JP2002178014A - Plate thickness control method in rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the error of predicted sheet crown which is caused by the prediction error of a predicted roll profile. SOLUTION: In a thickness control method in a rolling mill in which the thickness is controlled by predicting the sheet crown CH2 using a gagemeter model containing the predicted roll profile as a prime factor, the predicted roll profile is corrected on the basis of a sheet crown CH2' actually measured in the rolling line and the predicted sheet crown CH2 is calculated on the basis of the corrected predicted roll profile.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a thickness of a rolling mill.

[0002]

2. Description of the Related Art Flatness control in sheet rolling is an important issue for avoiding a straightening step which is an additional step and for achieving stable production. The flatness defect (rolling wave) that occurs in rolling occurs when the deviation of the elongation between the end and the center of the steel sheet before and after the reduction, that is, the change in the sheet crown ratio exceeds an allowable value. At present, the following methods are employed to secure flatness. Calculation of the target sheet thickness and the sheet crown of each rolling pass in which the sheet crown ratio change is equal to or less than a predetermined value.

[0003] In each rolling pass, a sheet crown is predicted using a gauge meter model, and a roll reduction position at which both values become predetermined values is calculated.

[0004]

In the above method, when the actual crown is displaced from the target crown, a change in the crown ratio exceeds a predetermined value, and a wave is generated. Therefore, it is indispensable in the flatness control to improve the accuracy of the sheet crown prediction. The sheet crown is determined by the initial crown of the rolling roll, the thermal crown that changes as the rolling progresses, the roll profile consisting of wear, and the deflection of the rolling roll. There has been proposed a method of predicting these in a gauge meter plate thickness model and calculating a plate crown. As this method, for example, there is a method of `` iron and steel '' Vol.79, No.3 (1992) p.86, the basic form of the gauge meter model disclosed herein is represented by the following equation .

H (x) = S ₀ + Y _H + 2Y _RR (x) 2C _{W
(0) + C B (0} ) + a , however, h: exit side thickness, S _0: Screw values, Y _H: housing deformation amount, a: learning term, x: position of the cylinder center (cylinder center: x = 0) , Y _RR (x): Amount of roll deformation (one-sided roll), C _W , C _B : Crown amount of WR, BUR Among the factors that determine the plate crown, the roll profile consisting of thermal crown and wear In some cases, a prediction error occurs due to a change in the cooling state, and as a result, an error occurs in the prediction plate crown.

[0006]

The present inventors have studied to solve the above problems, and as a result, the error of the predicted plate crown is caused by the prediction error of the roll profile. It has been found that calculating the roll profile prediction error and performing sheet crown prediction in consideration of the roll profile error is effective for highly accurate sheet crown prediction. That is, the feature of the present invention is a method for controlling a thickness of a rolling mill that performs a thickness control by predicting a thickness of a sheet using a gauge meter model including a predicted roll profile as a factor. In other words, the predicted roll profile is corrected based on the corrected predicted roll profile, and the predicted plate crown is calculated based on the corrected predicted roll profile.

Another aspect of the present invention is a sheet thickness control method for a rolling mill that performs sheet thickness control by predicting a sheet crown using a gauge meter model including a predicted roll profile as a factor. The roll profile prediction error is calculated based on the deviation between the actually measured plate crown and the predicted plate crown, and the predicted plate crown is calculated using the calculated roll profile prediction error. In the above case, it is preferable that at least one point at the measurement position is measured at the center position in the sheet width direction at a rolling line for measuring the sheet crown at two or more points in the sheet width direction and actually measuring the sheet crown. .

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. When the roll profile of the rolling rolls of the rolling mill is changed, the outlet plate crown changes as in the example of FIG. The rolling conditions at this time are as shown in Table 1 below.

[0009]

[Table 1]

As shown in FIG. 1, a plate crown (CH2)
Varies with the roll crown (Φ) and is related as follows: CH2 = F (Φ) Here, when an error occurs in the roll crown prediction and the actual plate crown (CH2 ′) fluctuates, it can be calculated as follows using the actual roll crown (Φ ′). The relationship between the roll crown and the sheet crown can be determined by the steel sheet size and rolling conditions.

Φ ′ = F ⁻¹ (CH2 ′) It is also possible to calculate the roll profile prediction error (ΔΦ) and reflect it in the gauge meter model.
The method is described below. Similarly to the above, the predicted and actual plate crowns can be calculated as follows. CH2 = F (Φ) CH2 ′ = F (Φ + ΔΦ) Accordingly, the roll profile error (ΔΦ) can be calculated as follows, and the actual roll crown can be calculated.

ΔΦ = F ⁻¹ (CH 2 ′) −F ⁻¹ (CH 2) From the above, the roll profile error can be corrected, so that a highly accurate strip crown prediction can be performed.

[0013]

Embodiment 1 Next, a specific example of a method for calculating a roll profile error will be described. Assuming that the roll profile error (ΔΦ) is err (x) in the coordinate system shown in FIG. 2, the plate crown prediction error is expressed as follows. CH2'-CH2 = F (Φ + ΔΦ) -F (Φ) = [α1 × [CWT '(0) -CWT' (x0)] + α2]-[α1 × [CWT (0) -CWT (x0) ] + α2] = α1 × [CWT '(0) -CWT (0)]-[CWT' (x0) -CWT (x0)] = α1 × [err (0) -err (x0)] where CH2 = α1 × [CWT (0) -CWT (x0)] + α2 CWT (x), CWT ′ (x): predicted and actual roll profile, x
0: Coordinate of sheet thickness definition point err (x) ≡ CWT '(x) -CWT (x) α1, α2: Constants determined by rolling size and rolling conditions, which indicate the effect of roll profile on sheet crown amount. err (x) = err0 × [1- (x / A) ² ] On the other hand, the prediction error (ΔCH2) of the plate crown can be calculated as follows using the predicted plate crown and the actual plate crown.

ΔCH2 = CH2 (r) -CH2 (c) CH2 (r) = h2 (C)-[h2 (W) + h2 (D)] / 2 (CH2 (c): predicted plate crown amount, CH2 ( r): Real board crown, h2
(W), h2 (c), h2 (D): Work side, center, drive side plate thickness on the delivery side) Therefore, the roll profile error can be formulated as follows based on the actual plate crown. err (x) = ΔCH2 / [α1 × (x0 / A) ² ] × [1- (x / A) ² ] The predicted roll profile is corrected using the roll profile error, and based on the corrected predicted roll profile. By using a gauge meter model to predict the crown of the sheet, highly accurate sheet crown prediction can be performed. The above-described prediction calculation is performed by a control device (plate thickness control device) of the rolling mill, and the rolling mill is controlled according to the prediction.

When actually measuring the sheet crown, the sheet thickness is measured at any two or more points in the sheet width direction, and the sheet thickness distribution in the sheet width direction is assumed using the sheet thicknesses at two or more points. The crown can be estimated. Further, the actual measurement of the sheet crown can be performed by providing a measuring device for measuring the sheet thickness at three points of the work side, center, and drive side sheet thickness on the delivery side. The sheet thickness is measured at the above three points, and the definition equation of the sheet crown is: CH2 = h2 (C)-[h2 (W) + h2 (D)] / 2
The plate crown can be calculated by performing the following calculation. Thus, at least one of the measurement positions
By setting the point at the center (center position in the plate width direction), the plate crown can be directly calculated from the definition formula of the plate crown instead of estimating the plate crown.

<Embodiment 2> The results of applying the present invention will be described below. The roll profile error was assumed as follows. err (x) = err0 × [1- (x / A) ² ] Further, learning was performed on err0 of each rolled material calculated by the above equation as follows. err0 (next material) = err0 (this material) + G × ΔCH2 / [α1 × (x0 / A) ² ] (G: learning rate) The error of the plate crown prediction is shown in FIG.
As shown in the figure, significant improvement was seen in both the average and the variation.

[0017]

[Table 2]

[0018]

According to the present invention, a highly accurate strip crown prediction can be performed by performing strip crown prediction in consideration of roll profile errors.

[Brief description of the drawings]

FIG. 1 shows the relationship between a roll crown and a plate crown.

FIG. 2A shows a roll profile in a coordinate system in which a roll body length direction is an X direction, and FIG.
Indicates a roll profile error in a coordinate system in which the roll body length direction is the X direction.

FIG. 3 shows the application result of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenichi Oe 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Inside Kobe Steel Works Kakogawa Works F term (reference) 4E024 AA03 AA07 BB01 DD01

Claims (3)

[Claims] 1. A method for controlling a thickness of a rolling mill, in which a thickness of a sheet is controlled by predicting a sheet crown (CH2) using a gauge meter model including a predicted roll profile as a factor, comprising: CH2 ')
A thickness control method for a rolling mill, wherein the predicted roll profile is corrected based on the calculated roll profile, and a predicted crown (CH2) is calculated based on the corrected predicted roll profile. 2. A method for controlling a thickness of a rolling mill, in which a thickness of a sheet is controlled by predicting a sheet crown (CH2) using a gauge meter model including a predicted roll profile as a factor, comprising: CH2 ')
And a roll profile prediction error (ΔΦ, err (x)) based on the deviation (ΔCH2) of the prediction plate crown (CH2), and the calculated roll profile prediction error (ΔΦ, er
r (x)) to calculate a predicted sheet crown (CH2). 3. In a rolling line for measuring a sheet crown by measuring two or more sheet thicknesses in the sheet width direction, at least one of the measurement positions has a sheet thickness (h2 (C)) at a center position in the sheet width direction. The method according to claim 1 or 2, wherein the thickness is measured.