JP7388459B2 - Pass schedule calculation method for steel plate rolling process, pass schedule calculation device for steel plate rolling process, and steel plate rolling method - Google Patents

Description

The present invention relates to a pass schedule calculation method for a steel plate rolling process, a pass schedule calculation device for a steel plate rolling process, and a steel plate rolling method.

In the steel plate rolling process, rolling equipment setup calculations (hereinafter also referred to as pass schedule calculations) are performed, including setting the rolling reduction amount for each pass, in order to satisfy the required rolling dimensions, shape, and structure of the steel plate. ing. This pass schedule calculation is an important operation that greatly affects the quality of steel sheets, and many methods have been studied so far to roll better quality steel sheets with higher productivity.

Guidelines for achieving high productivity in the steel plate rolling process include improving yield by controlling plate crown and reducing straightening rate by controlling flatness. Here, plate crown means the difference between the plate thickness at the center in the width direction of the steel plate and the plate thickness at both ends in the width direction, and flatness refers to the edge position relative to the elongation rate at the center position in the longitudinal direction of the steel plate. It means the difference in elongation rate between. Against this background, methods for controlling the plate crown and flatness of steel plates have been proposed.

For example, in Patent Document 1, based on the measurement results of the steel plate length two passes before the final pass, the reduction amount in the remaining passes is determined to keep the plate crown ratio (the ratio of the size of the plate crown to the plate thickness) constant. A method of suppressing the deterioration of the flatness of a steel plate by adjusting it is described. Furthermore, Patent Document 2 describes a method to achieve both rolling efficiency and plate shape by rolling a steel plate using a pass schedule that prioritizes efficiency up to a predetermined plate thickness, and switching to a pass schedule that prioritizes shape below a predetermined plate thickness. The method is described. Further, Patent Document 3 describes a method of changing the rolling reduction amount of each pass so as to minimize the evaluation function with respect to plate crown, flatness, and plate crown ratio change.

JP2004-322118A JP2014-42928A Japanese Patent Application Publication No. 2010-75994 Japanese Patent Application Publication No. 2001-269703

However, since the method described in Patent Document 1 is aimed at keeping the plate crown ratio constant, it is difficult to correct the disturbance in flatness that has occurred up to that point. On the other hand, the method described in Patent Document 2 cannot control the plate crown and flatness until the plate thickness of the steel plate becomes equal to or less than a predetermined plate thickness. For this reason, especially when rolling is performed continuously near the capacity limit of the rolling equipment in order to increase rolling efficiency, when switching to a pass schedule that emphasizes the shape, the rolling load may suddenly fluctuate, resulting in deterioration of the strip shape. , non-negligible plate crown and flatness may occur at the stage of efficiency-first pass scheduling.

In addition, the methods described in Patent Document 3 and Patent Document 4 first calculate the minimum number of passes by applying the maximum reduction amount in consideration of equipment limits to all passes, and then ensure that the plate crown, etc. is within the allowable range. Repeatedly adjusting the rolling reduction amount and increasing the number of passes. For this reason, it is difficult to converge the plate crown and flatness within the allowable range, especially for steel plates whose plate shape is easily distorted, such as steel plates with extremely thin plate thickness, and the number of passes is required to suppress the plate crown and flatness. There is a possibility that it will increase. Increasing the number of passes not only causes a decrease in rolling efficiency, but also increases the number of rolling passes in areas where the plate thickness is thin and the plate shape changes rapidly, making it difficult to achieve actual results due to model errors, equipment responsiveness, etc. During rolling, the plate crown and flatness may actually deteriorate. On the other hand, for example, in the case of a thick steel plate that does not easily affect the plate shape, the number of rolling passes is extremely reduced, which may lead to the occurrence of scale defects without lowering the finishing temperature.

In view of the above, there has been a need to provide a pass schedule calculation method that utilizes the entire pass and improves plate crown and flatness while keeping rolling efficiency constant.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a pass schedule calculation method and pass schedule for a steel plate rolling process that can improve plate crown and flatness while keeping rolling efficiency constant. An object of the present invention is to provide a schedule calculation device. Another object of the present invention is to provide a method of rolling a steel plate that can control the plate crown and flatness while keeping the rolling efficiency constant and roll the steel plate with good productivity.

A pass schedule calculation method for a steel plate rolling process according to the present invention includes a first step of calculating a pass schedule that specifies a reduction amount for each pass in a steel plate rolling process in consideration of rolling efficiency and plate crown ratio; The reduction amount of each pass in the pass schedule is changed so that the sum of the flatness error of the steel plate and the final plate crown error in satisfies a predetermined condition, and the pass schedule in which the reduction amount of each pass is changed is used as the final pass schedule. A second step of setting.

A pass schedule calculation method for a steel plate rolling process according to the present invention includes the steps of reducing the number of passes in the final pass schedule and re-executing the second step using the final pass schedule with the reduced number of passes. It is characterized by including.

A pass schedule calculation method for a steel plate rolling process according to the present invention is characterized in that it includes a step of changing weighting for the flatness error and the final plate crown error depending on the steel plate to be processed.

A pass schedule calculation device for a steel plate rolling process according to the present invention includes a first means for calculating a pass schedule that defines a rolling reduction amount for each pass in a steel plate rolling process in consideration of rolling efficiency and plate crown ratio; The reduction amount of each pass in the pass schedule is changed so that the sum of the flatness error of the steel plate and the final plate crown error in satisfies a predetermined condition, and the pass schedule in which the reduction amount of each pass is changed is used as the final pass schedule. and second means for setting.

The method for rolling a steel plate according to the present invention is characterized by including the step of rolling a steel plate according to the final pass schedule set by the pass schedule calculation method for a steel plate rolling process according to the present invention.

According to the pass schedule calculation method and pass schedule calculation device for a steel plate rolling process according to the present invention, it is possible to improve the plate crown and flatness while keeping the rolling efficiency constant. Further, according to the method for rolling a steel plate according to the present invention, the steel plate can be rolled with high productivity by controlling the plate crown and flatness while keeping the rolling efficiency constant.

FIG. 1 is a flowchart showing the flow of a pass schedule calculation process for a steel plate rolling process, which is an embodiment of the present invention. FIG. 2 is a diagram for explaining a conventional path schedule calculation method. FIG. 3 is a diagram showing an example of a plate crown deviation distribution when a steel plate is rolled using a pass schedule calculated according to a conventional example. FIG. 4 is a diagram showing an example of the plate crown deviation distribution when a steel plate is rolled according to the pass schedule calculated according to the example of the present invention. FIG. 5 is a diagram for explaining the effect of reducing the number of passes in the pass schedule according to the example of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to drawings, the pass schedule calculation method of the steel plate rolling process which is one Embodiment of this invention is demonstrated.

FIG. 1 is a flowchart showing the flow of a pass schedule calculation process for a steel plate rolling process, which is an embodiment of the present invention. The flowchart shown in FIG. 1 starts at the timing when an instruction to execute path schedule calculation processing is input to an information processing device such as a computer, and the path schedule calculation processing proceeds to step S1. Note that the path schedule calculation process described below is realized by the information processing apparatus executing a computer program in which execution instructions for each processing step of the path schedule calculation process are defined in a computer language.

In the process of step S1, the information processing device calculates a pass schedule in a steel plate rolling process using a conventional pass schedule calculation method. Specifically, first, the information processing device tentatively determines the temperature of the steel plate in each pass from the first pass to the final pass. Next, the information processing device calculates the amount of reduction for each pass and creates a provisionally determined pass schedule. Specifically, the information processing device first calculates the rolling load for the final pass from the desired final plate width and final plate thickness H _aim , as shown in FIG. 2(a). Next, the information processing device determines the rolling reduction amount of the final pass from the calculated rolling load of the final pass, and determines the sheet crown ratio in the final pass from the rolling reduction amount of the final pass.

Next, as shown in FIG. 2(b), the information processing device sequentially determines the rolling reduction amount of the previous pass from the final pass. At this time, the information processing device changes the method for setting the rolling reduction amount depending on whether the inlet thickness of the steel plate is larger than the shape control start thickness _Hcs . In other words, when the entrance side thickness of the steel plate is less than or equal to the shape control start thickness _Hcs , the information processing device determines the reduction amount for that pass by the reduction amount that makes the amount of change in the plate coulan ratio within the allowable range (with emphasis on plate shape control). (reduction amount). On the other hand, if the entrance side thickness of the steel plate is larger than the shape control start thickness _Hcs , the information processing device sets the reduction amount for that pass to the reduction amount at the upper limit of the constraints of the rolling equipment (reduction amount with emphasis on rolling efficiency). Set to . Through this series of processing, a tentatively determined path schedule is calculated.

When the tentatively determined pass schedule is calculated, next, as shown in _FIG . ) to a path upstream from the shape control start thickness _Hcs (roundoff target path). Next, the information processing device sequentially determines whether the finished temperature of the steel plate is within an allowable range, starting from the first pass. Then, when the finishing temperature of the steel plate is within the allowable range, the information processing device sets the tentatively determined pass schedule as the pass schedule in the steel plate rolling process. On the other hand, if the finished temperature of the steel plate is outside the allowable range, the information processing device resets the temperature of the steel plate in each pass, creates a tentative pass schedule again, and executes the above-described process again. Thereby, the process of step S1 is completed, and the path schedule calculation process proceeds to the process of step S2.

In the process of step S2, the information processing device optimizes the rolling reduction amount of each pass in the pass schedule calculated in the process of step S1. Specifically, the information processing device uses an optimization method such as convex quadratic programming to calculate the amount of reduction for each pass that minimizes the value of the evaluation function J shown in Equation (1) below.

Here, in formula (1), i is the pass number (=1 to n), λ _i ^ref is the target value of the flatness of the steel plate in each pass, λ _i is the flatness of the steel plate in each pass, and Cr ^ref is the final flatness of the steel plate in each pass. The target value of plate crown, Cr, indicates the final plate crown. Furthermore, W _i ^λ and W ^Cr represent weights for the flatness of the steel plate in each pass and the error in the final plate crown, respectively. The evaluation function J is evaluated by summing the flatness error of the steel plate and the final plate crown error in each pass.

The amount of operation for the value of the evaluation function J is the amount of reduction in each pass. The rolling reduction amount of each pass is determined from two coefficients: the flatness variation Δλ _i /Δh _i with respect to the rolling reduction variation Δh _i and the plate crown variation ΔCr/Δh _i with respect to the rolling reduction variation Δh _i . Therefore, minimizing the value of the evaluation function J is equivalent to finding a pass schedule that provides a steel plate with the flatness and plate crown closest to the ideal. Thereby, the process of step S2 is completed, and the path schedule calculation process proceeds to the process of step S3. Note that after executing the process of step S2 for the first time, the information processing apparatus advances the path schedule calculation process from the process of step S2 to the process of step S3.

Note that the temperature of the steel plate in each pass changes as the reduction amount in each pass is changed by the optimization calculation. Therefore, in order to prevent temperature changes in the steel plate from adversely affecting the quality of the steel plate, the condition of the steel plate, including the temperature and dimensions of the steel plate, is recalculated every time the optimization calculation of the reduction amount is performed. It is desirable to change the reduction amount, cooling time, etc. based on the recalculation results. In addition, for example, the value of the weight W ^Cr of the evaluation function J is increased for a thick steel plate that tends to have a large plate crown, and the value of the weight W ^λ is increased for a thin steel plate that tends to have uneven flatness. The values of W ^λ and weight W ^Cr may be set depending on the steel plate to be processed.

In the process of step S3, the information processing device calculates the flatness deviation and final plate crown deviation of each pass in the pass schedule in which the rolling reduction amount was optimized in the process of step S2, and each calculated deviation is within the allowable range. Determine whether it exists or not. If the result of the determination is that each deviation is within the allowable range (step S3: Yes), the information processing device determines that the optimization calculation has converged, and advances the path schedule calculation process to step S4. On the other hand, if each deviation is not within the allowable range (step S3: No), the information processing device advances the path schedule calculation process to step S5.

In the process of step S4, the information processing device reduces by one the number of passes in the pass schedule whose rolling reduction amount was optimized in the process of step S2. Specifically, the information processing device deletes the path schedule of the path with the least amount of reduction. Thereby, the process of step S4 is completed, and the path schedule calculation process returns to the process of step S2. Note that the process of step S4 does not necessarily need to be executed, and whether or not to execute it may be selected depending on the thickness and width of the steel plate, whether or not temperature adjustment is performed, and the like.

In the process of step S5, the information processing device adopts the pass schedule before reducing the number of passes by one as the final pass schedule. Thereafter, the information processing device transmits information regarding the adopted pass schedule to a rolling control device that controls the rolling equipment, and the rolling control device controls the rolling process of the steel plate according to the transmitted information regarding the pass schedule. By repeating the reduction of passes until the flatness deviation of each pass and the final plate crown deviation finally deviate from the allowable range, and finally by adopting a pass schedule in which each deviation is within the allowable range, the plate crown and flatness can be reduced. It is possible to set a pass schedule with good rolling efficiency and rolling efficiency. As a result, the process in step S5 is completed, and the series of path schedule calculation processes ends.

As is clear from the above description, in the pass schedule calculation process that is an embodiment of the present invention, the information processing device defines the rolling reduction amount for each pass of the steel plate rolling process in consideration of the rolling efficiency and plate crown ratio. The reduction amount of each pass in the pass schedule is changed so that the sum of the flatness error of the steel plate and the final plate crown error in each pass satisfies a predetermined condition, and the reduction amount of each pass is changed. Since the final pass schedule is set as the final pass schedule, the plate crown and flatness can be improved while keeping the rolling efficiency constant. In addition, by rolling the steel plate according to the pass schedule created by the pass schedule calculation process that is an embodiment of the present invention, the steel plate can be rolled with high productivity by controlling the plate crown and flatness while keeping the rolling efficiency constant. can do.

In addition, in the pass schedule calculation process that is an embodiment of the present invention, if the optimization calculation of the reduction amount fails in the process of step 2, or if the flatness deviation and the final plate crown deviation are within the allowable range in the process of step S3. Even if the pass schedule calculated in the process of step S1 is adopted based on the conventional pass schedule calculation method, the optimization calculation of the rolling reduction amount is performed again between passes, and the calculation result is determined to be within the allowable range of step S3. If it falls within the range, you can switch to a newly calculated path schedule. This is because the conventional path schedule calculation method is used as the base path schedule calculation method. As a result, according to the pass schedule calculation process that is an embodiment of the present invention, in order to improve the flatness and plate crown with respect to the current pass schedule, it is possible to perform calculations from a state where various constraint conditions are satisfied in advance. The amount of reduction after recalculation can be easily adjusted.

On the other hand, when the method described in Patent Document 3 and Patent Document 4 is based on a pass schedule calculation method that assumes the maximum reduction amount, an initial pass schedule is created from the advanced state of the pass. It's difficult to do. This is because there is a difference in rolling reduction amount and number of passes between the pass schedule used for rolling up to that point and the pass schedule with the maximum rolling reduction amount, so the difference in rolling reduction amount from the previous pass becomes large and machine constraints cannot be met, or temperature control cannot be achieved. This is because many problems arise, such as not being able to satisfy the thickness and target plate temperature. If these issues cannot be resolved, the optimization will fail, but in this case, the initial path schedule calculation that has not been optimized will remain as a set value. Furthermore, in order to solve this problem, it is conceivable to increase the number of passes to increase the degree of freedom in optimization, but in this case, the problem described in the problem to be solved by the invention may be exacerbated.

〔Example〕
3 and 4 are diagrams showing examples of sheet crown deviation distributions when steel sheets are rolled using pass schedules calculated according to the conventional example and the present invention, respectively. In this example, 15,000 steel plates with a thickness of 8 to 25 mm and a width of 2,650 to 4,600 mm were used as calculation targets. In addition, pass schedule calculations were performed under the same calculation conditions for all steel plates, without taking into account the chemical composition of the steel plates targeted for calculation or the presence or absence of controlled rolling. As is clear from the comparison between FIGS. 3 and 4, the example of the present invention (FIG. 4) has an average plate crown error of 24.5 μm (69.0%) compared to the conventional example (FIG. 3). The plate crown deviation σ could be improved by 16.5 μm (23.6%). Regarding the number of passes, when the process of step S4 shown in FIG. 1 was not executed, the average number of passes was 16.0 in both the example of the present invention and the conventional example. On the other hand, when the process of step S4 shown in FIG. 1 is executed, as shown in FIG. 5, according to the example of the present invention, the number of passes can be reduced by two passes compared to the conventional example. Note that the numbers in FIG. 5 indicate the number of passes. Furthermore, while the plate crown deviation in the conventional example at this time was 100 μm, the plate crown deviation in the example of the present invention was 75 μm. This confirms that according to the present invention, it is possible to improve rolling efficiency and reduce plate crown.

Although the embodiments applying the invention made by the present inventors have been described above, the present invention is not limited by the description and drawings that form part of the disclosure of the present invention by the present embodiments. That is, all other embodiments, examples, operational techniques, etc. made by those skilled in the art based on this embodiment are included in the scope of the present invention.

Claims (5)

a first step of calculating a pass schedule that specifies the amount of reduction for each pass in the rolling process of the steel plate in consideration of rolling efficiency and plate crown ratio;
The reduction amount of each pass in the pass schedule is changed so that the sum of the square of the flatness error of the steel plate and the square of the final plate crown error in each pass is minimized , and the reduction of each pass is a second step of setting the path schedule whose amount has been changed as the final path schedule;
A pass schedule calculation method for a steel plate rolling process, the method comprising: The pass of the steel plate rolling process according to claim 1, further comprising the step of reducing the number of passes of the final pass schedule and re-executing the second step using the final pass schedule with the reduced number of passes. Schedule calculation method. 3. The pass schedule calculation method for a steel plate rolling process according to claim 1, further comprising the step of changing weighting for the flatness error and the final plate crown error depending on the steel plate to be processed. A first means for calculating a pass schedule that specifies the amount of reduction for each pass in a steel plate rolling process in consideration of rolling efficiency and plate crown ratio;
The reduction amount of each pass in the pass schedule is changed so that the sum of the square of the flatness error of the steel plate and the square of the final plate crown error in each pass is minimized , and the reduction of each pass is a second means for setting the path schedule whose amount has been changed as the final path schedule;
A pass schedule calculation device for a steel plate rolling process, comprising: A method for rolling a steel plate, comprising the step of rolling a steel plate according to a final pass schedule set by the pass schedule calculation method for a steel plate rolling process according to any one of claims 1 to 3.

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