Method for controlling meandering of plate to be rolled

Abstract

To properly suppress meandering and camber of a plate to be rolled.SOLUTION: In a method for controlling meandering of a plate to be rolled of the present disclosure, the meandering amount of the plate to be rolled is separated into the meandering amount due to wedge ratio change, and the meandering amount due to left-right difference in friction coefficient from a rolling state of the plate to be rolled, and based on the meandering amount due to each cause, the meandering of the plate to be rolled of a control target is suppressed by at least one of leveling control, and friction coefficient left-right difference control for controlling left-right difference in friction coefficient.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for controlling meandering of a rolled sheet, which suppresses meandering and camber of the rolled sheet. [Background technology]

[0002] It is known that meandering (off-center behavior of the rolled sheet in the left-right direction from the pass line) and camber (left-right bending of the rolled sheet at the exit of the rolling pass) of a rolled sheet occur due to left-right asymmetry in the rolling state. Since meandering and camber of a rolled sheet impair sheet threadability in the rolling process, reduce productivity, and lower the straightness of the rolled product, thereby degrading quality, there is a need to suppress these. One factor that causes left-right asymmetry in the rolling state is the difference in the reduction rate between the left and right sides (i.e., a change in the wedge ratio). Numerous methods have been proposed to eliminate left-right asymmetry in the rolling state by adjusting the difference in the reduction amount between the left and right sides, i.e., by leveling adjustment, thereby bringing the change in the wedge ratio closer to zero (e.g., Non-Patent Document 1).

[0003] However, meandering and camber of a rolled sheet can also occur due to factors other than a change in the wedge ratio, a typical example of which is an asymmetric friction coefficient distribution (i.e., a difference between the left and right friction coefficients). For this reason, methods have been proposed for suppressing the occurrence of meandering and camber by adjusting the difference between the left and right friction coefficients (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 60-250818 [Patent Document 2] Japanese Patent Application Publication No. 5-237528 [Patent Document 3] Japanese Patent Application Publication No. 6-99211 [Non-patent literature]

[0005] [Non-Patent Document 1] Hiroe Nakajima and five others, "Study on the method of controlling meandering in hot strip rolling (1st report) - Theory on the mechanism of occurrence of meandering and camber -", Proceedings of the 1980 Spring Conference on the Technology of Plasticity, pp. 61-64, 1980 Summary of the Invention [Problem to be solved by the invention]

[0006] However, meandering and camber of the rolled sheet are not necessarily caused by a single factor, but can also be caused by two factors: a change in the wedge ratio and a difference in the coefficient of friction between the left and right sides. Because the behavior of meandering caused by these two factors is different, it is difficult to appropriately suppress meandering of the rolled sheet.

[0007] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a method for controlling the meandering of a rolled sheet, which can appropriately suppress the meandering and camber of the rolled sheet. [Means for solving the problem]

[0008] In order to solve the above problems, according to one aspect of the present invention, a method for controlling the meandering of a rolled sheet is provided, which separates the amount of meandering of the rolled sheet from the rolling state of the rolled sheet into an amount of meandering caused by a change in the wedge ratio and an amount of meandering caused by the difference in the left and right friction coefficients, and based on the amount of meandering caused by each cause, suppresses the meandering of the rolled sheet to be controlled by at least one of leveling control and left and right friction coefficient difference control, which controls the difference in the left and right friction coefficients.

[0009] The method for controlling the meandering of a rolled sheet may involve performing at least one of leveling control, which reduces the amount of meandering caused by a change in the wedge ratio, to zero, and left-right friction coefficient difference control, which reduces the amount of meandering caused by the difference in the left-right friction coefficient to zero, thereby suppressing the meandering of the rolled sheet to be controlled.

[0010] In controlling the difference in the coefficient of friction between the left and right rolls, at least one of the concentration and supply amount of lubricating oil injected between the work rolls and the rolled sheet may be adjusted.

[0011] Alternatively, in controlling the difference in the coefficient of friction between the left and right rolls, at least one of the roughness of the work rolls or the surface quality of the rolled sheet may be adjusted.

[0012] The meandering control method for the rolled sheet may be implemented by reducing the amount of meandering of the rolled sheet to zero by leveling control alone.

[0013] In this case, the leveling control amount at the front end of the rolled plate to be controlled and the leveling control amount at the tail end of the rolled plate to be controlled may be changed depending on the amount of meandering caused by the change in wedge ratio and the amount of meandering caused by the difference in the left and right friction coefficients.

[0014] Alternatively, a leveling control amount may be applied based on the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the left and right friction coefficients so that the wedge is constant over the entire length of the rolled plate to be controlled.

[0015] As the rolling state of the rolled sheet, the meandering in the rolling pass may be separated based on at least two or more factors of a change in the wedge ratio in the rolling pass, a difference in the rolling load between the left and right, the amount of meandering on the entry side, the amount of meandering on the exit side, and a difference in the load acting on the entry side edger device between the left and right or a difference in the load acting on the side guide between the left and right.

[0016] When the difference in rolling load between the left and right sides of the rolled sheet is included in the factors representing the rolling state of the rolled sheet, the difference in temperature between the left and right sides of the rolled sheet may be included in the factors to separate meandering. [Effects of the Invention]

[0017] As described above, according to the present invention, meandering caused by a change in the wedge ratio and meandering caused by a difference in the coefficient of friction between the left and right sides can be appropriately separated, thereby suppressing meandering and camber of the rolled sheet. Note that camber occurs as a result of meandering of the rolled sheet due to a change in the wedge ratio or a difference in the coefficient of friction between the left and right sides. In other words, if meandering caused by a change in the wedge ratio or a difference in the coefficient of friction between the left and right sides can be suppressed, then naturally camber caused by a change in the wedge ratio or a difference in the coefficient of friction between the left and right sides can also be suppressed. Therefore, the meandering control method according to the present invention can suppress not only meandering of the rolled sheet but also camber. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an explanatory diagram showing a rolling apparatus according to an embodiment of the present invention; [Figure 2] FIG. 1 is a schematic plan view showing an edger installed on the entry side of a rolling mill. [Figure 3] FIG. 2 is a schematic plan view showing a state in which a side guide is installed on the entry side of a rolling mill. [Figure 4] 1 is a graph showing an example of meandering behavior of a rolled sheet due to changes in wedge ratio. [Figure 5] 1 is a graph showing an example of meandering behavior of a rolled sheet due to a difference in friction coefficient between the left and right sides. [Figure 6] 10 is a flowchart showing an example of a method for controlling meandering of a rolled sheet according to the embodiment, showing a case (control example 1) in which meandering is suppressed by different meandering controls depending on the cause of the meandering. [Figure 7] 10 is a flowchart showing an example of a method for controlling meandering of a rolled sheet according to the embodiment, illustrating a case (control example 2) in which meandering of the rolled sheet is suppressed only by leveling control. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0020] [1. Configuration of rolling equipment] First, a schematic configuration of a rolling mill 1 equipped with a rolling mill 10 according to one embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is an explanatory diagram showing one configuration example of the rolling mill 1 according to this embodiment. Figure 2 is a schematic plan view showing a state in which an edger device 50 is installed on the entry side of the rolling mill 10. Figure 3 is a schematic plan view showing a state in which a side guide 60 is installed on the entry side of the rolling mill 10.

[0021] In the following description, the upstream side of the rolling mill 10 in the rolling direction (X direction) is also referred to as the "entrance side," and the downstream side of the rolling mill 10 in the rolling direction (X direction) is also referred to as the "exit side." The left-right direction of the rolling mill 10, i.e., the direction (Y direction) perpendicular to the rolling direction within the rolling plane (XY plane) on which the rolling mill 10 rolls the sheet S, is referred to as the reference direction. The reference direction is the direction along the longitudinal direction (i.e., the roll axis) of the barrels of the work rolls 11 and 12. Here, when viewing the rolling mill 10 from the upstream side in the rolling direction, one side of the barrels of the work rolls 11 and 12 located on the right side (the front side of the paper in FIG. 1, and the bottom side of the paper in FIGS. 2 and 3) is also referred to as the "work side," and the other side of the barrels of the work rolls 11 and 12 located on the left side (the back side of the paper in FIG. 1, and the top side of the paper in FIGS. 2 and 3) is also referred to as the "drive side."

[0022] As shown in FIG. 1 , the rolling mill 1 according to this embodiment includes a rolling mill 10, a meander gauge 20, lubricant supply devices 31 and 32, a screw down device 40, and a control device 100. The rolling mill 10 has a top work roll 11 and a bottom work roll 12. The rolling mill 10 rolls the sheet S passing between the top work roll 11 and the bottom work roll 12 to a predetermined thickness. The roll gap between the top work roll 11 and the bottom work roll 12 can be adjusted by a screw down device 40 that presses down the top work roll 11 in the reduction direction (negative side in the Z direction). The screw down device may also be arranged to press up the bottom work roll 12 in the reduction direction (positive side in the Z direction).

[0023] A meandering meter 20 for measuring the meandering amount of the rolled sheet S is installed on the delivery side of the rolling mill 10 shown in Figure 1. The meandering meter 20 may also be installed on the entry side of the rolling mill 10. The type of meandering meter 20 is not particularly limited, and for example, an image of the rolled sheet S may be taken with a CCD camera, and the edge position of the rolled sheet S may be detected by image processing to calculate the meandering amount. Measurement information from the meandering meter 20 is output to the control device 100.

[0024] At the entry side of the rolling mill 10, there are disposed a lubricant supply device 31 that supplies lubricant to the top work roll 11, and a lubricant supply device 32 that supplies lubricant to the bottom work roll 12. The lubricant supply devices 31, 32 are configured to be able to distribute the amount and concentration of lubricant supplied in the width direction, for example, by arranging a plurality of flat spray nozzles across the length of the roll barrels of the work rolls 11, 12. Furthermore, although this embodiment shows the case where the lubricant is sprayed onto the work rolls 11, 12, the lubricant may also be sprayed onto the rolled sheet S or an auxiliary roll. As the lubricant, for example, a synthetic ester-based lubricant oil that is generally used as hot rolling oil may be used.

[0025] Furthermore, as shown in FIG. 2, an edger device 50 that reduces the width of the rolled sheet S may be installed on the entry side of the rolling mill 10. The edger device 50 presses the rolled sheet S in the width direction (Y direction) using a pair of edger rolls 51, 52, thereby adjusting the rolled sheet S to a predetermined width. Alternatively, as shown in FIG. 3, a side guide 60 may be installed on the entry side of the rolling mill 10. The side guide 60 is composed of a pair of guides 61, 62 installed opposite each other in the width direction (Y direction) and is installed to center the rolled sheet S passing through the sheet threading line. The load or torque with which the edger device 50 presses the rolled sheet S and the load (repulsion force) that the side guide 60 receives from the rolled sheet S can be measured. The measured horizontal load or torque of the edger device 50 or the load that the side guide 60 receives from the rolled sheet S are output to the control device 100.

[0026] The control device 100 performs various controls of the rolling mill 1. In this embodiment, for example, when the control device 100 determines that the rolled sheet S is meandering based on the detection results of the meander meter 20, it controls the rolling mill 1 so that the amount of meandering is zero, thereby controlling the meandering of the rolled sheet S. At this time, the control device 100 appropriately suppresses the meandering or camber of the rolled sheet S by performing at least one of leveling control and left-right friction coefficient difference control, depending on the cause of the meandering or camber of the rolled sheet S. The meandering control method according to this embodiment will be described in detail later.

[0027] The above describes one example of the configuration of the rolling mill 1 according to this embodiment. While FIG. 1 shows a schematic configuration of the rolling mill 1, with the work rolls 11 and 12 shown without a cross angle, the rolling mill 10 may also be a cross rolling mill. In this case, at least one of the top work roll 11 and the bottom work roll 12 of the rolling mill 10 is installed so that the roll axis forms an angle with respect to a reference direction on the rolling surface, and the rolls cross within the rolling surface. In this case, the method for controlling the meandering of the rolled sheet S, which will be described in detail below, can also be applied. Furthermore, the rolling mill 1 may be a rolling mill equipped with a work roll shifting mechanism, or may be a four-high rolling mill, a six-high rolling mill, a cluster rolling mill, or the like.

[0028] [2. Controlling the meandering of rolled sheets] [2-1. Overview] As described above, the cause of meandering or camber in the rolled sheet S is asymmetry in the rolling state, such as a change in the wedge ratio or a difference in the coefficient of friction between the left and right sides. Here, the inventors of the present application have found that meandering caused by a change in the wedge ratio and meandering caused by a difference in the coefficient of friction between the left and right sides behave differently.

[0029] Figure 4 is a graph showing an example of the meandering behavior of the rolled sheet S due to a wedge ratio change ΔΨ. Figure 4 shows the rolling analysis results for cases where the wedge ratio change ΔΨ is positive and negative, and shows the trajectory of the center of the cross section of the rolled sheet S. The solid line represents the case where the wedge ratio change ΔΨ is negative (ΔΨ<0), and the dashed line represents the case where the wedge ratio change ΔΨ is positive (ΔΨ>0). Here, in this specification, wedge refers to the difference in thickness between the work side and drive side of the rolled sheet, and is considered positive when the work side thickness is thicker than the drive side thickness. The wedge ratio is the value obtained by dividing the wedge by the sheet thickness. The wedge ratio change refers to the difference between the wedge ratio at the exit side of a rolling pass and the wedge ratio at the entry side of that rolling pass. In Figure 4, there is no difference in the friction coefficient between the left and right sides.

[0030] As shown in Figure 4, whether the wedge ratio change ΔΨ is positive or negative, the trajectory of the rolled sheet S is linear at the entry side of the rolling mill and quadratic at the exit side. It can also be seen that the meandering direction is the same on the entry side and the exit side. That is, in the example of Figure 4, when the wedge ratio change ΔΨ is negative, the sheet meanders in the positive direction (drive side) at the entry side and the exit side of the rolling mill, and when the wedge ratio change ΔΨ is positive, the sheet meanders in the negative direction (work side) at the entry side and the exit side of the rolling mill.

[0031] On the other hand, Fig. 5 is a graph showing an example of the meandering behavior of the rolled sheet S due to the difference in the coefficient of friction between the left and right. DW (=μ DS -μ WS ) and shows the trajectory of the center of the cross section of the rolled sheet S. Here, the coefficient of friction between the work rolls 11, 12 and the rolled sheet S on the drive side (DS) from the center of the width direction of the rolled sheet S (hereinafter also referred to as the "drive side friction coefficient") is μ DS The coefficient of friction between the work rolls 11, 12 and the rolled sheet S on the work side (WS) from the center of the width direction of the rolled sheet S (hereinafter also referred to as the "work side coefficient of friction") is μ WS In Figure 5, the solid line represents the difference in the friction coefficient between the left and right, Δμ DW The dashed line indicates the difference in the friction coefficient between the left and right, Δμ DW is positive.

[0032] In the rolling analysis of Fig. 5, it was assumed that there was no difference between the friction coefficient between the top work roll 11 and the rolled sheet S and the friction coefficient between the bottom work roll 12 and the rolled sheet S on the drive side (DS) and work side (WS) with respect to the width direction center of the rolled sheet S. It was also assumed that there was no change in the wedge ratio of the rolled sheet S.

[0033] As shown in Figure 5, the difference in the friction coefficient between the left and right, Δμ DWRegardless of whether the value of is positive or negative, the trajectory of the rolled sheet S is linear on the entry side of the rolling mill and quadratic on the exit side. However, unlike the case of the wedge ratio change shown in Figure 4, the direction of meandering is opposite on the entry side and the exit side. That is, in the example of Figure 5, the difference in the friction coefficient between the left and right, Δμ DW When is negative, the rolling mill will snake in the negative direction (work side) on the entry side, but will snake in the positive direction (drive side) on the exit side. DW When is positive, the rolling mill meanders in the positive direction (drive side) at the entry side, but in the negative direction (work side) at the exit side.

[0034] In this way, meandering caused by a change in the wedge ratio has the same direction on the entry side and the exit side of the rolling mill, but meandering caused by a difference in the coefficient of friction between the left and right sides has different directions on the entry side and the exit side of the rolling mill.For this reason, for example, when trying to eliminate meandering occurring on the entry side of the rolling mill, even though the meandering is caused by a difference in the coefficient of friction between the left and right sides, if you assume that the meandering is caused by a change in the wedge ratio and try to suppress this meandering by leveling control, the meandering on the exit side of the rolling mill will end up becoming larger.

[0035] Therefore, in the method for controlling the meandering of the rolled sheet S according to this embodiment, the meandering or camber of the rolled sheet S is appropriately suppressed by performing at least one of leveling control and left-right friction coefficient difference control depending on the factor causing the meandering or camber of the rolled sheet S.

[0036] [2-2. Control method] In the method for controlling the meandering of a rolled sheet S according to this embodiment, first, the amount of meandering of the rolled sheet S is separated into the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the left-right friction coefficient based on the rolling state of the rolled sheet S. Then, based on the amount of meandering caused by each cause, the meandering of the rolled sheet S to be controlled is suppressed by at least one of leveling control and left-right friction coefficient difference control, which controls the difference in the left-right friction coefficient. Note that the rolled sheet S to be controlled may be the same as the rolled sheet S when the amount of meandering occurring for each cause of meandering is grasped, or it may be the rolled sheet S to be rolled next after the rolled sheet S when the amount of meandering occurring for each cause of meandering is grasped. In the following description, the rolled sheet S to be controlled is assumed to be the same as the rolled sheet S when the amount of meandering occurring for each cause of meandering is grasped.

[0037] Ideally, it is desirable to perform control to suppress meandering so that the amount of meandering caused by each factor approaches zero. Taking this into consideration, a specific meandering control method for separating the amount of meandering of the rolled sheet S that has occurred into each factor and appropriately suppressing the amount of meandering caused by each factor will be described below.

[0038] (Control example 1) Suppressing meandering by different meandering controls for each cause of meandering First, referring to Fig. 6, a case where meandering is suppressed by different meandering controls for different causes of meandering (control example 1) will be described in detail as an example of a method for controlling meandering of a rolled sheet S according to this embodiment. Fig. 6 is a flowchart showing a case where meandering is suppressed by different meandering controls for different causes of meandering, as an example of a method for controlling meandering of a rolled sheet S according to this embodiment. In control example 1, meandering occurring in the rolled sheet S is suppressed by performing at least one of leveling control, which reduces the amount of meandering caused by a change in the wedge ratio to zero, and left-right friction coefficient difference control, which reduces the amount of meandering caused by the difference in friction coefficient between the left and right sides to zero.

[0039] (S110: Meandering amount measurement) As shown in Fig. 6, first, the amount of meandering of the sheet S to be rolled is measured (S110). For example, an image of the sheet S to be rolled may be taken with a CCD camera, and the edge position of the sheet S to be rolled may be detected by image processing, and the amount of meandering may be calculated. The amount of meandering may be measured at least on either the entry side or exit side of the rolling mill 10, and the measurement position may be determined according to a method for separating the amount of meandering depending on the cause of occurrence, which will be described later. The measured amount of meandering of the sheet S to be rolled is output to the control device 100.

[0040] (S120: Separation of meandering amount according to the cause) Next, the control device 100 separates the amount of meandering measured in step S110 into meandering caused by a change in the wedge ratio and meandering caused by a difference in the coefficient of friction between the left and right sides (S120). The rolling state of the rolled sheet S is represented by values ​​of factors related to the occurrence of meandering. For example, the rolling state of the rolled sheet S is represented by factors such as a change in the wedge ratio, a difference in the rolling load between the left and right sides, the amount of meandering on the entry side, the amount of meandering on the exit side, a difference in the load acting on the entry side edger device between the left and right sides, or a difference in the load acting on the side guides between the left and right sides. In step S120, the meandering occurring in the rolled sheet S is separated into meandering caused by a change in the wedge ratio and meandering caused by a difference in the coefficient of friction between the left and right sides based on at least two or more factors representing the rolling state of the rolled sheet S. Specifically, the processing of step S120 may be performed using, for example, the following separation methods (A) to (I).

[0041] (A) Separation based on wedge ratio change and exit meander amount For example, by using the change in wedge ratio and the actual measured value of the amount of meandering on the delivery side as the rolling state of the rolled sheet S, the amount of meandering can be separated into the amount of meandering caused by the change in wedge ratio and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides. Separation method (A) can be applied regardless of whether the rolled sheet S is restrained on the entry side of the rolling mill.

[0042] The wedge ratio change may be calculated based on measured values ​​of the wedge at the entry and exit sides of the rolling pass. Alternatively, the wedge ratio change may be calculated using an estimated value of the wedge at the exit side of the rolling pass based on the difference in rolling load between the left and right sides and the difference in mill rigidity between the left and right sides in the rolling pass. The wedge at the entry side of the rolling pass can also be estimated based on the difference in rolling load between the left and right sides and the difference in mill rigidity between the left and right sides in the rolling pass immediately before the rolling pass.

[0043] Once a measured or estimated value of the wedge ratio change in the rolling pass is obtained, it is possible to estimate the amount of exit meandering based on a method for estimating the change in camber curvature due to a change in wedge ratio. A known method can be used to estimate the change in camber curvature due to a change in wedge ratio, and for example, the method described in Non-Patent Document 1 (relationship between wedge ratio change ΔΨ and camber curvature change Δκ) may be used. In this way, the exit camber curvature due to a change in wedge ratio can be estimated. If the exit camber curvature due to a change in wedge ratio can be estimated, the amount of meandering can be estimated at a meander meter position installed a predetermined distance downstream from the rolling mill, based on the fact that the trajectory of the rolled sheet becomes approximately parabolic downstream of the rolling mill.

[0044] Then, the difference between the estimated value of the amount of outlet meandering estimated from the change in wedge ratio and the actual measured value of the amount of outlet meandering is extracted as the amount of meandering caused by the difference in the coefficient of friction between the left and right sides. For example, assume that the estimated value of the amount of outlet meandering estimated from the change in wedge ratio is 80 mm, and the actual measured value of the amount of outlet meandering is 150 mm. In this case, of the actual measured value of the amount of outlet meandering of 150 mm, the amount of meandering caused by the change in wedge ratio is estimated to be 80 mm, and the difference between the two (70 mm) can be estimated to be caused by the difference in the coefficient of friction between the left and right sides. In this way, based on the measured or estimated value of the change in wedge ratio in the rolling pass and the amount of meandering on the outlet side of the rolling pass, it is possible to separate the meandering occurring in the rolled sheet S into meandering caused by the change in wedge ratio and meandering caused by the difference in the coefficient of friction between the left and right sides.

[0045] Although it has been described here that the amount of meandering of the rolled sheet can be measured using a meander meter, it goes without saying that this technology can also be applied to cases where the camber curvature can be measured using a camber meter.

[0046] (B) Separation based on wedge ratio change and inlet meander amount Furthermore, for example, by using the change in wedge ratio and the actual measured value of the entry-side meandering amount as the rolling state of the rolled sheet S, the meandering amount can be separated into the amount of meandering caused by the change in wedge ratio and the amount of meandering caused by the difference in the left and right friction coefficients. Separation method (B) can be applied when the rolled sheet S is not restrained on the entry side of the rolling mill.

[0047] Separation method (B) is a case where the entry-side meandering amount is used instead of the delivery-side meandering amount used in separation method (A), and can be carried out in the same manner as separation method (A). That is, the difference between the estimated entry-side meandering amount, which is estimated from the measured or estimated value of the wedge ratio change in the rolling pass, and the actually measured entry-side meandering amount is extracted as the amount of meandering caused by the difference in the left-right friction coefficient. In this way, the meandering occurring in the rolled sheet S can be separated into meandering caused by the change in the wedge ratio and meandering caused by the difference in the left-right friction coefficient.

[0048] (C) Separation based on wedge ratio change and load on side guide Furthermore, for example, by using the change in wedge ratio and the load on the side guide 60 as the rolling state of the rolled sheet S, the amount of meandering can be separated into the amount of meandering caused by the change in wedge ratio and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides. Separation method (C) can be applied when the rolled sheet S is restrained by the side guide 60 installed on the inlet side of the rolling mill.

[0049] As shown in Fig. 4, a side guide 60 is installed on the entry side of the rolling mill 10. If the sheet S to be rolled meanders during rolling, the sheet S comes into contact with the guide 61 (or guide 62), and the guide 61 (or guide 62) receives a load from the sheet S to be rolled.

[0050] Then, the difference between the estimated value of the difference in the load between the left and right sides of the side guides 60 received from the rolled sheet S, estimated from the measured or estimated value of the wedge ratio change in that rolling pass, and the actual measured value, is extracted as the influence of meandering caused by the difference in the left and right friction coefficient. In this way, the meandering occurring in the rolled sheet S can be separated into meandering caused by the change in the wedge ratio and meandering caused by the difference in the left and right friction coefficient.

[0051] (D) Separation based on the amount of meandering on the exit side and the amount of meandering on the entry side Furthermore, for example, by using the amount of meandering on the delivery side and the amount of meandering on the entry side as the rolling state of the rolled sheet S, the amount of meandering can be separated into the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the left and right friction coefficients. Separation method (D) can be applied when the rolled sheet S is not constrained at the entry side of the rolling mill. Separation method (D) does not require measurement and estimation of wedges at the entry and exit sides of the rolling mill, but it is necessary to obtain in advance the relationship between the meandering measurement position and the meandering amount according to the change in the wedge ratio as shown in Figure 4 (hereinafter also referred to as "wedge ratio change-meandering amount information"), and the relationship between the meandering measurement position and the meandering amount according to the difference in the left and right friction coefficients as shown in Figure 5 (hereinafter also referred to as "left and right difference in friction coefficient-meandering amount information").

[0052] The exit-side meandering amount and the entry-side meandering amount may be the amounts of meandering at the entry and exit of the rolling pass measured in step S110. Then, for example, a combination is searched for in which the sum of the exit-side meandering amount based on the wedge ratio change-meandering amount information and the exit-side meandering amount based on the friction coefficient left-right difference-meandering amount information matches the actual measured value of the exit-side meandering amount. There are multiple such combinations, but for each combination, there is only one combination in which the sum of the entry-side meandering amount based on the wedge ratio change-meandering amount information and the entry-side meandering amount based on the friction coefficient left-right difference-meandering amount information matches the actual measured value of the entry-side meandering amount. From the combination in which both the entry-side meandering amount and the exit-side meandering amount found in this way match the actual measured values, the wedge ratio change and the left-right difference in the friction coefficient in the rolling pass can be estimated. Then, based on the estimated wedge ratio change and the difference in the friction coefficient between the left and right sides, the meandering occurring in the rolled sheet S can be separated into meandering caused by the change in the wedge ratio and meandering caused by the difference in the friction coefficient between the left and right sides.

[0053] (E) Separation based on the amount of meandering on the exit side and the load on the edger device or side guide Furthermore, for example, by using the amount of meandering on the delivery side and the difference between the left and right loads (weight or torque) acting on the edger device 50 or the difference between the left and right loads acting on the side guides 60 as the rolling state of the rolled sheet S, the amount of meandering can be separated into the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference between the left and right friction coefficients. Separation method (E) can be applied when the rolled sheet S is restrained by the edger device 50 or side guides 60 installed on the entry side of the rolling mill. Separation method (E) does not require measurement or estimation of the wedge on the entry and exit sides of the rolling mill.

[0054] In separation method (E), for example, the amount of meandering at the exit side of the rolling pass measured in step S110 is assumed to have a zero difference in the friction coefficient between the left and right sides, and the difference between the left and right sides in the load (weight or torque) acting on the edger device 50 or the difference between the left and right sides in the load acting on the side guide 60 when caused only by a change in the wedge ratio is calculated.

[0055] When the difference in the coefficient of friction between the left and right sides is assumed to be zero, the actual measurement value and estimated value of the amount of meandering on the delivery side match, but the estimated value of the difference in the load (load or torque) acting on the edger device 50 between the left and right sides or the difference in the load acting on the side guides 60 between the left and right sides does not necessarily match the actual measurement value. Therefore, this estimated value is compared with the actual measurement value of the difference in the load (load or torque) acting on the edger device 50 between the left and right sides or the difference in the load acting on the side guides 60 between the left and right sides. Then, the difference in the coefficient of friction between the left and right sides is corrected so that the estimated value of the difference in the load (load or torque) acting on the edger device 50 between the left and right sides or the difference in the load acting on the side guides 60 between the left and right sides matches the actual measurement value.

[0056] After that, the amount of exit meandering is estimated in a state where the corrected difference between the left and right friction coefficients and the current wedge ratio change exist. The difference between the calculated (estimated) value of the difference between the left and right loads (weight or torque) acting on the edger device 50 or the difference between the left and right loads acting on the side guides 60 and the actual measured value is considered to be the effect of the difference between the left and right friction coefficients. In other words, the amount of deviation from the actual measured value of the amount of exit meandering occurs by the amount of correction of the difference between the left and right friction coefficients. For this reason, the assumed change in wedge ratio and the difference between the left and right friction coefficients are corrected so that the actual measured value and estimated value of the amount of exit meandering match in a state where the corrected difference between the left and right friction coefficients exist.

[0057] The values ​​of the wedge ratio change and the difference in the friction coefficient between the left and right sides are corrected and repeatedly calculated until the estimated values ​​and the actually measured values ​​match for the amount of delivery side meandering and the difference in the load (load or torque) acting on the edger device 50 between the left and right sides or the difference in the load acting on the side guide 60 between the left and right sides. Then, the values ​​of the wedge ratio change and the difference in the friction coefficient between the left and right sides when the estimated values ​​and the actually measured values ​​match for the amount of delivery side meandering and the difference in the load (load or torque) acting on the edger device 50 between the left and right sides or the difference in the load acting on the side guide 60 between the left and right sides are taken as the estimated values ​​of the wedge ratio change and the difference in the friction coefficient between the left and right sides for that rolling pass.

[0058] In this way, it is possible to estimate the wedge ratio change and the difference in the friction coefficient between the left and right sides in the rolling pass. Then, from the estimated wedge ratio change and the difference in the friction coefficient between the left and right sides, it is possible to separate the meandering occurring in the rolled sheet S into meandering caused by the wedge ratio change and meandering caused by the difference in the friction coefficient between the left and right sides.

[0059] (F) Separation based on wedge ratio change and left / right rolling load difference Furthermore, for example, by using the measured values ​​of the wedge ratio change and the difference in rolling load between the left and right sides as the rolling state of the rolled sheet S, the amount of meandering can be separated into the amount of meandering caused by the change in wedge ratio and the amount of meandering caused by the difference in the left and right friction coefficient. The difference in rolling load between the left and right sides is the difference between the rolling load on the working side and the rolling load on the driving side of the rolling mill. When there is a change in the wedge ratio or a difference in the left and right friction coefficient, a difference in rolling load between the left and right sides occurs. Therefore, in separation method (F), for example, the difference in rolling load between the left and right sides due to the change in wedge ratio is calculated, assuming that there is no difference in the left and right friction coefficient. Then, the calculated difference in rolling load between the left and right sides is compared with the measured value, and the difference between the two is considered to be due to the difference in the left and right friction coefficient, and the assumed value of the difference in the left and right friction coefficient is corrected.

[0060] In this way, the difference in the friction coefficient between the left and right sides can be estimated by repeatedly calculating the difference in the rolling load between the left and right sides until the estimated value and the measured value match. Then, from the estimated wedge ratio change and the difference in the friction coefficient between the left and right sides, the meandering occurring in the rolled sheet S can be separated into meandering caused by the change in the wedge ratio and meandering caused by the difference in the friction coefficient between the left and right sides.

[0061] (G) Separation based on the amount of meandering on the delivery side and the difference in rolling load between the left and right Furthermore, for example, the amount of meandering on the delivery side and the difference in rolling load between the left and right sides can be used as the rolling state of the rolled sheet S to separate the amount of meandering into the amount of meandering due to a change in the wedge ratio and the amount of meandering due to a difference in the left and right friction coefficient. Separation method (G) is a case in which the amount of meandering on the delivery side is used instead of the change in the wedge ratio used in separation method (F), and can be performed in the same manner as separation method (F). That is, the difference in the left and right friction coefficient and the change in the wedge ratio are assumed, and estimated values ​​of the amount of meandering on the delivery side and the difference in the rolling load between the left and right sides for the assumed difference in the left and right friction coefficient and the change in the wedge ratio are obtained. The difference in the left and right friction coefficient and the change in the wedge ratio can be estimated by performing a convergence calculation on the assumed difference in the left and right friction coefficient and the change in the wedge ratio until the estimated values ​​match the actually measured values. Then, based on the estimated change in the wedge ratio and the difference in the left and right friction coefficient, the meandering occurring in the rolled sheet S can be separated into the amount of meandering due to the difference in the left and right friction coefficient and the amount of meandering due to a change in the wedge ratio.

[0062] (H) Separation based on the amount of meandering on the entry side and the difference in rolling load between the left and right Furthermore, for example, the amount of meandering can be separated into the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides, using the amount of meandering on the entry side and the difference in rolling load between the left and right sides as the rolling state of the rolled sheet S. Separation method (H) is a case where the amount of meandering on the entry side is used instead of the change in the wedge ratio used in separation method (F), and may be carried out in the same manner as separation method (F).

[0063] That is, the difference between the left and right friction coefficients and the change in the wedge ratio are assumed, and the amount of entry meandering and the difference between the left and right rolling loads for the assumed difference between the left and right friction coefficients and the change in the wedge ratio are estimated. The difference between the left and right friction coefficients and the change in the wedge ratio can be estimated by performing a convergence calculation on the assumed difference between the left and right friction coefficients and the change in the wedge ratio until the estimated values ​​match the actually measured values. Then, from the estimated change in the wedge ratio and the difference between the left and right friction coefficients, the meandering occurring in the rolled sheet S can be separated into meandering caused by the difference between the left and right friction coefficients and meandering caused by the change in the wedge ratio.

[0064] (I) Separation based on the load on the edger or side guide and the difference in rolling load between the left and right sides Furthermore, for example, the amount of meandering can be separated into the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides, using the load on the edger device or side guide and the difference in rolling load between the left and right sides as the rolling state of the rolled sheet S. Separation method (I) is a case in which the load on the edger device or side guide is used instead of the change in the wedge ratio used in separation method (F), and can be carried out in the same way as separation method (F).

[0065] That is, the difference in the left-right friction coefficient and the change in the wedge ratio are assumed, and an estimated value is obtained for the difference in the left-right horizontal load or torque of the edger rolls 51, 52 of the edger device 50, or the load that the side guide 60 receives from the rolled sheet S, for the assumed difference in the left-right friction coefficient and change in the wedge ratio. The difference in the left-right friction coefficient and the change in the wedge ratio can be estimated by performing a convergence calculation on the assumed difference in the left-right friction coefficient and the change in the wedge ratio until the estimated value matches the actually measured value. Then, from the estimated change in the wedge ratio and the difference in the left-right friction coefficient, the meandering occurring in the rolled sheet S can be separated into meandering caused by the difference in the left-right friction coefficient and the meandering caused by the change in the wedge ratio.

[0066] By using these separation methods (A) to (I), it is possible to separate the meandering occurring in the rolled sheet S into the amount of meandering caused by a difference in the coefficient of friction between the left and right sides and the amount of meandering caused by a change in the wedge ratio. Note that in the above explanation, a case has been described in which the meandering occurring due to a difference in the coefficient of friction between the left and right sides and the amount of meandering caused by a change in the wedge ratio are separated using two factors as the rolling state of the rolled sheet S, namely, the change in the wedge ratio, the difference in the rolling load between the left and right sides, the amount of meandering on the entry side, the amount of meandering on the delivery side, and the difference in the load acting on the entry side edger device between the left and right sides or the difference in the load acting on the side guides between the left and right sides. However, the present invention is not limited to such an example, and the meandering may be separated using three or more factors.

[0067] Furthermore, the method of estimating the difference in the left-right friction coefficient or meandering caused by the difference in the left-right friction coefficient, and the change in wedge ratio or meandering caused by the difference in the wedge ratio using these factors is not limited to the examples described in the above separation methods (A) to (I). In other words, the above description illustrates a method of separating the meandering caused by the change in wedge ratio from the meandering caused by the difference in the left-right friction coefficient using convergence calculation, but the method of convergence calculation is not limited to the above example. Furthermore, for example, by determining the amount of meandering for various combinations of the change in wedge ratio and the difference in the left-right friction coefficient in advance, it is possible to separate the meandering caused by the change in wedge ratio from the meandering caused by the difference in the left-right friction coefficient without using convergence calculation.

[0068] Furthermore, in the separation methods (F) to (I) that use the difference in rolling load between the left and right sides as the rolling state of the rolled sheet S, the difference in rolling temperature between the left and right sides may be included as a factor. For example, in hot rolling, if a difference in rolling temperature between the left and right sides occurs, that is, if a temperature difference occurs between the work side and the drive side of the rolled sheet S, the hardness of the material (i.e., deformation resistance) differs between the work side and the drive side of the rolled sheet S, resulting in a difference in rolling load between the left and right sides. Therefore, the difference in rolling temperature between the left and right sides is taken into consideration as the rolling state of the rolled sheet S, and the difference in rolling load between the left and right sides caused by the difference in rolling temperature between the left and right sides is removed from the actually measured or estimated value of the difference in rolling load between the left and right sides. This makes it possible to accurately separate meandering caused by a change in wedge ratio from meandering caused by a difference in the left and right friction coefficient.

[0069] (S130, S140: Snake control) Returning to the explanation of Figure 6, in step S120, the meandering amount of the rolled sheet S is separated into the meandering amount due to the change in wedge ratio and the meandering amount due to the difference in the left and right friction coefficients, and the rolling device 1 is controlled to suppress each of the separated meandering amounts.

[0070] The control device 100 suppresses the amount of meandering caused by the change in wedge ratio through leveling control (S130). The control device 100 controls the reduction device 40 and adjusts the difference in the reduction amount of the rolled sheet S between the left and right sides so that the amount of meandering caused by the change in wedge ratio becomes zero.

[0071] The control device 100 also suppresses the amount of meandering caused by the difference in the left and right friction coefficients by controlling the difference in the left and right friction coefficients (S140). The control device 100 adjusts the difference in the left and right friction coefficients so that the amount of meandering caused by the difference in the left and right friction coefficients becomes zero. Possible ways to adjust the difference in the left and right friction coefficients are, for example, to change the amount or concentration of lubricant supplied by the lubricant supply devices 31, 32 between the work side and the drive side, or to change at least one of the surface roughness of the work rolls 11, 12 or the surface texture of the rolled sheet S between the work side and the drive side.

[0072] Increasing the amount of lubricant supplied by the lubricant supply devices 31, 32 reduces the coefficient of friction between the work rolls 11, 12 and the rolled sheet S. In addition, increasing the concentration of the lubricant supplied by the lubricant supply devices 31, 32 reduces the coefficient of friction between the work rolls 11, 12 and the rolled sheet S. Therefore, in step S130, the difference Δμ between the left and right friction coefficients is calculated. DW (=μ DS -μ WS ), it is possible to increase the lubricant supply rate or concentration supplied to the work side (WS) of the work rolls 11, 12, for example. Alternatively, it is possible to decrease the lubricant supply rate or concentration supplied to the drive side (DS) of the work rolls 11, 12, for example.

[0073] In the present invention, the lubricant supply amount or concentration is not limited to being changed only on the work side or the drive side of the roll barrel length, but may be changed at multiple positions along the roll barrel length. DW (=μ DS -μ WS ), the amount of lubricant supplied to the work side (WS) of the work rolls 11 and 12 can be increased or the concentration can be increased to increase the work side friction coefficient μ WS The driving side friction coefficient μ is reduced by reducing the amount of lubricant supplied to the driving side (DS) of the work rolls 11 and 12 or by lowering the concentration. DS may be increased.

[0074] The coefficient of friction between the work rolls 11, 12 and the sheet S to be rolled can also be adjusted by changing the surface roughness of the work rolls 11, 12 or the surface properties of the sheet S to be rolled. For example, by grinding the surfaces of the work rolls 11, 12 using a roll grinding device (not shown) installed in the rolling mill 10, the surface roughness of the work rolls 11, 12 can be reduced, thereby reducing the coefficient of friction between the work rolls 11, 12 and the sheet S to be rolled. Therefore, in step S140, the difference Δμ between the left and right friction coefficients is calculated. DW (=μ DS -μ WS ), for example, the roll surfaces of the work side (WS) of the work rolls 11 and 12 are ground to increase the work side friction coefficient μ WS On the other hand, in step S140, the difference Δμ DW (=μ DS -μ WS ) is desired to be smaller, for example, the roll surfaces of the driving side (DS) of the work rolls 11 and 12 are ground to reduce the driving side friction coefficient μ DS can be made smaller.

[0075] Similarly, by improving the surface quality of the rolled sheet S by increasing the pressure and flow rate of the descaling water in the descaling device (not shown) installed upstream of the rolling mill 10, it is possible to reduce the coefficient of friction between the work rolls 11, 12 and the rolled sheet S. By applying this principle, the difference Δμ DW (=μ DS -μ WS ) can be changed.

[0076] In step S140, the control device 100 generates, from the amount of meandering caused by the difference in the coefficient of friction between the left and right sides, control information such as the amount of lubricant supplied, the position at which the concentration is changed and the amount of lubricant supplied and the concentration after the change, the position and amount of grinding for the surfaces of the work rolls 11, 12, or the descaling conditions for the rolled sheet S. The control device 100 then outputs the control information to the lubricant supply devices 31, 32, the roll grinding device, or the descaling device, and drives these devices to adjust the difference in the coefficient of friction between the left and right sides.

[0077] In this case, it is preferable to obtain in advance the relationship between the amount of lubricant supplied, the concentration, the surface roughness of the work rolls 11 and 12, or the descaling conditions, and the amount of meandering of the rolled sheet S. However, even if these relationships are unknown, the amount of lubricant supplied, the concentration, the amount of surface grinding of the work rolls 11 and 12, or the descaling conditions may be adjusted by referring to the amount of meandering caused by the difference in the coefficient of friction between the left and right sides.

[0078] As an example of the method for controlling meandering of a rolled sheet according to one embodiment of the present invention, a case where meandering is suppressed by different meandering controls depending on the cause of meandering (control example 1) has been described above.

[0079] (Control Example 2) When meandering of the rolled sheet S is suppressed only by leveling control Next, a case where meandering of the rolled sheet S is suppressed only by leveling control (control example 2) will be described in detail with reference to Fig. 7 as an example of the method for controlling meandering of the rolled sheet S according to this embodiment. Fig. 7 is a flowchart showing a case where meandering of the rolled sheet S is suppressed only by leveling control as an example of the method for controlling meandering of the rolled sheet S according to this embodiment. In the description of Fig. 7, detailed description of the same processes as in Fig. 6 will be omitted.

[0080] Leveling control is relatively easy to implement because the screw down devices 40 are independent on the left and right sides of the work side and drive side of the rolling mill 10, whereas left-right friction coefficient difference control is relatively difficult to implement because it requires, for example, a mechanism that can set and control the concentration and injection amount of lubricant to different values ​​on the left and right. Therefore, in control example 2, left-right friction coefficient difference control is not performed, and the meandering amount of the rolled sheet S to be controlled (i.e., the sum of the meandering amount due to a change in the wedge ratio and the meandering amount due to the difference in friction coefficient between the left and right sides) is brought close to zero by leveling control alone.

[0081] Here, leveling control has the advantage that it is relatively easy to implement, as mentioned above. However, while meandering caused by changes in the wedge ratio is in the same direction at the entry side of the rolling mill (the tail end of the rolled sheet S) and the exit side of the rolling mill (the front end of the rolled sheet S), meandering caused by a difference in the left-right friction coefficient is in the opposite direction. For this reason, if an attempt is made to suppress meandering at the exit side of the rolling mill (the front end of the rolled sheet S) caused by a difference in the left-right friction coefficient using leveling control while maintaining the same rolling conditions, very large meandering will occur at the entry side of the rolling mill (the tail end of the rolled sheet S). In order to appropriately suppress meandering of the rolled sheet S, it is important to identify the amount of meandering caused by each factor before implementing leveling control.

[0082] (S210: Meandering amount measurement) As shown in Fig. 7, first, the amount of meandering of the sheet S to be rolled is measured (S210). Measurement of the amount of meandering of the sheet S to be rolled may be performed in the same manner as step S110 in Fig. 6. That is, for example, an image of the sheet S to be rolled may be taken with a CCD camera, and the edge position of the sheet S to be rolled may be detected by image processing, and the amount of meandering may be calculated. Measurement of the amount of meandering may be performed at least on either the entry side or exit side of the rolling mill 10, and the measurement position may be determined depending on a method of separating the amount of meandering depending on the cause of occurrence, which will be described later. The measured amount of meandering of the sheet S to be rolled is output to the control device 100.

[0083] (S220: Separation of meandering amount according to the cause) Next, the control device 100 separates the amount of meandering measured in step S210 into meandering caused by a change in the wedge ratio and meandering caused by a difference in the coefficient of friction between the left and right sides based on the rolling state of the rolled sheet S (S220). The separation of the amount of meandering according to the cause of occurrence may be performed in the same manner as step S120 of FIG. 6. That is, based on the rolling state of the rolled sheet S represented by values ​​of factors related to the occurrence of meandering (e.g., change in wedge ratio, difference in rolling load between the left and right sides, amount of meandering on the entry side, amount of meandering on the delivery side, difference in load acting on the entry side edger device between the left and right sides, or difference in load acting on the side guides between the left and right sides), the meandering occurring in the rolled sheet S is separated into meandering caused by a change in the wedge ratio and meandering caused by a difference in the coefficient of friction between the left and right sides based on at least two or more factors. Specifically, the processing of step S220 may be performed using the separation methods (A) to (I) described above.

[0084] (S230: Snake control) Then, in step S220, the meandering amount of the rolled sheet S is separated into the meandering amount caused by the change in wedge ratio and the meandering amount caused by the difference in the coefficient of friction between the left and right sides, and the rolling device 1 is controlled by leveling control based on the separated meandering amounts so as to suppress the meandering amount of the rolled sheet S (S230). There are, for example, the following two methods as a method for bringing the meandering amount of the rolled sheet S (i.e., the sum of the meandering amount caused by the change in wedge ratio and the meandering amount caused by the difference in the coefficient of friction between the left and right sides) close to zero by leveling control alone.

[0085] (1) A method of changing the amount of leveling control at the leading and trailing ends of the rolled sheet S. For example, the leveling control amount at the front end of the rolled sheet S and the leveling control amount at the tail end of the rolled sheet S may be changed depending on the amount of meandering due to each factor, so that the amount of meandering of the rolled sheet S (i.e., the sum of the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides) approaches zero. Specifically, when the front end of the rolled sheet S is bitten (hereinafter also referred to as "when the front end is threaded"), leveling control is performed so that the amount of meandering at the delivery side of the rolling mill approaches zero, and when the tail end of the rolled sheet S passes through the rolling mill (hereinafter also referred to as "when the tail end is threaded"), leveling control is performed so that the meandering at the entry side of the rolling mill approaches zero.

[0086] When the leading edge of the rolled sheet S is threaded, meandering on the delivery side (i.e., the downstream side of the rolling mill) becomes an issue in threading, while when the tail end of the rolled sheet S is threaded, meandering on the entry side (i.e., the upstream side of the rolling mill) becomes an issue in threading. This is because, for example, when the leading edge of the rolled sheet S is threaded, the length of the rolled sheet S downstream of the rolling mill is still short and the constraint due to its own weight is small, so it can meander easily, whereas when the leading edge of the rolled sheet S is threaded, the length of the rolled sheet S upstream of the rolling mill is long and it cannot meander easily due to constraints such as its own weight. For this reason, it is preferable to perform leveling control so as to suppress meandering on the delivery side (i.e., the downstream side of the rolling mill) when the leading edge is threaded, and to suppress meandering on the entry side (i.e., the upstream side of the rolling mill) when the tail end is threaded.

[0087] As a specific example, consider a case where the entry-side meandering amount is 30 mm, broken down as follows: 60 mm due to a change in the wedge ratio; −30 mm due to a difference in the coefficient of friction between the left and right sides; and 150 mm due to a change in the delivery-side meandering amount, broken down as follows: 80 mm due to a change in the wedge ratio; and 70 mm due to a difference in the coefficient of friction between the left and right sides. Even if leveling control is performed to suppress only the meandering caused by the change in the wedge ratio, the meandering caused by the difference in the coefficient of friction between the left and right sides (−30 mm on the entry side and 70 mm on the delivery side) remains. Therefore, a leveling control amount is applied during front-end threading to suppress the delivery-side meandering amount by 150 mm, and a leveling control amount is applied during tail-end threading to suppress the entry-side meandering amount by 30 mm. Note that in the middle portion (between the front and tail ends) of the rolled sheet S, for example, a leveling control amount is applied to bring the change in the wedge ratio close to zero.

[0088] (2) A method of controlling the leveling amount to a constant value over the entire length of the rolled sheet S. In the above-mentioned method of changing the leveling control amount between the front and rear ends of the rolled sheet S, the wedge of the rolled sheet S to be controlled does not remain constant over the entire length. For this reason, if the leveling control amount is changed when the front end, middle section, and tail end of the rolled sheet S are threaded, meandering may occur unless the leveling control amount is appropriately applied to subsequent passes or subsequent rolling mills when the front end, middle section, and tail end of the rolled sheet S are threaded. For this reason, there is a possibility that control that keeps the leveling control amount constant over the entire length is preferred.

[0089] Therefore, the meandering amount of the rolled sheet S may be separated into the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides. Then, a leveling control amount may be applied based on the amount of meandering caused by each factor so that the wedge of the rolled sheet S to be controlled remains constant over its entire length, thereby bringing the amount of meandering of the rolled sheet S (i.e., the sum of the amount of meandering caused by a change in the wedge ratio and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides) closer to zero. Specifically, a leveling control amount is applied so that the absolute value of the sum of the amount of meandering at the entry side of the rolling mill and the amount of meandering at the exit side of the rolling mill approaches zero. For example, a leveling control amount may be applied so that the absolute value of the sum of the amount of meandering at the exit side when the leading edge of the rolled sheet S is threaded and the amount of meandering at the entry side when the tail edge is threaded is minimized. This control keeps the wedge of the rolled sheet S constant over its entire length.

[0090] In the example shown in (1) above, it is predicted that if the entry-side meandering amount is changed by 30 mm with a constant leveling control amount over the entire length, the delivery-side meandering amount will change by 40 mm. Furthermore, if only the meandering caused by the change in the wedge ratio is suppressed by applying a constant leveling control amount over the entire length, it is predicted that meandering caused by the difference in the friction coefficient between the left and right sides (-30 mm on the entry side, 70 mm on the delivery side) will remain. From this, the relationship between the delivery-side meandering amount when the leading edge threading and the entry-side meandering amount when the tail edge threading for multiple leveling control amounts (constant leveling control amounts over the entire length) can be determined in advance, and from this relationship, it is possible to determine the leveling control amount that minimizes the absolute value of the sum of the delivery-side meandering amount when the leading edge threading and the entry-side meandering amount when the tail edge threading of the rolled sheet S.

[0091] For example, in this example, when a leveling control amount was applied that minimized the absolute value of the sum of the delivery meandering amount when the leading edge is threaded and the entry-side meandering amount when the tail edge is threaded, the delivery meandering amount when the leading edge is threaded was 50 mm, and the entry-side meandering amount when the tail edge is threaded was -50 mm. By performing this leveling control, it is possible to optimize the suppression of the delivery meandering amount when the leading edge of the rolled sheet S is threaded and the entry-side meandering amount when the tail edge is threaded, under the constraint that the leveling control amount must be constant over the entire length.

[0092] As an example of the method for controlling meandering of a rolled sheet S according to one embodiment of the present invention, a case where meandering of the rolled sheet S is suppressed only by leveling control (control example 2) has been described above.

[0093] Thus, according to the method for controlling the meandering of a rolled sheet S according to one embodiment of the present invention, the meandering or camber of the rolled sheet S can be appropriately suppressed by performing at least one of leveling control and left-right friction coefficient difference control depending on the factor causing the meandering or camber of the rolled sheet S.

[0094] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0095] For example, in the above description, the amount of meandering caused by a change in the wedge ratio during rolling and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides are determined based on the actual meandering data during rolling, and the rolling control amount for the rolled material is determined based on this. However, the present invention is not limited to this example. For example, the rolling control amount for the next rolled sheet may be determined based on the amount of meandering caused by a change in the wedge ratio during rolling and the amount of meandering caused by the difference in the coefficient of friction between the left and right sides determined during rolling. That is, the rolled sheet to be controlled may be the same as the rolled sheet when the amount of meandering caused by each cause of meandering is determined, or it may be the rolled sheet to be rolled after the rolled sheet when the amount of meandering caused by each cause of meandering is determined. Alternatively, for example, the rolling control amount for the next rolled sheet may be determined assuming that the difference in the coefficient of friction between the left and right sides of the rolled sheet when the amount of meandering caused by each cause of meandering is determined will be maintained in the next rolled sheet. [Explanation of symbols]

[0096] 1. Rolling equipment 10. Rolling Mill 11 Upper work roll 12 Lower work roll 20 Meandering meter 31, 32 Lubricant supply device 40 Screw down device 50 Edger device 51, 52 Edger roll 60 Side guide 61, 62 Guide 100 control device

Claims

1. Based on the rolling state of the rolled sheet, the meandering amount of the rolled sheet is separated into a meandering amount caused by a change in the wedge ratio and a meandering amount caused by a difference in the friction coefficient between the left and right sides, A method for controlling the meandering of a rolled sheet, in which the meandering of the rolled sheet to be controlled is suppressed by at least one of leveling control and left-right friction coefficient difference control, which controls the difference between the left and right friction coefficients, based on the amount of meandering due to each cause.

2. 2. A method for controlling the meandering of a rolled sheet according to claim 1, wherein at least one of the leveling control for reducing the amount of meandering caused by the change in the wedge ratio to zero and the left-right friction coefficient difference control for reducing the amount of meandering caused by the left-right difference in the friction coefficient to zero is performed to suppress meandering of the rolled sheet to be controlled.

3. 2. The method for controlling meandering of a rolled sheet according to claim 1, wherein the control of the difference in friction coefficient between the left and right rolls comprises adjusting at least one of the concentration and supply amount of lubricating oil injected between the work rolls and the rolled sheet.

4. 2. The method for controlling meandering of a rolled sheet according to claim 1, wherein the control of the difference in friction coefficient between the left and right sides comprises adjusting at least one of the roughness of the work rolls and the surface quality of the rolled sheet.

5. 2. The method for controlling meandering of a rolled sheet according to claim 1, wherein the amount of meandering of the controlled rolled sheet is made to approach zero by only the leveling control.

6. 6. A method for controlling the meandering of a rolled plate as described in claim 5, wherein the leveling control amount at the front end of the rolled plate to be controlled and the leveling control amount at the tail end of the rolled plate to be controlled are changed according to the amount of meandering caused by the change in the wedge ratio and the amount of meandering caused by the difference in the left and right friction coefficients.

7. 6. A method for controlling the meandering of a rolled plate according to claim 5, wherein a leveling control amount is applied based on the amount of meandering caused by the change in the wedge ratio and the amount of meandering caused by the difference in the friction coefficient between the left and right sides, so that the wedge is constant over the entire length of the rolled plate to be controlled.

8. 8. The method for controlling meandering of a rolled sheet according to claim 1, wherein the meandering in the rolling pass is separated based on at least two or more factors of the rolling state of the rolled sheet, including a change in wedge ratio in the rolling pass, a difference in rolling load between the left and right, an amount of entry-side meandering, an amount of exit-side meandering, and a difference in load acting on an entry-side edger device between the left and right, or a difference in load acting on a side guide between the left and right.

9. 9. The method for controlling meandering of a rolled sheet according to claim 8, wherein when the factor representing the rolling state of the rolled sheet includes the difference in rolling load between the left and right sides, the factor also includes the difference in temperature between the left and right sides of the rolled sheet, and the meandering is separated.

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