JP5263832B2 - Rolling equipment control device and control method - Google Patents

Description

  The present invention relates to a control apparatus and control method for cold rolling equipment.

  In cold rolling equipment, when the torque current of the motor is increased when the rolling line is stopped or when the rolling line is operated at an extremely low speed, the current is concentrated in some circuits of the motor or some switching elements of the inverter. To do. For this reason, some circuits of the motor and / or some switching elements of the inverter may be damaged. In order to prevent this, measures are taken such as reducing or limiting the torque current when the rolling line is stopped or not operating the rolling line at a very low speed.

  In the rolling facility described in Patent Document 1, the operation of the rolling line is continued at a low speed of 0 mpm (m / min) or more and 50 mpm or less until the welding of the material to be rolled is completed in the welded portion. Therefore, it is necessary to install an electric motor and an inverter having a sufficiently large current capacity. Actually, in addition to the operation at the normal line speed of the rolling line, in order to enable the rolling line to operate at a very low speed in the same rolling state as the operation at the normal line speed of the rolling line, Compared to conventional rolling equipment, a large capital investment that is excessive with respect to the achieved rolling performance is required.

International Publication No. 2008/062506 Pamphlet

  In a cold rolling facility, an AC motor and an inverter that drives the AC motor are generally used to drive a rolling mill, a take-up reel, a pay-out reel, and the like. An alternating current motor rotates when an alternating current is passed through a rotor or a stator to generate torque. The frequency of the alternating current is shifted by the slip frequency in the direction in which torque is generated from the rotational frequency of the electric motor. When operating at a low speed or an extremely low speed, the number of rotations of the AC motor also decreases, and the frequency on the inverter primary side (motor side) also decreases.

  When the motor generates torque in the rotation direction, the primary frequency of the inverter is larger than the rotation frequency of the motor by the slip frequency, but generates torque in the direction opposite to the rotation direction of the motor (regeneration direction). In this case, the primary frequency becomes smaller by the slip frequency than the rotation frequency of the electric motor.

  For this reason, when the motor is operated at a low speed in the regeneration direction, the primary frequency of the inverter becomes close to zero (direct current). An inverter is generally composed of a switching element, but since an electric motor is an inductance load, a direct current resistance is low, and an applied voltage is lowered at a low frequency, so that power consumption in the switching element generally increases.

  Further, when the primary frequency of the inverter is low, the current of each phase is held in a constant state, and the time during which the current concentrates on some switching elements also becomes long. In order to prevent the switching element from being damaged, it is a general principle not to provide a protection circuit for limiting the current or operate the motor and / or the inverter at such a low speed.

  However, in a rolling mill as described in Patent Document 1 (Pamphlet of International Publication No. 2008/062506), rolling is continued at a very low speed while the materials to be rolled on the rolling mill entrance side are welded.

  When the material to be rolled is discharged from the supply reel on the entry side, when the first coil is discharged, the second coil is discharged, and the tail end of the first coil and the tip of the second coil are welded with a welding machine. One coil is rolled. A strip storage facility for storing the strip is provided on the outlet side of the welder. During welding, the material to be rolled is supplied from the strip accumulating equipment to continue rolling. If the maximum length that can store the material to be rolled of the strip accumulating facility is increased, rolling can be continued at a relatively high speed.

  In this strip storage facility, the maximum strip storage length is limited to 100 meters or less in order to minimize capital investment. The shorter the strip storage length is, the less capital investment is required, and the configuration of the strip storage equipment can be simplified. If the maximum value of the strip storage length is set to several meters, the strip accumulating equipment can be constituted by a vertical one-stage looper.

  When the strip storage length is limited and shortened, the rolling must be continued without stopping the rolling mill for the time of welding on the entry side. For this reason, it is necessary to make the rolling speed very low.

  In such a rolling mill, it is necessary to generate tension and rolling torque necessary for rolling even when operating at a very low rolling speed. For this reason, an electric motor and an inverter that exhibit sufficient performance even at extremely low operating speeds are required. For this reason, even if the rolling equipment is designed to be compact and low-cost corresponding to the operating speed of a normal rolling mill, a large capital investment is required to realize an electric motor and an inverter that can be operated at an extremely low operating speed. The problem that it becomes necessary arises.

  An object of the present invention is to provide a control apparatus and a control method for a rolling facility that enables rolling at an extremely low speed while suppressing capital investment.

  In order to achieve the above object, a control device for a rolling facility according to the present invention includes a pay-out reel that feeds a material to be rolled to the entry side, at least one rolling mill capable of operating a roll position in the vertical direction, A control device provided in a rolling facility having a take-up reel that winds a material to be rolled on the exit side of the rolling mill, and a plurality of electric motors that respectively drive the payout reel, the rolling mill, and the take-up reel. An inverter that is connected to each of the motors and controls a rotation speed and / or a torque of each of the motors by operating a voltage and / or a frequency applied to the motor, and detects a primary frequency of the inverter 1 Based on the detected primary frequency of the inverter and the detected primary frequency, the inverter is controlled so that the primary frequency of the inverter is So as not to B, and having a control means and said controlling the rotational speed and / or torque of the motor.

  The method for controlling a rolling facility according to the present invention comprises a pay-out reel that feeds a material to be rolled to the entry side, at least one rolling mill capable of operating the roll position in the up-down direction, and a delivery reel on the delivery side of the rolling mill. A take-up reel that winds up the rolled material, a plurality of electric motors that respectively drive the payout reel, the rolling mill, and the take-up reel, and a voltage and / or frequency that is connected to each electric motor and applied to each electric motor A control method for controlling a rolling facility having an inverter for controlling the rotation speed and / or torque of each electric motor by operating a motor, the step of detecting a primary frequency of the inverter, and the detected inverter The electric motors are controlled based on the primary frequency of the motor so that the primary frequency of the inverter does not become zero. And controlling the rotational speed and / or torque, characterized in that it comprises a.

  By avoiding the primary frequency of the inverter being close to zero, it is possible to operate the rolling mill at an extremely low speed without causing damage to the apparatus while suppressing capital investment. Thus, it is possible to provide a control method and a control apparatus for rolling equipment capable of maintaining the quality of the product to be rolled.

It is a figure which shows the structure of the rolling equipment which concerns on embodiment of this invention, and its control apparatus. It is a figure which shows the relationship between a motor rotation speed and the primary frequency of an inverter. It is a figure explaining the method of avoiding the primary frequency of an inverter becoming zero by changing the rotational speed of an electric motor. It is a figure explaining the method of avoiding that an inverter primary frequency becomes zero by changing the torque of an electric motor. It is a figure which shows one example of a structure of a primary frequency detection apparatus. It is a figure which shows the flowchart of one example of a structure of a primary frequency detection apparatus. It is a figure which shows another example of a structure of a primary frequency detection apparatus. It is a figure which shows the flowchart of another example of a structure of a primary frequency detection apparatus. It is a figure which shows the flowchart of the operation setting change of a rolling mill. It is a figure which shows the flowchart of operation setting change of a payoff reel.

  A control apparatus and a control method for a rolling apparatus according to an embodiment of the present invention will be described by taking a control apparatus and a control method for a rolling facility including a two-stand rolling mill as an example. Of course, this invention is applicable also to the control apparatus and control method of a rolling apparatus provided with a rolling mill of 1 stand and 3 stands or more.

FIG. 1 shows an outline of a control device for a two-stunt continuous rolling facility according to an embodiment of the present invention. The rolling equipment control device according to the present embodiment includes an inverter primary frequency monitoring device 71 and an operation setting changing device 72.

  In the present embodiment, a coil to be rolled around which a material to be rolled is wound is inserted into a payoff reel (dispensing reel) 10. Then, the material to be rolled is paid out from the payoff reel (delivery reel) 10. Next, the strip accumulation facility (looper) 13 accumulates an amount of the material to be rolled that can be rolled during welding. In these states, the material to be rolled is rolled by the rolling mill stands 14 and 15 so as to have a desired plate thickness, and is wound around a tension reel (winding reel) 19 on the delivery side of the rolling mill with a desired tension.

  When the delivery of the first rolled material (coil) is finished, the second rolled material (coil) is inserted into the payoff reel 10, and the tail end of the first rolled material and the tip of the second rolled material are inserted. Are connected by welding with a welding machine 12. Since it is necessary to stop the material to be rolled in the welding machine during welding, the material to be rolled is supplied from the strip accumulating equipment 13 and the rolling is continued at an extremely low speed.

  Based on the speed command of the rolling mill and the set tension, the master controller 61 sends the electric motors 41 and 42 of the first rolling mill stand 14 and the second rolling mill stand 15 to the inverters 51 and 52, respectively. Rotational speed commands 611 and 612 are output. Inverters 51 and 52 control the rotation of the motor by manipulating the current flowing through the motor and its frequency based on motor rotation speed commands 611 and 612.

  Further, the master controller 61 calculates the torque required for the electric motor 40 of the payoff reel 10 based on the tension setting on the rolling mill entry side, and outputs a payoff reel current command 610 to the inverter 50. The payoff reel inverter 50 operates the voltage and frequency based on the payoff reel current command so that the current flowing through the payoff reel motor 40 becomes the same as the command.

  Similarly, on the delivery side of the rolling mill, the master controller 61 obtains a torque and a current value necessary for the motor 43 of the tension reel 19 based on the tension setting on the delivery side of the rolling mill, and outputs a current command 613 to the tension reel inverter 53. . The tension reel inverter 53 operates the voltage and frequency so that the current flowing through the tension reel motor becomes the same as the command.

  The sheet thickness controller 62 measures the sheet thickness of the material to be rolled on the entry side of the rolling mill by using the rolling mill entry side sheet thickness meter 20, detects the speed of the material to be rolled by the rolling mill entry side sheet speed meter 30, and From the speed of the rolled material, the entry side plate thickness directly under the first rolling mill stand is tracked.

  Further, the plate thickness control device 62 detects the plate speed on the exit side of the first rolling mill by means of the first rolling mill stand exit side plate speed meter 31, and determines the speed ratio between the entry side and the exit side of the first rolling mill stand. Obtaining and obtaining the first rolling mill outlet side plate thickness directly under the first rolling mill stand by multiplying the inlet side plate thickness directly under the first rolling mill stand by the speed ratio. This plate pressure is called the mass flow plate thickness. The plate thickness is controlled by manipulating the load of the first rolling mill stand or the position in the height direction of the roll so that the mass flow plate thickness becomes a set value.

  As for the second rolling mill stand, the thickness of the second rolling mill stand entrance side is measured by the first rolling mill stand exit side plate thickness meter 21 and the first rolling mill stand exit side plate speed meter 31 is used. Based on the results of the detected speed, the inlet side plate thickness directly under the second rolling mill stand is obtained, the plate speed on the outlet side of the rolling mill is detected by the rolling mill outlet side plate speed meter 32, and the plate speed on the outlet side of the first rolling mill stand is detected. And the speed ratio of the plate speed on the outlet side of the second rolling mill stand, and the mass flow plate thickness is obtained by multiplying the inlet side plate thickness directly under the second rolling mill stand by the speed ratio.

  The mass flow plate thickness is further tracked to the second rolling mill stand outlet side thickness meter 22 based on the speed record of the second rolling mill stand outlet side plate speed meter, and the presence of the thickness meter on the second rolling mill stand outlet side is measured. The second rolling mill stand mass flow plate thickness is obtained at the position where the second rolling mill stand exit side plate thickness is measured by the second rolling mill stand exit side plate thickness gauge. The second mass mill stand mass flow plate thickness is corrected to obtain an accurate mass flow plate thickness.

  Then, the speed change amount of the first rolling mill stand is output to the master controller 61 so that the accurate mass flow plate thickness becomes a desired thickness target value, and the roll of the second rolling mill stand is output. The thickness of the second rolling mill stand exit side is controlled by operating the position in the height direction. These methods are generally called mass flow plate thickness control.

  In an embodiment of the present invention, a rolling control device and a control method capable of rolling at an extremely low speed of 50 mpm or less, particularly 30 mpm or less, using an electric motor and an inverter having a necessary and sufficient capacity for normal operation. provide.

  In the embodiment of the present invention, in the rolling mill configured as described above, the inverters 50 to 53 that drive the electric motors are provided with the primary frequency detection device 71 that detects the primary frequency of the inverter. And the primary frequency of each electric motor is detected by the primary frequency detection device 71, and the primary frequency does not become near zero by changing the rolling speed, tension, load, and plate thickness setting value by the operation setting change device 72. To control. A control apparatus and a control method for avoiding the primary frequency of the present invention from being close to zero will be described below.

  FIG. 2 shows the relationship between the rotation speed (frequency) of the electric motor and the primary frequency of the inverter. FIG. 3 illustrates that the primary frequency of the inverter is prevented from becoming zero by changing the rotational speed of the electric motor. FIG. 4 illustrates that the primary frequency of the inverter is prevented from becoming zero by changing the torque of the motor while keeping the rotation speed of the motor constant.

  In the operation of a rolling mill at an extremely low speed, a regenerative operation is performed mainly by a discharge reel motor or a rolling mill motor on the rolling mill entrance side. In the regenerative operation of the electric motor, torque is generated on the side opposite to the rotation direction of the electric motor, and thereby the slip frequency is generated opposite to the rotation direction. For this reason, during the low speed rotation, the primary frequency of the inverter becomes smaller than the motor rotation speed, and the inverter is operated in a state where the primary frequency is very close to zero. For this reason, current concentrates on some switching elements, and the device may be destroyed.

  In order to control the primary frequency of the inverter, it is necessary to determine the primary frequency of the inverter. In order to control the primary frequency of the inverter and avoid the primary frequency becoming zero, the primary frequency of the inverter is obtained at a speed at which the slip frequency and the rotation speed of the motor are substantially the same. Necessary. The primary frequency of the inverter may be obtained by calculation from the torque and rotation speed of the electric motor, or may be measured directly from the current command of the inverter.

  In order to avoid the primary frequency of the inverter from becoming zero by controlling the primary frequency of the inverter, two types of methods can be considered. One method is to change the rotational speed of the electric motor as shown in FIG. In order to change the rotation speed of the electric motor, the operation speed of the rolling mill line is changed.

  As another method, as shown in FIG. 4, there is a method of changing the slip frequency by changing the torque of the electric motor. In order to change the torque of the electric motor and change the sliding frequency, the tension of the rolling mill is changed or the load of the rolling mill is changed to change the thickness target value.

  When changing the operating speed of the rolling mill line, it is sufficient to change the speed command for the entire rolling mill line, but it may not be able to accelerate due to the limitation of welding time and the remaining strip length of the strip accumulating equipment on the rolling mill entrance side is there. If the strip remaining length is below a certain value, the rolling mill line is decelerated.

  For the payoff reel on the rolling mill entry side, the torque of the electric motor can be changed by changing the tension. When changing the torque of the electric motor of the rolling mill, change the rolling torque by changing the tension on the entry side or the exit side of the relevant rolling mill, or changing the plate thickness target value and changing the rolling load. To do.

  According to the present invention, the primary frequency of the inverter is monitored so that the primary frequency does not become near zero. That is, the operation can be continued in the extremely low speed region by appropriately changing the rolling speed, tension, sheet thickness setting or rolling load setting according to the operation purpose at that time.

  The control device and the control method according to the embodiment of the present invention will be further described. FIG. 5 shows an example of the configuration of a primary frequency detection device that detects the frequency (primary frequency) of the electric motor primary current.

  In FIG. 5, the motor speed control devices 51 and 52 and the motor current control devices 50 and 53 send the revolution speed record, the torque current record, and the motor primary frequency record to the primary frequency detection device 71. As a result, the primary frequency of the electric motor is directly detected. As the control parameter, an avoidance frequency band Yrpm for preventing the primary frequency from becoming zero and causing damage to the apparatus is set in advance as a torque current X% for starting detection of the primary frequency zero.

  FIG. 6 is a flowchart showing the operation of an example of the configuration of the primary frequency detection device. It is determined whether the ratio of the torque current of each motor to the rated current is greater than a preset ratio (X%) (S61). When the ratio of the torque current of each motor to the rated current is greater than a preset ratio (X%), detection of the primary frequency is started.

  The primary frequency is detected by the motor speed control device or the motor current control device (S62). It is determined whether or not the absolute value of the detected primary frequency is smaller than Yrpm (S63). When the detected absolute value of the primary frequency is smaller than Yrpm, an operation setting change request is issued (S64).

  FIG. 7 shows another example of the configuration of the primary frequency detection device that detects the frequency (primary frequency) of the motor primary current. The motor speed control devices 51 and 52 and the motor current control devices 50 and 53 send the revolution speed record and the torque current record to the primary frequency detector 71. In the primary frequency detection device 71, the primary frequency of the motor is predicted and the primary frequency is detected. In this case, the slip frequency of each motor corresponding to the torque current is required as a control parameter, but the slip frequency of each motor is a known value as the characteristics of the motor. For this reason, it becomes possible to predict the primary frequency of the electric motor.

  FIG. 8 is a flowchart showing the operation of an example of the configuration of the primary frequency detection device. It is determined whether the ratio of the torque current of each motor to the rated current is greater than a preset ratio (X%) (S81). When the ratio of the torque current of each motor to the rated current is greater than a preset ratio (X%), detection of the primary frequency is started.

  A predicted value of the primary frequency is calculated from the actual torque current, the slip frequency setting value, and the actual rotational speed (S82). It is determined whether or not the calculated absolute value of the primary frequency is smaller than Yrpm (S83). When the calculated absolute value of the primary frequency is smaller than Yrpm, an operation setting change request is issued (S84).

  In the embodiment of the present invention, the first rolling mill motor and the payoff reel motor can be considered as the motors whose primary frequency can be zero. Therefore, setting changes such as the speed and tension of the first rolling mill and the payoff reel are performed.

  FIG. 9 shows a flowchart for changing the operation setting of the rolling mill. When there is an operation setting change request from the primary frequency detection device for the rolling mill motor, the operation setting is changed (S91). First, the remaining length of the material to be rolled in the strip accumulation facility is calculated (S92a). The welding process of the welding machine 12 installed on the entry side from the strip accumulation facility 13 is detected, and the necessary stop time is calculated (S92b). The maximum speed that the rolling mill can take out is calculated from the stop time on the entry side and the remaining length of the material to be rolled in the strip accumulation facility (S92c). If the absolute value of the primary frequency is expected to be Yrpm or more when accelerating to the maximum speed (S93), it is determined that acceleration is possible and the rolling mill is accelerated (S94).

  If the absolute value of the primary frequency does not exceed Yrpm even when accelerating to the maximum speed (S93), it is determined that acceleration is impossible, and the entire rolling mill is decelerated (S94). When the speed is reduced, the friction between the rolling mill roll and the material to be rolled increases, so the load increases. It is determined whether the rolling mill load is equal to or less than a predetermined value (S96).

  If the rolling mill load is larger than the specified value, set the upper and lower limits of the motor torque, mechanical and operational tension to suppress the increase in load, and if the tension can be increased. The tension target values on the entry side and the exit side of the rolling mill are increased (S98).

  When the tension setting reaches the upper limit value and the target tension value cannot be increased, the tension value is held while being decelerated and the rolling mill load is limited (S99). In this case, a deviation occurs in the sheet thickness on the delivery side of the first rolling mill, but the second rolling mill is adjusted so as to obtain a desired sheet thickness.

  FIG. 10 shows the operation setting change flow of the payoff reel. The primary frequency zero is detected for the payoff reel motor. When there is an operation setting change request (S101), the length of material to be rolled that can be accumulated in the strip accumulation facility is calculated (S102a), the low-speed operation time of the rolling mill is calculated (S102b), and the payoff reel is stopped. The maximum speed that can be taken out without calculation is calculated (S102c).

  When the absolute value of the primary frequency is expected to be Yrpm or more when the calculated payoff reel is accelerated to the maximum speed, it is determined that acceleration is possible (S103), and the payoff reel is accelerated (S104). If the absolute value of the primary frequency does not exceed Yrpm even when accelerating to the maximum speed, it is determined that acceleration is impossible (S103), and the payoff reel is decelerated (S105).

  By increasing the tension, the primary frequency is shifted, and when the absolute value of the primary frequency is Yrpm or more (S106), the tension is increased (S107). If the absolute value of the primary frequency does not reach Yrpm even if the tension is increased (S106), the tension is decreased to decrease the torque current, and the primary frequency is shifted in the direction opposite to the motor rotation. At this time, the load of the rolling mill is checked, and if the rolling mill load is equal to or greater than Z tons (S109), a load limit is provided (S110).

  The present invention is used for control of cold rolling equipment.

  DESCRIPTION OF SYMBOLS 1 ... Rolled material, 10 ... Payoff reel, 11 ... Welding machine entrance side pinch roll, 12 ... Welding machine, 13 ... Strip accumulation | storage equipment (looper), 14 ... 1st rolling mill, 15 ... 2nd rolling mill, 16 ... Shear entry side pinch roll, 17 ... rolling mill exit side shear, 18 ... shear exit side pinch roll, 19 ... tension reel, 20 ... first rolling mill entry side plate thickness detector, 21 ... first rolling mill exit side plate thickness detector , 22 ... second rolling mill outlet side plate thickness detector, 30 ... rolling mill inlet side plate speed detector, 31 ... first rolling mill outlet side plate speed detector, 32 ... second rolling mill outlet side plate speed detector, 40 ... payoff Reel drive motor, 41 ... first rolling mill drive motor, 42 ... second rolling mill drive motor, 43 ... tension reel drive motor, 50 ... payoff reel motor current control device, 51 ... first rolling mill drive motor speed control device, 52 ... Second Extender drive motor speed control device, 53 ... tension reel drive motor current control device, 61 ... rolling equipment master control device, 62 ... plate thickness control device, 71 ... primary frequency detection device, 72 ... operation setting change device, 73 ... Speed / tension change command, 74 ... thickness / load change command, 131 ... strip accumulation equipment strip remaining length, 500 ... pay-off reel drive motor results data, 510 ... first rolling mill drive motor results data, 520 ... second rolling mill Drive motor performance data, 530 ... tension reel drive motor performance data, 610 ... payoff reel drive motor current command, 611 ... first rolling mill drive motor speed command, 612 ... second rolling mill drive motor speed command, 613 ... tension reel drive Motor current command, 700 ... Power converter primary frequency

Claims (10)

A pay-out reel that feeds the material to be rolled to the entry side;
At least one rolling mill capable of operating the roll position up and down;
A take-up reel that winds up the material to be rolled on the exit side of the rolling mill;
A control device provided in a rolling facility having a plurality of electric motors that respectively drive the payout reel, the rolling mill, and the take-up reel,
An inverter connected to each electric motor and controlling the number of revolutions and / or torque of each electric motor by operating a voltage and / or frequency applied to the electric motor;
Primary frequency detection means for detecting a primary frequency of the inverter;
Control means for controlling the inverter based on the detected primary frequency of the inverter to control the rotation speed and / or torque of each electric motor so that the primary frequency of the inverter does not become zero;
A control apparatus for rolling equipment, comprising:   The rolling mill control apparatus according to claim 1, wherein the rolling equipment includes a strip accumulating facility on an entry side of a rolling mill, and the rolling facility is accelerated or decelerated according to a strip remaining length of the strip accumulating facility. .   3. The rolling equipment according to claim 1, wherein a torque applied to the material to be rolled is changed to change a torque of the electric motor, and a primary frequency of the inverter is prevented from becoming zero. Control device.   The thickness target value of the said rolling material or the load target value of the said rolling mill is changed, The torque of the electric motor which drives the said rolling mill is changed, The any one of Claims 1-3 characterized by the above-mentioned. Rolling equipment control device.   According to the operation state of the material to be rolled, change operation speed of the material to be rolled, change of tension applied to the material to be rolled, and / or change operation of load applied to the material to be rolled The rolling equipment control device according to any one of claims 1 to 4, wherein the control is performed. A pay-out reel that feeds the material to be rolled to the entry side;
At least one rolling mill capable of operating the roll position up and down;
A take-up reel that winds up the material to be rolled on the exit side of the rolling mill;
A plurality of electric motors that respectively drive the payout reel, the rolling mill, and the take-up reel;
A control method for controlling a rolling facility having an inverter connected to each electric motor and controlling a rotation speed and / or torque of each electric motor by operating a voltage and / or a frequency applied to each electric motor. ,
Detecting a primary frequency of the inverter;
Controlling the inverter based on the detected primary frequency of the inverter to control the rotation speed and / or torque of each electric motor so that the primary frequency of the inverter does not become zero;
A control method for rolling equipment, comprising:   The method of controlling a rolling facility according to claim 6, wherein the rolling facility comprises a strip accumulating facility on the entry side of the rolling mill, and the rolling facility is accelerated or decelerated according to a strip remaining length of the strip accumulating facility. . The rolling equipment according to claim 6 or 7, wherein a torque applied to the material to be rolled is changed to change a torque of the electric motor, and a primary frequency of the inverter is prevented from becoming zero. Control method . 9. The thickness target value of the material to be rolled or the load target value of the rolling mill is changed to change the torque of an electric motor that drives the rolling mill. Method for controlling rolling mills. According to the operation state of the material to be rolled, change operation speed of the material to be rolled, change of tension applied to the material to be rolled, and / or change operation of load applied to the material to be rolled The rolling facility control method according to any one of claims 6 to 9, wherein the control is performed.

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