KR100417517B1 - Camber control method of plate pass mill - Google Patents

Abstract

The present invention is a method for controlling a camber generated in a thick plate during finishing rolling of a thick plate, the purpose of which is to provide a method for calculating a wedge using a formula and controlling the camber using such a wedge value. have.

The camber control method of the thick plate of the present invention calculates the amount of elongation at the working side and the driving side of the mill by interpolation using data of the rolling position load according to the cylinder position change amount and cylinder position change amount at the working side and the driving side of the mill, Using the draw amount of the mill, the exit wedge of the thick plate after rolling was calculated by Equation 1, the wedge ratio change was calculated from the calculated exit wedge and the entrance wedge of the thick plate before rolling, and the curvature of the exit of the thick plate passed through the mill was calculated. Calculated by 2, and the difference between the roll gaps is calculated by Equation 3 in the form of reducing the next pass camber from the calculated exit curvature and the amount of wedge and mill draw and apply to the next pass mill.

Equation 1 Equation 2 is Equation 3 is to be.

Description

Camber control method during plate rolling mill {Camber control method of plate pass mill}

The present invention relates to a method for controlling a camber generated when rolling a thick steel sheet (hereinafter referred to as 'thick plate'), in particular, to calculate the wedge using a mathematical model and to control the camber using the calculated wedge value It is about how to.

Camber refers to a phenomenon in which the amount of stretching at both ends of the steel sheet is different in the rolling direction of the steel sheet, which is curved in the longitudinal direction in which the steel sheet is rolled. It is caused by various factors such as off center, deviation of temperature of steel sheet, and difference of roll gap.

1: A is sectional drawing in the width direction of the steel plate 1 which shows a wedge, FIG. 1: B is a top view which shows the off center which the center of the work roll 3 to roll and the steel plate 1 shifted, FIG. Fig. 1 is a schematic diagram showing the camber amount in a state of curvature in the longitudinal direction.

The camber as shown in FIG. 1C is generated due to the operation as shown in FIGS. 1A and 1B.

When the camber is generated as shown in FIG. 1C, the camber control method according to an exemplary embodiment of the present invention provides the camber shape of the rear plate 1 rolled to the neck side, that is, the X direction and the size of the rear plate 1. The method of measuring and controlling the camber of the thick plate 1 which passes through by adjusting the difference of left and right roll gap empirically is used. However, according to such a camber control method, it is a problem that the feed back method of controlling the roll gap through the camber generated on the driver's incorrect neck side and the already rolled thick plate 1 is problematic.

In addition, another camber control method is to use a camber measuring instrument. The camber control method measures a camber of a steel sheet by installing a camber measuring instrument at the inlet and outlet sides of a finishing mill for rolling the steel sheet, and uses the measured value of the camber as the measured value. How to control.

However, the camber system should be installed close to the mill in the case of feedback control using such a camber measuring instrument.However, when the high pressure water is injected to remove the scale, the measuring accuracy of the measuring instrument is deteriorated. Often installed on the back of the mill. In addition, the back of the mill is provided with a number of measuring instruments, such as a thickness gauge for controlling the thickness, a shape measuring instrument for measuring the shape, there is a problem that must be installed at a distance away from the rolling mill.

The present invention is provided to solve the problems of the prior art as described above, and before rolling the thick plate to predict the camber may occur in the thick plate and calculate the roll gap deviation control amount on the left and right of the mill to control such camber in advance The purpose is to provide a camber control method to be applied.

1A is a cross-sectional view in the width direction of a steel plate showing a wedge,

1B is a plan view showing an off center in which the work roll to be rolled and the steel sheet are shifted from their centers;

Figure 1c is a schematic diagram showing the camber amount in a state of curvature in the longitudinal direction of the steel sheet,

2 is a graph for explaining an interpolation method for calculating the amount of wheat draw according to the present invention;

3A is a graph showing the relationship between a wedge calculated with the adjustment coefficient α of 1 and the wedge actually measured,

3B is a graph showing the relationship between the wedges calculated while varying the adjustment coefficient α according to the plate width and the actual measured wedges.

4 is a graph showing the relationship between the curvature calculated by the camber control method according to an embodiment of the present invention and the curvature actually measured using a camber measuring instrument.

According to the present invention for achieving the object as described above, in the camber control method for controlling the camber generated while the thick plate passes through the mill, the cylinder position change amount and the cylinder position change amount of the working side and the driving side of the mill; Calculating the draw amount of the working side and the driving side of the mill by interpolation using the data of the rolling load, and calculating the exit wedge of the thick plate after rolling using the draw amount of the mill through Equation 6; Calculating a wedge ratio change amount from the calculated exit wedge and the entrance wedge of the thick plate before rolling; calculating the curvature of the exit of the thick plate passed through the mill by Equation 4; and the calculated exit curvature and the Calculating the difference between the roll gaps by the following equation (10) in the form of reducing the next pass camber from the wedge and the mill drawing amount and applying it to the next pass mill. There is provided a camber control method comprising a.

Further, according to the present invention, in the step of calculating the exit wedge of the thick plate after rolling, the parameters b and c are the side plate thickness, the exit plate thickness, the plate width, the rolling load, the constant of the mill, the length of the work roll choke, The camber control method is set by the work roll barrel length.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of a camber control method occurring during thick plate finishing rolling according to the present invention will be described in detail.

The size and direction of the camber is proportional to the wedge rate change. The relationship between the camber and the wedge rate change can be seen through Equation 1.

Here, ΔΦ is a change in the wedge rate, k is an integer indicating the relationship between the change in the wedge rate and the curvature.

The wedge ratio is again defined as in Equation 2.

Here, h _df is wedge after i pass rolling, W is plate | board width after i pass rolling, and h is exit thickness after i pass rolling. The i-pass represents passing through the i-th mill.

On the other hand, the thick plate rolling is reverse type rolling, whereby the exit thickness of the i-1 pass becomes the entrance thickness at the time of i pass rolling, and the i-1 pass exit wedge becomes the i pass entrance wedge. Therefore, the exit curvature is expressed by Equation 3 when the material has no change in wedge rate before rolling and the entrance material only has a camber initially.

Where ρ _o is the exit curvature, ρ _i is the exit curvature, H is the exit thickness, and h is the exit thickness.

However, when the wedge ratio is changed in the entry material, and the entry material has a curvature before rolling, the exit curvature may be represented by Equation 4 in which Equation 1 and Equation 3 are added.

The change in wedge ratio ΔΦ can be expressed as shown in Equation 5.

Here, phi _i is the wedge rate after i pass rolling, and phi _i-1 shows the wedge rate before i pass rolling.

Meanwhile, in order to derive the camber control amount of the next pass using the exit curvature shown in Equation 4, the wedge of the exit and the wedge to be generated in the next pass should be predicted.

In general, the occurrence of the left and right thickness differences of the thick plate is caused by rolling elements which are asymmetrical left and right. The asymmetrical rolling elements include the difference between the left and right rigidity of the mill, the difference of the roll gap, the wedge formed in the entry material entering the finishing rolling mill, the off center, and the asymmetrical rolls. Factors influencing are the difference between the left and right stiffness of the mill, the difference of the roll gap, and the wedge of the entry material.

As such, the wedges formed on the thick plate are estimated by combining the influencing elements. Hereinafter, a method of estimating wedges will be described.

Equation 6 is a wedge calculation formula model.

Where h _df is the exit wedge, S _df is the difference in roll gap, MS _df is the difference in mill elongation, H _df is the entrance wedge, W is the plate width, L is the distance between the roll chokes, b and c are parameters.

In addition, in order to calculate the wedge through Equation 6, it is necessary to obtain a mill elongation difference and an adjustment coefficient. Hereinafter, a description will be given of such a close elongation difference, the adjustment coefficient and the calculation method for obtaining the adjustment coefficient.

First, the mill drawing car contacts the upper and lower work rolls without a thick plate, and then lowers the cylinder to generate rolling force. At this time, the positions of the left and right cylinders, the work site, and the drive site Each load change is measured and stored in the memory. Table 1 and Table 2 are examples of the cylinder position vs. load data of the working side and the driving side, respectively, converted from the data to the amount of close drawing for a constant load interval.

Table 1 is a table regarding load vs. mill stretching on the working side, and Table 2 is a table regarding load vs. mill stretching on the driving side.

Ton 300 450 600 750 900 1050 1200 . . . 3500 Wheat elongation (mm) X1 X2 X3 X4 X5 X6 X7 . . . Xn

Ton 300 450 600 750 900 1050 1200 . . . 3500 Wheat elongation (mm) X1 X2 X3 X4 X5 X6 X7 . . . Xn

Table 1 shows an example of storing the data storage interval for 150 tons of load. The interpolation method, which is a method of generating data with a constant load interval, is adjusted according to the changed weight during a sample time during actual milling constant measurement. Calculate using

That is, the cylinder position when the load is N · 150 tons using the data of the load is greater than N · 150 tons and the previous data while reading the load sequentially, as shown in equation (7) Calculate

2 is a graph for explaining an interpolation method for calculating the amount of wheat draw according to the present invention.

The graph shown in FIG. 2 may be represented by Equation 7.

Here, Y is the amount of wheat stretching calculated by the interpolation method, and X is the value which showed N * 150 (ton).

As such, when the drawing tables of the driving and working sides are provided, the amount of drawing of the mill generated according to the mill constants, which is inherent in the mill, is calculated according to the rolling loads of the working and driving sides, and these values are represented by the wedge of the equation (6). It is used as an element to calculate.

On the other hand, the rolling load is predicted by a computer set up for each pass, and the calculation of the wedge by the milling aberration before rolling is obtained by using the predicted rolling load and the load versus mill elongation data of Table 1, and after the rolling Obtained using the rolling loads and the load versus tight draw data in Table 1.

Thereby, the change in the density stiffness with respect to the rolling load variation can be reflected in the control more precisely than the conventional method of calculating the amount of mill draw with the fixed stiffness values on the working side and the driving side fixed.

The difference between the roll gaps is calculated by reading the cylinder positions on the driving side and the working side, and the entrance wedge amount uses the value calculated using the equation (6).

In Equation 6, the adjustment coefficient α is set to have a value of c ≦ α ≦ 1 according to the plate width, but is set such that the larger the plate width, the smaller the value.

Here, W is a rolled sheet width, Wm is a rolled minimum sheet width, and coefficients A and B are set values arbitrarily set through actual rolling data analysis.

On the other hand, it can be obtained from the actual data analysis that the degree of confidence of the wedge (h _df ) formula is higher when α is set as a function of the plate width than when all the plate widths are fixed and used in the equation (6).

Figure 3a is a graph showing the relationship between the wedge calculated by the adjustment coefficient α as 1 and the wedge actually measured, Figure 3b shows the relationship between the wedge and the wedge measured while varying the adjustment coefficient α depending on the width of the plate The graph shown.

According to the data analysis results shown in FIGS. 3A and 3B, it can be seen that the wedge estimation error is reduced when α is varied according to Equation 8 according to the plate width.

Next, a method of setting parameters b and c of Equation 6 will be described.

Parameter b is a parameter that shows the effect of exiting wedges when the entry material has wedges among the factors of wedges after rolling. It is a material factor such as plate thickness and width of entry and exit, rolling load, mill constant and work roll. Set in consideration of the rolling conditions of the barrel length.

Where W is the plate width, H is the side thickness, h is the exit thickness, F is the rolling load, K is the mill constant, Q is the plasticity coefficient representing the rigidity of the plate, and Ls is the length between roll chokes Lr is the working roll barrel length.

On the other hand, the parameter c is also set in accordance with the rolling conditions such as the rolling load and the like, such as b, the variation of the material such as the plate thickness and the plate width.

If each factor value of Equation 6 is set in the manner described above, the wedge can be predicted before rolling.

4 is a graph showing the relationship between the curvature calculated by the camber control method according to an embodiment of the present invention and the curvature actually measured using a camber measuring instrument.

As shown in FIG. 4, the calculated curvature value and the measured curvature value are concentrated around a straight line having a slope of 1, and thus, the calculated curvature value and the measured curvature value are almost identical.

Next, the wedge calculated by Equation 6 and the curvature of Equation 4 will be used to provide a method of providing a gap between a roll gap between a work side and a drive side to minimize the camber.

An exit wedge for which the exit curvature is zero from Equation 4 can be obtained by using Equation 10 by leaving the left side of Equation 4 at zero.

The calculation of the roll gap difference to obtain the target exit wedge h _df 'from the relationship between the exit wedge of the equation (6) and the roll gap is performed by calculating the equation (10) and the equation (6), and a roll for making the exit curvature zero. When the gap set amount S _df of the gap is obtained, it can be expressed as in Equation 11.

Equation 11 shows how to determine the control amount of the difference between the roll gaps with respect to the size of the entrance material when the mill stretching car, wedge, curvature, off-center, etc., which are the causes of camber generation, occur.

As described in detail above, the camber control method generated in the thick plate finishing rolling of the present invention uses a wedge formula model, a model for calculating the mill draw difference, and a curvature formula to prevent the roll gap from occurring in the rolled thick plate. How to control. Therefore, the camber of the thick plate can be controlled without a camber measuring instrument, and the measurement of the camber is not influenced by the surrounding working environment.

In addition, the method of the present invention has the advantage that a measure suitable for the thick plate to be rolled is made because the calculation for controlling the camber is calculated and acted before the thick plate passes through the upper and lower work rolls.

In the above description, the technical idea of the camber control method generated during thick plate finishing rolling of the present invention has been described with the accompanying drawings, but this is by way of example and not by way of limitation. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (2)

In a camber control method of controlling a camber generated while a thick plate passes through a mill, Calculating the draw amount of the working side and the driving side of the mill by interpolation method using data of the cylinder position change amount of the working side and the driving side of the mill and the rolling load according to the cylinder position change amount; Calculating the exit wedge of the thick plate after rolling by using the draw amount of the mill through Equation 1, Calculating a wedge ratio change amount from the calculated exit wedge and the entrance wedge of the thick plate before rolling; Calculating the curvature of the outboard side of the thick plate passing through the mill by Equation 2, And calculating the difference between the roll gaps in the form of reducing the next pass camber from the calculated exit curvature, exit wedge and mill draw amount, and applying it to the next pass mill. Equation 1 Equation 2 is Equation 3 is to be. Where h _df is the exit wedge, S _df is the difference in roll gap, MS _df is the difference in mill draw, H _df is the entrance wedge, W is the plate width, L is the distance between the roll chokes, and α is the adjustment Coefficient. Ρ _o is the exit curvature, ρ _i is the entrance curvature, H is the entrance thickness, h is the exit thickness, λ is h / H, h _df 'is the target exit wedge, and ΔΦ is the change in wedge rate. Where b and c are parameters. The method of claim 1, In the step of calculating the exit wedge of the thick plate after rolling, the parameters b and c are determined by the side plate thickness, the exit plate thickness, the plate width, the rolling load, the mill constant, the length of the work roll choke, and the work roll barrel length. A camber control method, characterized in that the set value.