Cold rolling method and cold rolling equipment

Abstract

To provide a cold rolling method and a cold rolling facility which can perform cold rolling with good productivity and yield while securing stability of cold rolling even when a hard-to-rolled material having a thin plate thickness before rolling is cold rolled at high load.SOLUTION: A cold rolling method includes: a calculation step of calculating a leveling amount of a rolling machine using an out-of-plane deformation amount of a steel plate measured on the upstream side of a rolling machine; a control step of controlling the leveling of the rolling machine, on the basis of the leveling amount calculated in the calculation step; and a cold rolling step of performing cold rolling on the steel plate, using the rolling machine controlled in the control step.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a cold rolling method and cold rolling equipment.

Background Art

[0002] Generally, when cold rolling rolled materials such as cold-rolled thin steel sheets, it is desirable to perform cold rolling in a state where the through-feedability of the rolled material is stabilized by improving the shape (or flatness) of the rolled material while maintaining good thickness accuracy in the longitudinal and width directions of the rolled material. On the other hand, for the purpose of suppressing fuel consumption by weight reduction, etc., the need for difficult-to-roll materials such as high-load and thin, hard materials with a thin plate thickness before rolling is increasing. When cold rolling such difficult-to-roll materials, in order to suppress the rolling load, the difficult-to-roll materials are lightly drawn in the previous hot rolling process and then sent to the cold rolling process.

[0003] In recent years, many control factors of cold rolling mills are automatically controlled by actuators mounted on the cold rolling mills. As a method of automatic shape control, shape feedback (FB) control that installs a shape meter on the output side of the rolling mill and automatically controls the leveling and bender of the rolling mill using the shape data of the shape meter is often used. However, when cold rolling difficult-to-roll materials as described above, there are cases where they are joined to the next coil in a state where the bending of the coil head and tail ends due to shape defects during hot rolling remains. When the bending and shape defects fluctuate steeply along the coil longitudinal direction, fluctuations in the rolling load (and the advance rate and torque calculated accordingly), as well as roll gap, leveling, work roll bender, intermediate roll shift, and roll deflection correction represented by roll expansion due to thermal crown of the cold rolling mill, cannot be absorbed by automatic control. Therefore, the shape of the rolled material after cold rolling is often poor, or plate breakage often occurs during cold rolling. The weakness of FB control is that it cannot cope with rapid fluctuations, and feedforward (FF) control is also used to compensate for this.

[0004] ; Patent Document 1 discloses an FF control method that predicts uneven elongation or bending of the steel sheet at the entrance of the rolling mill from the differential tension measured by a differential tension meter upstream of the rolling mill, and controls the leveling to correct the predicted uneven elongation or bending. Patent Document 2 discloses a method to suppress rolling defects by FF control of the rolling mill's bender based on the twist and C-reverse height of the steel sheet shape data from a cross-sectional profile meter upstream of the rolling mill. Patent Document 3 discloses a method to suppress rolling defects by stopping rolling if the twist and C-reverse height of the steel sheet shape data from a cross-sectional profile meter upstream of the rolling mill are outside a predetermined range. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-161806 [Patent Document 2] Japanese Patent Publication No. 2022-14800 [Patent Document 3] Japanese Patent Publication No. 2021-133411 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The method disclosed in Patent Document 1 measures the differential tension between stands, but this differential tension predicts the average elongation or bending between stands. Therefore, while this method works well when the change in elongation or bending is gradual, when the change is abrupt, such as at a joint, a discrepancy arises between the elongation or bending predicted from the differential tension and the elongation or bending at the exit of the rolling mill, making effective control difficult. This is because if the elongation or bending is too large, the steel plate cannot adhere to the rolls, and the differential tension cannot be measured by the differential tension meter. The methods disclosed in Patent Documents 2 and 3 calculate the elongation or bending of a steel plate with large elongation or bending by measuring the cross-sectional shape of the steel plate and calculating the twist and C-curve height of the steel plate cross-section. However, twist and C-curve height are only a small part of the steel plate shape information, and it is difficult to accurately calculate the elongation or bending from the cross-sectional shape, making effective control difficult.

[0007] The present invention has been made in view of the above problems, and its objective is to provide a cold rolling method and cold rolling equipment that can perform cold rolling with high productivity and yield while ensuring the stability of the cold rolling process, even when cold rolling difficult-to-roll materials that are under high load and have a thin thickness before rolling. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the cold rolling method according to the present invention is characterized by comprising: a calculation step of calculating the leveling amount of the rolling mill using the out-of-plane deformation amount of the steel sheet measured upstream of the rolling mill; a control step of controlling the leveling of the rolling mill based on the leveling amount calculated in the calculation step; and a cold rolling step of performing cold rolling on the steel sheet using the rolling mill controlled by the control step.

[0009] Furthermore, the cold rolling method according to the present invention is characterized in that, in the above invention, the amount of out-of-plane deformation of the steel sheet is the amount of out-of-plane deformation measured upstream of the rolling mill and directly upstream or downstream of the steering device that changes the conveying direction of the steel sheet.

[0010] Furthermore, the cold rolling method according to the present invention is characterized in that, in the above invention, if the amount of out-of-plane deformation of the steel sheet measured upstream of the rolling mill exceeds a threshold, cold rolling of the steel sheet in the cold rolling step is not performed.

[0011] Furthermore, the cold rolling method according to the present invention is characterized in that, in the calculation step described above, the leveling amount is calculated using a value obtained as a result of applying a leveling amount calculation program to the out-of-plane deformation amount, and the leveling amount calculation program is characterized in that it is machine-trained using the out-of-plane deformation amounts of multiple steel plates as input variables and the leveling amounts obtained as a result of physical simulation as target variables for each of the out-of-plane deformation amounts.

[0012] Furthermore, the cold rolling method according to the present invention is characterized in that, in the calculation step described above, the leveling amount is calculated using the out-of-plane deformation amount of the steel sheet upstream of the rolling mill and the out-of-plane deformation amount of the steel sheet measured downstream of the rolling mill.

[0013] Furthermore, the cold rolling equipment according to the present invention is characterized by comprising: a rolling mill for cold rolling a steel sheet; a shape measuring device positioned upstream of the rolling mill for measuring the out-of-plane deformation of the steel sheet; a calculation device for calculating the leveling amount of the rolling mill using the out-of-plane deformation of the steel sheet measured by the shape measuring device; and a control device for controlling the leveling of the rolling mill based on the leveling amount calculated by the calculation device.

[0014] Furthermore, the cold rolling equipment according to the present invention is characterized in that, in the above invention, it is equipped with a steering device located upstream of the rolling mill and used to change the direction of transport of the steel sheet, and the out-of-plane deformation of the steel sheet is the out-of-plane deformation measured upstream of the rolling mill and directly upstream or downstream of the steering device.

[0015] Further, the cold rolling equipment according to the present invention, in the above invention, when the out-of-plane deformation amount of the steel sheet measured on the upstream side of the rolling mill exceeds a threshold value, the rolling mill does not perform cold rolling on the steel sheet, which is characterized in that.

[0016] Further, the cold rolling equipment according to the present invention, in the above invention, the calculation device calculates the leveling amount using the value obtained as a result of applying a leveling amount calculation program to the out-of-plane deformation amount, and the leveling amount calculation program uses the out-of-plane deformation amounts of a plurality of steel sheets as input variables, and each leveling amount obtained as a result of physical simulation for each out-of-plane deformation amount as an objective variable, and is characterized in that it is machine-learned.

[0017] Further, the cold rolling equipment according to the present invention, in the above invention, the calculation device calculates the leveling amount using the out-of-plane deformation amount of the steel sheet on the upstream side of the rolling mill and the out-of-plane deformation amount of the steel sheet measured on the downstream side of the rolling mill, which is characterized in that.

Effect of the Invention

[0018] The cold rolling method and cold rolling equipment according to the present invention can perform cold rolling with productivity and yield while ensuring the stability of cold rolling even when cold rolling a difficult-to-roll material with high load and a thin thickness of the sheet before rolling, which has the effect of.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is an overall view showing a schematic configuration of a cold rolling line according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an example of a method for measuring the out-of-plane deformation amount. [Figure 3] FIG. 3 is a diagram showing the measurement results of one-sided elongation or bending, which is the out-of-plane deformation amount of the steel sheet measured by a shape measuring device installed on the outlet side of the inlet looper. [Figure 4] FIG. 4 is an explanatory diagram regarding leveling control. [Figure 5]FIG. 5 is a diagram showing the transition of true elongation or bending as a result of simulation of cold rolling a steel sheet with elongation or bending on one side. [Figure 6] FIG. 6 is a diagram showing the transition of elongation or bending converted from differential tension as a result of simulation of cold rolling a steel sheet with elongation or bending on one side. [Figure 7] FIG. 7 is a diagram showing the transition of true elongation or bending as a result of simulation of cold rolling a steel sheet with elongation or bending on one side when leveling FB control is performed. [Figure 8] FIG. 8 is a diagram showing the transition of elongation or bending converted from differential tension as a result of simulation of cold rolling a steel sheet with elongation or bending on one side when leveling FB control is performed. [Figure 9] FIG. 9 is a diagram showing the transition of true elongation or bending as a result of leveling FB control so as to reduce the true elongation or bending on the outlet side of the first rolling mill by simulation. [Figure 10] FIG. 10 is a diagram showing the transition of elongation or bending converted from differential tension as a result of leveling FB control so as to reduce the true elongation or bending on the outlet side of the first rolling mill by simulation. [Figure 11] FIG. 11 is a diagram showing the transition of true elongation or bending as a result of simulation of cold rolling a steel sheet S with elongation or bending on one side by performing leveling FF control and leveling FB control. ​​​​​​​​​Embodiments of the cold rolling method and cold rolling equipment according to the present invention will be described below. The cold rolling equipment according to the embodiment includes a rolling mill for cold rolling a steel sheet, a shape measuring device positioned upstream of the rolling mill for measuring the out-of-plane deformation of the steel sheet, a calculation device for calculating the leveling amount of the rolling mill using the out-of-plane deformation of the steel sheet measured by the shape measuring device, and a control device for controlling the leveling of the rolling mill based on the leveling amount calculated by the calculation device. The cold rolling method applied to the cold rolling equipment according to the embodiment includes a calculation step for calculating the leveling amount of the rolling mill using the out-of-plane deformation of the steel sheet measured upstream of the rolling mill, a control step for controlling the leveling of the rolling mill based on the leveling amount calculated in the calculation step, and a cold rolling step for cold rolling a steel sheet using the rolling mill controlled by the control step. However, the present invention is not limited to this embodiment.

[0021] Figure 1 is an overall diagram showing the schematic configuration of a cold rolling mill 1 according to an embodiment. The cold rolling mill 1 according to this embodiment is equipped with a payoff reel 2 at the uppermost part for discharging steel sheets S from coils. The cold rolling mill 1 according to this embodiment is also equipped with a welding machine 3 for joining the tail end of the discharged steel sheet S to the tip end of the steel sheet discharged from the next coil, and a notcher 4 for cutting the steel sheet S in a semi-elliptical shape at the end of the weld line to suppress stress concentration. The cold rolling mill 1 according to this embodiment is also equipped with an entry looper 5 to absorb the line speed difference between the joining process and the rolling process. A steering device 6 equipped with CPC meandering control is installed on the exit side of the entry looper 5, and a shape measuring device 7 is installed directly downstream thereof. The shape measuring device 7 may be placed directly upstream of the steering device 6. Furthermore, the cold rolling equipment 1 according to this embodiment is equipped with a deflector steering roll 8 with CPC meandering control, a group of bridle rolls 9 for creating a tension step between the rolling process and its upstream process, and a deflector steering roll 10 equipped with CPC meandering control directly downstream of the group of bridle rolls 9. The cold rolling equipment 1 is also equipped with a five-stage continuous cold rolling mill 11 for rolling steel sheets S. The cold rolling equipment 1 is also equipped with a bridle roll 12 for creating a tension step between the rolling process and its downstream process, a cutting machine 13, and a tension reel 14 for winding up the steel sheets S.

[0022] The leading and trailing ends of the steel plate S discharged from the payoff reel 2 have shape defects, including uneven stretching or bending, which originate from the hot rolling process. Furthermore, if the steel plate S is not straight when joined by the welding machine 3, it will be welded in a "V" shape, further increasing the uneven stretching or bending. When such shape defects are cold-rolled by the cold rolling mill 11, cracks occur at the width edges of the steel plate S during the rolling process, and fracture occurs starting from these cracks. In addition, if the differential tension between the rolling mills (between stands) of the cold rolling mill 11, caused by uneven stretching or bending, is applied to the steel plate S, fracture occurs due to cracks, or even if there are no cracks. Note that differential tension refers to the difference in tension at both ends of the steel plate S in the width direction, as detected by pressure detection means such as a tension meter placed on the exit side of the rolling mill.

[0023] Here, we will explain the geometry of the steel sheet S. Shape defects in the steel sheet S mainly occur due to non-uniform elongation in the longitudinal direction and non-uniformity in the width direction during the rolling process. These shape defects are a combination of unilateral elongation or bending and ear waves (antinodes), and unilateral elongation or bending is the shape defect that has the greatest impact on fracture during rolling. In particular, with thin sheets, when the sheet is cut, the out-of-plane deformation caused by unilateral elongation or bending disappears, making it difficult to measure unilateral elongation or bending. On the other hand, ear waves (antinodes) can be measured because the out-of-plane deformation remains even when the sheet is cut.

[0024] When the steel plate S is a curve, the geometric definition of the curvature κ of the elongation or bending can be expressed by the following formula (1).

[0025]

number

[0026] Here, in equation (1) above, x is the position in the line direction, v is the displacement in the width direction at the width center, w is the vertical displacement at the width center, and ω is the torsional angle. Since it is difficult to calculate equation (1) above, we consider the longitudinal average of the stretch or curvature. The mean curvature K can be defined as shown in equation (2) below.

[0027]

number

[0028] Here, in equation (2) above, L is the length for averaging. Substituting equation (1) above into equation (2), the mean curvature K can be expressed by the following equation (3).

[0029]

number

[0030] The first term on the right-hand side of equation (3) above is the quantity observed as meandering or skew. The second term on the right-hand side of equation (3) above is the quantity observed as out-of-plane deformation. From equation (3) above, it can be seen that even if only meandering is observed, unilateral stretching or curvature cannot be determined. If there is no meandering, the first term on the right-hand side of equation (3) above becomes zero, and the average unilateral stretching or curvature can be determined from the observed quantity of out-of-plane deformation alone. Here, if the twist angle ω is small, equation (3) above becomes equation (4) below.

[0031]

number

[0032] Furthermore, the above formula (4) can be transformed into the following formula (5).

[0033]

number

[0034] Now, let's consider the observed out-of-plane deformation in the second term on the right-hand side of equation (5) above. Assuming that the torsional angle ω is small, the deflection W of the steel plate S is expressed by the following equation (6).

[0035]

number

[0036] Here, in equation (6) above, y represents the position in the width direction. Furthermore, the length l along the curved surface of the steel plate S can be expressed by the following equation (7).

[0037]

number

[0038] Also, the growth rate Δε l It can be defined as shown in formula (8) below.

[0039]

number

[0040] Here, in the above formula (8), l0 is the average length in the width direction, and can be expressed by the following formula (9).

[0041]

number

[0042] Here, in equation (9) above, b is the width of the board. Substituting equations (6) and (7) above into equation (9), we obtain equation (10) below.

[0043]

number

[0044] If we assume that the deflection w and the torsional angle ω are small, then equation (10) above becomes equation (11) below.

[0045]

number

[0046] Furthermore, by transforming the above formula (11), we obtain the following formula (12).

[0047]

number

[0048] Substituting equations (6), (7), and (12) above into equation (8), we get the difference in elongation Δε l This can be expressed by the following formula (13).

[0049]

number

[0050] Growth rate Δε l The average curvature K1 of the average single-sided elongation (average curvature) calculated from can be defined as shown in the following formula (14).

[0051]

number

[0052] Substituting equation (13) above into equation (14) above, we obtain equation (15) below.

[0053]

number

[0054] Equation (15) above is the second term on the right-hand side of equation (5) above, and equation (5) above can be expressed as equation (16) below.

[0055]

number

[0056] The curvature K1 can be calculated using the above formula (14) based on the measured out-of-plane deformation amount or its gradient measured by the shape measuring device 7. If there is no meandering of the steel plate S and the first term on the right-hand side of the above formula (14) is zero, then the curvature K1 of the intrinsic stretching or bending will be the same as the measurable curvature K1. Since the first term on the right-hand side of the above formula (16), which is related to meandering, is difficult to measure, it is desirable to measure the out-of-plane deformation amount of the steel plate S using the shape measuring device 7 in a location where the steel plate S does not meander.

[0057] Here, out-of-plane deformation is one of the indicators showing the bending and elongation of the steel plate S. Two methods for measuring out-of-plane deformation are possible, as shown in Figure 2. Figure 2 is a diagram showing an example of a method for measuring out-of-plane deformation.

[0058] The first method involves applying a normal force to the steel plate S by winding it onto a roll 20 or by pressing the steel plate S, as shown in Figure 2(a), to straighten out the wrinkles, and then measuring the curvature (unilateral elongation) of the straightened steel plate S.

[0059] The second method involves straightening the steel plate S in the longitudinal direction (without causing it to meander) as shown in Figure 2(b), and calculating the curvature (one-sided stretch) from the height of the wrinkles in the steel plate S.

[0060] In the first method, measurement becomes difficult if the length in the longitudinal direction for smoothing out wrinkles in the steel plate S is short. Therefore, it is preferable to adopt the second method, and in this embodiment, the out-of-plane deformation is measured (converted) using the second method.

[0061] In the field of rolling, the shape of asymmetric components is often expressed by the left-right difference (shape parameter) in the elongation rate distribution. The shape parameter λ1, which represents unilateral elongation or bending, is defined as shown in the following equation (17).

[0062]

number

[0063] The unit of the shape parameter λ1 is I-unit. Here, y' can be expressed by the following formula (18).

[0064]

number

[0065] Substituting equation (18) and equation (14) into equation (17) yields equation (19).

[0066]

number

[0067] As can be seen from the above equation (19), the shape parameter λ1 is proportional to the curvature K1.

[0068] Figure 3 shows the measurement results of the out-of-plane deformation of the steel plate S, which is the elongation or bending, measured by a shape measuring device 7 installed on the exit side of the entry side looper 5. In Figure 3, the horizontal axis represents time, and the vertical axis represents the shape parameter λ1 defined by the above formulas (17) and (19). In this case, the shape parameter λ1 changes rapidly at the joint point. In the leading material, there is no elongation or bending originating from the hot rolling process, while in the following material, there is elongation or bending originating from the hot rolling process, and the magnitude of elongation or bending gradually decreases as you move away from the tip.

[0069] In order for the shape measuring device 7 to detect uneven stretching or bending, it is preferable that the steel plate S does not meander, and in this embodiment, the shape measuring device 7 is installed directly downstream of the steering device 6. The shape measuring device 7 is a real-time 3D laser scanner that measures the position of the steel plate surface as a point cloud by rotating multiple laser beams and measuring the distance and rotation angle between the rotation center and the steel plate surface. The rotation period of the laser beams is, for example, 0.1 seconds. By making the shape measuring device 7 a 3D scanner, it can be installed outside the line with a single sensor, resulting in fewer installation constraints and easier maintenance. In addition, it has advantages such as being able to measure the steel plate surface in an instant, being resistant to vibration and independent of line speed, and being able to measure large shapes because it can measure without contact. Since there is a measurement error in the position of the point cloud and it is an irregular point cloud, the measurement error is removed by the smoothed thin plate spline method and the curved surface W of the steel plate is calculated from the point cloud. Furthermore, since the calculation of the smoothed thin plate spline method is time-consuming, it is preferable to use, for example, the technology disclosed in Japanese Patent Publication No. 2017-49071 to speed up the calculation. Then, the curvature K1 is calculated from the above formula (14) and the curved surface W of the steel plate, and the shape parameter λ1 is calculated from the above formula (19).

[0070] In this case, if the steel sheet S on the rolling mill entry side exhibits uneven stretching or bending as shown in Figure 3, the steel sheet S will fracture due to cold rolling by the cold rolling mill 11. Since the shape measuring device 7 is installed upstream of the cold rolling mill 11, it can obtain information about the shape of the steel sheet S on the rolling mill entry side before cold rolling. Based on the magnitude of the uneven stretching or bending obtained from this information, the risk of the steel sheet S fracturing can be predicted. Therefore, if the uneven stretching or bending on the rolling mill entry side is too large, the operation can be modified to prevent the steel sheet S from fracturing by not rolling it. In the cold rolling equipment 1 according to this embodiment, the shape measuring device 7 measures the uneven stretching or bending on the rolling mill entry side as the out-of-plane deformation amount of the steel sheet S, and if the measured out-of-plane deformation amount (uneven stretching or bending) exceeds a preset threshold, cold rolling of the steel sheet S by the cold rolling mill 11 is not performed. However, if it is not rolled, that part will not become a product, resulting in a decrease in yield.

[0071] Therefore, in order to more actively utilize the shape information of the steel sheet S on the inlet side of the rolling mill, leveling control will be explained using Figure 4. Generally, leveling FB control is performed in the cold rolling mill 11 to correct uneven elongation or bending of the steel sheet S. As shown in Figure 4, in the cold rolling mill 11, the first shape measuring roll 111a, the second shape measuring roll 110b, the third shape measuring roll 110c, the fourth shape measuring roll 110d, and the fifth shape measuring roll 111e are installed on the outlet side of the first rolling mill 110a, the second shape measuring roll 110b, the third shape measuring roll 111c, the fourth shape measuring roll 111d, and the fifth shape measuring roll 111e, respectively. In the following explanation, unless otherwise specified, the first rolling mill 110a, the second rolling mill 110b, the third rolling mill 110c, the fourth rolling mill 110d, and the fifth rolling mill 110e will simply be referred to as rolling mill 110. Similarly, unless otherwise specified, the first shape-measuring roll 111a, the second shape-measuring roll 111b, the third shape-measuring roll 111c, the fourth shape-measuring roll 111d, and the fifth shape-measuring roll 111e will simply be referred to as shape-measuring roll 111.

[0072] The shape measuring roll 111 measures the contact force distribution between the shape measuring roll 111 and the steel plate S, and estimates the out-of-plane deformation of the steel plate S, which is either elongation or bending, from this contact force distribution. Although the measurement method of the shape measuring roll 111 is highly accurate, it is difficult to measure large shape defects because it is necessary to make contact with the steel plate S. Therefore, if elongation or bending is estimated only from the contact force distribution measured by the shape measuring roll 111, the bending stress during rolling by the rolling mill 110 may cause fracture.

[0073] Furthermore, the cold rolling mill 11 is equipped with a first leveling control device 151a, a second leveling control device 151b, a third leveling control device 151c, a fourth leveling control device 151d, and a fifth leveling control device 151e, corresponding to the first rolling mill 110a, the second rolling mill 110b, the third rolling mill 110c, the fourth rolling mill 110d, and the fifth rolling mill 110e, respectively. In the following description, when the first leveling control device 151a, the second leveling control device 151b, the third leveling control device 151c, the fourth leveling control device 151d, and the fifth leveling control device 151e are not specifically distinguished, they will simply be referred to as leveling control device 151.

[0074] The leveling control device 151 calculates a leveling target value (the difference in reduction position between the left and right bearings of the backup rolls of the rolling mill 110, which is equal to the difference in reduction amount between one side in the thickness direction and the other side in the thickness direction, with the center of the steel plate S in the thickness direction as the boundary (the difference in reduction amount between the left and right sides of the steel plate S)) by multiplying the time integral of the elongation or bending on the exit side of the rolling mill by a gain. Then, leveling FB control is performed on the corresponding rolling mill 110 so that the calculated leveling target value is achieved. By performing such leveling FB control on the rolling mill 110, the contact force distribution on the shape measuring roll 111 on the exit side of the rolling mill becomes symmetrical, and as a result, elongation or bending on the exit side can be reduced. However, a drawback of leveling FB control is that it cannot respond to sudden disturbances and is insufficient in responding to elongation or bending on the exit side as shown in Figure 3.

[0075] In the cold rolling equipment 1 according to this embodiment, five stages of rolling mills 110 are provided in the cold rolling mill 11. However, the rolling mills 110 to be controlled to the leveling target value only need to include at least the rolling mill 110 located furthest upstream in the conveying direction of the steel sheet S. Therefore, in the cold rolling equipment 1 according to this embodiment, one or more rolling mills 110, including the rolling mill 110 located furthest upstream (first rolling mill 110a), are subject to leveling FB control.

[0076] Figure 5 shows the true progression of elongation or bending of a steel sheet S with uneven elongation or bending, as a result of a simulation of cold rolling. Figure 6 shows the progression of elongation or bending of an uneven steel sheet S with uneven elongation or bending, calculated from the differential tension, as a result of a simulation of cold rolling. Note that the elongation or bending on the first rolling mill entry side is based on the elongation or bending shown in Figure 3.

[0077] As shown in Figure 5, the true unilateral elongation or bending at the exit of the first rolling mill is smaller than the true unilateral elongation or bending at the entry of the first rolling mill. This is thought to be because the rolling phenomenon itself has the effect of reducing unilateral elongation or bending. However, as shown in Figure 5, during the time when the true unilateral elongation or bending at the entry of the first rolling mill changes rapidly (0 to 10 seconds), the magnitude of the true unilateral elongation or bending at the exit of the first rolling mill also increases.

[0078] Comparing the true unilateral elongation or bending at the exit of the first rolling mill shown in Figure 5 with the unilateral elongation or bending calculated from the differential tension at the exit of the first rolling mill shown in Figure 6, it can be seen that during the time when the true unilateral elongation or bending changes rapidly (0 to 10 seconds), the unilateral elongation or bending calculated from the differential tension differs from the true unilateral elongation or bending. On the other hand, during the time when the change is relatively gradual (10 to 50 seconds), the two are in relatively good agreement. Furthermore, the unilateral elongation or bending calculated from the differential tension at the exit of the first rolling mill shown in Figure 6 is in relatively good agreement with the unilateral elongation or bending calculated from the differential tension at the first shape measuring roll 111a.

[0079] From the above, it can be seen that the uneven elongation or bending calculated from the difference tension at the first shape measuring roll 111a located on the exit side of the first rolling mill 110a does not necessarily coincide with the true uneven elongation or bending. Therefore, it is not possible to observe the true uneven elongation or bending in an actual machine. Accordingly, Figures 7 and 8 show the results of a simulation in which a steel plate S with uneven elongation or bending was cold-rolled with leveling FB control.

[0080] Figure 7 shows the true progression of elongation or curvature of a steel sheet S with uneven elongation or curvature as a result of a simulation in which the steel sheet S with uneven elongation or curvature is cold-rolled under leveling FB control. Figure 8 shows the progression of elongation or curvature of an unevenly elongated or curvature converted from differential tension as a result of a simulation in which the steel sheet S with uneven elongation or curvature is cold-rolled under leveling FB control.

[0081] In leveling FB control, the leveling of the first rolling mill 110a to the fifth rolling mill 110e is controlled to reduce the magnitude of the differential tension in each of the first shape measuring rolls 111a to the fifth shape measuring rolls 111e, which are located at the exit sides of each of the first rolling mills 110a to the fifth rolling mill 110e. As a result, the magnitude of the elongation or bending calculated from the differential tension shown in Figure 8 can be made significantly smaller than the magnitude of the elongation or bending calculated from the differential tension shown in Figure 6. On the other hand, the magnitude of the true elongation or bending at the exit side of the first rolling mill shown in Figure 7 is smaller than the true elongation or bending at the exit side of the first rolling mill shown in Figure 5 during the time when the true elongation or bending changes slowly (10 to 50 seconds), but it is almost the same during the time when the true elongation or bending changes rapidly (0 to 10 seconds), indicating that the leveling FB control is unable to cope.

[0082] Ideally, we would like to minimize the true uneven elongation or bending at the exit of the first rolling mill, but these cannot be observed in an actual machine. Therefore, Figures 9 and 10 show the results of leveling FB control performed through simulation to minimize the true uneven elongation or bending at the exit of the first rolling mill.

[0083] Figure 9 shows the progression of true uneven elongation or bending as a result of leveling FB control performed to reduce true uneven elongation or bending at the exit of the first rolling mill through simulation. Figure 10 shows the progression of uneven elongation or bending calculated from differential tension as a result of leveling FB control performed to reduce true uneven elongation or bending at the exit of the first rolling mill through simulation.

[0084] In this embodiment, the leveling FB control controls leveling to reduce the true magnitude of the unilateral elongation or bending at the exit of the first rolling mill. Therefore, the true magnitude of the unilateral elongation or bending at the exit of the first rolling mill shown in Figure 9 can be made significantly smaller than the true magnitude of the unilateral elongation or bending at the exit of the first rolling mill shown in Figures 5 and 7. On the other hand, the magnitude of the unilateral elongation or bending calculated from the differential tension shown in Figure 10 is larger than the unilateral elongation or bending calculated from the differential tension shown in Figure 8. The true unilateral elongation or bending at the exit of the first rolling mill cannot be observed, but the unilateral elongation or bending at the inlet of the first rolling mill can be measured. Therefore, using simulation, it is possible to calculate a leveling amount that reduces the true magnitude of the unilateral elongation or bending at the exit of the first rolling mill from the unilateral elongation or bending at the inlet of the first rolling mill. In principle, even in actual machines, if a simulation is performed once the unilateral elongation or bending at the inlet of the first rolling mill is known, an appropriate leveling amount can be calculated in advance. Then, when the uneven stretching or bending reaches the first rolling mill 110a, leveling FF control is performed on the actual first rolling mill 110a with the calculated leveling amount. This makes it possible to reduce the true uneven stretching or bending at the exit of the first rolling mill.

[0085] However, the simulation takes time to compute. Therefore, by calculating the elongation or bending on the first rolling mill entry side and the appropriate leveling amount for multiple cases, and by using machine learning to output the appropriate leveling amount from the elongation or bending on the first rolling mill entry side, the appropriate leveling amount can be determined online.

[0086] For example, the calculation device 150 shown in Figure 4 calculates the leveling amount used for leveling FF control of the first rolling mill 110a using the value obtained by applying the leveling amount calculation program to the out-of-plane deformation amount (one-sided elongation or bending) on ​​the first rolling mill entry side acquired from the shape measuring device 7. The leveling amount calculation program used takes the out-of-plane deformation amounts of multiple steel plates as input variables and uses the leveling amounts obtained from physical simulations for each out-of-plane deformation amount as the target variable, and is trained using machine learning.

[0087] In practice, there are differences between simulations and actual machines, so it is preferable to use leveling FF control in combination with leveling FB control rather than using it alone. Therefore, Figures 11 and 12 show the results of a simulation in which a steel sheet S with uneven elongation or bending was cold-rolled using both leveling FF control and leveling FB control. Note that in the first rolling mill 110a, the control output is obtained by adding the leveling FF control output and the leveling FB control output together.

[0088] Figure 11 shows the true progression of elongation or curvature as a result of a simulation in which a steel sheet S with uneven elongation or curvature was cold-rolled using leveling FF control and leveling FB control. Figure 12 shows the progression of elongation or curvature converted from differential tension as a result of a simulation in which a steel sheet S with uneven elongation or curvature was cold-rolled using leveling FF control and leveling FB control.

[0089] The true unilateral elongation or bending at the exit of the first rolling mill shown in Figure 11 is smaller than the true unilateral elongation or bending at the exit of the first rolling mill shown in Figure 7, but larger than the true unilateral elongation or bending at the exit of the first rolling mill shown in Figure 9. By adjusting the weighting of the leveling FF control and the leveling FB control, it is possible to adjust whether the true unilateral elongation or bending at the exit of the first rolling mill is closer to the result of the leveling FF control or the result of the leveling FB control.

[0090] In the leveling control applied to the cold rolling equipment 1 according to the embodiment, data processing is performed on the shape measuring device 7, which is a shape meter located on the inlet side of the first rolling mill 110a, to calculate the elongation or bending on the inlet side of the first rolling mill. Then, using a machine learning program, a leveling FF control output, which is an appropriate leveling, is calculated from the calculated elongation or bending on the inlet side of the first rolling mill. The first leveling control device 151a calculates the leveling amount of the first rolling mill 110a using the elongation or bending on the outlet side of the first rolling mill, which is the out-of-plane deformation amount of the steel plate S measured by the first shape meter roll 111a. Then, the first leveling control device 151a performs leveling FB control to control the leveling of the first rolling mill 110a based on the calculated leveling amount. Furthermore, the first leveling control device 151a tracks the steel plate S from the line speed, and when the elongation or bending measured by the shape measuring device 7 reaches the first rolling mill 110a, it weights and adds the leveling FF control output and the leveling FB control, and controls the leveling using the added value as the target value. By performing this leveling control, the probability of fracture, which was 2% due to poor leveling control, was reduced to 1%. [Explanation of Symbols]

[0091] 1. Cold rolling equipment 2 Payoffriel 3. Welding machine 4 Notchers 5. Inlet Louver 6. Steering System 7 Shape measuring device 8. Deflector Steering Roll 9 Bridle Roll Group 10 Deflector Steering Roll 11 Cold rolling mill 12 Bridle Rolls 13 Cutting machine 14 Tension Reels 110 Rolling mill 110a First Rolling Mill 110b Second Rolling Mill 110c Third Rolling Mill 110d Rolling Mill No. 4 110e Rolling Mill No. 5 111 Shape Measuring Roll 111a First shape measuring roll 111b Second shape measuring roll 111c Third Shape Measuring Roll 111d Fourth shape measuring roll 111e Fifth Shape Measuring Roll 150 Calculation device 151 Leveling control device 151a First Leveling Control Device 151b Second Leveling Control Device 151c Third Leveling Control Device 151d Fourth leveling control device 151e Fifth Leveling Control Device

Claims

1. A calculation step to calculate the leveling amount of the rolling mill using the out-of-plane deformation amount, which is the elongation or bending of the steel sheet on the incoming side of the rolling mill, measured on the upstream side of the rolling mill, and the out-of-plane deformation amount, which is the elongation or bending of the steel sheet on the outgoing side of the rolling mill, measured on the downstream side of the rolling mill. A control step which includes: a leveling feedforward control that controls the leveling of the rolling mill based on the leveling amount calculated using the out-of-plane deformation amount of the steel plate measured upstream of the rolling mill in the calculation step, and a leveling feedback control that controls the leveling of the rolling mill based on the leveling amount calculated using the out-of-plane deformation amount of the steel plate measured downstream of the rolling mill in the calculation step; A cold rolling step in which the steel plate is cold-rolled using the rolling mill controlled by the control step, Includes, In the control step, the weighting of the leveling feedforward control and the leveling feedback control is adjusted. A cold rolling method characterized by the following features.

2. The cold rolling method according to Claim 1, characterized in that the amount of out-of-plane deformation of the steel sheet measured upstream of the rolling mill is the amount of out-of-plane deformation measured upstream of the rolling mill and directly upstream or downstream of the steering device that changes the conveying direction of the steel sheet.

3. The cold rolling method according to claim 1 or 2, characterized in that if the amount of out-of-plane deformation of the steel sheet measured upstream of the rolling mill exceeds a threshold, cold rolling of the steel sheet in the cold rolling step is not performed.

4. In the calculation step, The leveling amount is calculated using the value obtained by applying the leveling amount calculation program to the out-of-plane deformation amount, The leveling amount calculation program is, The cold rolling method according to claim 1 or 2, characterized in that the out-of-plane deformation amounts of multiple steel plates are used as input variables, and the leveling amounts obtained from physical simulations are used as target variables for each of the out-of-plane deformation amounts, and machine learning is performed on this machine.

5. In the calculation step, The leveling amount is calculated using a value obtained by applying a leveling amount calculation program to the out-of-plane deformation amount of the steel plate. The leveling amount calculation program is, The cold rolling method according to claim 3, characterized in that the out-of-plane deformation amounts of multiple steel plates are used as input variables, and the leveling amounts obtained from physical simulations are used as target variables for each of the out-of-plane deformation amounts, and machine learning is performed.

6. A rolling mill that cold-rolls steel plates, A shape measuring device positioned upstream of the rolling mill, which measures the elongation or bending of the steel plate on the rolling mill entry side as the out-of-plane deformation of the steel plate, A shape measuring roll is positioned downstream of the rolling mill and measures the elongation or bending of the steel sheet at the exit of the rolling mill as the out-of-plane deformation of the steel sheet. A calculation device that calculates the leveling amount of the rolling mill using the out-of-plane deformation amount on the inlet side of the rolling mill measured by the shape measuring device and the out-of-plane deformation amount on the outlet side of the rolling mill measured by the shape measuring roll, A control device that performs leveling feedforward control to control the leveling of the rolling mill based on the leveling amount calculated by the calculation device using the out-of-plane deformation amount on the rolling mill entry side, and leveling feedback control to control the leveling of the rolling mill based on the leveling amount calculated by the calculation device using the out-of-plane deformation amount on the rolling mill exit side, Equipped with, The control device controls the leveling of the rolling mill by adjusting the weighting of the leveling feedforward control and the leveling feedback control. A cold rolling mill characterized by the following features.

7. It is positioned upstream of the aforementioned rolling mill and is equipped with a steering device that changes the direction of conveyance of the steel plate. The cold rolling equipment according to claim 6, characterized in that the amount of out-of-plane deformation of the steel plate measured by the shape measuring device is the amount of out-of-plane deformation measured upstream of the rolling mill and directly upstream or downstream of the steering device.

8. The cold rolling equipment according to claim 6 or 7, characterized in that if the amount of out-of-plane deformation of the steel sheet measured upstream of the rolling mill exceeds a threshold, the rolling mill does not perform cold rolling on the steel sheet.

9. The calculation device calculates the leveling amount using the value obtained as a result of applying the leveling amount calculation program to the out-of-plane deformation amount. The leveling amount calculation program is, The cold rolling equipment according to claim 6 or 7, characterized in that the out-of-plane deformation amounts of multiple steel plates are used as input variables, and the leveling amounts obtained from physical simulations are used as target variables for each of the out-of-plane deformation amounts, and machine learning is performed on this equipment.

10. The calculation device calculates the leveling amount using the value obtained as a result of applying the leveling amount calculation program to the out-of-plane deformation amount. The leveling amount calculation program is, The cold rolling equipment according to claim 8, characterized in that the out-of-plane deformation amounts of multiple steel plates are used as input variables, and the leveling amounts obtained from physical simulations are used as target variables for each of the out-of-plane deformation amounts, and machine learning is performed on this equipment.

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