JP2574520B2 - Rolled material flatness control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for controlling flatness of a rolled material when performing reverse rolling such as thick plate rolling based on a rolling pass schedule.

[Prior art]

In rolling and manufacturing a thick plate such as a steel slab, a single rolling mill performs rolling while reversing the rolling direction until the thick plate reaches a required size. Such rolling of a thick plate is called reverse rolling (reversible rolling), and such a rolling mill is called a reverse rolling mill. In such reverse rolling, flatness defects are likely to occur in the latter half of the pass when the sheet thickness is reduced. Therefore, in general, in a pass called a shape control pass approaching a predetermined plate thickness, a rolling pass schedule is determined in advance by calculation of a prediction model formula so as to prevent flatness defects from occurring. The rolling is performed with the aiming plate crown or aiming steepness of each pass determined according to the following formula. However, in the rolling pass schedule calculated in advance and the actual rolling, there is an error (hereinafter referred to as a prediction error) between the predicted value obtained by the normal prediction model formula and the actually measured value, and the rolling load prediction error or the roll profile Due to the prediction error (caused by heat crown and roll wear) and the error of the prediction model formula of the plate crown, the change of the plate crown differs from the prediction. There is a case where a difference occurs in the elongation rate in the width direction of the plate, resulting in poor flatness. Also, due to the prediction error of the flatness prediction model formula, even if rolling is performed so that the target steepness calculated in advance in the schedule calculation is different from the actual steepness, and a predetermined plate crown change is obtained. In some cases, poor flatness occurs in the thick plate. On the other hand, in order to prevent the flatness defect from occurring in the rolled material, conventionally, a method of controlling the bending force of the work roll based on the shape measurement information of the rolled material and controlling the flatness of the rolled material, For example, JP-A-59-159208 and JP-A-52-17
Proposed in 355. However, the prior art disclosed in these publications and the like is advantageous to be applied to a mill that can be rolled only in a steady state because the rolling schedule does not change in each rolling such as a tandem mill. In a mill that performs reverse rolling, sufficient effects cannot be obtained because the rolling pass schedule changes for each pass such as a slab. On the other hand, a rolling load prediction model, a roll profile prediction model, a sheet crown prediction model, a flatness prediction model, and the like used for the rolling pass schedule calculation are usually calculated by computer simulation results, Although a simple formula based on data is used, in reality, good accuracy is not always obtained.

[Problems to be solved by the invention]

Therefore, conventionally, in the case of reverse rolling, there may be cases where good flatness cannot be obtained in the rolled material, and due to the poor flatness, narrowing occurs in the rolled material, or the load of straightening rolling increases, There have been problems such as an increase in the refining process. The present invention has been made to solve the above-mentioned conventional problems, and it is possible to accurately predict the flatness of a rolled material in each pass in reverse rolling and control the flatness with high accuracy. It is an object to provide a method for controlling flatness of a rolled material.

[Means for Solving the Problems]

The present invention relates to a method for controlling the flatness of a rolled material when performing reverse rolling such as plate rolling based on a rolling pass schedule, and detects a steepness, a sheet crown, and a rolling load of a rolled material at an i-th pass. Then, the steepness of the rolled material at the i-th pass, the sheet crown, and the rolling load are predicted from the model formula for calculating the pass schedule, and the detected steepness of the rolled material at the i-th pass, the sheet crown are detected. , And the rolling load and the predicted steepness of the rolled material at the i-th pass, the strip crown, and the rolling load, based on the steepness prediction error, the strip crown prediction error, and the rolling load prediction error at the i-th pass. This problem is solved by controlling the roll bending force of the rolling mill during the (i + 1) th pass so as to prevent the flatness of the rolled material from being bad based on the estimated prediction errors.

[Action]

A factor that directly affects the flatness of the rolled material is that a difference in the elongation rate in the rolling direction occurs at any position in the width direction of the rolled material, and that a plate wave having an allowable steepness or more is generated. ing. Therefore, in order to keep the elongation constant and improve the flatness, rolling is generally performed in each i-pass at a constant crown ratio Cir / Hi expressed by the following equation (1). Cir / Hi = Mill exit plate crown Cir / Mill exit plate thickness Hi…
(1) However, when rolling is performed with a fixed crown ratio, the number of passes increases, and the rolling ratio decreases.
As shown in the figure, rolling is performed with a slight change in the crown ratio within an allowable steepness that does not hinder rolling.
When there is a prediction error of the plate crown, a steepness prediction error, or the like, there is a possibility that a flatness defect of an allowable steepness or more may easily occur. Here, the plate crown prediction model Cr for each i-pass
i, the steepness prediction model is represented by the following equations (2) to (4). In this case, in the equation (4), the flatness prediction model is represented by the steepness λi of the sheet crown which is proportional to the rolled material elongation difference εi in the equation (3). _{Cri = f (Pi, C W} , C B, Fi, Hi, Wi, Cri-1) ... (2) However, Cri: i path of the strip crown, Cri-1: i-1 path of the strip crown, Pi: rolling load of i path, C _W: work roll crown, C _B: backup roll of the crown, Fi: bending force of i path of the work rolls, Hi: thickness at delivery side of the i path, Wi: a plate width of the i path is there. εi = βi · εi−1−ξi (Cri / Hi−Cri−1 / Hi−1) (3) where εi: elongation difference of i-pass, εi−1: elongation difference of i-pass, βi: the input side flatness influence coefficient of the i-pass, and ξi: the shape change coefficient of the i-pass. Further, the steepness λi of the plate crown in the i-th pass is expressed by the following equation (4). Regarding the steepness, the sheet crown, and the rolling load in the i-th pass, the actual measured values are λi ^* , Cri ^* , and Pi ^* ,
Also, each predicted value obtained from the schedule calculation is λ
₀ i, Cr ₀ i, and P ₀ i, and the difference between the actually measured value and the predicted value, that is, the prediction error is represented by Δλ as shown in the following equations (5) to (7).
i, ΔCri, and ΔPi. Δλi = λi ^* −λ ₀ i (5) ΔCri = Cri ^* −Cr ₀ i (6) ΔPi = Pi ^* −P ₀ i (7) In consideration of these prediction errors Δλi, ΔCri, and ΔPi,
In the next pass (the (i + 1) th pass), a bending force that does not cause flatness failure is determined. FIG. 2 shows the flow of information processing for determining the bending force. In FIG. 2, the calculations of the above equations (1) to (7) are performed in steps 101 to 104, and in step 105, the next pass (i.
It is shown that the bending force Fi + 1 of (+1 pass) is calculated, and the details of this step 105 are as follows. That is, the prediction error Δλi is added to the steepness λi in the i-th pass.
Is one of the factors that causes the strip crown prediction error ΔCri to affect the steepness λi. The change in steepness caused by the plate crown prediction error ΔCri is represented by Δλcri
Then, taking this effect into account, the steepness prediction error Δλεi generated by the error of the flatness prediction model of the above equations (3) and (4) is expressed by the following equation (8). Δλεi = Δλi−Δλcri (8) One of the factors that cause the prediction error ΔCri to occur in the sheet crown is that the prediction error ΔPi of the rolling load affects the plate crown. The plate crown caused by this prediction error ΔPi is represented by Δ
If Crpi is taken into account, the sheet crown prediction error ΔCrci generated by the error of the sheet crown prediction model of the above equation (2) in consideration of this effect is expressed by the following equation (9). ΔCrci = ΔCri−ΔCrpi (9) From the above, first, the bending force Fi + 1 for the strip crown prediction error ΔCri and the rolling load prediction error ΔPi.
Can be determined as follows. Considering the strip crown prediction error ΔCrci and the rolling load prediction error ΔPi, the next (i + 1) th pass sheet crown C ′
The prediction of r ₀ i + 1 can be performed using the following formula (10). _{C'r 0 i + 1 = f (} P 0 i + 1 + α1ΔPi, C W, C B, Fi + 1, Hi + 1, Wi + 1, Cri *) + α2 · ΔCrci ... (10) However, α1 · α2: is a correction coefficient. This predicted sheet crown C′r ₀ i + 1 becomes equal to the sheet crown Cr ₀ i + 1 predicted at the time of schedule calculation,
(10) so as to cancel the plate crown ΔCrci of the equation (9).
Determine the bending force Fi + 1 in the equation. Also, the bending force F ₂ i for the steepness prediction error Δλi
+1 can be determined as follows. That is, since the steepness Δεi expressed by the above equation (8) also affects the steepness prediction model, the following equation (11) is provided between the steepness prediction value λ ₀ i + 1 of the (i + 1) th pass and the elongation difference εi + 1. There is a relationship. In this case, the elongation difference εi + 1 in the (i + 1) th pass is
Like the equation (3), it can be obtained by the following equation (12). εi + 1 = βi + 1 εi + ξi + 1 (Cri + 1 / Hi-Cri / Hi) ... (12) Cri + 1 = f (P 0 i + 1 + α 1 ΔPi, C W, C B, F 1 i + 1 + F 2 i + 1, Hi + 1, Wi + 1, Cri *) + α 2 · ΔCrci ... (13) The bending force F2i + 1 is determined so that λ ₀ i + 1 becomes the target steepness in the equation (11). The two bending forces Fi + 1 and F2 obtained as described above
The target flatness can be obtained for the rolled material by bending the rolling mill roll according to the sum of i + 1 and rolling the next (i + 1) th pass. The present invention has been made based on the above principle. According to the present invention, it is possible to accurately predict and control the flatness of a rolled material by eliminating the prediction errors of the steepness, the sheet crown, and the rolling load during reverse rolling. Therefore, it is possible to prevent the occurrence of narrowing during rolling based on poor flatness. In addition, since the flatness can be improved, the correction load can be reduced, and the load in the refining process can be reduced.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. This embodiment has a structure as shown in FIG. 3 and FIG. 4 This embodiment has a structure as shown in FIG. 3 to control the flatness of a thick plate when it is rolled in a quadruple reverse rolling mill. System. As shown in FIG. 3, the reverse rolling mill includes upper and lower work rolls 12A and 12B for biting a thick plate 10 such as a slab and rolling from above and below.
Left for bending A, 12B by hydraulic pressure for example,
It includes right bending devices 14A and 14B and upper and lower backup rolls 16A and 16B for clamping the upper and lower work rolls 12A and 12B from above and below and applying a rolling force. Further, the control unit for controlling the bending force of the bending device 14A, 14B, a load cell 18 for detecting the rolling load applied to the thick plate 10 of the rolling mill, and the front and rear surfaces of the reverse rolling mill. A flatness meter 20 for detecting the steepness of the thick plate 10 installed on one or both sides, a plate crown measuring device 22 for measuring the sheet crown of the thick plate 10 similarly installed, and the detection A central processing unit (CPU) 24 for calculating the bending force from the determined flat condition, and controlling the bending force of the bending devices 14A and 14B to the left and right rolls based on the determined bending force signal. And a roll balance pressure controller 26 composed of a hydraulic unit. The flatness meter 20 measures the distance from the measurement position to the surface of the thick plate 10 at a certain pitch at both ends and the center in the plate width direction, and calculates the undulation of each measurement surface in the plate length direction from the difference in the measurement distance. Is calculated to detect the steepness. The flatness meter 20 is provided on one of the front surface and the rear surface when reciprocating rolling is performed in one pass, and is provided on both the front surface and the rear surface when one-way rolling is performed in one pass. Further, rolling condition data based on a rolling pass schedule is input to the central processing unit 24 from a higher-level process computer 28. Also, the bending device
The bending pressure of 14A and 14B depends on the central processing unit.
This is fed back to 24, and the bending pressure is feedback controlled. Next, the operation of the embodiment will be described. In the reverse rolling mill according to the embodiment, the bending force Fi + 1 of the bending devices 14A and 14B is determined by the procedure shown in FIG. 2 in order to roll the thick plate 10 into a target flatness shape. First, based on the rolling conditions in the rolling pass schedule input from the upper process computer 28, the rolling load predicted value P ₀ i in the i-th pass, the strip crown predicted value Cr ₀ i,
Calculate the steepness predicted value λ ₀ i and apply it to the central processing unit 24
(Steps 101 and 102). On the other hand, flatness meter 20,
Strip crown actual measurement value measured by strip crown measuring instrument 22
Along with Cri ^* , the measured steepness value λi ^* , the measured rolling load value Pi ^* detected by the load cell 18 and the bending devices 14A, 1
Roll bending power Fi, fed back from 4B ^*
Is input to the central processing unit 24 (steps 103A to 103).
D). The central processing unit 24 calculates a rolling load prediction error ΔPi, a sheet crown prediction error ΔCri, and a steepness prediction error Δλi from the above equations (5) to (7) based on the measured values (step 104). Next, the central processing unit 24 calculates the bending force F1i + 1 for the strip crown prediction error ΔCrci and the rolling load prediction error ΔPi from the above equation (10). At the same time, the bending force F2 for the steepness prediction error Δλεi
i + 1 is calculated from the above equations (11) to (13). The sum of the bending forces F1i + 1 and F2i + 1 calculated in this way is determined as the bending force Fi + 1 in the next (i + 1) th pass (step 105). The determined bending force Fi + 1 signal is output to the roll balance pressure controller 26 to control the bending force in the next i + 1 pass. Thereby, the flatness of the thick plate 10 in each pass is accurately controlled. In addition, in the said Example, although the case where the present invention was implemented with a quadruple reverse rolling mill as illustrated in FIG. 1 was illustrated, the rolling mill that implements the present invention illustrated this case.
The rolling mill for carrying out the present invention is not limited to this, and the present invention can be carried out on another rolling mill, for example, a double rolling mill without a backup roll. In this case, the bending force Fi + 1 is determined without considering the items related to the backup roll in the above-described equations (1) to (13).

【The invention's effect】

As described above, according to the present invention, when performing reverse rolling, it is possible to accurately predict and control the flatness of a rolled material. Therefore, excellent effects such as preventing the occurrence of narrowing at the time of rolling, reducing the correction load, and further reducing the load of the refining process can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a rolling schedule for explaining the principle of the present invention, FIG. 2 is a flowchart showing a procedure for determining a bending force, and FIG. 3 is an embodiment of the present invention. 1 is a front view, partially including a block diagram, showing an entire configuration of a flatness control system in a reverse rolling mill according to the first embodiment. 10 ... thick plate, 12A, 12B ... upper and lower work rolls, 14A, 14B ... left and right bending devices, 16A, 16B ... upper and lower backup rolls, 18 ... load cell, 20 ... flat Depth meter, 22 ... plate crown measuring device, 24 ... central processing unit (CPU), 26 ... roll balance pressure control unit, 28 ... process computer.

Continued on the front page (72) Inventor Isamu Okamura 1-chome, Kawasaki-dori Mizushima, Kurashiki-shi, Okayama Pref. (Without address) Inside Mizushima Works, Kawasaki Steel Corporation (72) Inventor Junichi Hiraishi 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama None) Kawasaki Steel Corporation, Mizushima Works (56) References: Japanese Patent Publication No. 54-2177 (JP, B2)

Claims (1)

(57) [Claims] 1. A method for controlling flatness of a rolled material in performing reverse rolling such as thick plate rolling based on a rolling pass schedule, wherein a steepness of a rolled material, a sheet crown, and a rolling load during an i-th pass are determined. From the model formula for detecting and calculating the path schedule,
The steepness of the rolled material at the i-th pass, the sheet crown and the rolling load are predicted, and the detected steepness of the rolled material at the i-th pass, the sheet crown and the rolling load, and the predicted i-th pass at the i-th pass Based on the steepness of the rolled material, the strip crown and the rolling load, the steepness prediction error at the i-th pass, the strip crown prediction error, and the rolling load prediction error are estimated. Based on the estimated prediction errors, the rolled material is estimated. A flatness control method for a rolled material, wherein the roll bending force of a rolling mill is controlled during the (i + 1) th pass so as to prevent the flatness failure of the rolled material.