Meandering control method and meandering control device

Abstract

To reduce thickness defects at a tail end part of a rolled material, reduce a meandering amount of the rolled material, and suppress occurrence of drawing, in continuous rolling.SOLUTION: There is provided a meandering control method of a rolled material for controlling meandering a rolled material in an M-th stand (1≤M≤N) in rolling of a rolled material by N pieces (N is natural number) of rolling stands which controls at least any one of a roll gap of the M-th stand, roll speed, a lubricant supply amount, a bending force, a roll cross angle, a roll shift amount and a roll crown so that a first kind of parallel rigidity that is an index indicating a degree of meandering of the rolled material when a tail end part of the rolled material passes through the M-th stand decreases while passing the rolled material through the stand at any time.SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] The present invention relates to a meandering control method and a meandering control device for controlling the meandering of a rolled material. [Background technology]

[0002] For example, in continuous rolling, where a material to be rolled (e.g., steel) passes through multiple rolling stands in succession, the center of the material's width may shift from the mill center (the center position of the rolling stand in the width direction, i.e., the center position in the direction of the work roll's rotation axis), causing the material to move toward the end of the work roll, a phenomenon known as meandering. This meandering can reduce the flatness of the material, potentially leading to a decline in product quality. Furthermore, if the amount of meandering is significant, the tail end of the material may come into contact with the side guide and bend, resulting in the material being trapped in a double-folded state by the subsequent rolling stand, a defect known as "squeezing." When squeezing occurs, the bent material scratches the surface of the work roll, necessitating the production line being stopped for maintenance work, such as inspection, maintenance, or replacement of the work roll, which can reduce the production line's operating rate.

[0003] In continuous rolling, when the material to be rolled is bitten between the work rolls of both the front and rear rolling stands, tension acts on the material in the longitudinal direction, and the material is constrained, making it difficult for large meandering to occur. Large meandering that causes reduction is likely to occur when the tail end of the material to be rolled leaves the front rolling stand. It has also been known that the greater the reduction ratio in the rolling stands, the more likely meandering is to occur.

[0004] Therefore, for example, Patent Document 1 listed below discloses a technology for detecting the passage (tail clearance) of the tail end of a rolled material in a previous (N-1th) rolling stand, and at the timing when the tail clearance is detected, opening the reduction position of the work rolls of the next (Nth) rolling stand (i.e., the roll gap between the upper and lower work rolls). According to the technology described in Patent Document 1, when a region of a predetermined length including the tail end of the rolled material (hereinafter also referred to as the tail end portion) passes through the Nth rolling stand, the reduction rate in the Nth rolling stand becomes smaller, and therefore the amount of meandering of the rolled material can be reduced.

[0005] Furthermore, Patent Document 2 discloses a method for preventing the rolled material from being squeezed due to interference with the side guides by narrowing the ends of the work rolls in the barrel length direction using a roll bending device when the rear end of the rolled material passes through, thereby suppressing movement of the rolled material toward the plate end. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 55-161505 [Patent Document 2] Japanese Patent Application Laid-Open No. 58-145303 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the methods of controlling meandering by opening the roll gap or applying a bending force when the tail end of the rolled material passes through the rolling stand, as in the techniques described in Patent Documents 1 and 2, there are cases where the amount of control is too small, resulting in narrowing, or where the amount of control is too large, resulting in the tail end of the rolled material not being rolled to the desired thickness or shape, thereby reducing the production yield.

[0008] Furthermore, as a result of investigations by the present inventors, it was found that the amount of meandering does not necessarily decrease even when the reduction ratio is reduced, i.e., when the roll gap is increased, depending on other rolling conditions such as bending force, roll cross angle, roll shift amount, and roll crown. Thus, when an attempt is made to control the meandering of the rolled material by adjusting the roll gap, the amount of meandering may instead increase depending on the rolling conditions.

[0009] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a meandering control method and a meandering control device that can reduce thickness defects at the tail end of the rolled material, reduce the amount of meandering of the rolled material, and suppress the occurrence of constriction. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a method for controlling the meandering of a rolled material in an Mth stand (1≦M≦N) when the material is rolled using N rolling stands (N is a natural number), wherein the method controls at least one of the roll gap, roll speed, amount of lubricant supplied, bending force, roll cross angle, roll shift amount, and roll crown of the Mth stand as needed while the material is being passed through, so that the first type parallel stiffness, which is an index showing the degree of meandering of the material, becomes smaller when the tail end of the material passes through the Mth stand.

[0011] In addition, in this meandering control method, the first type parallel stiffness is a constant that represents the wedge amount when the center of the rolled material in the plate width direction is shifted by a unit amount from the mill center while the line load applied to the rolled material from the work rolls is constant in the plate width direction of the rolled material, and may depend on at least the line load, bending force, roll cross angle, roll shift amount, and roll crown.

[0012] Furthermore, in the meandering control method, the rolling conditions in the Mth stand are constantly changing, and a current value of the first type parallel stiffness before the rolling conditions are changed and a predicted value of the first type parallel stiffness after the rolling conditions are changed are calculated, and at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown may be controlled to be at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown included in the rolling condition corresponding to the smaller value of the current value or the predicted value of the first type parallel stiffness.

[0013] Furthermore, in the meandering control method, a changeable range of at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown may be calculated based on constraint conditions including at least one of equipment constraint conditions and constraint conditions related to shape control of the rolled material, and at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown may be controlled so that the first type parallel stiffness is minimized within the changeable range.

[0014] In the meandering control method, the tail end portion may be a region from the tail end of the material to the portion where it is bitten into the Mth stand.

[0015] Furthermore, in order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a meandering control device for controlling the meandering of a rolled material at an Mth stand (1≦M≦N) in rolling of the rolled material using N rolling stands (N is a natural number), the meandering control device comprising: a drive control unit that controls drive of at least one of the following devices as needed during the threading of the rolled material: a screw down device that adjusts the roll gap of the Mth stand; a mill motor that adjusts the roll speed of the Mth stand; a lubricant supply device that adjusts the amount of lubricant supplied to the Mth stand; a bending device that adjusts the bending force; a roll chock drive device that adjusts the roll cross angle of the Mth stand; a roll shift device that adjusts the amount of roll shift of the Mth stand; and a roll crown changing device that adjusts the roll crown of the Mth stand, so that the first type parallel stiffness, which is an index showing the degree of meandering of the rolled material, becomes smaller when the tail end of the rolled material passes through the Mth stand.

[0016] In addition, in the meandering control device, the first type parallel stiffness is a constant that represents the wedge amount when the center of the rolled material in the plate width direction is shifted by a unit amount from the mill center while the line load applied to the rolled material from the work roll is constant in the plate width direction of the rolled material, and may depend on at least the line load, bending force, roll cross angle, roll shift amount, and roll crown.

[0017] Moreover, the meandering control device may further include a first type parallel stiffness calculation unit that calculates a current value of the first type parallel stiffness before the rolling conditions are changed and a predicted value of the first type parallel stiffness after the rolling conditions are changed, and in a situation where the rolling conditions in the Mth stand are constantly changing, the drive control unit may control the drive of at least one of the screw down device, mill motor, lubricant supply device, bending device, roll chock drive device, roll shift device and roll crown changing device so that at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount and roll crown becomes at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount and roll crown included in the rolling condition corresponding to the smaller value of the current value or the predicted value of the first type parallel stiffness.

[0018] In addition, the meandering control device may further include a changeable range calculation unit that calculates a changeable range for at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown based on constraint conditions including at least one of equipment constraint conditions and constraint conditions related to shape control of the rolled material, and the drive control unit may control the drive of at least one of the screw down device, mill motor, lubricant supply device, bending device, roll chock drive device, roll shift device, and roll crown changing device so that the first type parallel stiffness is minimized within the changeable range.

[0019] In the meandering control device, the tail end portion may be a region from the tail end of the material to the portion where it is bitten into the Mth stand. [Effects of the Invention]

[0020] As described above, according to the present invention, it is possible to reduce thickness defects at the tail end of the rolled material, reduce the amount of meandering of the rolled material, and suppress the occurrence of reduction. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram schematically illustrating the state of a deformation region in a rolled material in which meandering and camber have occurred. [Figure 2] FIG. 10 is a diagram showing deformation of a rolling stand when a material to be rolled meanders. [Figure 3] FIG. 10 is a diagram showing the distribution of line loads. [Figure 4] FIG. 10 is a graph showing the relationship between line load and first-type parallel stiffness E. [Figure 5] FIG. 10 is a graph showing the relationship between line load and first-type parallel stiffness E. [Figure 6] FIG. 2 is a graph showing the relationship between line load and first-type parallel stiffness under certain rolling conditions. [Figure 7] FIG. 7 is a graph showing the relationship between the line load and the first kind of parallel stiffness under rolling conditions different from those in FIG. 6. [Figure 8] FIG. 1 is a graph showing the relationship between bending force and first-type parallel stiffness under certain rolling conditions. [Figure 9] 9 is a graph showing the relationship between bending force and first type parallel stiffness under rolling conditions different from those in FIG. 8. FIG. [Figure 10] FIG. 2 is a graph showing the relationship between the roll cross angle and the first type parallel stiffness under certain rolling conditions. [Figure 11] 11 is a graph showing the relationship between the roll cross angle and the first kind of parallel stiffness under rolling conditions different from those in FIG. 10. FIG. [Figure 12] FIG. 2 is a graph showing the relationship between the amount of roll shift and the first type parallel stiffness under certain rolling conditions. [Figure 13] 13 is a graph showing the relationship between the amount of roll shift and the first kind of parallel stiffness under rolling conditions different from those in FIG. 12. FIG. [Figure 14] FIG. 2 is a graph showing the relationship between roll crown and first-type parallel stiffness under certain rolling conditions. [Figure 15] FIG. 15 is a graph showing the relationship between roll crown and first kind of parallel stiffness under rolling conditions different from those in FIG. [Figure 16]FIG. 1 is a diagram showing an example of the configuration of a rolling stand according to a first embodiment. [Figure 17] FIG. 2 is a block diagram showing an example of the functional configuration of a control device that controls the operation of a rolling stand according to the first embodiment. [Figure 18] 4 is a flowchart showing an example of a processing procedure of a meandering control method according to the first embodiment, showing a case where a roll gap is used as a control parameter. [Figure 19] FIG. 10 is a schematic diagram illustrating measurement timing of control data. [Figure 20] 4 is a flowchart showing an example of a processing procedure of a meandering control method according to the first embodiment, showing a case where a roll speed is used as a control parameter. [Figure 21] 4 is a flowchart showing an example of a processing procedure of a meandering control method according to the first embodiment, showing a case where a lubricant supply amount is used as a control parameter. [Figure 22] FIG. 10 is a block diagram showing an example of the functional configuration of a control device that controls the operation of a rolling stand according to a second embodiment. [Figure 23] 10 is a flowchart showing an example of a processing procedure of a meandering control method according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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.

[0023] In the following description, a preferred embodiment of the present invention will be described in terms of a case where meandering in a finishing tandem rolling mill in hot rolling is controlled. In first and second embodiments of the present invention described later, in order to control meandering, when the tail end of the rolled material passes through at least one of the rolling stands constituting the finishing tandem rolling mill, at least one control parameter of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown of the rolling stand is controlled. A finishing tandem rolling mill may be composed of, for example, seven rolling stands, but the rolling stand to be controlled may be any rolling stand other than the frontmost rolling stand. Furthermore, the rolling stand to be controlled may be one or more. In the first and second embodiments, for example, when it is detected that the tail end of the rolled material has passed through a rolling stand installed in a stage before the rolling stand to be controlled, control of the control parameters is started in the rolling stand to be controlled.

[0024] (1.Class 1 parallel stiffness) In the first and second embodiments of the present invention described below, rolling is performed using a physical quantity called first-class parallel stiffness as a control target. The first-class parallel stiffness is a physical quantity that serves as an index showing the degree of meandering of the material to be rolled, and it is known that the smaller the value of the first-class parallel stiffness, the more the meandering of the material to be rolled during rolling is suppressed. In addition, the first-class parallel stiffness is a physical quantity that depends on the line load applied to the material to be rolled from the work rolls in the rolling stand, the bending force of the work rolls, the roll cross angle, the amount of roll shift, and the roll crown.

[0025] Therefore, in the first and second embodiments, control parameters that affect the first-type parallel stiffness are controlled during rolling so that the value of the first-type parallel stiffness becomes smaller. The control parameters include the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown.

[0026] The roll gap, roll speed, and lubricant supply rate are control parameters for controlling the line load. The roll gap can be controlled by changing the reduction position of the work rolls. The roll speed is a control element that changes the tension of the rolled material between the rolling stands, and can be controlled by a mill motor that adjusts the roll speed of the rolling stand to be controlled or the rolling stands before and after it. The lubricant supply rate is a control element that changes the coefficient of friction between the work roll and the rolled material, and can be controlled by adjusting the lubricant supply rate using a lubricant supply device installed in the rolling stand to be controlled.

[0027] The bending force, roll cross angle, roll shift amount, and roll crown are control parameters for changing the mechanical plate crown. Here, mechanical plate crown is defined as the plate crown at the plate crown definition point, which is achieved when the load distribution in the width direction between the rolled material and the work rolls is uniform. The bending force can be controlled by a bending device installed in the rolling stand to be controlled. The roll cross angle can be controlled if the rolling stand is, for example, a pair-cross rolling mill, and can be changed by moving the roll chocks. The roll shift amount can be controlled if the rolling stand is capable of shifting the work rolls or intermediate rolls in the axial direction, such as a CVC (continuous variable crown) rolling mill or a six-high rolling mill. The roll crown can be controlled if the rolling stand is capable of changing the roll crown of the work rolls, such as a VC (variable crown) rolling mill. The roll crown can be changed, for example, by using variable crown rolls as work rolls, which have hydraulic expansion chambers located inside the center of the roll barrel length.

[0028] By controlling the control parameters that affect this first-class parallel stiffness, it becomes possible to further reduce the amount of meandering of the rolled material.

[0029] Before describing in detail the configuration of the meandering control method and the meandering control device according to this embodiment, the first-type parallel stiffness and the relationship between the first-type parallel stiffness and the meandering amount of the rolled material will be described. The results of the inventors' investigation into the dependency of the first-type parallel stiffness on the above control parameters will also be described.

[0030] Here, the first-class parallel stiffness is a constant that represents the difference in thickness (wedge amount) in the width direction when the center of the rolled material in the width direction is displaced by a unit amount from the mill center (the center of the rolling stand in the width direction (the center in the direction of the rotation axis of the work rolls)) while the line load applied to the rolled material from the work rolls is constant in the left-right direction (the width direction of the rolled material). Therefore, below, we first derive the relationship between the meandering amount and the wedge amount, and then we derive the relationship between the first-class parallel stiffness and the wedge amount. Finally, by combining these relationship formulas, we derive the relationship between the meandering amount and the first-class parallel stiffness.

[0031] (1-1. Derivation of the equation relating meandering amount and wedge amount) First, we derive the equation for the relationship between the amount of meandering and the amount of wedge. As shown in Figure 1, consider a model in which meandering and camber occur in the rolled material in a specified region including directly below the work roll. Figure 1 is a diagram that schematically shows the state of the deformation region in a rolled material in which meandering and camber occur. In Figure 1, the x and y coordinates are set in a horizontal plane (a plane parallel to the surface of the rolled material), with the origin O being the center of the barrel of the work roll. The direction parallel to the rotation axis of the work roll (left and right direction) is defined as the y axis.

[0032] The movement of the rolled material can be considered as rigid body movement in a horizontal plane. If the position of a specific point in the rolled material at time t is defined as x and y, the velocities v and u of that point in the x and y directions can be expressed by the following equations (1) and (2).

[0033]

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[0034]

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[0035] Here, the feed direction of the rolled material directly below the work roll is assumed to be the same as the circumferential direction of the work roll. ω(t) and V(t) are the angular velocity of the rolled material in the horizontal plane and its velocity at the origin, respectively. ω(t) and V(t) are functions of time only, but because the rolled material deforms at x=0, they can generally be different functions at the entry and exit sides. Therefore, hereinafter, when distinguishing between the entry and exit sides, ω(t) and V(t) will be represented by different symbols. That is, the angular velocity and velocity of the rolled material at the entry side will be ω1(t) and v1(t), respectively, and the angular velocity and velocity of the rolled material at the exit side will be ω2(t) and v2(t), respectively.

[0036] Now, let us take a certain time (for example, the time when the rolling stand bites into the leading edge of the rolled material) as the reference (t=0), and express the centerline shape of the entry-side rolled material in the width direction at t=0 as y0=f0(x0)(x0≦0) using the coordinates (x0, y0) of a point on the centerline. The position of point (x0, y0) on the centerline at time t is given by the following equations (3) and (4) by integrating the above equations (1) and (2).

[0037]

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[0038]

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[0039] Here, assuming that the left-right asymmetry of meandering, camber, etc. is a small first-order amount, it is sufficient to use the value of the formula (3) obtained by approximating the formula (3) to the zeroth order as x in the formula (4). Therefore, x in the formula (4) is regarded as x(t) = x0 + v1t. By substituting this x(t) = x0 + v1t into the formula (4), the following formula (5) is obtained.

[0040]

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[0041] Furthermore, by eliminating x0 and y0 from the above equation (5) and rearranging it, we can obtain the following equation (6) which represents the shape of the center line on the entry side at time t.

[0042]

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[0043] In the above equation (6), the first term on the right-hand side represents the effect of parallel movement of the rolled material in the x direction, the second term represents the effect of rotation of the rolled material in the horizontal plane, and the third term represents the effect of parallel movement of the rolled material in the y direction.

[0044] Amount of meandering of the rolled material y c is defined by the y-coordinate of the strip center line directly below the work roll (x=0), so by substituting x=0 into the above equation (6), the following equation (7) is obtained. The following equation (7) expresses the relationship between the amount of meandering and the rotational speed on the inlet side.

[0045]

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[0046] The above equation (7) is equivalent to the differential equation expressed by the following equation (8), except for the initial condition.

[0047]

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[0048] Here, the elongation λ of the rolled material can be expressed as λ = v2 / v1. The difference between the elongation λ on the work side and the elongation λ on the drive side (left-right difference in elongation λ) is λ df If the difference in thickness between the left and right sides and the change in thickness ratio (wedge ratio) from the entry side to the exit side (wedge ratio change) is ΔΨ and the sheet width is b, the following equation (9) can be obtained from the law of conservation of volume in the rolled material.

[0049]

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[0050] Furthermore, since the forward rate and backward rate of the rolled material are approximately proportional, it is assumed that the relationship expressed by the following formula (10) holds.

[0051]

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[0052] From the above equations (9) and (10), the relationship expressed by the following equation (11) is obtained.

[0053]

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[0054] By combining the above equations (8) and (11), the meandering amount y c and the wedge ratio change ΔΨ can be obtained.

[0055] (1-2. Derivation of the relationship between the first-class parallel stiffness and the wedge amount) Next, we will derive the relational expression between the first-class parallel stiffness and the wedge amount. As shown in Figure 2, we consider a model in which the rolling stand is deformed due to the meandering of the material to be rolled. Figure 2 is a diagram showing how the rolling stand deforms when the material to be rolled meanders. The model shown in Figure 2 is known as the parallel stiffness model of the rolling stand.

[0056] As shown in Figure 2, when the rolled material meanders, the rolling stand deforms asymmetrically, causing a wedge in the rolled material. Here, points A and A' in Figure 2 are the set points for the reduction position, points B and B' are the positions of the axial centers of the backup rolls at the reduction point, Σ is the distance (BB') between the axial centers of the upper and lower backup rolls at the reduction point, a is the distance between the left and right reduction points, b is the strip width, y c represents the amount of meandering, P represents the load on each side, and K0 represents the spring stiffness between A and B.

[0057] In order to simply represent the characteristics of the rolling stand in the model shown in Fig. 2, it is assumed that the line load applied to the work rolls of the rolling stand has a linear distribution as shown in Fig. 3. Fig. 3 is a diagram showing the distribution of the line load.

[0058] As shown in Figure 3, the strip width center is moved from the origin by the meandering amount y c By assuming that the line load is distributed linearly, the line load at the center of the plate width is p c , the difference in the line load at both ends in the plate width direction is p df Then, y=y c The line load at +b / 2 is p=p c +(1 / 2)×p df In addition, the other end in the strip width direction (for example, the end on the drive side) is y = y c The line load at -b / 2 is p=p c -(1 / 2)×p df It can be expressed as:

[0059] The difference in thickness (i.e., wedge amount) h that occurs when a line load is applied as shown in Figure 3df can be expressed by a known calculation method such as roll deformation calculation used to calculate the plate crown. For example, the wedge amount h df can be expressed by the following equation (12).

[0060]

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[0061] Here, as shown in Figure 2, a is the distance between the left and right rolling points, i.e., the distance between the supporting points of the work rolls, and b is the plate thickness. df is the difference in the opening between the left and right work rolls (leveling value). df (y c ,p df ) is the meandering amount y c and difference in line load between left and right p df This is a term that depends on and is derived by a known calculation method such as roll deformation calculation as described above, but to avoid complicating the explanation, a detailed explanation thereof will be omitted.

[0062] By taking a first approximation of the above equation (12), the following equation (13) is obtained.

[0063]

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[0064] Here, E and D are basic constants of the rolling stand related to the meandering phenomenon, and are constants called the first type parallel stiffness and the second type parallel stiffness, respectively. The first type parallel stiffness and the second type parallel stiffness have the following physical meanings.

[0065] That is, the first-class parallel stiffness E represents the amount of wedge that occurs when the center of the rolled material in the width direction is shifted by a unit amount from the mill center when the line load applied from the work rolls to the rolled material is constant in the width direction of the rolled material (i.e., when there is no difference in line load between the left and right sides). The second-class parallel stiffness D represents the amount of wedge that occurs when the center of the rolled material in the width direction is located at the mill center and there is a difference in the line load applied from the work rolls to the rolled material in the width direction of the rolled material (i.e., when there is a difference in line load between the left and right sides). Both the first-class parallel stiffness E and the second-class parallel stiffness D are constants that depend on the width of the rolled material, line load, bending force, roll cross angle, roll shift amount, roll crown, etc.

[0066] Here, by differentiating the rolling load equation when there is no tension and no constraint on either the entry or delivery side with respect to the entry side plate thickness H and the delivery side plate thickness h, the following equation (14) can be obtained.

[0067]

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[0068] where m is the plastic modulus per unit width, and p 0df is a disturbance term due to the difference in hardness between the left and right sides. df is the wedge amount at the inlet side, and h df is the wedge amount at the exit side.

[0069] From the above equations (13) and (14), p df By eliminating the above equation, the following equation (15) can be obtained, which expresses the relationship between the first-type parallel stiffness and the wedge amount.

[0070]

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[0071] (1-3. Derivation of the relational expression between the amount of meandering and the first-class parallel stiffness) Finally, we derive the relational expression between the amount of meandering and the first-class parallel stiffness. From the above equations (8), (11), and (15), h df By eliminating the above equation, we can obtain the following equation (16) that expresses the relationship between the amount of meandering and the first-class parallel stiffness. However, the disturbance terms are combined into one term.

[0072]

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[0073] The differential equation shown in the above equation (16) is c From the above equation (16), it can be said that the system is stable against slight disturbances (i.e., the amount of meandering y c remains in a finite range), or the system is unstable (i.e., the meandering amount y c It can be seen that whether the system diverges or not is determined by the value of the first parallel stiffness E. In other words, when the value of the first parallel stiffness E is sufficiently small (including negative values), the system is stable, and when the value of the first parallel stiffness E is large, the system diverges.

[0074] Therefore, in the first and second embodiments of the present invention described later, the rolling conditions are controlled as needed during rolling so that the value of the first parallel stiffness E becomes smaller. For example, the first parallel stiffness E is calculated by subtracting the difference in the gap between the left and right work rolls S in the above formula (13). df =0, difference between left and right linear load p df = 0, the calculation can be performed using the following equation (17).

[0075]

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[0076] Here, the difference in thickness between the left and right sides is h dfFor example, in a method of calculating roll deformation by dividing the roll barrel in the barrel length direction (division model), as described on page 94 of "Theory and Practice of Plate Rolling (Revised Edition)," edited by the Rolling Theory Committee, Production Technology Division, Iron and Steel Institute of Japan, published on September 30, 2010, Iron and Steel Institute of Japan, the difference in opening angle S between the left and right work rolls is df =0, difference between left and right linear load p df =0, meandering amount y c In this case, the meandering amount y in the above formula (17) can be calculated by inputting c The meandering amount y used as the input value of the division model is c The same value can be used.

[0077] As an example, Figures 4 and 5 show the results of calculating the first-class parallel stiffness E using a division model. Figures 4 and 5 are graphs showing the relationship between the line load and the first-class parallel stiffness E calculated using the division model. Figures 4 and 5 show the results of calculating the effect of the line load on the first-class parallel stiffness E using the roll bending force as a parameter for plate widths of 1600 (mm) and 800 (mm), respectively.

[0078] As shown in Figures 4 and 5, it is possible to obtain the line load dependency and bending force dependency of the first type parallel stiffness E by performing calculations using a division model. If the calculation time using the division model is long, it is also possible to perform the calculation using the division model offline and approximate the results using a regression equation.

[0079] In continuous rolling, when the material to be rolled is caught between the work rolls of both the front and rear rolling stands, the material is constrained and therefore is unlikely to meander significantly. Therefore, in the first and second embodiments, when the tail end of the material to be rolled passes through the rolling stand to be controlled, the rolling conditions of that rolling stand are controlled so that the value of the first-class parallel stiffness E becomes smaller. This reduces the amount of meandering and makes it possible to suppress the occurrence of reduction.

[0080] (1-4. Dependence of the first-class parallel stiffness on the control parameters) As described above, the first-class parallel stiffness E is a constant that depends on the width, line load, bending force, roll cross angle, roll shift amount, roll crown, and other factors of the material to be rolled. Of these, the width of the material to be rolled is a value that is preset according to the product thickness. Therefore, in the first and second embodiments, the value of the first-class parallel stiffness E is adjusted by controlling at least one of the line load, bending force, roll cross angle, roll shift amount, and roll crown. Specifically, the line load can be controlled by controlling the roll gap of the work rolls, controlling the tension of the material to be rolled between the rolling stands by controlling the roll speed of the work rolls, or controlling the coefficient of friction between the work rolls and the material to be rolled by controlling the amount of lubricant supplied.

[0081] The inventors investigated the dependency of the first type parallel stiffness E on the control parameters under various rolling conditions in order to consider how to control the control parameters of roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown in order to adjust the value of the first type parallel stiffness E. The above-mentioned division model was used for the calculation. As a result, it was found that the tendency of the dependency of the first type parallel stiffness E on the control parameters differs depending on the rolling conditions.

[0082] 6 to 15 show the results of investigations conducted by the present inventors. FIG. 6 is a graph showing the relationship between the line load and the first type parallel stiffness E under certain rolling conditions. FIG. 7 is a graph showing the relationship between the line load and the first type parallel stiffness E under rolling conditions different from those in FIG. 6. In FIGS. 6 and 7, the horizontal axis represents the line load applied to the rolled material from the work rolls, and the vertical axis represents the first type parallel stiffness E, and the relationship between the two is plotted. The line load decreases as the roll gap increases, the tension of the rolled material between the rolling stands increases, or the coefficient of friction decreases (i.e., the amount of lubricant supplied increases). For this reason, it can be said that the horizontal axes of the graphs shown in FIGS. 6 and 7 represent the roll gap, the tension of the rolled material between the rolling stands, or the amount of lubricant supplied.

[0083] Referring to Figure 6, as the line load decreases, that is, as the roll gap increases, the tension of the material being rolled between the rolling stands increases, or the amount of lubricant supplied increases, the first type parallel stiffness E decreases monotonically. Under rolling conditions where there is a trend between the line load and the first type parallel stiffness E as shown in Figure 6, it is thought that the first type parallel stiffness E can be lowered and the amount of meandering can be reduced by controlling the reduction position of the work rolls to increase the roll gap, controlling the roll speed of the work rolls to increase the tension of the material being rolled between the rolling stands, or controlling the lubricant supply device to increase the amount of lubricant supplied.

[0084] On the other hand, referring to Figure 7, there is a minimum value in the first type parallel stiffness E. In the case of rolling conditions where there is a tendency as shown in Figure 7 between the line load and the first type parallel stiffness E, it is not possible to reduce the first type parallel stiffness E simply by increasing the roll gap, increasing the tension of the material being rolled between the rolling stands, or increasing the amount of lubricant supplied. Therefore, taking into consideration that the first type parallel stiffness E has a minimum value, it is necessary to set control target values for the roll gap, the tension of the material being rolled between the rolling stands, or the amount of lubricant supplied so that the first type parallel stiffness E is as small as possible. The tendency as shown in Figure 7 can occur, for example, when rolling is performed under rolling conditions where a bending force is applied to the work roll chocks in a direction that reduces the roll gap or where the roll crown becomes concave.

[0085] Moreover, Fig. 8 is a graph showing the relationship between the bending force and the first type parallel stiffness E under certain rolling conditions. Fig. 9 is a graph showing the relationship between the bending force and the first type parallel stiffness E under rolling conditions different from those in Fig. 8. In Figs. 8 and 9, the horizontal axis represents the bending force of the work roll in the rolling stand, and the vertical axis represents the first type parallel stiffness E, and the relationship between the two is plotted.

[0086] Referring to Fig. 8, as the bending force becomes smaller, the first type parallel stiffness E decreases monotonically. In the case of rolling conditions where there is a trend between the bending force and the first type parallel stiffness E as shown in Fig. 8, it is thought that by controlling the bending device so as to reduce the bending force, the first type parallel stiffness E can be reduced and the amount of meandering can be reduced.

[0087] On the other hand, referring to Fig. 9, there is a minimum value in the first parallel stiffness E. In the case of rolling conditions where there is a tendency as shown in Fig. 9 between the bending force and the first parallel stiffness E, it is not possible to reduce the first parallel stiffness E simply by reducing the bending force. Therefore, taking into consideration that the first parallel stiffness E has a minimum value, it is necessary to set a control target value for the bending force such that the first parallel stiffness E becomes as small as possible. For example, in a rolled material with a relatively small width, the first parallel stiffness becomes a minimum value when the bending force is near zero, and from the point where it becomes a minimum value, whether the bending force is changed to the increase side or the decrease side, the first parallel stiffness increases, as shown in Fig. 9.

[0088] Fig. 10 is a graph showing the relationship between the roll cross angle and the first type parallel stiffness E under certain rolling conditions. Fig. 11 is a graph showing the relationship between the roll cross angle and the first type parallel stiffness E under rolling conditions different from those in Fig. 10. In Fig. 10 and Fig. 11, the horizontal axis represents the roll cross angle of the rolling stand, and the vertical axis represents the first type parallel stiffness E, and the relationship between the two is plotted.

[0089] With reference to Fig. 10, as the roll cross angle becomes smaller, the first type parallel stiffness E decreases monotonically. In the case of rolling conditions where there is a trend between the roll cross angle and the first type parallel stiffness E as shown in Fig. 10, it is thought that by controlling the roll chocks so as to reduce the roll cross angle, the first type parallel stiffness E can be lowered and the amount of meandering can be reduced.

[0090] On the other hand, referring to Figure 11, there is a minimum value in the first parallel stiffness E. In the case of rolling conditions where there is a tendency as shown in Figure 11 between the roll cross angle and the first parallel stiffness E, it is not possible to reduce the first parallel stiffness E simply by reducing the roll cross angle. Therefore, taking into consideration that the first parallel stiffness E has a minimum value, it is necessary to set a control target value for the roll cross angle that will make the first parallel stiffness E as small as possible. For example, in a rolled material with a relatively small width, the first parallel stiffness will take a minimum value at a predetermined roll cross angle, and whether the roll cross angle is set to have a positive angle or a negative angle from the predetermined angle at the minimum value, the first parallel stiffness will increase, as shown in Figure 11.

[0091] Fig. 12 is a graph showing the relationship between the roll shift amount and the first type parallel stiffness E under certain rolling conditions. Fig. 13 is a graph showing the relationship between the roll shift amount and the first type parallel stiffness E under rolling conditions different from those in Fig. 12. In Figs. 12 and 13, the horizontal axis represents the roll shift amount of the rolling stand, and the vertical axis represents the first type parallel stiffness E, and the relationship between the two is plotted.

[0092] With reference to Fig. 12, as the roll shift amount becomes smaller, the first type parallel stiffness E decreases monotonically. In the case of rolling conditions where there is a trend between the roll shift amount and the first type parallel stiffness E as shown in Fig. 12, it is considered that by shifting the rolls in the axial direction so as to reduce the roll shift amount, the first type parallel stiffness E can be lowered and the amount of meandering can be reduced.

[0093] On the other hand, referring to Figure 13, there is a minimum value in the first parallel stiffness E. In the case of rolling conditions where there is a tendency as shown in Figure 13 between the roll shift amount and the first parallel stiffness E, it is not possible to reduce the first parallel stiffness E simply by reducing the roll shift amount. Therefore, taking into consideration that the first parallel stiffness E has a minimum value, it is necessary to set a control target value for the roll shift amount that will make the first parallel stiffness E as small as possible. For example, in a rolled material with a relatively small width, the first parallel stiffness will take a minimum value at a specified roll shift amount, and whether the roll shift amount is changed to the work side or the drive side from the specified amount at that minimum value, the first parallel stiffness will increase, as shown in Figure 13.

[0094] Moreover, Fig. 14 is a graph showing the relationship between roll crown and first type parallel stiffness E under certain rolling conditions. Fig. 15 is a graph showing the relationship between roll crown and first type parallel stiffness E under rolling conditions different from those in Fig. 14. In Figs. 14 and 15, the horizontal axis represents the roll crown of the work rolls in the rolling stand, and the vertical axis represents the first type parallel stiffness E, and the relationship between the two is plotted.

[0095] With reference to Fig. 14, as the roll crown becomes smaller, the first parallel stiffness E decreases monotonically. In the case of rolling conditions where there is a trend between the roll crown and the first parallel stiffness E as shown in Fig. 14, it is considered that by controlling the roll crown to be smaller, the first parallel stiffness E can be lowered and the amount of meandering can be reduced.

[0096] On the other hand, referring to Figure 15, there is a minimum value in the first parallel stiffness E. In the case of rolling conditions where there is a tendency as shown in Figure 15 between the roll crown and the first parallel stiffness E, it is not possible to reduce the first parallel stiffness E simply by reducing the roll crown. Therefore, taking into consideration that the first parallel stiffness E has a minimum value, it is necessary to set a control target value for the roll crown such that the first parallel stiffness E is as small as possible. For example, in a rolled material having a relatively small width, the first parallel stiffness takes a minimum value at a predetermined roll crown amount, and whether the roll crown is increased or decreased from the predetermined roll crown amount at the minimum value, the first parallel stiffness increases, as shown in Figure 15.

[0097] The dependency of the first type parallel stiffness E on the control parameters has been described above with reference to Figs. 6 to 15. As described above, it has been found that the dependency of the first type parallel stiffness E on the control parameters changes in a variety of ways depending on the rolling conditions. In the first and second embodiments described below, such differences in the dependency of the first type parallel stiffness E on the control parameters depending on the rolling conditions are taken into consideration, and the control parameters are controlled so that the value of the first type parallel stiffness E becomes smaller.

[0098] (2. Examination of conventional meandering control methods) Here, the results of the study conducted by the present inventors on conventional meandering control methods will be described.

[0099] It has been known that the greater the reduction in a rolling stand, the more likely meandering occurs. Furthermore, large meandering that causes reduction is likely to occur when the tail end of the rolled material passes through the preceding rolling stand. Therefore, in the techniques described in Patent Documents 1 and 2 above, when the tail end of the rolled material passes through the rolling stand to be controlled, the roll gap is opened or a bending force is applied, thereby reducing the reduction, thereby reducing the amount of meandering of the rolled material. Hereinafter, opening the roll gap at the tail end of the rolled material to reduce the amount of meandering is also referred to as bottom gap up.

[0100] As described above regarding the dependency of the first type parallel stiffness on the control parameters, the inventors investigated the dependency of the first type parallel stiffness E on the line load (Figs. 6 and 7). The first type parallel stiffness E is a physical quantity that serves as an index showing the degree of meandering, and as shown in the above formula (16), the larger the first type parallel stiffness E, the more the amount of meandering tends to diverge. Therefore, the graphs shown in Figs. 6 and 7 can be said to represent the degree of meandering of the rolled material when the roll gap, roll speed, or lubricant supply amount is changed.

[0101] For example, the graph shown in Fig. 6 above can be said to represent a state in which the amount of meandering decreases as the roll gap increases, the tension of the material being rolled between the rolling stands increases, or the friction coefficient decreases (i.e., the amount of lubricant supplied increases).On the other hand, the graph shown in Fig. 7 above can be said to represent a state in which the amount of meandering does not necessarily decrease even when the roll gap is increased, the tension of the material being rolled between the rolling stands increases, or the amount of lubricant supplied increases.

[0102] For example, in the case of rolling conditions where there is a tendency between the line load and the first-class parallel stiffness as shown in Fig. 6, the techniques described in Patent Documents 1 and 2 are considered to be effective in reducing the amount of meandering. On the other hand, in the case of rolling conditions where there is a minimum value in the first-class parallel stiffness as shown in Fig. 7, with the techniques described in Patent Documents 1 and 2, when the line load is reduced, that is, when the roll gap is increased, when the tension of the rolled material between the rolling stands is increased, or when the amount of lubricant supplied is increased, there is a possibility that the amount of meandering will increase instead.

[0103] As described above, conventional meandering control methods such as those described in the above Patent Documents 1 and 2 may increase the amount of meandering depending on the rolling conditions, making it impossible to suppress the occurrence of reduction.

[0104] The present invention has been conceived based on the above-mentioned study of the prior art. As described above, in the first and second embodiments of the present invention, rather than simply opening the roll gap or applying a bending force, at least one of the control parameters, namely the roll gap, the roll speed, the lubricant supply rate, the bending force, the roll cross angle, the roll shift amount, and the roll crown, is controlled so as to reduce the first parallel stiffness E when the tail end of the rolled material passes through. Therefore, even when the first parallel stiffness E has a minimum value, as shown in Figures 7, 9, 11, 13, and 15, for example, the control parameters can be controlled to more appropriate control target values that can reduce the amount of meandering.

[0105] Generally, in continuous rolling, such as in a finishing tandem rolling mill, in which a material to be rolled is continuously passed through a plurality of rolling stands, thickness control is performed during rolling, adjusting the rolling conditions at predetermined intervals as needed to respond to disturbances and the like so as to obtain the desired thickness. However, in the techniques described in Patent Documents 1 and 2, when the tail end of the material to be rolled passes, the thickness control is stopped to perform meandering control, and the roll gap is opened or a bending force is applied without any consideration of the thickness. Therefore, rolling is not performed on the tail end of the material to be rolled, and the tail end becomes a defective product, resulting in a problem of reduced yield.

[0106] On the other hand, in the first and second embodiments of the present invention, when the tail end of the rolled material passes through, the thickness control that had been performed up until then is stopped and meandering control is started. However, in the first and second embodiments, the roll gap is not unconditionally opened or a bending force is applied. Instead, as described above, at least one of the control parameters, i.e., the roll gap, roll speed, lubricant supply rate, bending force, roll cross angle, roll shift amount, and roll crown, is controlled so as to reduce the first-type parallel stiffness E. Furthermore, as will be described later, in the second embodiment, at least one of the control parameters, i.e., the roll gap, roll speed, lubricant supply rate, bending force, roll cross angle, roll shift amount, and roll crown, is controlled in accordance with constraints required from the perspective of shape control of the rolled material, for example, so that the thickness does not deviate from the standard. As such, in the first and second embodiments, unlike the techniques described in Patent Documents 1 and 2, the tail end of the rolled material is not unconditionally opened. Therefore, thickness defects at the tail end of the rolled material do not necessarily occur, and a decrease in yield can be suppressed.

[0107] Hereinafter, first and second embodiments of the present invention will be described in detail. The first and second embodiments are the same in that at least one of the control parameters, namely, the roll gap, the roll speed, the lubricant supply amount, the bending force, the roll cross angle, the roll shift amount, and the roll crown, is controlled so as to reduce the first-type parallel stiffness E, but the details of the control methods are different from each other.

[0108] (3. First Embodiment) First, a first embodiment of the present invention will be described. In the first embodiment, immediately before the rolling conditions are changed during rolling, a current value of the first type parallel stiffness E before the change of the rolling conditions and a predicted value of the first type parallel stiffness E after the change of the rolling conditions are calculated, and the control parameters are controlled so that the control parameters are included in the rolling conditions corresponding to the smaller of the current value and the predicted value. As a result, in the first embodiment, the control parameters are controlled so that the first type parallel stiffness E becomes smaller within the change range of the rolling conditions.

[0109] 6 to 15, the first-type parallel stiffness E depends on the line load, bending force, roll cross angle, roll shift amount, and roll crown. Therefore, in order to adjust the value of the first-type parallel stiffness E, it is sufficient to control at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown as a control parameter. Therefore, in the following description of the first embodiment, a case will be described in which the value of the first-type parallel stiffness E is adjusted by controlling the roll gap, roll speed, and lubricant supply amount as control parameters.

[0110] Specifically, in the following description of the first embodiment, similar to the technologies described in Patent Documents 1 and 2, when the tail end of the rolled material passes through the rolling stand to be controlled, the plate thickness control that had been carried out up until that point is stopped and control of the control parameters is started.

[0111] For example, in bottom gap up that is performed when the roll gap is used as a control parameter, the roll gap is opened in accordance with a predetermined change rate of the roll gap position. In the example described below, immediately before the roll gap is changed in the bottom gap up, a current value of the first type parallel stiffness E before the roll gap change (i.e., before the rolling conditions are changed) and a predicted value of the first type parallel stiffness E after the roll gap change (i.e., after the rolling conditions are changed) are calculated, the current value and the predicted value are compared, and it is selected whether to control the roll gap so as to continue the bottom gap up or to control the roll gap so as to stop the bottom gap up so that the first type parallel stiffness E becomes smaller. In the first embodiment, when bottom gap up is performed and the roll gap is about to change in accordance with a predetermined change rate of the roll gap position, the above series of processes are executed at predetermined intervals as needed.

[0112] However, the first embodiment is not limited to this example, and the rolling conditions may be changed by performing control other than bottom gap up. For example, before and after the change in rolling conditions, instead of or together with the roll gap, at least one of the roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown may be controlled. For example, when bending force control is performed, any other control other than bottom gap up that can change the bending force is performed at the tail end of the rolled material.

[0113] (3-1. Rolling stand configuration) The configuration of the rolling stand according to the first embodiment will be described with reference to Fig. 16. Fig. 16 is a diagram showing an example of the configuration of the rolling stand according to the first embodiment. Fig. 16 shows the rolling stand according to the first embodiment as viewed from the left and right direction (the direction of the rotation axis of the work rolls). However, in order to show the configuration inside the housing and the threading position of the material to be rolled (pass line), some components are shown as transparent. Fig. 16 also shows a control device that controls the drive of the rolling stand according to the first embodiment.

[0114] Although FIG. 16 shows only one rolling stand 1, the rolling stand 1 may be one rolling mill that constitutes a finishing tandem rolling mill in hot rolling. A finishing tandem rolling mill is configured with multiple rolling stands 1 arranged in one direction. The material to be rolled 10 is gradually thinned as it passes through the multiple rolling stands 1 in succession, and is thereby processed to a desired final thickness. The present technology is also applicable to a single-stand rolling mill equipped with one rolling stand 1.

[0115] As shown in Fig. 16, the rolling stand 1 according to this embodiment is provided with a pair of upper and lower work rolls 1-1, 1-2, and backup rolls 2-1, 2-2 that are installed above and below the work rolls 1-1, 1-2 and support the work rolls 1-1, 1-2, within a housing 9. The rolling stand 1 shown in Fig. 16 is a so-called four-high rolling mill equipped with four rolls.

[0116] The work rolls 1-1 and 1-2 rotate at a predetermined roll rotation speed and apply a predetermined pressure from above and below to reduce the material 10 to a predetermined thickness while passing the material 10 in one direction. The reduction position (roll gap) of the work rolls 1-1 and 1-2 is adjusted as appropriate by a reduction device 11, which will be described later, depending on the rolling conditions, such as the target thickness of the material 10 after rolling and the reduction rate.

[0117] A pair of upper and lower work rolls 1-1 and 1-2 are rotatably supported by work roll chocks 3-1 and 3-2, respectively, and backup rolls 2-1 and 2-2 are rotatably supported by backup roll chocks 4-1 and 4-2, respectively.

[0118] The housing 9 is provided with an entry project block 5-1 and an exit project block 5-2 that protrude into the housing 9. The entry project block 5-1 and the exit project block 5-2 support the work roll chocks 3-1 and 3-2 via increase bending devices 6-1 to 6-4. In addition, decrease bending devices 7-1 to 7-4 are provided between the work roll chocks 3-1 and 3-2 and the backup roll chocks 4-1 and 4-2.

[0119] The increase-bending devices 6-1 to 6-4 are devices that apply a force to the work roll chocks 3-1, 3-2 in a direction that increases the roll gap. The increase-bending devices 6-1 to 6-4 are configured by a driving device such as a hydraulic cylinder, for example.

[0120] The decrease-bending devices 7-1 to 7-4 are devices that apply a force to the work roll chocks 3-1, 3-2 in a direction that reduces the roll gap. The decrease-bending devices 7-1 to 7-4 are configured by a driving device such as a hydraulic cylinder, for example.

[0121] In the first embodiment, at least one of the increase bending devices 6-1 to 6-4 and the decrease bending devices 7-1 to 7-4 is driven to control the bending force of the work rolls 1-1, 1-2 so as to reduce the first-type parallel stiffness E. In the following explanation, at least one of the increase bending devices 6-1 to 6-4 and the decrease bending devices 7-1 to 7-4 will be referred to simply as the bending device.

[0122] The upper backup roll chock 4-1 is provided with a screw down device 11 that adjusts the vertical position of the backup roll chock 4-1. The screw down device 11 is configured with a drive device such as a hydraulic cylinder. The screw down device 11 adjusts the vertical positions of the upper backup roll chock 4-1 and the upper work roll chock 3-1, thereby controlling the screw down position of the work roll 1-1, i.e., the roll gap. In addition to the screw down device 11, the backup roll chock 4-1 is provided with a load cell 12. The load cell 12 measures the rolling load. In the first embodiment, the screw down device 11 is driven to control the roll gap of the work rolls 1-1 and 1-2 so as to reduce the first-type parallel stiffness E.

[0123] 16 shows an example of an apparatus configuration in which the screw down device 11 is provided on the upper backup roll chock 4-1, but the screw down device 11 may be provided on the lower backup roll chock 4-2 instead of on the upper backup roll chock 4-1. By driving the screw down device 11 provided on either the upper backup roll chock 4-1 or the lower backup roll chock 4-2, the vertical position of either the upper or lower work rolls 1-1, 1-2 is adjusted, and the roll gap is controlled.

[0124] The rolling stand 1 shown in Fig. 16 is equipped with a driving device (not shown) such as a mill motor for controlling the roll speed of the work rolls 1-1 and 1-2. In addition, a lubricant supplying device (not shown) for supplying a lubricant to the material S to be rolled during rolling may be installed on the entry side of the rolling stand 1.

[0125] The rolling stand 1 may be, for example, a pair-cross rolling mill, in which the roll cross angle can be changed by moving the work roll chocks 3-1 and 3-2 and the backup roll chocks 4-1 and 4-2 using a roll chock drive device. Alternatively, the rolling stand 1 may be, for example, a CVC (continuous variable crown) rolling mill, in which the work rolls 1-1 and 1-2 can be shifted axially using a roll shift device. In this case, if the rolling stand 1 is a six-high rolling mill, the intermediate rolls may be shifted axially. Furthermore, the rolling stand 1 may be, for example, a VC (variable crown) rolling mill, in which the roll crowns of the work rolls 1-1 and 1-2 can be changed using a roll crown changing device. The roll crowns can be changed, for example, by using variable crown rolls having hydraulic expansion chambers located inside the center of the roll barrel length as the work rolls 1-1 and 1-2.

[0126] The control device 20 (corresponding to the meandering control device of the present invention) comprehensively controls the operation of the rolling stand 1. The control device 20 controls the driving of each member of the rolling stand 1 so that rolling is performed under desired rolling conditions. In the first embodiment, the control device controls the driving of at least one of the bending device, mill motor, lubricant supply device, screw down device, roll chock driving device, roll shift device, and roll crown changing device so as to reduce the first type parallel stiffness E. The functional configuration of the control device 20 will be described in detail below in (3-2. Functional configuration of the control device).

[0127] The control device 20 is configured by various processors such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor), and the functions of the control device 20 can be realized by the processors operating in accordance with predetermined programs. The control device 20 is not limited to a specific configuration as long as it has the function of controlling the operation of the rolling stand 1. For example, the control device 20 may be one of the various processors described above, or may be a so-called microcomputer in which a processor and a storage device such as a memory are integrated. Alternatively, the control device 20 may be one of various information processing devices such as a PC (Personal Computer) or a server.

[0128] The configuration of the rolling stand 1 according to the first embodiment has been described above with reference to Figure 16. However, the specific device configuration of the rolling stand 1 according to the first embodiment is not limited to this example. The first embodiment is characterized primarily by the method of controlling the rolling stand 1, and the device configuration of the rolling stand 1 itself may be the same as that of a general rolling stand. Figure 16 illustrates, as an example, an example of the configuration of a rolling stand that constitutes a finishing tandem rolling mill that is generally used for finishing rolling in hot rolling.

[0129] (3-2. Functional configuration of the control device) The functional configuration of the control device 20 that controls the operation of the rolling stand 1 will be described with reference to Fig. 17. Fig. 17 is a block diagram showing an example of the functional configuration of the control device 20 that controls the operation of the rolling stand 1 according to the first embodiment.

[0130] Referring to FIG. 17 , the control device 20 according to the first embodiment has, as its functions, a change amount calculation unit 21, a first-type parallel stiffness calculation unit 22, a control target value determination unit 23, and a drive control unit 24. Note that FIG. 17 illustrates only the functions related to meandering control according to the first embodiment, among the functions of the control device 20. In addition to the functions illustrated, the control device 20 may have various functions that a general control device for a rolling stand has, such as changing various settings of the rolling stand 1 according to rolling conditions. For example, the control device 20 may have a function of performing thickness control to control the thickness of the material to be rolled to a desired value. Functions not illustrated may be similar to well-known functions that may be installed in a control device for a general rolling stand, and therefore detailed description thereof will be omitted here.

[0131] As described above, in the first embodiment, when the tail end of the material to be rolled reaches the rolling stand 1, which is the control target, the plate thickness control that had been carried out up until then is stopped and the meandering control according to the first embodiment is started. Specifically, in the rolling stand 1, when the tail end of the material to be rolled reaches the rolling stand 1, control is carried out to start bottom gap up, and a process of calculating the first type parallel stiffness E is carried out.

[0132] Here, in this specification, the region indicated by the "tail end" of the material to be rolled is not limited to a unique region. For example, when the rolling target is the M-th rolling stand (1≦M≦N) among N (N is a natural number) rolling stands, and the meandering control according to the first embodiment is performed in the M-th stand, the tail end may refer to the region from the tail end to the part of the material that is bitten into the M-th stand at the time when the tail end of the material to be rolled passes through the M-1-th stand that is installed immediately before the M-th stand that is the target of control. Alternatively, it may refer to the region from the tail end to the part of the material that is bitten into the M-th stand at the time when the tail end of the material to be rolled passes through the 1-th stand.

[0133] In the former case, the meandering control according to the first embodiment is started in the M stand at the timing when the passage (release) of the tail end of the material to be rolled at the M-1 stand is detected. On the other hand, in the latter case, the meandering control according to the first embodiment is started in the M stand at the timing when the release of the tail end of the material to be rolled at the 1st stand is detected. In the first embodiment, it is sufficient that meandering control is carried out in the M stand so as to reduce the first-type parallel stiffness E while a region of a predetermined length including at least the tail end of the material to be rolled (i.e., the tail end portion) passes through the M stand that is the control target, and how to set the "tail end portion" at which the meandering control is to be executed, i.e., the timing at which the meandering control is to be started, may be set appropriately.

[0134] Each function of the control device 20 shown in Fig. 17 starts executing the processes described below at a preset timing for starting meandering control, such as when the tail end of the rolled material has left the M-1 stand. A general jamming detection device that detects whether the rolled material is jammed into the rolling stand can be used to detect when the tail end of the rolled material has left the rolling stand. This detection device can detect jamming and release of the rolled material based on changes in measured values such as the rolling load, torque, and the sum of rolling direction forces.

[0135] In the first embodiment, the control device 20 acquires information that the tail end of the rolled material has been detected to have come off in a rolling stand that is set in advance as a reference rolling stand for starting meandering control, which is located upstream of the rolling stand 1 to be controlled, from a bite detection device provided in the reference rolling stand.The control device 20 then starts controlling the control parameters, using the acquisition of this information as the timing for starting control.

[0136] For example, in bottom gap-up that is performed when the roll gap is used as a control parameter, the control device 20 can start bottom gap-up based on various information required to execute bottom gap-up (hereinafter also referred to as bottom gap-up control data). The bottom gap-up control data includes, for example, information about a control target value of the roll gap and information about a change rate of the roll gap position until the roll gap position is changed from the current value to the control target value. The bottom gap-up control data may be set in advance by a user and may be stored in, for example, a storage device (not shown) communicably connected to the control device 20. The control device 20 can acquire the bottom gap-up control data by referring to the storage device.

[0137] The change amount calculation unit 21 calculates the change amount of the control data for the next step from the control data for the current step of the control parameters at the timing when the meandering control is started. For example, in bottom gap up, which is performed when the roll gap is used as the control parameter, the change amount calculation unit 21 calculates the roll gap position change amount ΔS when transitioning from the current step to the next step based on the bottom gap up control data at the same time as roll gap control based on the bottom gap up is started. The current step is the step immediately before the bottom gap up is started, and the next step is the step after a predetermined time (for example, a time corresponding to a predetermined interval at which the meandering control according to the first embodiment is repeatedly executed) has elapsed. As described above, the bottom gap up control data includes information about, for example, the change rate of the roll gap position, and the change amount calculation unit 21 can calculate the roll gap position change amount ΔS based on the change rate of the roll gap position. Note that the change amount calculation unit 21 can acquire the information about the change rate of the roll gap position from the bottom gap up control data stored in the storage device by referring to the storage device described above.

[0138] The change amount calculation unit 21 provides the first type parallel stiffness calculation unit 22 with information on the calculated change amount of the control data, such as the press-down position change amount ΔS.

[0139] The first-class parallel stiffness calculation unit 22 calculates the first-class parallel stiffness E0 in the current step (i.e., the first-class parallel stiffness E0 before the rolling conditions are changed) based on the rolling achievement data. Here, the rolling achievement data are achievement values (measured values) of various rolling conditions acquired during rolling, such as the plate thickness, rolling load (line load), bending force, and rolling speed. The rolling achievement data is acquired at predetermined intervals by a measuring device such as a plate thickness gauge or a speedometer, and is stored in, for example, the above-mentioned storage device. The first-class parallel stiffness calculation unit 22 can calculate the first-class parallel stiffness E0 in the current step by appropriately using information necessary for calculating the first-class parallel stiffness, such as the line load and bending force, from the rolling achievement data that reflects the rolling conditions in the current step acquired at the most recent timing, for example.

[0140] Furthermore, the first type parallel stiffness calculation unit 22 calculates a predicted value E1 of the first type parallel stiffness in the next step (i.e., a predicted value E1 of the first type parallel stiffness after the change in the rolling conditions) based on the rolling actual data and the change amount of the control data calculated by the change amount calculation unit 21. Specifically, the first type parallel stiffness calculation unit 22 can calculate the predicted value E1 of the first type parallel stiffness in the next step by, for example, calculating a rolling load predicted value P1 when the roll gap position changes by ΔS, and using the value of the rolling load predicted value P1 instead of the actual value to perform the same calculation as when the first type parallel stiffness E0 was calculated.

[0141] Note that calculation of the first type parallel stiffness requires physical quantities specific to the rolling stand 1, such as constants related to the deformation of the housing 9 of the rolling stand 1. Information about these physical quantities specific to the rolling stand 1 is stored in advance, for example, in the storage device described above, and the first type parallel stiffness calculation unit 22 can acquire various pieces of information required for calculation of the first type parallel stiffness by referring to the storage device.

[0142] The first-type parallel stiffness calculation unit 22 provides the control target value determination unit 23 with information about the calculated first-type parallel stiffness E0 in the current step (i.e., the current value of the first-type parallel stiffness) and information about the predicted value E1 of the first-type parallel stiffness in the next step.

[0143] The control target value determination unit 23 compares the first type parallel stiffness E0 in the current step (i.e., the current value of the first type parallel stiffness) with the predicted value E1 of the first type parallel stiffness in the next step after the rolling conditions are changed, and determines the control target value of the control parameter such that the first type parallel stiffness E becomes smaller.

[0144] Specifically, when the current value E0 of the first-type parallel stiffness is equal to or smaller than the predicted value E1 of the first-type parallel stiffness in the next step, the control target value determiner 23 determines the control target values of the control parameters to maintain the current control state of the control parameters so that the first-type parallel stiffness E in the next step becomes the smaller current value E0 of the first-type parallel stiffness. For example, the control target value before the change of the roll gap related to bottom gap up is determined as the control target value of the roll gap position in the next step. In this case, bottom gap up is not executed.

[0145] On the other hand, when the current value E0 of the first type parallel stiffness is greater than the predicted value E1 of the first type parallel stiffness in the next step, the control target value determiner 23 determines the control target values of the control parameters so that the first type parallel stiffness E in the next step becomes the smaller predicted value E1 of the first type parallel stiffness. For example, the control target value of the roll gap position changed to realize the roll gap position in the next step based on the roll gap position change rate for bottom gap up is determined as the control target value of the roll gap position for the next step. In this case, the roll gap control is executed in the same way as when the bottom gap up is continued.

[0146] The control target value determination unit 23 provides information on the determined control target values of the control parameters to the drive control unit 24 .

[0147] The drive control unit 24 controls various devices that control the control parameters in accordance with the control target values of the control parameters determined by the control target value determination unit 23. For example, when the control parameter is a roll gap, the drive control unit 24 controls the drive of the screw down device 11 to change the roll gap in the rolling stand 1. Furthermore, when the control parameter is a roll speed, the drive control unit 24 controls either the mill motor 13 of the rolling stand to be controlled or of the rolling stands before and after it to change the roll speed. Furthermore, when the control parameter is a lubricant supply amount, the drive control unit 24 controls the lubricant supply device 15 of the rolling stand to be controlled to change the lubricant supply amount. As a result, the control parameters of the rolling stand 1 are controlled so that the first type parallel stiffness becomes the smaller of the current value E0 of the first type parallel stiffness or the predicted value E1 of the first type parallel stiffness.

[0148] The functional configuration of the control device 20 of the rolling stand 1 according to the first embodiment has been described above with reference to Fig. 17. As described above, according to the first embodiment, at the tail end of the material to be rolled, the current value E0 of the first type parallel stiffness before the change of rolling conditions is compared with the predicted value E1 of the first type parallel stiffness after the change of rolling conditions, and the control parameters of the rolling stand 1 are controlled so that the control parameters are included in the rolling conditions corresponding to the smaller value of the first type parallel stiffness E. Therefore, even if the first type parallel stiffness E has a minimum value with respect to the line load as shown in Fig. 7 above, for example, the control parameters of the rolling stand 1 are controlled so that the first type parallel stiffness becomes smaller, and the amount of meandering of the material to be rolled can be further reduced.

[0149] In the first embodiment, the series of processes in the control device 20 described above are executed at predetermined intervals as needed while the tail end of the material to be rolled passes through the rolling stand 1. Therefore, the control parameters are controlled so that the first-type parallel stiffness E is always smaller at the tail end of the material to be rolled, and the amount of meandering in the material to be rolled can be reduced over the entire longitudinal area of the tail end.

[0150] Furthermore, according to the first embodiment, unlike the techniques described in Patent Documents 1 and 2, control is not performed to unconditionally open the roll gap or apply a bending force at the tail end. Within the range of changes in rolling conditions, the control parameters of the rolling stand 1 are controlled so that the first-type parallel stiffness E becomes smaller. Therefore, depending on the magnitude relationship between the current value and the predicted value of the first-type parallel stiffness E, control of the control parameters is not performed more than necessary. In other words, there may be cases where the roll gap is not opened even though the plate thickness control functions effectively. In this case, since the plate thickness control can function effectively even at the tail end, there is a possibility that the plate thickness can be controlled to the desired thickness all the way to the tail end, which reduces thickness defects at the tail end and improves product yield.

[0151] 17 shows, as an example of the first embodiment, devices for controlling control parameters for adjusting the value of the first-type parallel stiffness E, including a screw down device 11 for adjusting the roll gap, a mill motor 13 for changing the roll speed, and a lubricant supply device 15 for controlling the amount of lubricant supplied, all of which are controlled by the control device 20. However, the present invention is not limited to this example. The control device 20 can also control devices for controlling other control parameters, such as a bending device for adjusting the bending force, a roll chock drive device for adjusting the roll cross angle, a roll shift device for adjusting the amount of roll shift, and a roll crown changing device for adjusting the roll crown. The control device 20 can control devices for controlling the control parameters using at least one of the roll gap, roll speed, amount of lubricant supplied, bending force, roll cross angle, amount of roll shift, and roll crown as the control parameter.

[0152] In the first embodiment, which control parameter to control among the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown may be appropriately determined taking into consideration the content of control performed in the rolling stand 1 (for example, the above-mentioned bottom gap up control), constraints on the equipment, constraints related to shape control of the rolled material, etc. For example, in a case where both the roll gap and bending force are controllable and changing the roll gap would result in a large change in the thickness of the rolled material to the extent that it deviates from the standard, the control device 20 may preferably control only the bending force so as to reduce the first type parallel stiffness.

[0153] (3-3.Meandering Control Method) The processing procedure of the meandering control method according to the first embodiment will be described with reference to FIGS.

[0154] (a. When the control parameter is the roll gap) First, a meandering control method when the control parameter is the roll gap will be described with reference to Fig. 18 and Fig. 19. Fig. 18 is a flowchart showing an example of the processing procedure of the meandering control method according to the first embodiment, showing a case where the roll gap is used as the control parameter. Fig. 19 is a schematic diagram explaining the measurement timing of the control data. Note that each process shown in Fig. 18 can be executed by each function of the control device 20 shown in Fig. 17 described above.

[0155] The meandering control method according to the first embodiment is started at the timing when the release of the tail end of the rolled material is detected in a rolling stand (Mth stand) which is located upstream of the rolling stand 1 to be controlled and serves as a reference for starting meandering control. In the meandering control method according to the first embodiment, first, bottom gap-up is started and the first type parallel stiffness (current value of first type parallel stiffness) E0 in the current step is calculated (step S101). The calculation process of the current value E0 of the first type parallel stiffness in step S101 corresponds to the process executed by the first type parallel stiffness calculation unit 22 shown in FIG. 17, for example.

[0156] Next, a roll position change amount ΔS for the next step is calculated based on the roll position change rate for the bottom gap up (step S103). The processing shown in step S103 corresponds to, for example, the processing executed by the change amount calculation unit 21 shown in Fig. 17. The roll position change rate is included in, for example, the bottom gap up control data, and the change amount calculation unit 21 can calculate the roll position change amount ΔS by using the bottom gap up control data.

[0157] Here, the control data of each control parameter such as the bottom gap-up control data in step S103 is acquired during the period from when the front end of the material to be rolled is bitten into the Mth stand to be controlled until the tail end of the material to be rolled is rolled by the Mth stand. Specifically, the measurement timing of the control data is as shown in Fig. 19.

[0158] First, in a tandem rolling mill equipped with N (N≧2) rolling stands, if the Mth stand is one of the 2nd stand to the Nth stand, as shown in the upper part of FIG. 19, the control data is calculated from the timing (measurement timing 1) when the leading end T of the rolled material 10 is bitten into the Mth stand (#M) to the timing (measurement timing 2) when the tail end 10 of the rolled material 10 is bitten into the Mth stand (#M). b The tail end 10 is measured before it is rolled in the Mth stand (#M) (measurement timing 2). b As described above, the range is from the tail end T to a predetermined length. When the first stand (#1) of the tandem rolling mill is the object of control, as shown in the center of FIG. 19, the control data is calculated from the timing (measurement timing 1) when the front end T of the material 10 to be rolled is bitten into the first stand (#1) to the tail end 10 of the material 10 to be rolled. b is measured before rolling in the first stand (#1) (measurement timing 2).

[0159] In the case of a single-stand rolling mill, as shown in the lower part of FIG. 19, the control data is calculated from the timing (measurement timing 1) when the leading end T of the rolled material 10 is bitten into the first stand (#1) to the timing (measurement timing 2) when the tail end 10 of the rolled material 10 is bitten into the first stand (#2). b is measured before rolling in the first stand (#1) (measurement timing 2).

[0160] If there is sufficient time for calculation, the control data should be as close as possible to the tail end 10 b It is preferable to measure when the portion close to the Mth stand is rolled by the Mth stand to be controlled.

[0161] Returning to the explanation of Fig. 18, next, a rolling load predicted value P1 when the roll gap position changes by ΔS is calculated (step S105). Then, based on the calculated rolling load predicted value P1, a predicted value E1 of first-class parallel stiffness in the next step is calculated (step S107). The processing shown in steps S105 and S107 corresponds to, for example, the processing executed by the first-class parallel stiffness calculation unit 22 shown in Fig. 17.

[0162] Next, the current value E0 of the first type parallel stiffness in the current step is compared with the predicted value E1 of the first type parallel stiffness in the next step (step S109).

[0163] If it is determined in step S109 that the current value E0 of the first type parallel stiffness is equal to or less than the predicted value E1, then a roll gap position corresponding to the current value E0 of the first type parallel stiffness, i.e., a roll gap position that maintains the current roll gap position before the change in rolling conditions (before the change in the roll gap related to bottom gap up) is determined as the control target value of the roll gap position so that the first type parallel stiffness E in the next step becomes the smaller current value E0 of the first type parallel stiffness (step S111).Then, the roll gap of the rolling stand 1 is controlled based on the control target value of the roll gap position that maintains the current roll gap position, i.e., so as to stop bottom gap up (step S113).

[0164] On the other hand, if it is determined in step S109 that the current value E0 of the first type parallel stiffness is greater than the predicted value E1 of the first type parallel stiffness, a roll gap position corresponding to the predicted value E1 of the first type parallel stiffness is determined as the control target value of the roll gap position so that the first type parallel stiffness E of the next step becomes the smaller predicted value E1 of the first type parallel stiffness, i.e., a roll gap position that realizes the roll gap position of the next step after the rolling conditions are changed (after the roll gap related to bottom gap up is changed) (step S115). Then, the roll gap of the rolling stand 1 is controlled based on the control target value of the roll gap position that realizes the roll gap position of the next step, i.e., so that bottom gap up is continued in accordance with the roll gap position change rate (step S117).

[0165] The processes shown in steps S109, S111, and S115 correspond to, for example, the processes executed by the control target value determination unit 23 shown in Fig. 17. The processes shown in steps S113 and S117 correspond to, for example, the processes executed by the drive control unit 24 shown in Fig. 17.

[0166] (b. When the control parameter is the roll speed) Next, a meandering control method when the control parameter is the roll speed will be described with reference to Fig. 20. Fig. 20 is a flowchart showing an example of the processing procedure of the meandering control method according to the first embodiment, showing a case where the roll speed is used as the control parameter. The processes shown in Fig. 20 can be executed by the functions of the control device 20 shown in Fig. 17 described above. In the description of Fig. 20, detailed description of the same processes as those in Fig. 18 will be omitted.

[0167] When meandering control is started, first, the first type parallel stiffness (current value of the first type parallel stiffness) E0 in the current step is calculated (step S121). The processing in step S121 may be performed in the same manner as step S101 in FIG.

[0168] Next, a roll speed change amount ΔV in the next step is calculated (step S123). The process shown in step S123 corresponds to, for example, the process executed by the change amount calculation unit 21 shown in Fig. 17. The change amount calculation unit 21 can calculate the roll speed change amount ΔV by using control data for the current roll speed V. The measurement timing of the control data for the current roll speed V may be set as shown in Fig. 19.

[0169] Furthermore, a rolling force predicted value P1 when the roll speed changes by ΔV is calculated (step S125). Then, based on the calculated rolling force predicted value P1, a predicted value E1 of the first type parallel stiffness in the next step is calculated (step S127). The processing shown in steps S125 and S127 may be performed in the same manner as steps S105 and S107 in FIG. 18.

[0170] Next, the current value E0 of the first type parallel stiffness in the current step is compared with the predicted value E1 of the first type parallel stiffness in the next step (step S129).

[0171] If it is determined in step S129 that the current value E0 of the first-type parallel stiffness is equal to or smaller than the predicted value E1, a control target value is determined to maintain the roll speed corresponding to the current value E0 of the first-type parallel stiffness so that the first-type parallel stiffness E in the next step becomes the smaller current value E0 of the first-type parallel stiffness (step S131).Then, the mill motor is controlled based on the control target value that maintains the current roll speed, and roll speed control is performed (step S135).

[0172] On the other hand, if it is determined in step S129 that the current value E0 of the first-type parallel stiffness is greater than the predicted value E1 of the first-type parallel stiffness, a control target value is determined to realize a roll speed corresponding to the predicted value E1 of the first-type parallel stiffness so that the first-type parallel stiffness E of the next step becomes the smaller predicted value E1 of the first-type parallel stiffness (step S133).Then, the mill motor is controlled based on the control target value that realizes the roll speed of the next step, and roll speed control is performed (step S135).

[0173] The processes shown in steps S129, S131, and S133 correspond to, for example, the processes executed by the control target value determination unit 23 shown in Fig. 17. The process shown in step S135 corresponds to, for example, the processes executed by the drive control unit 24 shown in Fig. 17.

[0174] (c. When the control parameter is the amount of lubricant supplied) Next, a meandering control method when the control parameter is the lubricant supply amount will be described with reference to Fig. 21. Fig. 21 is a flowchart showing an example of the processing procedure of the meandering control method according to the first embodiment, in which the lubricant supply amount is used as the control parameter. The processes shown in Fig. 21 can be executed by the functions of the control device 20 shown in Fig. 17 described above. In the description of Fig. 21, detailed description of processes similar to those in Fig. 18 will be omitted.

[0175] When meandering control is started, first, the first type parallel stiffness (current value of the first type parallel stiffness) E0 in the current step is calculated (step S141). The processing in step S141 may be performed in the same manner as step S101 in FIG.

[0176] Next, a lubricant supply amount change amount ΔQ in the next step is calculated (step S143). The process shown in step S143 corresponds to, for example, the process executed by the change amount calculation unit 21 shown in FIG. 17. The change amount calculation unit 21 can calculate the lubricant supply amount change amount ΔQ by using control data for the current lubricant supply amount Q. The measurement timing of the control data for the current lubricant supply amount Q may be set as shown in FIG. 19.

[0177] Furthermore, a rolling load predicted value P1 when the lubricant supply amount changes by ΔQ is calculated (step S145). Then, based on the calculated rolling load predicted value P1, a predicted value E1 of the first type parallel stiffness in the next step is calculated (step S147). The processing shown in steps S145 and S147 may be performed in the same manner as steps S105 and S107 in FIG. 18.

[0178] Next, the current value E0 of the first type parallel stiffness in the current step is compared with the predicted value E1 of the first type parallel stiffness in the next step (step S149).

[0179] If it is determined in step S149 that the current value E0 of the first-type parallel stiffness is equal to or smaller than the predicted value E1, a control target value is determined to maintain the lubricant supply amount corresponding to the current value E0 of the first-type parallel stiffness so that the first-type parallel stiffness E in the next step becomes the smaller current value E0 of the first-type parallel stiffness (step S151).Then, the lubricant supply device is controlled based on the control target value that maintains the current lubricant supply amount, and lubricant supply amount control is performed (step S155).

[0180] On the other hand, if it is determined in step S149 that the current value E0 of the first-type parallel stiffness is greater than the predicted value E1 of the first-type parallel stiffness, a control target value is determined to realize a lubricant supply amount corresponding to the predicted value E1 of the first-type parallel stiffness so that the first-type parallel stiffness E of the next step becomes the smaller predicted value E1 of the first-type parallel stiffness (step S153).Then, the lubricant supply device is controlled based on the control target value that realizes the lubricant supply amount of the next step, and lubricant supply amount control is performed (step S155).

[0181] The processes shown in steps S129, S131, and S133 correspond to, for example, the processes executed by the control target value determination unit 23 shown in Fig. 17. The process shown in step S135 corresponds to, for example, the processes executed by the drive control unit 24 shown in Fig. 17.

[0182] The processing procedure of the meandering control method according to the first embodiment has been described above with reference to Figures 18 to 21. In the first embodiment, a series of processes shown in Figure 18, 20 or 21 is executed at predetermined intervals at the tail end of the material to be rolled. Therefore, the roll gap is controlled so that the first-type parallel stiffness E is always smaller at the tail end of the material to be rolled, and the amount of meandering in the material to be rolled can be reduced over the entire longitudinal direction of the tail end.

[0183] As an example of the first embodiment, Fig. 18 illustrates a processing procedure for a meandering control method in which the roll gap is controlled, Fig. 20 illustrates a processing procedure for controlling the roll speed, and Fig. 21 illustrates a processing procedure for controlling the amount of lubricant supplied to adjust the value of the first parallel stiffness E. However, the present invention is not limited to this example, and the value of the first parallel stiffness E may be adjusted by controlling other control parameters. The control device 20 can control devices for controlling the control parameters, using at least one of the roll gap, roll speed, amount of lubricant supplied, bending force, roll cross angle, roll shift amount, and roll crown as the control parameter, and adjust the value of the first parallel stiffness E.

[0184] In the examples shown in FIGS. 18, 20, and 21, the processes shown in steps S109, S129, and S149 are classified into two cases: when the current value E0 of the first-type parallel stiffness is equal to or less than the predicted value E1, and when the current value E0 of the first-type parallel stiffness is greater than the predicted value E1. However, the first embodiment is not limited to such examples. The expressions "equal to or less than" and "greater than" are merely examples and do not limit the boundary conditions used to express the magnitude relationship between the current value E0 and the predicted value E1 of the first-type parallel stiffness. In the first embodiment, when the current value E0 and the predicted value E1 of the first-type parallel stiffness are equal, how to determine the magnitude relationship may be arbitrarily set. For example, unlike the examples shown in FIGS. 18, 20, and 21, the process may proceed to steps S115, S133, and S153 when the current value E0 and the predicted value E1 of the first-type parallel stiffness are equal.

[0185] (4. Second Embodiment) Next, a second embodiment of the present invention will be described. In the second embodiment, a changeable range of at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown is calculated based on constraint conditions including at least one of constraint conditions on the equipment and constraint conditions related to shape control of the rolled material, and at least one of the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown is controlled so that the first-type parallel stiffness is minimized within the changeable range.

[0186] The second embodiment is different from the first embodiment in that the details of the meandering control method are changed, and the device configuration of the rolling stand to which the meandering control method according to the second embodiment is applied may be the same as the rolling stand 1 according to the first embodiment described with reference to Fig. 16. Therefore, in the following description of the second embodiment, a description of the device configuration of the rolling stand will be omitted, and the functional configuration of the control device that controls the operation of the rolling stand and the processing procedure of the meandering control method will be mainly described.

[0187] In the following description of the second embodiment, a case will be described as an example in which the bending force is controlled to adjust the value of the first-type parallel stiffness E. However, the second embodiment is not limited to this example, and the roll gap of the work rolls may be controlled instead of or in addition to the bending force.

[0188] (4-1. Functional configuration of the control device) The functional configuration of a control device for controlling the operation of a rolling stand according to the second embodiment will be described with reference to Fig. 22. Fig. 22 is a block diagram showing an example of the functional configuration of a control device for controlling the operation of a rolling stand according to the second embodiment. In the second embodiment, the control device shown in Fig. 22 controls the operation of the rolling stand 1 in place of the control device 20 shown in Fig. 16.

[0189] Referring to FIG. 22, a control device 30 according to the second embodiment (corresponding to the meandering control device of the present invention) has, as its functions, a changeable range calculation unit 31, a control target value determination unit 32, and a drive control unit 33. Note that FIG. 22 illustrates only the functions of the control device 30 that are related to meandering control according to the second embodiment. In addition to the illustrated functions, the control device 30 may also have various functions that a typical rolling stand control device has, such as changing various settings of the rolling stand 1 according to rolling conditions. For example, the control device 30 may have a function of performing thickness control to control the thickness of the material to be rolled to a desired value. Functions not illustrated may be similar to well-known functions that may be included in a typical rolling stand control device, and therefore detailed description thereof will be omitted here.

[0190] The hardware configuration of the control device 30 may be the same as that of the control device 20 according to the first embodiment. That is, the control device 30 may be, for example, various types of processors such as a CPU or a DSP, or may be a microcomputer. Alternatively, the control device 30 may be various types of information processing devices such as a PC or a server. The functions of the control device 30 may be realized by the processor installed in the control device 30 operating in accordance with a predetermined program.

[0191] Here, in the second embodiment, as in the first embodiment, the thickness control that had been carried out up until that point is stopped at the tail end of the rolled material, and meandering control according to the second embodiment is started. The timing for starting control may be, for example, the timing when the removal of the tail end of the rolled material is detected in any of the rolling stands upstream of the rolling stand to be controlled. Each function of the control device 30 shown in FIG. 22 starts executing each process described below at the preset timing for starting meandering control.

[0192] The changeable range calculation unit 31 calculates a changeable range for at least one of the roll gap, roll speed, lubricant supply rate, bending force, roll cross angle, roll shift amount, and roll crown based on the constraints. Here, the constraints include, for example, equipment constraints and constraints related to shape control. For example, when bending force is used as a control parameter, the equipment constraints are conditions regarding the range of bending force that can be applied due to the device configuration of the rolling stand 1. Furthermore, the constraints related to shape control are constraints required from the perspective of shape control of the rolled material. For example, when bending force is used as a control parameter, the constraints are conditions regarding the allowable range of bending force so that rolling is performed so that the plate thickness after rolling does not deviate from the standard. The constraints related to shape control can be acquired, for example, during plate thickness control as control target values for various control targets in the plate thickness control (e.g., roll speed, leveling amount, reduction position (roll gap), bending force, etc.).

[0193] For example, at least one of information on equipment constraints and information on shape control constraints is stored in advance in a storage device (not shown) communicatively connected to the control device 30. By referring to the storage device, the changeable range calculation unit 31 can acquire at least one of information on equipment constraints and information on shape control constraints, which is necessary for calculating the changeable range of the control parameters.

[0194] The changeable range calculation unit 31 provides the control target value determination unit 32 with information on the calculated changeable range of the control parameter.

[0195] The control target value determination unit 32 calculates the value of the control parameter that minimizes the first type parallel stiffness within the calculated changeable range, and determines the value of the control parameter as the control target value of the control parameter. For example, when the bending force is the control parameter, the control target value determination unit 32 can calculate the bending force that minimizes the first type parallel stiffness by solving a minimum value problem in which the bending force is an unknown quantity in the formula for calculating the first type parallel stiffness and the changeable range is the boundary condition.

[0196] In order to calculate the value of the control parameter that minimizes the first-type parallel stiffness, various information for calculating the first-type parallel stiffness (for example, information about the rolling load (line load) and information about physical quantities specific to the rolling stand 1) is required. For example, the control target value determination unit 32 can acquire information about the rolling load based on rolling performance data. Furthermore, information about physical quantities specific to the rolling stand 1 may be stored in advance in the storage device described above, and the control target value determination unit 32 can acquire various information required to calculate the value of the control parameter that minimizes the first-type parallel stiffness by referring to the storage device.

[0197] The control target value determination unit 32 provides the drive control unit 33 with information on the determined control target values of the control parameters.

[0198] The drive control unit 33 controls devices for controlling the control parameters based on the control target values of the control parameters to change the control parameters. For example, when the bending force is the control parameter, the drive control unit 33 controls the driving of the bending devices 35 (increase bending devices 6-1 to 6-4 and decrease bending devices 7-1 to 7-4 shown in FIG. 16) to change the bending force in the rolling stand 1. The drive control unit 33 drives the bending devices 35 based on the control target value of the bending force determined by the control target value determination unit 32. As a result, the bending force of the rolling stand 1 is controlled so that the first type parallel stiffness is minimized within the changeable range determined by the constraint conditions.

[0199] Furthermore, for example, when the roll cross angle is used as the control parameter, the drive control unit 33 controls the roll cross angle by driving the roll chocks using the roll chock driving device 36. Furthermore, when the roll shift amount is used as the control parameter, for example, the drive control unit 33 controls the roll shift amount by moving the work rolls (or intermediate rolls in the case of a six-high rolling mill) in the axial direction using the roll shift device 37. Furthermore, when the roll crown is used as the control parameter, for example, the drive control unit 33 controls the roll crown by changing the roll crown of the work rolls using the roll crown changing device 38. Although not shown in FIG. 22, the drive control unit 33 can also control devices that control other control parameters, such as the screw down device 11, mill motor 13, and lubricant supply device 15 shown in FIG. 17.

[0200] The functional configuration of the control device 30 of the rolling stand 1 according to the second embodiment has been described above with reference to Fig. 22. As described above, according to the second embodiment, the changeable range of the control parameters is calculated at the tail end of the material to be rolled, taking into account constraints. Then, within this changeable range, the control parameters of the rolling stand 1 are controlled so that the first-type parallel stiffness is minimized. Therefore, even if the first-type parallel stiffness E has a minimum value with respect to the bending force, as shown in Fig. 9 above, for example, the bending force of the rolling stand 1 is controlled so that the first-type parallel stiffness is made smaller, and the amount of meandering of the material to be rolled can be further reduced.

[0201] In the second embodiment, the series of processes in the control device 30 described above are executed at predetermined intervals as needed while the tail end portion of the material to be rolled passes through the rolling stand 1. Therefore, the control parameters are controlled so that the first-type parallel stiffness E is always smaller at the tail end portion of the material to be rolled, and the amount of meandering in the material to be rolled can be reduced over the entire longitudinal area of the tail end portion.

[0202] Furthermore, according to the second embodiment, the target control values of the control parameters are determined in consideration of constraints related to shape control of the rolled material. Therefore, even at the tail end of the rolled material, the thickness can be controlled without deviating significantly from the standard, reducing thickness defects at the tail end and improving product yield.

[0203] In the second embodiment, which control parameters to control among the roll gap, roll speed, lubricant supply amount, bending force, roll cross angle, roll shift amount, and roll crown can be appropriately determined taking into consideration constraints on the equipment, constraints related to shape control of the rolled material, etc. For example, if changing the roll gap would result in a large change in the thickness of the rolled material that would deviate from the standard, the control device 30 can preferably control only the bending force so as to reduce the first type parallel stiffness.

[0204] (4-2.Meandering Control Method) The processing procedure of the meandering control method according to the second embodiment will be described with reference to Fig. 23. Fig. 23 is a flowchart showing an example of the processing procedure of the meandering control method according to the second embodiment. Note that each process shown in Fig. 23 can be executed by each function of the control device 30 shown in Fig. 22 described above.

[0205] The meandering control method according to the second embodiment is initiated at the timing when the release of the tail end of the rolled material is detected in a rolling stand that serves as a reference for starting meandering control and is located upstream of the rolling stand (Mth stand) 1 to be controlled. In the meandering control method according to the second embodiment, first, a changeable range of the control parameters is calculated based on constraint conditions (step S201). The constraint conditions include, for example, constraint conditions on the equipment and constraint conditions related to shape control of the rolled material. The processing shown in step S201 corresponds to, for example, the processing executed by the changeable range calculation unit 31 shown in FIG. 22.

[0206] Next, the value of the control parameter that minimizes the first-type parallel stiffness is calculated within the calculated changeable range (step S203). Then, the calculated value of the control parameter that minimizes the first-type parallel stiffness is determined as the control target value of the control parameter (step S205). The processes shown in steps S203 and S205 correspond to, for example, the processes executed by the control target value determiner 32 shown in FIG. 22.

[0207] Next, the control parameters of the rolling stand 1 are controlled based on the determined control target values (step S207). The processing shown in step S207 corresponds to the processing executed by the drive control unit 33 shown in FIG.

[0208] The processing procedure of the meandering control method according to the second embodiment has been described above with reference to Fig. 23. The processing of Fig. 23 is performed for one or more control parameters selected from the roll gap, roll speed, lubricant supply rate, bending force, roll cross angle, roll shift amount, and roll crown. In the second embodiment, the series of processing shown in Fig. 23 is performed as needed at predetermined intervals for the tail end portion of the material to be rolled. Therefore, the control parameters are controlled so that the first-type parallel stiffness E is always smaller at the tail end portion of the material to be rolled, and the amount of meandering in the material to be rolled can be reduced over the entire longitudinal direction of the tail end portion. [Example]

[0209] In order to confirm the effect of reducing the amount of meandering in the rolled material according to the present invention, an example will be described in which the above-described first and second embodiments are applied to a finishing tandem rolling mill for hot rolling in a steel plant.

[0210] In Examples 1, 3, 4, and 8, the meandering control method according to the first embodiment shown in FIG. 18 was applied to a finishing tandem hot rolling mill. Similarly, in Examples 2, 5 to 7, and 9, the meandering control method according to the second embodiment shown in FIG. 23 was applied to a finishing tandem hot rolling mill. Comparative Example 1 is a case in which no meandering control was performed for the tail end portion of the steel plate, and Comparative Example 2 is a case in which a meandering control method that simply performs bottom gap-up without considering the first-class parallel stiffness at the tail end portion of the rolled material, as described in Patent Document 1, was applied to a finishing tandem hot rolling mill.

[0211] In all of Examples 1 to 9 and Comparative Examples 1 and 2, the sixth stand in a finishing tandem rolling mill consisting of a total of seven rolling stands was the rolling stand to be controlled, and each meandering control method was started when the tail end of the rolled material left the preceding rolling stand (the fifth stand). The rolling conditions for the sixth stand were an outlet thickness of 2 to 3 mm, a reduction of 15 to 25%, a rolling speed of 400 to 700 mpm, a steel sheet temperature of approximately 1000°C, and a bending force of -60 (tons / chock). Table 1 below shows the verification results.

[0212] [Table 1]

[0213] As can be seen from Table 1 above, in Comparative Example 1, since meandering control at the tail end of the steel plate was not performed, meandering occurred and 0.100% of the rolling was reduced. In Comparative Example 2, meandering control at the tail end of the steel plate was performed, and as a result, the rate of meandering occurrence decreased compared to Comparative Example 1, and as a result, the rate of reduction in the rolling was reduced. However, the thickness accuracy at the tail end was worse than in Comparative Example 1.

[0214] On the other hand, in Examples 1 to 9, in which meandering control of the tail end of a steel plate was performed based on the meandering control method according to the first or second embodiment of the present invention, the occurrence rate of meandering was reduced compared to Comparative Example 1, and as a result, the occurrence rate of tapering was reduced. Furthermore, the thickness accuracy of the tail end was improved, and the yield loss rate at the tail end was also reduced. It is believed that Examples 1, 3, and 4 used the reduction position, roll speed, and lubricant supply amount as control parameters, which reduced the thickness defect at the tail end and reduced the yield loss rate at the tail end. It is believed that Examples 2, 5 to 7 used the bending force, roll shift amount, roll cross angle, and roll crown as control parameters, which reduced the occurrence of tapering. In Examples 8 and 9, a combination of control parameters highly effective in reducing thickness defect and control parameters highly effective in preventing tapering was used, which enabled both the occurrence rate of tapering and the yield loss rate at the tail end to be reduced compared to other Examples.

[0215] These results show that by controlling the roll gap and bending force so that the first-class parallel stiffness E is smaller, meandering can be further suppressed even when the first-class parallel stiffness E has a minimum value, as shown in Figures 7, 9, 11, 13, and 15. From these results, it was possible to confirm the effect of the present invention in reducing the amount of meandering in the rolled material.

[0216] (5. Supplementary Information) 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. [Explanation of symbols]

[0217] 1 rolling stand 1-1, 1-2 work rolls 2-1, 2-2 backup role 3-1, 3-2 Work roll chock 4-1, 4-2 Backup roll chocks 5-1 Incoming project block 5-2 Output project block 6-1~6-4 Work roll increase bending device 7-1~7-4 Decrease bending device 9. Housing 10 Rolled material 10 b tail end 11 Screw down device 12 load cells 13 Mill motor 15 Lubricant supply device 20, 30 Control device 21 Change amount calculation unit 22 Type 1 parallel stiffness calculation section 23, 32 Control target value determination unit 24, 33 Drive control unit 31 Changeable range calculation unit 35 Bending device 36 Roll chock drive device 37 Roll shift device 38 Roll crown change device

Claims

1. A method for controlling meandering of a rolled material, in rolling of the rolled material by N rolling stands (N is a natural number), wherein when a tail end portion of the rolled material passes through an M-th stand (1≦M≦N), at least one rolling condition of the M-th stand, including a roll gap, a roll speed, a lubricant supply amount, a bending force, a roll cross angle, a roll shift amount, and a roll crown, is changed to control meandering of the rolled material, This represents the wedge amount when the center of the rolled material in the width direction is shifted by a unit amount from the mill center while the line load applied to the rolled material from the work rolls is constant in the width direction of the rolled material, and when variables that depend on at least the line load, the bending force, the roll cross angle, the roll shift amount, and the roll crown are defined as first type parallel stiffness, Calculating a current value of the first type parallel stiffness before the change of rolling conditions and a predicted value of the first type parallel stiffness after the change of rolling conditions; A method for controlling meandering of a rolled material, which controls at least one of the roll gap, the roll speed, the lubricant supply amount, the bending force, the roll cross angle, the roll shift amount, and the roll crown so that the roll gap, the roll speed, the lubricant supply amount, the bending force, the roll cross angle, the roll shift amount, and the roll crown are included in the rolling conditions corresponding to the smaller value of the current value and the predicted value of the first type parallel stiffness.

2. A method for controlling meandering of a rolled material, in rolling the rolled material using N rolling stands (N is a natural number), wherein when the tail end of the rolled material passes through the Mth stand (1≦M≦N), at least one of the rolling conditions of the Mth stand, including the roll gap, roll speed, amount of lubricant supplied, bending force, roll cross angle, amount of roll shift, and roll crown, is changed to control the meandering of the rolled material, This represents the wedge amount when the center of the rolled material in the width direction is shifted by a unit amount from the mill center while the line load applied to the rolled material from the work rolls is constant in the width direction of the rolled material, and when variables that depend on at least the line load, the bending force, the roll cross angle, the roll shift amount, and the roll crown are defined as first type parallel stiffness, calculating a changeable range of a control parameter selected from at least one of the roll gap, the roll speed, the lubricant supply amount, the bending force, the roll cross angle, the roll shift amount, and the roll crown based on constraint conditions including at least one of constraint conditions on equipment and constraint conditions related to shape control of the rolled material; a meandering control method for controlling at least one of the roll gap, the roll speed, the lubricant supply amount, the bending force, the roll cross angle, the roll shift amount, and the roll crown so that the first type parallel stiffness is minimized within a changeable range of the selected control parameter.

3. A meandering control device that controls meandering of a rolled material when a tail end of the rolled material passes through an Mth stand (1≦M≦N) in rolling of the rolled material by N rolling stands (N is a natural number), comprising: a drive control unit that controls the drive of at least one of a screw down device that adjusts the roll gap of the M stand, a mill motor that adjusts the roll speed of the M stand, a lubricant supply device that adjusts the amount of lubricant supplied to the M stand, a bending device that adjusts the bending force, a roll chock drive device that adjusts the roll cross angle of the M stand, a roll shift device that adjusts the amount of roll shift of the M stand, and a roll crown changing device that adjusts the roll crown of the M stand while the rolled material is being threaded; This represents the wedge amount when the center of the rolled material in the width direction is shifted by a unit amount from the mill center while the line load applied to the rolled material from the work rolls is constant in the width direction of the rolled material, and when variables that depend on at least the line load, the bending force, the roll cross angle, the roll shift amount, and the roll crown are defined as first type parallel stiffness, a first type parallel stiffness calculation unit that calculates a current value of the first type parallel stiffness before a change in rolling conditions and a predicted value of the first type parallel stiffness after a change in rolling conditions, The drive control unit controls driving of at least one of the screw down device, the mill motor, the lubricant supply device, the bending device, the roll chock drive device, the roll shift device, and the roll crown changing device so that at least one of the roll gap, the roll speed, the lubricant supply amount, the bending force, the roll cross angle, the roll shift amount, and the roll crown is included in the rolling condition corresponding to the smaller value of the current value and the predicted value of the first type parallel stiffness.

4. A meandering control device that controls the meandering of a rolled material when the tail end of the rolled material passes through an Mth stand (1≦M≦N) in rolling the rolled material using N rolling stands (N is a natural number), comprising: a drive control unit that controls the drive of at least one of a screw down device that adjusts the roll gap of the M stand, a mill motor that adjusts the roll speed of the M stand, a lubricant supply device that adjusts the amount of lubricant supplied to the M stand, a bending device that adjusts the bending force, a roll chock drive device that adjusts the roll cross angle of the M stand, a roll shift device that adjusts the amount of roll shift of the M stand, and a roll crown changing device that adjusts the roll crown of the M stand while the rolled material is being threaded; This represents the wedge amount when the center of the rolled material in the width direction is shifted by a unit amount from the mill center while the line load applied to the rolled material from the work rolls is constant in the width direction of the rolled material, and when variables that depend on at least the line load, the bending force, the roll cross angle, the roll shift amount, and the roll crown are defined as first type parallel stiffness, a changeable range calculation unit that calculates a changeable range of a control parameter selected from at least one of the roll gap, the roll speed, the lubricant supply amount, the bending force, the roll cross angle, the roll shift amount, and the roll crown based on constraint conditions including at least one of constraint conditions on equipment and constraint conditions related to shape control of the rolled material, The drive control unit for the selected control parameter controls the drive of at least one of the screw down device, the mill motor, the lubricant supply device, the bending device, the roll chock drive device, the roll shift device, and the roll crown changing device so that the first type parallel stiffness is minimized within the changeable range.

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