Control device for rolling device, control unit, rolling equipment, control method for rolling device, and rolling method for metal strip

Abstract

A control device for a rolling mill apparatus which includes a pair of mill rolls for rolling a metal strip and an unwinder for unwinding the metal strip toward the pair of mill rolls includes: a tension adjustment part configured to reduce unwinder-side tension applied to the metal strip in a first period until a tail end of the metal strip exits the unwinder during rolling of the metal strip with the pair of mill rolls; and a leveling adjustment part configured to adjust leveling of the pair of mill rolls on the basis of a strip width end position of the metal strip in a strip width direction at an unwinder side of the pair of mill rolls in the first period.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a control device for a rolling mill apparatus, a control unit, a rolling mill facility, and a control method for a rolling mill apparatus and a rolling method for a metal strip.BACKGROUND ART

[0002] With a rolling mill apparatus including mill rolls, rolling may be performed in a state where the tail end of a metal strip is out of an unwinder and the tension between the unwinder and the rolling mill (hereinafter, unwinder-side tension) is zero (a unwinder-side no tension state), in order to improve the yield.

[0003] For instance, Patent Document 1 discloses a reverse-type rolling mill which rolls a strip (metal strip) while unwinding the strip from an entry reel (unwinder) and winding the strip at the delivery side winding reel (winder) and allows the tail end of the strip to exit the roll mill while rolling the tail end of the strip at the end of rolling.

[0004] Furthermore, Patent Document 1 discloses providing a mechanism which holds a strip between a rolling mill and an entry reel, and holding the strip at the entry side (unwinder side) of the rolling mill using the mechanism to apply tension when the tail end of the strip being rolled exits the entry reel in order to prevent meandering of the strip.Citation ListPatent Literature

[0005] Patent Document 1: JP3624619BSUMMARYProblems to be Solved

[0006] Meanwhile, in a case where the metal strip is rolled in the unwinder-side no tension state, the differential load (difference in the rolling loads at both end portions in the strip width direction) changes considerably and rapidly due to disappearance of the unwinder-side tension applied to the metal strip when the tail end of the metal strip exits the unwinder. As a result, the metal strip may meander, for instance, or the shape of the metal strip may become distorted due to the differential load, which may hinder appropriate operation. Thus, shape of deterioration of the metal strip is more likely to occur.

[0007] In the rolling method described in Patent document 1, the mechanism disposed between the rolling mill and the entry reel (unwinder) still holds the strip (metal strip) and applies tension after the tail end of the strip exits the entry reel, and thus the differential load does not rapidly increase when the tail end of the strip exits the entry reel. However, providing the mechanism for holding the strip and applying unwinder-side tension leads to a complex device configuration. Furthermore, when the tail end of the strip exits the mechanism, the unwinder-side tension becomes zero and the differential load rapidly increases, and thus there is still a problem of shape deterioration which may occur due to the rapid change in the differential load.

[0008] In view of the above, an object of at least one embodiment of the present invention is to provide a control device for a rolling mill apparatus, a control unit, a rolling mill facility, a control method for a rolling mill apparatus and a rolling method for a metal strip, capable of effectively suppressing shape deterioration of a metal strip while improving the yield.Solution to the Problems

[0009] A control device for a rolling mill apparatus according to at least one embodiment of the present invention is a control device for a rolling mill apparatus which includes a pair of mill rolls for rolling a metal strip and an unwinder for unwinding the metal strip toward the pair of mill rolls, and includes: a tension adjustment part configured to reduce unwinder-side tension applied to the metal strip in a first period until a tail end of the metal strip exits the unwinder during rolling of the metal strip with the pair of mill rolls; and a leveling adjustment part configured to adjust leveling of the pair of mill rolls on the basis of a strip width end position of the metal strip in a strip width direction at an unwinder side of the pair of mill rolls in the first period.

[0010] Furthermore, a control unit according to at least one embodiment of the present invention includes: a strip width end position detection part configured to detect at least one strip width end position in a width direction of the metal strip; and the control device for a rolling mill apparatus described above. The leveling adjustment part is configured to adjust the leveling on the basis of the strip width end position detected by the strip width end position detection part.

[0011] Furthermore, a rolling mill facility according to at least one embodiment of the present invention includes: a rolling mill apparatus including a pair of mill rolls for rolling a metal strip and an unwinder for unwinding the metal strip toward the pair of mill rolls; and the above described control device configured to control the rolling mill apparatus.

[0012] Furthermore, a control method according to at least one embodiment of the present invention is a control method for controlling a rolling mill apparatus including a pair of mill rolls for rolling a metal strip and an unwinder for unwinding the metal strip toward the pair of mill rolls, and includes: a step of reducing unwinder-side tension applied to the metal strip in a first period until a tail end of the metal strip exits the unwinder during rolling of the metal strip with the pair of mill rolls; and a step of adjusting leveling of the pair of mill rolls on the basis of a strip width end position of the metal strip in a strip width direction at an unwinder side of the pair of mill rolls in the first period.

[0013] Furthermore, a rolling method for a metal strip according to at least one embodiment of the present invention includes: a step of rolling a metal strip using a rolling mill apparatus including a pair of mill rolls; and an unwinder for unwinding a metal strip toward the pair of mill rolls; and a step of controlling the rolling mill apparatus by the control method according to the above control method.Advantageous Effects

[0014] According to at least one embodiment of the present invention, it is possible to provide a control device for a rolling mill apparatus, a control unit, a rolling mill facility, a control method for a rolling mill apparatus and a rolling method for a metal strip, capable of effectively suppressing shape deterioration of a metal strip while improving the yield.BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 is a schematic configuration diagram of a rolling mill facility according to an embodiment. FIG. 2 is a schematic diagram of a rolling mill according to an embodiment as seen in the conveyance direction of a metal strip. FIG. 3 is a schematic partial diagram of the rolling mill facility depicted in FIG. 1. FIG. 4 is a schematic configuration diagram of a control device according to an embodiment. FIG. 5 is a schematic flowchart of a control method for a rolling mill apparatus according to an embodiment. FIG. 6 is a graph showing time change of the rolling speed, the unwinder-side tension and the differential load when the metal strip is rolled according to the control method for a rolling mill apparatus according to an embodiment. DETAILED DESCRIPTION

[0016] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions and the like of components described in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present invention.(Configuration of rolling mill facility)

[0017] FIG. 1 is a schematic configuration diagram of a rolling mill facility to which a control device and a control method according to an embodiment are to be applied. As depicted in FIG. 1, the rolling mill facility 1 includes a rolling mill apparatus 2 for rolling a metal strip S (e.g., a steel plate having a strip shape) and a control device 30 for controlling the rolling mill apparatus 2.

[0018] The rolling mill apparatus 2 includes a rolling mill 10 including a pair of mill rolls (work rolls) 12A, 12B, a unwinder 4 disposed at the unwinder side of the rolling mill 10 (that is, the upstream side of the rolling mill 10 or the entry side to the rolling mill 10 in the traveling direction of the metal strip S being rolled) and a winder 6 disposed at the winder side of the rolling mill 10 (that is, the downstream side of the rolling mill 10 or the delivery side from the rolling mill 10 in the traveling direction of the metal strip S being rolled). In the rolling mill apparatus 2 depicted in FIG. 1, a single rolling mill 10 is disposed between the unwinder 4 and the winder 6. In some embodiments, two or more rolling mills 10 may be disposed between the unwinder 4 and the winder 6.

[0019] FIG. 2 is a schematic diagram of a rolling mill 10 according to an embodiment as seen in the conveyance direction of the metal strip S. As depicted in FIGs. 1 and 2, the rolling mill 10 includes a pair of mill rolls (work rolls) 12A,12B disposed on both surface sides of the metal strip S across the metal strip S. As depicted in FIGs. 1 and 2, the rolling mill 10 may include a pair of intermediate rolls 14A, 14B and a pair of backup rolls 16A, 16B disposed at opposite sides of the metal strip S and across the pair of mill rolls 12A, 12B. The intermediate rolls 14A, 14B and the backup rolls 16A, 16B are configured to support the mill rolls 12A, 12B. As depicted in FIG. 2, the pair of mill rolls 12A, 12B are supported rotatably by bearings (not depicted) housed in bearing boxes 22D, 22W, respectively. The pair of intermediate rolls 14A,14B are supported rotatably by bearings (not depicted) housed in bearing boxes 24D, 24W, respectively. The pair of backup rolls 16A,16B are supported rotatably by bearings (not depicted) housed in bearing boxes 26D, 26W, respectively. The rolling mill 10 includes a rolling reduction device 18 (such as a hydraulic cylinder) for rolling the metal strip S between the pair of mill rolls 12A, 12B by applying a load to the pair of mill rolls 12A, 12B.

[0020] A motor 13 is connected to the mill rolls 12A, 12B via a spindle (not depicted) or the like, such that the mill rolls 12A, 12B are rotary driven by the motor 13. When the metal strip S is rolled, the motor 13 rotates the mill rolls 12A, 12B while the rolling reduction device 18 rolls the metal strip S, and thereby a friction force is generated between the mill rolls 12A, 12B and the metal strip S. The friction force sends the metal strip S to the winder side of the mill rolls 12A, 12B.

[0021] As depicted in FIG. 2, the rolling reduction device 18 may include a pair of hydraulic cylinders 18D, 18W disposed on both sides (the first side and the second side; i.e., both sides of the mill rolls 12A, 12B in the axial direction) in the width direction (strip width direction) of the metal strip S. The pair of hydraulic cylinders 18D ,18W may be connected to the bearing boxes 26D, 26W of the upper backup roll 18A, and configured to apply a load to the mill rolls 12A, 12B via the bearing boxes 26D, 26W.

[0022] The unwinder 4 is configured to unwind the coil of the metal strip S toward the rolling mill 10. The winder 6 is configured to wind the metal strip S from the rolling mill 10. The unwinder 4 and the winder 6 may be configured to be rotary driven by motors 5, 7, respectively. Guide rolls 8, 9 for guiding conveyance of the metal strip S may be disposed between the rolling mill 10 and the unwinder 4 or the winder 6.

[0023] In some embodiments, as depicted in FIG. 1 for instance, the rolling mill apparatus 2 may be a reverse-type rolling mill apparatus (reverse mill) which reciprocate the metal strip S inserted between the pair of mill rolls 12A, 12B to roll the metal strip S. The rolling mill apparatus 2 depicted in FIG. 1 includes a pair of tension reels 3A, 3B disposed on both sides of the rolling mill 10 in the conveyance direction of the metal strip S, and is configured to roll the metal strip S with the rolling mill 10 while reciprocating the metal strip S between the pair of tension reels 3A, 3B. The respective tension reels 3A, 3B are configured to be rotary driven by the motors 5, 7 when the metal strip S is rolled and apply unwinder-side tension (tension between the unwinder and the rolling mill, that is, the entry-side tension) or winder-side tension (tension between the winder and the rolling mill, that is, the delivery-side tension) to the metal strip S, and is configured to function as the unwinder 4 and the winder 6 described above.

[0024] In the reverse-type rolling mill apparatus 2 depicted in FIG. 1, n-th (n is an odd number) rolling (e.g., first path rolling) is performed while the tension reel 3A (the tension reel functioning as the unwinder) unwinds the metal strip S toward the rolling mill 10, and the tension reel 3A (the tension reel functioning as the winder) winds the metal strip S. Once the n-th (n is an odd number) rolling (e.g. first path rolling) is completed, n-th (n is an even number) rolling (e.g., second path rolling) is performed moving the metal strip S in a traveling direction opposite to the previous traveling direction, while the tension reel 3B (the tension reel functioning as the unwinder) unwinds the metal strip S toward the rolling mill 10, and the tension reel 3A (the tension reel functioning as the winder) winds the metal strip S.. That is, the roles of the pair of tension reels 3A, 3B switch in accordance with the traveling direction (conveyance direction) of the metal strip S.

[0025] As depicted in FIG. 1, the rolling mill facility 1 includes a strip width end position detection part 42 for detecting at least one strip width end position in the width direction (strip width direction) of the metal strip S at the unwinder side (that is, the pair of mill rolls 12A, 12B) of the rolling mill 10. Herein, FIG. 3 is a diagram schematically showing a part of the rolling mill facility 1 depicted in FIG. 1, illustrating the mill rolls 12A, 12B and the strip width end position detection part 42 in a planar view. In the illustrative embodiment depicted in FIGs. 1 and 3, the strip width end position detection part 42 is configured to detect the strip width end position at the first side in the strip width direction. The signal indicating the strip width end position of the metal strip S detected by the strip width end position detection part 42 is sent to the control device 30.

[0026] As depicted in FIG. 2, the rolling mill facility 1 includes a load detection part 44 for detecting the load (rolling load) at both end portions of the mill rolls 12A, 12B. The load detection part 44 depicted in FIG. 2 includes load detectors 44D, 44W for detecting loads at respective end portions at the first side and the second side of the mill rolls 12A, 12B. The load detectors 44D, 44W may be load cells, for instance. The signals indicating loads at the end portions of the mill rolls 12A, 12B detected with the load detectors 44D, 44W are sent to the control device 30.

[0027] Furthermore, as depicted in FIG. 1, the rolling mill facility 1 includes a tension detection part 41 for detecting unwinder-side tension applied to the metal strip S. The signals indicating the unwinder-side tension of the metal strip S detected with the tension detection part 41 are sent to the control device 30.

[0028] FIG. 4 is a schematic configuration diagram of a control device 30 according to an embodiment. As depicted in FIG. 4, the control device 30 includes a tension adjustment part 32 and a leveling adjustment part 38. The control device 30 may further include a strip width end position acquisition part 34, a differential load acquisition part 36, and a rolling speed adjustment part 40.

[0029] The control device 30 includes a calculator including a processor (CPU), a main storage device (memory device; RAM and the like), an auxiliary storage device and an interface, for instance. The control device 30 is configured to receive signals indicating detection values from the tension detection part 41, the strip width end position detection part 42, and / or the load detection part 44 via an interface. The processor is configured to process the accordingly received signals. Furthermore, the processor is configured to process the program expanded in the main storage device. Accordingly, the functions of the respective functional parts described above (the tension adjustment part 32, the leveling adjustment part 38, the strip width end position acquisition part 34, the differential load acquisition part 36 and / or the rolling speed adjustment part 40) are implemented.

[0030] The content of process at the control device 30 is implemented as a program to be executed by the processor. The program may be stored in an auxiliary storage device, for instance. When the program is executed, the program is expanded in the main storage device. The processor is configured to read out the program from the main storage device, and executes the orders contained in the programs.

[0031] The tension adjustment part 32 is configured to adjust the unwinder-side tension applied to the metal strip S. The tension adjustment part 32 may be configured to adjust the unwinder-side tension applied to the metal strip S on the basis of the detection result of the tension detection part 41. The tension adjustment part 32 may be configured to adjust the unwinder-side tension by adjusting the supply current to the motor 5 (the motor for driving the unwinder 4) so as to achieve the torque of the motor 5 necessary to achieve desired unwinder-side tension. The tension adjustment part 32 may be configured to adjust the winder-side tension applied to the metal strip S.

[0032] The strip width end position acquisition part 34 is configured to obtain the strip width end position (at least one strip width end position in the width direction of the metal strip S; in the example illustrated in FIGs. 1 and 3, the strip width end position at the first side) of the metal strip S detected by the above described strip width end position detection part 42.

[0033] The differential load acquisition part 36 is configured to obtain loads at both end portions of the mill rolls 12A, 12B detected by the above described load detection part 44, that is, the load at the first end side (detection value of the load detector 44D) and the load at the second end side (detection value of the load detector 44W), and calculate the difference of the loads to obtain a differential load.

[0034] The leveling adjustment part 38 is configured to adjust leveling of the mill rolls 12A, 12B on the basis of the strip width end position of the metal strip S obtained by the strip width end position acquisition part 34 or the differential load of the mill rolls 12A, 12B obtained by the differential load acquisition part 36. Herein, the leveling of the pair of mill rolls 12A, 12B is the difference of the roll gaps at both end portions of the pair of mill rolls 12A, 12B. In the example illustrated in FIG. 2, the leveling of the pair of mill rolls 12A, 12B is the difference (G D -G W between the roll gap G D at the end portion at the first side and the roll gap G W at the end portion at the second side of the mill rolls 12.

[0035] The leveling adjustment part 38 may be configured to adjust the leveling of the mill rolls 12A, 12B by adjusting supply of oil to the hydraulic cylinders 18D, 18W (rolling devices 18) for rolling the metal strip S and discharge of oil from the hydraulic cylinders 18D, 18W.

[0036] The rolling speed adjustment part 40 is configured to adjust the rotation speed of the pair of mill rolls 12A, 12B.

[0037] The rolling speed adjustment part 40 may be configured to adjust the rotation speed of the mill rolls 12A, 12B by adjusting the supply current to the motor 13 (motor for driving the mill rolls 12A, 12B) so as to achieve the torque of the motor 13 necessary to achieve the desired rotation speed of the mill rolls 12A, 12B.

[0038] The above described control device 30 constitutes a control unit according to some embodiments with the strip width end position detection part 43 and / or the load detection part 44. It is possible to perform the control method for a rolling mill apparatus described below by applying the control unit to an existing facility (rolling mill apparatus or the like).(Control method for rolling mill apparatus)

[0039] Next, the control method for a rolling mill apparatus according to some embodiments will be described. While the following description describes a case in which the above described control device 30 is used to control a rolling mill apparatus, another device may be used to control the rolling mill apparatus or a part of the procedure or the entire procedure described below may be performed manually in some other embodiments.

[0040] To describe briefly in advance, in some embodiments, the tension adjustment part 32 reduces the unwinder-side tension applied to the metal strip S in the first period before the tail end of the metal strip S exits the unwinder 4 during rolling of the metal strip S with the pair of mill rolls 12A, 12B, and the leveling adjustment part 38 adjusts leveling of the pair of mill rolls 12A, 12B on the basis of the strip width end position in the strip width direction of the metal strip S at the unwinder side of the pair of mill rolls 12A, 12B (S400 in the flow chart in FIG. 5 described below).

[0041] Hereinafter, the control method according to some embodiments will be described more specifically. FIG. 5 is a schematic flowchart of a control method for a rolling mill apparatus according to an embodiment. FIG. 6 is a graph showing time change of the rolling speed (rotation speed of the mill rolls), the unwinder-side tension and the differential load when the metal strip S is rolled according to the control method for a rolling mill apparatus according to an embodiment. In the graph of FIG. 6, the solid line indicates a case where the control method according to an embodiment of the present invention is applied, and the dashed line indicates a case where a conventional control method is applied.

[0042] As illustrated in FIG. 5, in an embodiment, firstly, the metal strip S is rolled with the rolling mill apparatus 2 while being unwound from the unwinder 4 (S100). For instance, as shown in the graph of FIG. 6, the rolling reduction device 18 rolls the metal strip S and applies a load at time t0, and reduce the roll gap of the mill rolls 12A, 12B to be smaller than the thickness of the metal strip S. Then, at time t1, rotation of the mill rolls 12A, 12B starts, and the metal strip S is rolled while being unwound with the unwinder 4. In the example illustrated in FIG. 6, after rolling is started at time t1, the rolling speed (rotation speed of the mill rolls 12A, 12B) is increased to V1, and rolling is performed at the constant speed V1 in the third period T3 from time t2 to time t3.

[0043] Normally, during rolling of the metal strip S, the unwinder 4 applies unwinder-side tension as illustrated in FIG. 6. Accordingly, meandering of the metal strip S during rolling is suppressed. In the example illustrated in FIG. 6, a constant unwinder-side tension Te1 is applied from time t1 when rolling of the metal strip S is started to the above described time t3.

[0044] In some embodiments, in the third period T3 in which the metal strip S is rolled at the constant speed V1, the leveling adjustment part 38 may adjust leveling so that the differential load of the mill rolls 12A, 12B approaches zero (S200). If rolling is performed in a state where there is a differential load, the risk of shape deterioration of the metal strip S increases, such as corrugation of the shape of the metal strip S. It is possible to perform rolling while suppressing shape deterioration of the metal strip by adjusting the leveling so that the differential load of the mill rolls 12A, 12B approaches zero as described above.

[0045] Next, the control device 30 determines whether it is the first period T1 at the end of unwinding of the metal strip S (S300). A period at the end of unwinding of the metal strip S is a period just before the unwinder 4 releases the tail end portion of the metal strip S and the tail end exits (separates from) the unwinder 4. It is possible to determine whether it is the first period T1 at the end of unwinding of the metal strip S by, for instance, obtaining the remaining rounds of the coil of the metal strip S at the unwinder 4 or the coil diameter visually or by calculation, and determining whether the obtained value is at a predetermined value or below. It is possible to calculate the remaining rounds of the coil of the metal strip S at the unwinder 4 or the coil diameter of the coil remaining at the unwinder 4 from the rotation speed of the unwinder 4 calculated from the speed of the metal strip S.

[0046] In step S300, while it is not determined that it is the first period T1 (No in S300), rolling at the constant speed V1 and leveling adjustment based on the differential load are performed continuously.

[0047] In step S300, if it is determined that it is the first period T1 (Yes in S300), as described above, the tension adjustment part 32 reduces the unwinder-side tension applied to the metal strip S and the leveling adjustment part 38 adjusts leveling of the pair of mill rolls 12A, 12B on the basis of the strip width end position in the strip width direction of the metal strip S at the unwinder side of the pair of mill rolls 12A, 12B while rolling the metal strip S with the mill rolls 12A, 12B (S400), in the first period T1 until the tail end of the metal strip S exits the unwinder 4 (from time t3 to time t5 in FIG. 6; No in step S500 in FIG. 5).

[0048] In step S400, as depicted in FIG. 6 for instance, the tension adjustment part 32 may adjust the unwinder-side tension so that the unwinder-side tension applied to the metal strip S gradually decreases from the unwinder-side tension Te1 in the third period T3 to zero. In the example illustrated in FIG. 6, the unwinder-side tension is reduced linearly from Te1 to Te2 smaller than Te1 (a value close to zero) in the first section T1a (from time t3 to t4) of the first period T1, and maintained at Te2 in the second section T1b (from time t4 to t5) of the first period T1. At the end of the first period T1 (time t5), the tail end of the metal strip S exits the unwinder 4, and thus the unwinder-side tension is zero.

[0049] In step S400, during the first period T1 (the first section T1a and the second section T1b), the leveling adjustment part 38 may adjust the leveling of the mill rolls 12A, 12B so that the strip width end position of the metal strip S falls within a predetermined range. For instance, the leveling adjustment part 38 may adjust the leveling of the mill rolls 12A, 12B so that the strip width end position of the metal strip S falls within a range where the distance from a predetermined position X1 in the strip width direction falls within the range α (see FIG. 3).

[0050] In the second period T2 (period from time t5 to t6 in FIG. 6) after the tail end of the metal strip S exits the unwinder 4 (that is, after the first period T1; Yes in S500 in FIG. 5), the mill rolls 12A, 12B are rotated while rolling the metal strip S with the mill rolls 12A, 12B in a state where the unwinder-side tension of the metal strip S is zero (that is, in the unwinder-side no tension state). As described above, while the metal strip S is rolled in the unwinder-side no tension state in the second period T2, the leveling adjustment part 38 may adjust the leveling of the mill rolls 12A, 12B so that the strip width end position of the metal strip S falls within a predetermined range continuously from the first period T1 (that is, over the first period T1 and the second period T2) (S600). For instance, the leveling adjustment part 38 may adjust the leveling of the mill rolls 12A, 12B so that the strip width end position of the metal strip S is within a range where the distance from a predetermined position X1 in the strip width direction is α (see FIG. 3). Accordingly, it is possible to suppress meandering of the metal strip which is likely to occur when the metal strip S is rolled in the unwinder-side no tension state.

[0051] In S600, rolling may be continued until the tail end of the metal strip S reaches the vicinity of the unwinder side of the mill rolls 12A, 12B (until time t6 in FIG. 6). Then, the rolling mill 10 may pause, and perform rolling of the next path. In rolling of the next path, the rolling direction (traveling direction of the metal strip S) is opposite to that of the previous path, where rolling is performed while the unwinder 4 in the previous path becomes the winder 6 and winds the metal strip S.

[0052] Typically, in a case where rolling is performed in the unwinder-side no tension state of the metal strip S, the unwinder-side tension applied to the metal strip S in a period until the tail end of the metal strip S exits the unwinder is normally constant (see the dashed line indicating the unwinder-side tension in the graph of FIG. 6). In this case, the unwinder-side tension disappears immediately when the tail end of the metal strip S exits the unwinder 4 (time 5 in FIG. 6), and thus the differential load rapidly increases (see the dashed line indicating the differential load in the graph of FIG. 6). An increase in the differential load may cause meandering of the metal strip S, and may lead to shape deterioration of the metal strip S being rolled.

[0053] Contrary to this, in the method according to the above described embodiment, in step S400, the unwinder-side tension is reduced gradually in the first period T1 (the period at the end of unwinding of the metal strip S) until the tail end of the metal strip S being rolled exits the unwinder 4 (see the solid line indicating the unwinder-side tension in the graph of FIG. 6). Thus, in a case where rolling is performed in the unwinder-side no tension state after the tail end of the metal strip S exits the unwinder 4 (i.e., the above described step S600), it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip S exits the unwinder 4 (see the solid line indicating the differential load in the graph of FIG. 6). Accordingly, it is possible to suppress shape deterioration of the metal strip S when the metal strip S is rolled in the unwinder-side no tension state.

[0054] Furthermore, conventionally, in typical control of rolling of the metal strip S, shape deterioration is suppressed by adjusting the leveling so that the differential load of the mill rolls approaches zero while the unwinder-side tension is applied to the metal strip S, and meandering of the metal strip S is suppressed by adjusting the leveling so that the strip width end position of the metal strip S falls within a predetermined range once the tail end of the metal strip S exits the unwinder 4 and the unwinder-side tension is released. However, in this case, the differential load rapidly increases when the tail end of the metal strip S exits the unwinder 4, and thereby meandering is likely to occur rapidly. Even if leveling adjustment on the basis of the strip width end position is started in such a state, it may be difficult to perform an appropriate control, and it may be difficult to appropriately suppress meandering of the metal strip S.

[0055] Contrary to this, with the method according to the above described embodiment, the leveling adjustment is performed (started) on the basis of the strip width end position of the metal strip S at the unwinder side of the mill rolls 12A, 12B while the unwinder-side tension decreases (the first period T1), and thus it is possible to perform an appropriate control on meandering compared to a case where the leveling adjustment on the basis of the strip width end position of the metal strip S is started after the unwinder-side tension is released in a case rolling is performed in the unwinder-side no tension state. Thus, it is possible to further suppress shape deterioration of the metal strip S when the metal strip S is rolled in the unwinder-side no tension state.

[0056] Therefore, according to the above described embodiment, it is possible to effectively suppress shape deterioration of the metal strip S when the metal strip S is rolled in the unwinder-side no tension state. That is, according to the above described embodiment, it is possible to improve the yield while suppressing shape deterioration of the metal strip S effectively.

[0057] In some embodiments, in step S400, the leveling adjustment part 38 may adjust the leveling of the mill rolls 12A, 12B on the basis of the strip width end position of the metal strip S in the strip width direction at the unwinder side of the mill rolls 12A, 12B and the differential load of the mill rolls 12A, 12B in the first period T1.

[0058] More specifically, in step S400 (that is, during the first period T1 (the first section T1a and the second section T1b)), the leveling adjustment part 38 may adjust the leveling so that the strip width end position of the metal strip S in the strip width direction at the unwinder side of the mill rolls 12A, 12B is within a predetermined range and so that the differential load of the mill rolls 12A, 12B does not exceed a limit value LD A (see FIG. 6).

[0059] That is, in step S400, the leveling adjustment part 38 may limit the adjustment amount of the leveling so that the differential load does not exceed the limit value LD A when the differential load of the mill rolls 12A, 12B is about to exceed the limit value LD A as a result of leveling adjustment on the basis of the strip width end position.

[0060] Even in a case where meandering control is performed on the metal strip S by leveling adjustment on the basis of the strip width end position at the unwinder side of the mill rolls 12A, 12B in step S400, if the differential load of the mill rolls 12A, 12B is too high, the shape of the metal strip S may deteriorate, which may rather cause meandering of the metal strip S. In this regard, according to the above embodiment, the leveling is adjusted so that the differential load does not exceed the limit value LD A on the basis of the differential load of the mill rolls 12A, 12B in addition to the strip width end position of the metal strip S at the unwinder side of the mill rolls 12A, 12B while the unwinder-side tension decreases (in the first period T1), and thus meandering of the metal strip S is less likely to occur when the tail end of the metal strip S exits the unwinder 4 and the unwinder-side tension becomes zero. Thus, it is possible to further suppress meandering of the metal strip S when the metal strip S is rolled in the unwinder-side no tension state.

[0061] In some embodiments, in step S400, the rolling speed adjustment part 40 may reduce the rotation speed of the pair of mill rolls 12A, 12B in the first period T1 (see FIG. 6).

[0062] In the above described embodiment, the rotation speed of the mill rolls 12A, 12B is reduced (that is, the rolling speed is reduced) in the first period T1 in which the unwinder-side tension is reduced and the leveling adjustment is performed on the basis of the strip width end position at the unwinder side. Accordingly, it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip S exits the unwinder 4 more effectively, and suppress meandering of the metal strip S which may occur when rolling is performed in the unwinder-side no tension state after the tail end of the metal strip S exits the unwinder 4 more effectively. Therefore, according to the above described embodiment, it is possible to effectively suppress shape deterioration of the metal strip S when the metal strip S is rolled in the unwinder-side no tension state.

[0063] The contents described in the above respective embodiments can be understood as follows, for instance. (1) A control device (30) for a rolling mill apparatus according to at least one embodiment of the present invention is a control device for controlling a rolling mill apparatus (2) which includes a pair of mill rolls (12A, 12B) for rolling a metal strip (S) and an unwinder (4) for unwinding the metal strip toward the pair of mill rolls and includes: a tension adjustment part (32) configured to reduce unwinder-side tension applied to the metal strip in a first period (T1) until a tail end of the metal strip exits the unwinder during rolling of the metal strip with the pair of mill rolls; and a leveling adjustment part (38) configured to adjust leveling of the pair of mill rolls on the basis of a strip width end position of the metal strip in a strip width direction at an unwinder side of the pair of mill rolls in the first period.

[0064] With the above configuration (1), the unwinder-side tension is reduced gradually in the first period until the tail end of the metal strip being rolled exits the unwinder (the period at the end of unwinding of the metal strip). Thus, in a case where rolling is performed in the unwinder-side no tension state, it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip is released from the unwinder. Accordingly, it is possible to suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. Furthermore, with the above configuration (1), the leveling adjustment is performed on the basis of the strip width end position of the metal strip at the unwinder side of the mill rolls while the unwinder-side tension decreases (the first period), and thus it is possible to perform an appropriate meandering control compared to a case where the leveling adjustment on the basis of the strip width end position of the metal strip is started after the unwinder-side tension is released in a case rolling is performed in the unwinder-side no tension state. Thus, it is possible to further suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0065] Therefore, with the above configuration (1), it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. That is, with the above configuration (1), it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0066] (2) In some embodiments, in the above configuration (1), the leveling adjustment part is configured to adjust the leveling so that the strip width end position falls within a predetermined range in the first period.

[0067] With the above configuration (2), the leveling is adjusted so that the strip width end position of the metal strip at the unwinder side of the mill rolls falls within a predetermined range while the unwinder-side tension decreases (in the first period), and thus meandering of the metal strip is less likely to occur when the tail end of the metal strip exits the unwinder and the unwinder-side tension becomes zero. Thus, it is possible to suppress meandering of the metal strip more appropriately when the metal strip is rolled in the unwinder-side no tension state.

[0068] (3) In some embodiments, in the above configuration (1) or (2), the control device is configured to rotate the pair of mill rolls while rolling the metal strip with the pair of mill rolls in the unwinder-side no tension state in a second period (T2) after the first period.

[0069] With the above configuration (3), the metal strip is rolled in the unwinder-side no tension state in the second period after the first period in which the unwinder-side tension is reduced and the leveling is adjusted on the basis of the strip width end position at the unwinder side. Thus, it is possible to suppress shape deterioration of the metal strip effectively in the second period in which the metal strip is rolled in the unwinder-side no tension state. Accordingly, it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0070] (4) In some embodiments, in the above configuration (3), the leveling adjustment part is configured to adjust the leveling of the pair of mill rolls so that the strip width end position falls within a predetermined range over the first period and the second period.

[0071] With the above configuration (4), in the second period in which the metal strip is rolled in the unwinder-side no tension state, the leveling is adjusted so that the strip width end position of the metal strip falls within a predetermined range at the unwinder side of the mill rolls, and thus it is possible to appropriately suppress meandering of the metal strip when the metal strip is rolled in the unwinder-side no tension state. Therefore, it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0072] (5) In some embodiments, in any one of the above configurations (1) to (4), the leveling adjustment part is configured to adjust the leveling of the pair of mill rolls on the basis of the strip width end position and a differential load of the pair of mill rolls in the first period.

[0073] Even in a case where a meandering control is performed on the metal strip by leveling adjustment on the basis of the strip width end position at the unwinder side of the mill rolls, if the differential load of the mill rolls is too high, the shape of the metal strip may deteriorate, which may rather cause meandering of the metal strip. In this regard, with the above configuration (5), the leveling is adjusted on the basis of the differential load of the mill rolls in addition to the strip width end position of the metal strip at the unwinder side of the mill rolls while the unwinder-side tension decreases (in the first period), and thus meandering of the metal strip is even less likely to occur when the tail end of the metal strip exits the unwinder and the unwinder-side tension becomes zero. Thus, it is possible to further suppress meandering of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0074] (6) In some embodiments, in the above configuration (5), the leveling adjustment part is configured to adjust the leveling so that the strip width end position falls within a predetermined range and the differential load does not exceed a limit value in the first period.

[0075] With the above configuration (6), the leveling is adjusted so that the strip width end position of the metal strip falls within a predetermined range at the unwinder side of the mill rolls and so that the differential load of the mill rolls does not exceed the limit value while the unwinder-side tension decreases (in the first period), and thus meandering of the metal strip is less likely to occur when the tail end of the metal strip exits the unwinder and the unwinder-side tension becomes zero. Thus, it is possible to suppress meandering of the metal strip appropriately when the metal strip is rolled in the unwinder-side no tension state.

[0076] (7) In some embodiments, in the above configuration (6), the leveling adjustment part is configured to limit an adjustment amount of the leveling such that the differential load does not exceed the limit value when the differential load is about to exceed the limit value as a result of leveling adjustment on the basis of the strip width end position.

[0077] With the above configuration (7), the adjustment amount of the leveling is limited so that the differential load does not exceed the limit value when the differential load of the mills rolls is about to exceed the limit value as a result of the leveling adjustment so that the strip width end position of the metal strip falls within a predetermined range at the unwinder side of the mill rolls while the unwinder-side tension decreases (in the first period), and thus meandering of the metal strip is less likely to occur when the tail end of the metal strip exits the unwinder and the unwinder-side tension becomes zero. Thus, it is possible to suppress meandering of the metal strip appropriately when the metal strip is rolled in the unwinder-side no tension state.

[0078] (8) In some embodiments, in any one of the above configurations (1) to (7), the leveling adjustment part is configured to adjust the leveling such that the differential load of the pair of mill rolls approaches zero during a third period (T3) in which the metal strip is rolled in a state where the unwinder-side tension is constant, and configured to adjust the leveling so that the strip width end position falls within a predetermined range in the first period after the third period.

[0079] With the above configuration (8), the leveling is adjusted so that the differential load of the mill rolls approaches zero in the third period in which the metal strip is rolled at a constant unwinder-side tension, and then the leveling is adjusted so that the strip width end position of the metal strip at the unwinder side of the mill rolls falls within a predetermined range while the unwinder-side tension decreases (the first period). Thus, it is possible to suppress shape deterioration of the metal strip due to the differential load in the third period (normal operation) in which the metal strip is rolled while the unwinder-side tension is constant, and the leveling adjustment is switched to adjustment on the basis of the strip width end position in the first period at the end of unwinding of the metal strip, whereby meandering of the metal strip is less likely to occur when the tail end of the metal strip exits the unwinder and the unwinder-side tension becomes zero. Thus, it is possible to effectively suppress shape deterioration of the metal strip being rolled during normal operation before decreasing the unwinder-side tension and during rolling in the unwinder-side no tension state after the unwinder-side tension is decreased to zero. Thus, with the above configuration (8), it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0080] (9) In some embodiments, in any one of the above configurations (1) to (8), the control device further includes a rolling speed adjustment part (40) configured to reduce a rotation speed of the pair of mill rolls in the first period.

[0081] With the above configuration (9), the rotation speed of the mill rolls is reduced (that is, the rolling speed is reduced) in the first period in which the unwinder-side tension is reduced and the leveling adjustment is performed on the basis of the strip width end position at the unwinder side. Accordingly, it is possible to suppress a rapid increase in the differential load more effectively when the tail end of the metal strip exits the unwinder, and suppress meandering of the metal strip which may occur when rolling is performed in the unwinder-side no tension state after the tail end of the metal strip exits the unwinder more effectively. Therefore, with the above configuration (9), it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0082] (10) According to at least one embodiment of the present invention, a control unit includes: a strip width end position detection part (42) configured to detect at least one strip width end position in a width direction of the metal strip; and the control device (30) for a rolling mill apparatus according to any one of the above (1) to (9). The leveling adjustment part is configured to adjust the leveling on the basis of the strip width end position detected by the strip width end position detection part.

[0083] With the above configuration (10), the unwinder-side tension is reduced gradually in the first period until the tail end of the metal strip being rolled exits the unwinder (the period at the end of unwinding of the metal strip). Thus, in a case where rolling is performed in the unwinder-side no tension state, it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip exits from the unwinder. Accordingly, it is possible to suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. With the above configuration (10), the leveling adjustment is performed on the basis of the strip width end position of the metal strip at the unwinder side of the mill rolls while the unwinder-side tension decreases (the first period), and thus it is possible to perform an appropriate meandering control compared to a case where the leveling adjustment on the basis of the strip width end position of the metal strip is started after the unwinder-side tension becomes zero in a case rolling is performed in the unwinder-side no tension state. Thus, it is possible to further suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0084] Therefore, with the above configuration (10), it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. That is, with the above configuration (10), it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0085] (11) According to at least one embodiment of the present invention, a rolling mill facility (1) includes: a rolling mill apparatus (2) including a pair of mill rolls (12A, 12B) for rolling a metal strip and an unwinder (4) for unwinding the metal strip toward the pair of mill rolls; and the control device (30) according to any one of the above (1) to (9) configured to control the rolling mill apparatus.

[0086] With the above configuration (11), the unwinder-side tension is reduced gradually in the first period until the tail end of the metal strip being rolled exits the unwinder (the period of the end of unwinding of the metal strip). Thus, in a case where rolling is performed in the unwinder-side no tension state, it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip is released from the unwinder. Accordingly, it is possible to suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. Furthermore, with the above configuration (11), the leveling adjustment is performed on the basis of the strip width end position of the metal strip at the unwinder side of the mill rolls while the unwinder-side tension decreases (the first period), and thus it is possible to perform an appropriate meandering control compared to a case where the leveling adjustment on the basis of the strip width end position of the metal strip is started after the unwinder-side tension becomes zero in a case where rolling is performed in the unwinder-side no tension state. Thus, it is possible to further suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0087] Therefore, with the above configuration (11), it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. That is, with the above configuration (11), it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0088] (12) In some embodiments, in the above configuration (11), the rolling mill facility further includes: a strip width end position detection part (42) for detecting at least one strip width end position in a width direction of the metal strip at an unwinder side of the pair of mill rolls. The leveling adjustment part of the control device is configured to adjust the leveling on the basis of the strip width end position detected by the strip width end position detection part.

[0089] With the above configuration (12), the unwinder-side tension is reduced gradually in the first period until the tail end of the metal strip being rolled exits the unwinder (the period at the end of unwinding of the metal strip). Thus, in a case where rolling is performed in the unwinder-side no tension state, it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip exits the unwinder. Accordingly, it is possible to suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. Furthermore, with the above configuration (12), the leveling adjustment is performed on the basis of the strip width end position of the metal strip at the unwinder side of the mill rolls while the unwinder-side tension decreases (the first period), and thus it is possible to perform an appropriate meandering control compared to a case where the leveling adjustment on the basis of the strip width end position of the metal strip is started after the unwinder-side tension is released in a case rolling is performed in the unwinder-side no tension state. Thus, it is possible to further suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0090] Therefore, with the above configuration (12), it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. That is, with the above configuration (12), it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0091] (13) A control method for a rolling mill apparatus according to at least one embodiment of the present invention is a control method for controlling a rolling mill apparatus (2) including a pair of mill rolls (12A, 12B) for rolling a metal strip (S) and an unwinder (4) for unwinding the metal strip toward the pair of mill rolls and includes: a step (S400) of reducing unwinder-side tension applied to the metal strip in a first period (T1) until a tail end of the metal strip exits the unwinder during rolling of the metal strip with the pair of mill rolls; and a step (S400) of adjusting leveling of the pair of mill rolls on the basis of a strip width end position of the metal strip in a strip width direction at an unwinder side of the pair of mill rolls in the first period.

[0092] With the above method (13), the unwinder-side tension is reduced gradually in the first period until the tail end of the metal strip being rolled exits the unwinder (the period at the end of unwinding of the metal strip). Thus, in a case where rolling is performed in the unwinder-side no tension state, it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip exits the unwinder. Accordingly, it is possible to suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. Furthermore, according to the above method (13), the leveling adjustment is performed on the basis of the strip width end position of the metal strip at the unwinder side of the mill rolls while the unwinder-side tension decreases (the first period), and thus it is possible to perform an appropriate meandering control compared to a case where the leveling adjustment on the basis of the strip width end position of the metal strip is started after the unwinder-side tension becomes zero in a case rolling is performed in the unwinder-side no tension state. Thus, it is possible to further suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0093] Therefore, according to the above method (13), it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. That is, according to the above method (13), it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0094] (14) A rolling method for a metal strip according to at least one embodiment of the present invention includes: a step (S100) of rolling a metal strip (S) using a rolling mill apparatus (2) including a pair of mill rolls (12A, 12B) and an unwinder (4) for unwinding a metal strip toward the pair of mill rolls; and a step (S400) of controlling the rolling mill apparatus by the control method according to the above (13).

[0095] According to the above method (14), the unwinder-side tension is reduced gradually in the first period until the tail end of the metal strip being rolled exits the unwinder (the period at the end of unwinding of the metal strip). Thus, in a case where rolling is performed in the unwinder-side no tension state, it is possible to suppress a rapid increase in the differential load when the tail end of the metal strip is released from the unwinder. Accordingly, it is possible to suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. Furthermore, according to the above method (14), the leveling adjustment is performed on the basis of the strip width end position of the metal strip at the unwinder side of the mill rolls while the unwinder-side tension decreases (the first period), and thus it is possible to perform an appropriate meandering control compared to a case where the leveling adjustment on the basis of the strip width end position of the metal strip is started after the unwinder-side tension becomes zero in a case rolling is performed in the unwinder-side no tension state. Thus, it is possible to further suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state.

[0096] Therefore, according to the above method (14), it is possible to effectively suppress shape deterioration of the metal strip when the metal strip is rolled in the unwinder-side no tension state. That is, according to the above method (14), it is possible to improve the yield while suppressing shape deterioration of the metal strip effectively.

[0097] Embodiments of the present invention were described in detail above, but the present invention is not limited thereto, and various amendments and modifications may be implemented.

[0098] Further, in the present specification, an expression of relative or absolute arrangement such as "in a direction", "along a direction", "parallel", "orthogonal", "centered", "concentric" and "coaxial" shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function.

[0099] For instance, an expression of an equal state such as "same" "equal" and "uniform" shall not be construed as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or a difference that can still achieve the same function.

[0100] Further, for instance, an expression of a shape such as a rectangular shape or a cylindrical shape shall not be construed as only the geometrically strict shape, but also includes a shape with unevenness or chamfered corners within the range in which the same effect can be achieved.

[0101] On the other hand, an expression such as "comprise", "include", "have", "contain" and "constitute" are not intended to be exclusive of other components.

[0102] 1Rolling mill facility 2Rolling mill apparatus 3ATension reel 3ATension reel 4Unwinder 5Motor 6Winder 7Motor 8Guide roll 9Guide roll 10Rolling mill 12Mill roll 12AMill roll 12BMill roll 13Motor 14AIntermediate roll 14BIntermediate roll 16ABackup roll 16BBackup roll 18Rolling reduction device 18AUpper backup roll 18DHydraulic cylinder 18WHydraulic cylinder 20Scratch detection device 22DBearing box 22WBearing box 24DBearing box 24WBearing box 26DBearing box 26WBearing box 30Control device 32Tension adjustment part 34Strip width end position acquisition part 36Differential load acquisition part 38Leveling adjustment part 40Rolling speed adjustment part 41Tension detection part 42Strip width end position detection part 44Load detection part 44DLoad detector 44WLoad detector SMetal strip

Claims

1. A control device for a rolling mill apparatus which includes a pair of mill rolls for rolling a metal strip and an unwinder for unwinding the metal strip toward the pair of mill rolls, the control device comprising: a tension adjustment part configured to reduce unwinder-side tension applied to the metal strip in a first period until a tail end of the metal strip exits the unwinder during rolling of the metal strip with the pair of mill rolls; and a leveling adjustment part configured to adjust leveling of the pair of mill rolls on the basis of a strip width end position of the metal strip in a strip width direction at an unwinder side of the pair of mill rolls in the first period.

2. The control device for a rolling mill apparatus according to claim 1, wherein the leveling adjustment part is configured to adjust the leveling so that the strip width end position falls within a predetermined range in the first period.

3. The control device for a rolling mill apparatus according to claim 1 or 2, wherein the control device is configured to rotate the pair of mill rolls while rolling the metal strip with the pair of mill rolls in the unwinder-side no tension state in a second period after the first period.

4. The control device for a rolling mill apparatus according to claim 3, wherein the leveling adjustment part is configured to adjust the leveling of the pair of mill rolls so that the strip width end position falls within a predetermined range over the first period and the second period.

5. The control device for a rolling mill apparatus according to claim 1 or 2, wherein the leveling adjustment part is configured to adjust the leveling of the pair of mill rolls on the basis of the strip width end position and a differential load of the pair of mill rolls in the first period.

6. The control device for a rolling mill apparatus according to claim 5, wherein the leveling adjustment part is configured to adjust the leveling so that the strip width end position falls within a predetermined range and the differential load does not exceed a limit value in the first period.

7. The control device for a rolling mill apparatus according to claim 6, wherein the leveling adjustment part is configured to limit an adjustment amount of the leveling such that the differential load does not exceed the limit value when the differential load is about to exceed the limit value as a result of leveling adjustment on the basis of the strip width end position.

8. The control device for a rolling mill apparatus according to claim 1 or 2, wherein the leveling adjustment part is configured to adjust the leveling such that the differential load of the pair of mill rolls approaches zero during a third period in which the metal strip is rolled in a state where the unwinder-side tension is constant, and configured to adjust the leveling so that the strip width end position falls within a predetermined range in the first period after the third period.

9. The control device for a rolling mill apparatus according to claim 1 or 2, further comprising a rolling speed adjustment part configured to reduce a rotation speed of the pair of mill rolls in the first period.

10. A control unit, comprising: a strip width end position detection part configured to detect at least one strip width end position in a width direction of the metal strip; and the control device for a rolling mill apparatus according to claim 1 or 2, wherein the leveling adjustment part is configured to adjust the leveling on the basis of the strip width end position detected by the strip width end position detection part.

11. A rolling mill facility comprising: a rolling mill apparatus including a pair of mill rolls for rolling a metal strip and an unwinder for unwinding the metal strip toward the pair of mill rolls; and the control device according to claim 1 or 2 configured to control the rolling mill apparatus.

12. The rolling mill facility according to claim 11, further comprising: a strip width end position detection part for detecting at least one strip width end position in a width direction of the metal strip at an unwinder side of the pair of mill rolls, wherein the leveling adjustment part of the control device is configured to adjust the leveling on the basis of the strip width end position detected by the strip width end position detection part.

13. A control method for controlling a rolling mill apparatus including a pair of mill rolls for rolling a metal strip and an unwinder for unwinding the metal strip toward the pair of mill rolls, the method comprising: a step of reducing unwinder-side tension applied to the metal strip in a first period until a tail end of the metal strip exits the unwinder during rolling of the metal strip with the pair of mill rolls; and a step of adjusting leveling of the pair of mill rolls on the basis of a strip width end position of the metal strip in a strip width direction at an unwinder side of the pair of mill rolls in the first period.

14. A rolling method for a metal strip, comprising: a step of rolling a metal strip using a rolling mill apparatus including a pair of mill rolls; and an unwinder for unwinding a metal strip toward the pair of mill rolls; and a step of controlling the rolling mill apparatus by the control method according to claim 13.

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