Method for controlling warpage of metal strip

Abstract

To provide a method for controlling the warpage of a metal strip by which the warpage generated in the metal strip is further reduced when a line is stopped after the shape of the continuously conveyed metal strip is straightened using a leveler.SOLUTION: In the metal strip camber control method for controlling the elongation rate of the metal strip S to be conveyed to a target value by controlling the rotation speed of each bridle roll, and controlling the intermesh by the leveler part, when conveyance of the metal strip is stopped, the conveyance speed is switched to tension control when it becomes less than a predetermined operation lower limit speed, the intermesh by the tension leveler is released, the intermesh is released on the inlet side of the roller leveler, and the intermesh is released after being tightened by a predetermined amount on the outlet side of the roller leveler.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for controlling warpage of a metal strip that is applied when the shape of a continuously transported metal strip is corrected using a leveler. [Background technology]

[0002] Conventionally, in order to obtain flatness of metal strips such as cold-rolled steel sheets, tension levelers are generally used to straighten the shape of the metal strip. Here, a tension leveler is a device that repeatedly bends the metal strip with rolls while applying tension to the metal strip, thereby applying slight elongation strain to the metal strip and homogenizing the strain inside the metal strip to obtain good flatness. However, even with such a tension leveler, it is sometimes difficult to obtain sufficient flatness of the metal strip. For this reason, a shape straightening device is known in which a roller leveler for straightening warpage is installed downstream of the tension leveler (see, for example, Patent Document 1). Here, a roller leveler is a device that repeatedly bends the metal strip with a number of small-diameter rolls, plastically deforming the surface layer of the metal strip and relieving the internal stress of the metal strip itself.

[0003] As shown in Fig. 5, the shape straightening device described in Patent Document 1 has a payoff reel 101 that pays out a metal strip S, and a tension reel 102 that applies tension to the metal strip S while winding up the straightened metal strip S. An entry bridle roll 103, a central bridle roll 104, and an exit bridle roll 105 are arranged in this order between the payoff reel 101 and the tension reel 102. A tension leveler 110 is arranged between the entry bridle roll 103 and the central bridle roll 104, and a roller leveler 120 is arranged between the central bridle roll 104 and the exit bridle roll 105. Hereinafter, the tension leveler 110 and the roller leveler 120 will be collectively referred to as the leveler unit 100.

[0004] In the shape straightening device having such a configuration, the metal strip S leaves the payoff reel 101, passes through a tension leveler 110 and a roller leveler 120 in this order, and is wound up on a tension reel 102. In the tension leveler 110, tension is applied by an entry bridle roll 103 and a central bridle roll 104 provided before and after the tension leveler 110, and the flatness of the metal strip S is straightened. By adjusting the tension at this time, the plastic elongation of the metal strip S can be controlled.

[0005] Next, the metal strip S delivered from the central bridle roll 104 is straightened in a roller leveler 120 while being tensioned by the central bridle roll 104 and the delivery-side bridle roll 105. That is, according to the shape straightening device described in Patent Document 1, the shape of the metal strip S is first straightened by the tension leveler 110, and then the roller leveler 120 gradually reduces the residual stress difference in the metal strip S, thereby straightening the warp of the metal strip S. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-259736 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-45911 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-180331 Summary of the Invention [Problem to be solved by the invention]

[0007] In the shape straightening device described in Patent Document 1, the leveler unit 100 may need to be stopped due to an equipment malfunction or the cutting of a defective coil portion. This can cause defects called press marks or warpage in the metal strip S present inside the leveler unit 100. The warped portion cannot be used as a product and is discarded, resulting in a reduced yield. Furthermore, warpage of the metal strip S can easily cause jamming in the shear line in the subsequent process. While the example shown in FIG. 5 has been described based on an example in which a bridle roll (central bridle roll) 104 is provided between the tension leveler 110 and the roller leveler 120, the same problems as described above also occur when such a central bridle roll is not provided.

[0008] In contrast, the technology described in Patent Document 2 performs tension control to apply tension to the metal strip S before the conveyance of the stopped metal strip S begins again. This allows the target tension to be reached quickly after conveyance begins, and warpage formed in the tension leveler can be corrected with high tension. Therefore, when the conveyance of the metal strip S is stopped and operation is restarted, warpage occurring in the metal strip S can be reduced, improving yield. However, simply performing this type of tension control leaves warpage formed in the leveler section remaining.

[0009] Patent Document 3 describes a technology developed to address these problems. In the technology described in Patent Document 3, the shape of a continuously transported metal strip is corrected using a leveler, and then the intermesh formed by the tension leveler is released when the transport speed of the metal strip falls below a predetermined lower limit speed before the transport of the metal strip is stopped. This prevents or suppresses the occurrence of an unsteady tension portion directly below the tension leveler, further reducing warping of the metal strip and further improving yield.

[0010] However, according to the research of the present inventors, it has been found that although the control of opening the intermesh before stopping the conveyance can reduce the warpage of the metal strip, sufficient warpage correction effect is not obtained only in the portion where the warpage is unstable while the intermesh is being opened. The reason for the insufficient warpage correction effect is that the strip passes through the roller leveler under low tension.

[0011] Therefore, the present invention has been made in consideration of such problems, and aims to provide a method for controlling warpage of a metal strip, which can further reduce the warpage that occurs in the metal strip when the line is stopped after the shape of the continuously transported metal strip has been corrected using a leveler. [Means for solving the problem]

[0012] (1) According to one aspect of the present invention, the present invention is used in a steel sheet production line including two bridle rolls disposed on the inlet side and outlet side of the line so as to stretch a metal strip, and a leveler unit having a tension leveler and a roller leveler that press the rolls against the metal strip that is stretched between the two bridle rolls and continuously transported, and A method for controlling warpage of a metal strip, the method comprising: controlling the elongation rate of the transported metal strip to a target value by controlling the rotation speed of each bridle roll; and controlling intermeshing by the leveler unit, When the conveyance of the metal strip is stopped, the method for controlling warpage of the metal strip is provided, in which the tension control is switched to when the conveyance speed falls below a predetermined lower limit speed, and the intermesh is opened by the tension leveler, and the intermesh is opened on the inlet side of the roller leveler, and the intermesh is tightened by a predetermined amount on the outlet side of the roller leveler and then opened.

[0013] (2) According to one aspect of the present invention, the present invention is used in a steel sheet production line including two bridle rolls disposed on the inlet side and outlet side of the line so as to stretch a metal strip, and a leveler unit having a tension leveler and a roller leveler that press the rolls against the metal strip that is stretched between the two bridle rolls and continuously transported, and A method for controlling warpage of a metal strip, the method comprising controlling tension of the metal strip between the entry bridle roll and the leveller section and tension of the metal strip between the leveller section and the exit bridle roll to a predetermined tension setting value by controlling the torque of each bridle roll, and controlling intermeshing by the leveller section, When the conveyance of the metal strip is stopped, the method for controlling warpage of the metal strip is provided, in which, when the conveyance speed falls below a predetermined lower limit speed, the intermesh is opened on the inlet side of the roller leveler, and the intermesh is tightened by a predetermined amount on the outlet side of the roller leveler and then opened. (3) In the method for controlling warpage of a metal strip according to (1) or (2), the tension setting value is reduced before the transport of the metal strip is stopped. [Effects of the Invention]

[0014] According to a method for controlling warpage of a metal strip according to one aspect of the present invention, when the conveyance of the metal strip is stopped, the intermesh of the tension leveler of the leveler section is opened when the conveyance speed falls below a predetermined lower limit speed. At this time, the intermesh of the roller leveler is tightened slightly, so that the roller leveler can suppress the unstable warpage portion that occurs directly below the tension leveler while the intermesh of the tension leveler is being opened. Therefore, according to the present invention, there is provided a method for controlling warpage of a metal strip that can further reduce the warpage that occurs in the metal strip when the line is stopped after the shape of the continuously conveyed metal strip has been straightened using the leveler. [Brief explanation of the drawings]

[0015] [Figure 1]1 is a diagram showing an outline of an embodiment of a leveler facility to which a method for controlling warpage of a metal strip according to an aspect of the present invention is applied. [Figure 2] 4 is a time chart showing the characteristics of elongation control, tension control, and intermesh control according to the present embodiment. [Figure 3] 4 is a time chart showing the characteristics of tension control and intermesh control according to the present embodiment. [Figure 4] 10 is a time chart showing characteristics of elongation control, tension control, and intermesh control in a comparative example. [Figure 5] FIG. 1 is a diagram showing an outline of a conventional leveler facility (a shape correction device described in Patent Document 1). DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following detailed description, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations will be omitted. The drawings are schematic and may differ from the actual product. Furthermore, the embodiments shown below exemplify devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not specify the materials, structure, arrangement, etc. of component parts as described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0017] <Leveling equipment> With reference to FIG. 1, a leveler apparatus to which a method for controlling warpage of a metal strip S according to one embodiment of the present invention is applied will be described. As shown in FIG. 1, the leveler apparatus 1 includes a leveler section 10 through which a metal strip S, which is a strip-shaped steel plate continuously conveyed in the direction of the arrow indicated by the symbol H, passes and corrects its shape. The leveler section 10 includes a tension leveler 11 and a roller leveler 12, and adjusts the intermesh of the metal strip S passing through the leveler section 10 (the depth of the rolls pressing the metal strip S in the vertical direction from a state in which the rolls are just in contact with the metal strip S while sandwiching the metal strip S). In other words, the leveler apparatus 1 is configured to perform intermesh control. The intermesh setting values ​​for the intermesh control executed here are set based on a setting table created in advance depending on the type, size, etc. of the metal strip S (the same applies to other intermesh settings in the leveler section hereinafter).

[0018] Specifically, the tension leveler 11 has two extension roll units 11A and 11B and a straightening roll unit 11C. Each of the extension roll units 11A and 11B has a pair of upper and lower rolls, and the intermeshing of the metal strip S is adjusted by moving the upper or lower roll vertically. In the extension roll units 11A and 11B and the straightening roll unit 11C (described later), the upper roll is also referred to as the upper roll, and the lower roll is also referred to as the lower roll. The leveler section control device 36 receives a preset control command for opening or tightening the intermeshing from the host computer 34 and outputs a drive signal based on the opening or tightening control command to PLGs (Pulse Generators) 45A and 45B. The opening or tightening control command is based on a detection signal from the elongation / tension control device 32, and will be described in detail later.

[0019] As a result, when drive pulses corresponding to the amount of intermeshing required to be loosened or tightened are output from the PLGs 45A, 45B to the main motors (M) 43A, 43B, the main motors 43A, 43B are driven to rotate, and the leveling roll blocks 38A, 38B, which support the lower roll relative to the upper roll via the transmissions (Gears) 41A, 41B, are moved up and down together with the lower roll, thereby adjusting the intermeshing of the metal strip S to a predetermined value.

[0020] The straightening roll unit 11C, like the stretching roll units 11A and 11B, is configured with multiple rolls arranged on both the upper and lower sides, and a leveling roll block 38C that supports the lower roll relative to the upper roll is configured integrally with the lower roll. In the straightening roll unit 11C, the leveler section control device 36 receives control commands from the host computer 34 and detection signals from the elongation / tension control device 32 and outputs a drive signal to the PLG 45C, which then drives the main motor 43C to rotate. The drive signal is based on a control command to release or tighten. As a result, the leveling roll block 38C that supports the lower roll is moved up and down via the transmission device 41C, thereby adjusting the intermesh of the metal strip S to a predetermined value.

[0021] The roller leveler 12 has a plurality of leveling rolls 12A arranged in a staggered pattern on the front and back sides of the metal strip S. The plurality of leveling rolls 12A may be any of a variety of rolls, including those that are individually adjusted to rise and fall, those that are adjusted to rise and fall as a single leveling roll block, and those that have pinch rolls on the inlet and outlet sides.

[0022] In this embodiment, similar to the configuration of the tension leveler 11, the leveler section control device 36 receives control commands from the host computer 34 and detection signals from the elongation / tension control device 32, and outputs drive signals to PLGs 46A and 46B based on the control command to open or tighten. Then, the PLGs 46A and 46B that receive the drive signals drive the main motors 44A and 44B to rotate. As a result, the leveling roll blocks 40 that support the lower rolls are moved up and down together with the lower rolls via the transmission devices 42A and 42B, thereby adjusting the intermeshing of the metal strip S to a predetermined value.

[0023] Furthermore, two bridle rolls 13A, 13B are arranged before and after the leveler section 10 so as to stretch the metal strip S. The bridle roll 13A arranged on the entry side of the line is also called the entry bridle roll, and the bridle roll 13B arranged on the exit side of the line is also called the exit bridle roll. The bridle rolls 13A, 13B adjust the conveying speed and tension of the metal strip S passing through the leveler section 10, i.e., tension control and elongation control are performed.

[0024] More specifically, rotational speed detectors 14A, 14B made of PLG are installed on the bridle rolls 13A, 13B, respectively, and a tension meter (TM) 16 for measuring the tension of the metal strip S is disposed between the leveler 10 and the exit bridle roll 13B. The rotational speed detector 14A installed on the entry bridle roll 13A is also referred to as the entry-side rotational speed detector, and the rotational speed detector 14B installed on the exit bridle roll 13B is also referred to as the exit-side rotational speed detector.

[0025] Furthermore, each of the bridle rolls 13A, 13B is rotated by a main motor (M (Motor)) 18 via a transmission device (Gear) 20A, 20B, and is also rotated by a stretching rate control motor (SM (Stretching Motor)) 22 via a transmission device 20C. This allows the stretching rate of the metal strip S passing through the leveler 10 to be controlled.

[0026] The rotation speed of the main motor 18 is controlled by a speed control device (ASR (Automatic Speed ​​Regulator)) 26A based on a command signal input from a speed command device (MRH (Master Rheostat)) 24. The rotation speed or torque of the elongation / tension control motor (SM) 22 can be controlled by either a speed command device 26B based on a command signal from the speed command device 24 or a tension control device (ATR (Automatic Tension Regulator)) 28.

[0027] In addition, either the speed control device 26B or the tension control device 28, which controls the elongation / tension control motor 22, can be selected by a changeover switch 30. The changeover switch 30 is configured to be switched by an elongation / tension control device 32 having a switching function.

[0028] The elongation / tension control device 32 receives the rotation speed of the bridle roll 13A from the rotation speed detector 14A and the rotation speed of the bridle roll 13B from the rotation speed detector 14B. The elongation / tension control device 32 also receives detected tension values ​​from the tension meter 16. The elongation / tension control device 32 also receives preset set values ​​(target values) for the elongation and tension from a host computer 34.

[0029] Furthermore, the elongation / tension control device 32 calculates the actual elongation value by taking the ratio between the input rotation speed of the bridle roll 13A and the input rotation speed of the bridle roll 13B. When the calculated actual elongation value reaches a predetermined reference range with respect to the input elongation set value, the changeover switch 30 switches between tension control by the tension control device 28 and elongation control by the speed control device 26B.

[0030] The tension control by the tension control device 28 is characterized by fast control response because it is mediated by current control of the elongation / tension control motor 22. Therefore, tension control by the tension control device 28 is applied a predetermined time before the start of line operation (0 mpm), and when the actual elongation falls, for example, within ±0.1% of the set elongation value, the tension control is switched to normal elongation control by the speed control device 26B. For example, tension control by the tension control device 28 may be applied in stages during low-speed operation down to 55 mpm. In this embodiment, the unit of "mpm" is "meters per minute." The set value for tension control executed here is set based on a setting table created in advance according to the type, size, etc. of the metal strip.

[0031] <Control action> Next, the control operation of this embodiment will be described. In this embodiment, in the normal line operation state, elongation control is performed by controlling the rotation of the elongation / tension control motor 22 using the tension control device 28, or tension control is performed by controlling the torque of the elongation / tension control motor 22 using the tension control device 28.

[0032] (elongation control) First, the case where elongation control is performed in a normal line operation state will be described with reference to Figures 1 and 2. As shown in Figure 2, first, in a normal line operation state, elongation control is performed by controlling the rotation of the elongation / tension control motor 22 using the tension control device 28. Next, when it becomes necessary to stop line operation, a signal to decelerate is sent from the speed command device 24 to the speed control device 26A, thereby decelerating the conveying speed of the metal strip S.

[0033] Thereafter, the elongation / tension control device 32 detects via the PLGS 14A, 14B that the conveying speed of the metal strip S has fallen below a predetermined lower limit operational speed, controls the changeover switch 30 to switch to tension control, and sends this detection signal to the leveler section control device 36. Here, the lower limit operational speed is the lowest speed that can be maintained as the conveying speed of the metal strip during normal operation, and is set appropriately depending on the conveying conditions of the metal strip.

[0034] When the leveler unit controller 36 receives a detection signal indicating that the operating speed has fallen below a predetermined minimum operating speed, it outputs a control command to open the intermesh to PLGs 45A, 45B, 45C, and 46A and a tightening command to PLG 46B. This opens the two extension roll units 11A and 11B, the straightening roll unit 11C, and the entrance side of the roller leveler 12 of the tension leveler 11, and tightens the exit side of the roller leveler 12. The tightening amount at the exit side of the roller leveler 12 is small, preferably between 0.5 mm and 1.0 mm. After a predetermined time has elapsed, the leveler unit controller 36 outputs a control command to open the intermesh to PLG 46B. It is preferable that the timing at which the leveler unit controller 36 outputs the control command to open the intermesh to PLG 46B coincides with the timing at which the entrance side of the roller leveler 12 is opened, i.e., when the opening operation by PLG 46A is completed. This opens the exit side of the roller leveler 12. The opening operation of the tension leveler 11 is completed before the conveyance of the metal strip S completely stops. The opening operation on the inlet side of the roller leveler 12 and the tightening and opening operation on the outlet side are also completed before the conveyance of the metal strip S completely stops.

[0035] As described above, when stopping the transport of the metal strip S, the intermesh is opened at the inlet side of the tension leveler 11 and the roller leveler 12 before the transport of the metal strip S completely stops. This prevents or suppresses the occurrence of an unsteady tension portion directly below the tension leveler 11. In addition, by controlling the intermesh to be tightened at the outlet side of the roller leveler 12, unstable warpage during the intermesh opening can be corrected, further reducing the occurrence of warpage in the rolling direction. Furthermore, when stopping the transport of the metal strip S, it is preferable to lower the tension setting value just before the stoppage, and more preferably to lower the tension setting value stepwise as shown in Figure 2. If the tension setting value before the stoppage is too high, press marks (contact marks between the metal strip S and the rolls of the tension leveler 11 and the roll leveler 12 that occur when the line is stopped) may worsen. However, lowering the tension setting value just before the stoppage not only prevents the worsening of press marks but also suppresses the occurrence of warpage.

[0036] Therefore, according to this method for controlling warpage of a metal strip, it is possible to further reduce the warpage that occurs in the metal strip S when the transport of the metal strip S is stopped and then operation is started again, thereby further improving the yield.

[0037] (tension control) Next, tension control in a normal line operation state will be described with reference to Figures 1 and 3. As shown in Figure 3, first, in a normal line operation state, tension control is performed by the tension control device 28, which controls the torque of the bridle rolls 13A, 13B, i.e., the torque of the elongation / tension control motor 22, which is the drive motor for the bridle rolls 13A, 13B. Also, operation is performed with the intermesh of the tension leveler 11 open. Next, when it becomes necessary to stop line operation, a deceleration signal is sent from the speed command device 24 to the speed control device 26A, thereby decelerating the conveying speed of the metal strip S.

[0038] Thereafter, the elongation / tension controller 32 detects via the PLGs 14A and 14B that the conveying speed of the metal strip S has fallen below a predetermined lower limit speed for operation, and sends a detection signal to the leveler section controller 36.

[0039] When the leveler unit control device 36 receives a detection signal indicating that the speed has fallen below a predetermined minimum operating speed, it outputs a control command to open the intermesh to PLG 46A and a tightening command to PLG 46B. This opens the two extension roll units 11A and 11B, the straightening roll unit 11C, and the entrance side of the roller leveler 12 of the tension leveler 11, and tightens the exit side of the roller leveler 12. The amount of tightening at the exit side of the roller leveler 12 is small, as in the first embodiment. Then, after a predetermined time has elapsed, the leveler unit control device 36 outputs a control command to open the intermesh to PLG 46B. It is preferable that the timing at which the leveler unit control device 36 outputs the control command to open the intermesh to PLG 46B coincides with the timing at which the entrance side of the roller leveler 12 is opened, i.e., when the opening operation by PLG 46A is completed. This opens the exit side of the roller leveler 12. The opening operation of the tension leveler 11 is completed before the conveyance of the metal strip S completely stops. The opening operation on the inlet side of the roller leveler 12 and the tightening and opening operation on the outlet side are also completed before the conveyance of the metal strip S completely stops.

[0040] As described above, when the conveyance of the metal strip S is stopped, the intermesh is controlled to open on the inlet side of the roller leveler 12 before the conveyance of the metal strip S is completely stopped. This makes it possible to prevent or suppress in advance the occurrence of an unsteady portion of tension directly below the tension leveler 11. At the same time, by controlling the tightening of the intermesh on the outlet side of the roller leveler 12, unstable warpage portions during the intermesh opening can be corrected, and the occurrence of warpage in the rolling direction can be further reduced.

[0041] Therefore, according to this method for controlling warpage of a metal strip, it is possible to further reduce the warpage that occurs in the metal strip S when the transport of the metal strip S is stopped and then operation is started again, thereby further improving the yield.

[0042] <Modification> Although the present invention has been described above with reference to specific embodiments, it is not intended that the invention be limited by these descriptions. By referring to the description of the present invention, other embodiments of the present invention that include various modifications in addition to the disclosed embodiments will be apparent to those skilled in the art. Therefore, it should be understood that the embodiments of the invention set forth in the claims also encompass embodiments that include these modifications described herein, either alone or in combination.

[0043] For example, in the above embodiment, an example has been described in which a facility does not have a bridle roll between the tension leveler 11 and the roller leveler 12, but the present invention is not limited to such an example. The method for controlling warpage of a metal strip S according to the present invention can also be applied to a facility that further has a bridle roll (central bridle roll) between the tension leveler 11 and the roller leveler 12. In this case as well, it is possible to reduce warpage of the metal strip S and improve the yield, similarly to the above embodiment. [Example]

[0044] Next, an example of a method for controlling warpage of a steel sheet using a leveler equipment according to one embodiment of the present invention will be described below. In this example, the sheet was threaded and stopped using tension control under normal operating conditions, and the amount of warpage of the metal strip S in the L direction was compared with the presence or absence of intermesh opening control of the roller leveler when the conveyance of the metal strip S was stopped. As a comparative example in which intermesh opening control was not performed, the tension control described in JP 2013-180331 A was used. Specifically, in the comparative example, as shown in Fig. 4, when the conveyance speed of the metal strip was stopped, control to open the intermesh by the tension leveler was performed.

[0045] The results of the examples are shown in Table 1. The amount of warpage in the rolling direction is preferably ±30 mm or less. In this example, the amount of intermesh tightening at the delivery side of the roller leveler 12 is set to 1 mm. In Table 1, #1 unit indicates the amount of warpage in the extension roll unit 11A, #2 unit indicates the amount of warpage in the extension roll unit 11B, #3 unit indicates the amount of warpage in the straightening roll unit 11C, and the multi-unit indicates the amount of warpage in the roller leveler 12.

[0046] [Table 1]

[0047] As shown in Table 1, it was confirmed that the amount of warpage in the rolling direction was smaller in all units in the Examples in which open control was performed when the rolling was stopped compared to the Comparative Example in which open control was not performed when the rolling was stopped. [Explanation of symbols]

[0048] 1 Leveling equipment 10,100 Leveller 11,110 Tension Leveler 12,120 Lola Levela 13A Bridle roll (entrance bridle roll) 13B Bridle roll (exit bridle roll) 14A Rotational speed detector (inlet rotational speed detector) 14B Rotational speed detector (output rotational speed detector) 16 Tension meter 18 Main motor 101 Payoff Reel 102 Tension reel 103 Inlet bridle roll 104 Central Bridle Roll 105 Exit bridle roll 20A~20C Transmission Device 22 Elongation / tension control motor 24 Speed ​​command device 26A, 26B Speed ​​control device 28 Tension control device 30 Changeover switch 38A~C,40 Leveling Roll Block 41A~C, 42A, 42B Transmission device 43A~C, 44A, 44B Main motor 45A~C, 46A, 46B PLG (pulse generator) S Metal Strip

Claims

1. The present invention is used in a steel sheet production line including two bridle rolls disposed at the inlet and outlet sides of the line so as to stretch a metal strip, and a leveler unit having a tension leveler and a roller leveler that press the metal strip, which is stretched between the two bridle rolls and continuously transported, against the rolls, and passes the metal strip through the leveler unit, A method for controlling warpage of a metal strip, the method comprising: controlling the elongation rate of the transported metal strip to a target value by controlling the rotation speed of each bridle roll; and controlling intermeshing by the leveler unit, When the conveyance of the metal strip is stopped, the method switches to tension control when the conveyance speed falls below a predetermined lower limit operating speed, and controls the intermesh by the tension leveler to be opened, open the intermesh on the inlet side of the roller leveler, and tighten the intermesh by a predetermined amount on the outlet side of the roller leveler and then open it.

2. The present invention is used in a steel sheet production line including two bridle rolls disposed at the inlet and outlet sides of the line so as to stretch a metal strip, and a leveler unit having a tension leveler and a roller leveler that press the metal strip, which is stretched between the two bridle rolls and continuously transported, against the rolls, and passes the metal strip through the leveler unit, A method for controlling warpage of a metal strip, the method comprising: controlling tension of the metal strip between the entry bridle roll and the leveler section and between the leveler section and the exit bridle roll to a predetermined tension setting value by controlling the torque of each bridle roll; and controlling intermeshing by the leveler section, When the conveyance of the metal strip is stopped, when the conveyance speed falls below a predetermined lower limit speed, the intermesh is opened on the inlet side of the roller leveler, and the intermesh is tightened by a predetermined amount on the outlet side of the roller leveler and then opened.

3. 3. The method for controlling warpage of a metal strip according to claim 1, further comprising the step of: lowering a tension setting value before stopping the transport of the metal strip.

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