.

Here, c in parentheses means the center value of the strip, and i in parentheses means one section of the split model.

Finally, it is checked whether the calculated roll gap distribution coincides with the target thickness distribution, and if it does not match, substitute Equation 16 below, which is a modified bender force equation, into Equation 8, which is an equation of force balance. Is repeated until a match is made, and if it is matched, this value is stored in the bending force storage units 738 and 739 to input the shape output value (work roll bender force) to the feed forward work roll bending force on the next pass.

Is the corrective bender force.

In addition, since the feedforward control value and the feedback control value are excessively entered where they enter the vendor's input value of the work role, the weight calculation units 740 and 741 are decided.

Equations in the weight calculators 740 and 741 are as shown in Equation 17 below.

Here, U _tot is a total workflow bender control input value, U _FB is a flatness feedback control input value, U _FF is a feed forward control input value, and α (= 0 to 1) is a predetermined weight.

While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited by the appended claims, and should be construed as including all such changes, modifications or adjustments.

According to the present invention as described above, by providing the flatness feed forwarding controller, there is an effect that can greatly improve the flatness of the entire strip, and improve the degree of Top / End portion shape of the rolled product.

Claims (5)

In a feedback control device for performing flatness control by measuring the tension distribution in the lengthwise direction of the exit direction of the steel sheet in a reversible rolling mill which rolls the steel sheet in the forward / reverse direction a number of times to obtain a desired thickness of the steel sheet. , A thickness profile meta for measuring the width direction thickness distribution of the steel sheet; A target thickness calculator for minimizing waves; An optimal work roll bending force calculation unit configured to calculate an optimal bending force by receiving mill information, rolling conditions, and values measured in the thickness profile meta; And An optimum work roll bending force storage unit for storing an optimum bending force value from the optimum work roll bending force calculation unit to be applied at a later pass; Flatness feedback control device comprising a. In a feedback control method of performing a flatness control by measuring the tension distribution in the longitudinal direction of each exit direction of the steel sheet in a reversible rolling mill to obtain a desired thickness of the steel sheet by rolling the steel sheet in a number of forward / reverse directions , Measuring a width direction thickness distribution of the steel sheet; Calculating a target thickness to minimize the wave; Calculating an optimal bending force by receiving mill information, rolling conditions, and the thickness distribution value; Storing the optimal bending force value for application at a later pass; And Performing shape control of a steel sheet using the stored optimal bending force value; Flatness feedback control method comprising a. The method of claim 2, The optimal bending force calculating step, A substep of obtaining a rolling load distribution for each section in the width direction from the mill information, the side thickness profile, and the exit target thickness profile for minimizing the wave; Obtaining an equilibrium equation formed by the rolling load distribution for each section, the bender force of the work roll initially set by the operator, and the forces acting on the contact surface of the backup roll; A substep of obtaining a suitable condition equation according to the roll and the roll being stuck together during rolling; A substep of calculating the repulsive force between the backup roll and the work roll using the equilibrium equation and the fit condition equation; A substep of calculating an axial displacement of the work roll and the backup roll by using the repulsive force between the backup roll and the work roll; A substep of calculating a contact pressure distribution between the work roll and the backup roll using the equilibrium equation, the fit condition equation, and the axial displacement values of the work roll and the backup roll; Calculating a roll flat deformation amount from the rolling load, and then adding it for each section to obtain a roll gap distribution; And A sub step of obtaining an optimum bending force from the roll gap distribution; Flatness feedback control method comprising a. The method of claim 3, wherein If the roll gap distribution does not coincide with the target thickness distribution, the optimum bending force is repeatedly inputted into the equilibrium equation until it is matched, and if it is matched, the feed forward work roll bending force is subsequently passed to the optimum bending force. Flatness feedback control method characterized in that the input. The method of claim 4, wherein And calculating a weight so that the feedback control value or the feed forward control value is not excessively input when the feed forward work bending force is input.