KR19990052681A - Prediction of High-Precision Plate Crown Considering Thickness Profile of Hot-rolled Plate Width - Google Patents

Abstract

The present invention relates to a method for predicting a plate crown of a high precision in consideration of a width direction thickness profile of a hot rolled plate.

The present invention basically comprises a step of forming a thickness profile of the plate in the width direction as shown in the conceptual diagram of the plate crown of Figure 2 by means of an edge drop or a flat deformation of the work roll 2, The plate crown is divided into two sections, that is, a plate edge of 100 mm, which is greatly influenced by thermal expansion and wear of the work roll 2 and axial bending of the work roll 2, and a central section of the plate.

Therefore, according to the present invention, the setting of the pair cross angle and the bender force becomes accurate, and a desired target plate crown can be expected, and the wave form defects can be reduced.

Description

Prediction of High-Precision Plate Crown Considering Thickness Profile of Hot-rolled Plate Width

The present invention relates to a method for predicting a plate crown of a high precision in consideration of a width direction thickness profile of a hot rolled plate.

In general, the plate crown, which is the widthwise thickness distribution of the plate during hot rolling, affects the quality of the product, the error rate of its own process, and workability. In the hot rolling process, the material is rolled and the material is rolled into the rolling mill in order to obtain a product shape having good flatness indicating the degree of longitudinal bending of the desired target plate crown and the plate on the final stand. A pair cross angle and a bender force suitable for a working condition are calculated in a setting model in a supervisory control computer (SCC), and the information is transmitted to a digital controller (DDC) And is prepared to be rolled in a state where the pair cross angle and the vendor are manipulated by hardware. In order to calculate the final pair cross angle and the bender force in software in the upper computer, the pair crown angle and the bender force are adjusted so that the predicted value approaches the target value by referring to the model crown predicted in advance, If the predicted result does not reflect the working condition of the coil and it deviates from the target value, the pair cross angle or the bender force calculation result is also inaccurate. Therefore, a wave such as polarization, medium wave, Resulting in poor flatness.

Conventionally, a plate crown is generally defined as a difference in thickness between a center of a plate and a point 25 mm from an edge of the plate as shown in the concept of the plate crown of FIG. 1. The conventional plate crown model is expressed by the following formula A pair cross angle of the upper and lower work rolls 2 and a bender force acting on the chock portion of the work roll 2 and a bending force acting on the chuck portion of the work roll 2, It is expressed as a function of the roll profile, which is a function of the initial crown, wear crown, and thermal crown.

Where C _KC is the rolling load correction factor, R _F is the roll force, K _C is the lateral stiffness coefficient of the work roll 2, C _EF is the bender force correction factor, E _F is the bender force influence coefficient, Bender force, C _ζθ the pair cross angle correction coefficient, ζ _θ are fair cross angle influence coefficient, x is the width conversion factor, C _θ is equivalent to the mechanical (mechanical) crown, C _ζW the work rolls 2, the profile correction factor , ζ _W is the work rolls 2, the profile influence coefficient, C _R is a work roll (2) the initial crown, C _η crown dielectric constant, η is the crown genetic influence coefficient, C _CC is a constant term correction coefficient, C _C is a constant term .

However, in the conventional method, when the plate crown for the working conditions is predicted by the conventional plate crown model formula which is calculated by the thickness of the central portion of the plate end face and the thickness difference of 25 mm from the plate edge, The influence of the edge drop generated at the edge of the work roll 2 and the flat deformation of the work roll 2 appearing at the edge of the plate is not reflected and since the plate shape is controlled based on the predicted plate crown, There was a falling problem.

In order to solve the above problems, the present invention proposes a method of predicting a plate crown by dividing a thickness profile of the plate in the width direction of the plate into two sections of 20 to 100 mm of the edge and 100 mm of the edge to the center of the plate, The present invention is to provide a method for predicting a high-grade plate crown considering a thickness profile of a hot-rolled plate in a width direction of a hot-rolled plate, which can predict the plate crown of a high precision.

FIG. 1 is a view showing a concept of a plate crown by a conventional method

Fig. 2 is a conceptual view of the plate crown according to the present invention

FIG. 3 is a flowchart of a method for predicting a high-resolution plate crown according to the present invention.

Fig. 4 is a graph showing the degree of plate crown prediction by the conventional method

5 is a graph showing the degree of plate crown prediction according to the present invention

Description of the Related Art

1: Backup Roll

2: Work Roll

3: Strip (Hot Strip)

4: Profile-meter

5: Plate Profile Collector

6: Pair Cross information collector

7: Finishing Mill Setup Information Collector

8: Input processor

In order to achieve the above object, according to the present invention, as shown in the plate crown conceptual diagram of FIG. 2, the thickness profile of the plate in the width direction is directly influenced by the edge drop or the flat deformation of the work roll 2, The plate crown is divided into two sections, that is, a plate edge of 20 mm to 100 mm and a plate edge of 100 mm, which is greatly affected by thermal expansion and wear of the work roll 2 and axial bending of the work roll 2, .

The method of the present invention is based on the fact that, as shown in the calculation flowchart of FIG. 3, based on the actual plate profile detected from the profile meter 4, the fair cross performance, the setting information and the finishing mill setup rolling information, The plateau crown of the present invention, which takes into consideration the thickness profile of the hot rolled steel sheet in the widthwise direction, has a model C _25-100 for _25-100 mm at the plate edge, a plate crown It is a new type of plate crown model which is composed of model formula C ₁₀₀ and combines the above two model equations.

Hereinafter, the derivation process of the two model equations will be described.

First, as shown in the calculation flowchart of FIG. 3, the width profile measured in the profile meter 4 is collected in the plate profile collector 5. The item to be collected is the amount of the actual edge drop at the actual plate crown, the plate edge 25 mm, and the 100 mm point with respect to the plate edge 25 mm. The fair cross angle information, the pair cross angle, the bender force, and setting information, the crown of the work roll 2 and the wear crown are collected by the fair cross information collector 6, and the finish rolling mill setup information collector 7 measures the actual rolling load , The diameter of the work roll (2), the plate width and the stand out plate thickness are collected. Based on the collected information, the input processor 8 classifies the input data into the steel type, the thickness, and the width type.

On the other hand, in general, the shearing stands F1 to F3 do not adopt a pair crossmill, so that the plate shape is controlled by using the bender force as a control end. In the rear stand F4 to F6 or F7, a pair cross- The plate shape is controlled by the bender force. Since the control stage is different between the front stage and the rear stage as described above, the following equation (2) is used.

On the other hand, the equivalent mechanical crown corresponding to the pair cross angle and the plate width conversion coefficient are used in the second model, the C ₁₀₀ (i) model equation. The equations for calculating the above values are expressed by the following equations 3 and 4 .

Where L _B is the barrel length of the work roll 2, θ is the cross cross angle, D _W is the diameter of the work roll 2, B ^* is the target plate width, and a is the plate crown defining point distance.

On the other hand, since the profile meter 4 is installed only at the rear end of the final stand, the actual plate crown at each stand out side can not be obtained because the plate crown C _{25m corresponding} to the 25mm edge of the plate edge of the final stand input to the input processor 8 . Accordingly, the equivalent plate crown C ₂₅ (i) of each stand out is obtained based on the following equation (5).

In the same manner as above, the equivalent plate crown C ₁₀₀ (i) of each stand is obtained from the plate crown C _{100 m} from which the edge drop amount is removed from the actual plate crown on the exit side of the final stand. At this time, in order to construct the C ₁₀₀ (i) model equation having the measured value C _{100 m} and the equivalent measured value C ₁₀₀ (i) as the dependent variable, the input processor 8 calculates the pair cross information and the finishing mill setup information Based on the data, the rolling factors affecting C ₁₀₀ (i) are determined. The rolling factors are as follows.

CRF (i) = RF (i ) / K C (i)

CBND (i) = E _F (i) * BNDm (i)

_{CRA (i) = ζ θ (} i) * x * C θ (i)

_{CWRC (i) = ζ W (} i) * {x * C R (i) - C W (i) + C T (i)}

CINH (i) = η (i ) * C 100 (i-1)

Where RF is the roll force and K _C is the transverse stiffness coefficient of the work roll 2.

The regression coefficients for the independent variables that optimally reflects C ₁₀₀ (i) are determined by using multiple regression analysis of each of the rolling factors as independent variables and using the equivalent measured value C ₁₀₀ (i) as a dependent variable. The plate crown ₁₀₀ (i) model equation for the plate edge 100 mm to the center section can be derived as shown in the following equation (6).

Thereafter, since the flatness of the work roll 2 can not be measured in practice, it is obtained through a strict analysis method. In order to apply the above method, it is necessary to comprehensively set the range of variation such that the plate width, the rolling load and the reduction rate, which are factors affecting the flat deformation of the work roll 2, Calculate basis weights. The following model equation 7, which determines the flatness of the work roll 2 from the correlation of influencing factors, is then derived, and the model equation is plotted on the plate edges 25 - The model formula for the 100mm point is C _25-100 .

_{C 25-100 (i) = a 1} (i) ⋅W + a 2 (i) ⋅RF (i) + a 3 (i) ⋅r (i) 2 + a 4 (i) ⋅r (i) + a ₅ (i)

Where a is the plate crown defined point distance, W is the hot-rolled plate width, and r is the reduction rate.

When the model C _25-100 and the plate crown model C ₁₀₀ (i) for the plate edge 100 to the center portion of the plate edge 25 to 100 mm are determined as described above, the plate crown model formula C ₁₀₀ It should be readjusted. In other words, the model equations in the above two sections with C ₁₀₀ (i) and C _25-100 (i) as independent variables are used as the dependent variable and the equivalent measured crown C ₂₅ (i) The regression coefficients are obtained by regression analysis. From this, a high-precision plate crown model formula C ₂₅ (i) considering the final widthwise thickness profile is derived as shown in the following equation (8).

C ₂₅ (i) = C _{ζ 1} (i) ⋅C ₁₀₀ (i) + C _{ζ 2} (i) ⋅C _25-100 (i) + C _{ζ 3}

In order to investigate the effect of the present invention derived as described above, a large number of rolling coils corresponding to the following layers are collected and a fixed plate crown model formula considering the width direction profile of the present invention is applied. Here, the thickness of the steel is 2.0 to 2.2 mm, the width of the steel is 1,200 to 1,300 mm, and the type of steel is a general steel having a tensile strength of less than 33 kgf / mm ^2. Here, the influence coefficient of C ₁₀₀ (i) Is as follows.

K _C E _F ζ _θ ζ _W η C _C F1 8888.7 0.55629e-3 0.81504 0.10000 0.10000 0.12712e + 0 F2 10867.0 0.43384e-3 0.63387 0.84218 0.10749 0.83259e-1 F3 13097.0 0.35355e-3 0.51464 0.68599 0.19229 0.56156e-1 F4 12311.0 0.43254e-3 0.38515 0.59197 0.33580 0.28774e-1 F5 14741.0 0.36136e-3 0.32170 0.49147 0.43135 0.15794e-1 F6 16967.0 0.31458e-3 0.27993 0.42559 0.50436 0.89139e-2 F7 16914.0 0.32166e-3 0.27977 0.41886 0.55963 0.31670e-2

In the meantime, the coefficient of each model equation for the layer determined according to the calculation flow of FIG. 3 is calculated according to the present invention. First, the model edge of the plate edge 100 mm to the center section is applied to the model equation 6 of the plate crown ₁₀₀ (i) The regression coefficients obtained by regression analysis are as follows.

C _KC C _EF C _ζθ C _ζW C _η C _CC F1 0.050571 -0.075740 0.000000 -0.017489 5.227318 -0.183106 F2 -0.071584 -0.053916 0.000000 0.036295 5.230578 0.175314 F3 -0.068656 -0.033236 0.000000 0.011485 3.174593 0.180898 F4 -0.059191 -0.009919 -0.005094 -0.002023 1.889288 0.293912 F5 -0.043444 0.001243 0.015484 0.001321 1.618826 0.308152 F6 -0.044369 -0.009235 -0.004764 -0.000824 1.526865 0.267830 F7 -0.005704 -0.002156 0.002507 0.003717 1.494169 0.085503

The coefficients of the model formula C _25-100 (i) for the 25 to 100 mm plate edge are as follows.

a1 a2 a3 a4 a5 F1 -1.5e-5 1.30e-5 0.0489 -0.0484 0.030 F2 -1.7e-5 1.45e-5 0.1076 -0.0873 0.038 F3 -1.9e-5 1.57e-5 -0.3328 0.2886 -0.039 F4 -2.0e-5 1.64e-5 -0.7218 0.6156 -0.1059 F5 -2.1e-5 1.73e-5 1.5567 -0.7130 0.101 F6 -2.1e-5 1.71e-5 -0.0770 0.0516 0.018 F7 -2.2e-5 1.80e-5 0.3060 -0.1020 0.034

The coefficients of the high-crown crown model C ₂₅ (i), which is composed of the plate crown C ₁₀₀ (i) model formula and the C _25-100 (i) model formula, are as follows.

C _ζ1 C _ζ2 C _ζ3 F1 1.077654 -3.814508 0.317888 F2 1.083662 -3.320825 0.212279 F3 1.077842 -1.202903 0.106179 F4 1.072418 -0.186631 0.048822 F5 1.076201 -0.372104 0.039887 F6 1.063477 0.222532 0.019439 F7 1.071005 -0.163939 0.021845

The plate crown predicted by the conventional method exhibits a considerable deviation from the plate crown measured by the profile meter 4 as shown in the graph of Fig. 4, and shows almost no correlation. However, by using the above-described coefficients, the plate crown was predicted for the hot-rolled coils of the same layer using the method of predicting the degree of fixation of the present invention, and they were measured by the profile meter 4, As shown in Table 1, most of the hot-rolled coils having a deviation of ± 20 μm exhibited a large correlation.

Therefore, according to the present invention, the setting of the pair cross angle and the bender force becomes accurate, and a desired target plate crown can be expected, and the wave form defects can be reduced.

Claims (1)

A method for predicting a plate crown of a high precision in consideration of a width direction thickness profile of a hot rolled plate, comprising the steps of: applying an edge drop or an influence of a flat deformation of the work roll (2) And is divided into two sections: a plate edge of 20 mm to 100 mm and a plate edge of 100 mm, which is greatly influenced by thermal expansion and wear of the work roll 2 and axial bending of the work roll 2, A method for predicting a high-precision plate crown in consideration of a thickness profile of a hot-