Hot rolling equipment and method for manufacturing hot-rolled steel sheets

Abstract

We provide a hot rolling technology that can be applied to existing facilities and offers excellent protection features with low installation costs and easy maintenance. [Solution] A hot rolling mill comprising a heating furnace, a rolling mill, and a winding machine, wherein an electric motor is connected to the rolling mill via a spindle, and at least one of the rolling mills has a torque measuring device, the torque measuring device comprising a torque sensor installed on the surface of a cylindrical body constituting the spindle, and a torque meter that supplies power to the torque sensor and collects data from the torque sensor, the torque meter is configured to transmit the measured torque value to a higher-level computer, and the equipment has a determination means that constantly monitors the transmitted measured torque value to detect abnormalities in hot rolling or the torque measuring device.

Description

Technical Field

[0001] The present invention relates to a hot rolling facility capable of constantly monitoring the torque actual value of a drive shaft and taking abnormality avoidance measures, and a method for manufacturing a hot rolled steel sheet using the facility.

Background Art

[0002] As a method for overload protection of a conventional drive facility using an electric motor, there is an abnormality detection method using the current value of the electric motor. In this method, for the following formula A, known values are put in as the output W, reference rotational speed N, and rated current value I0 of the electric motor, and the feedback of the actual current value I of the electric motor measured constantly is applied to calculate the generated torque T. And based on the calculated torque, when an abnormal torque occurs, it is a method of rapidly stopping the electric motor. (Formula A) T=(974·W / N)·(I / I0) Here, T: torque [kgf·m] (×9.8 Nm), W: output of the electric motor [kW], N: reference rotational speed [rpm] (1 / min), I: actual current value [A], I0: rated current value of the electric motor [A].

[0003] Also, Patent Document 1 discloses a part called a shear pin that protects other drive devices including a spindle by breaking itself by a shearing force when an excessive torque acts on the fastening part between the spindle and the drive facility.

[0004] Also, Patent Document 2 discloses a method in which a hydraulic device called a safety set generates a frictional force on the contact surface between the inner cylinder and the outer cylinder to transmit the driving force, and when an excessive torque is applied, the hydraulic pressure is released and the driving force is not transmitted.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, the above-mentioned conventional technology had the following problems. In other words, in torque calculations based on the current value of an electric motor, the external disturbances in the current value used in the calculation are large, making the factors causing torque fluctuations unclear. Therefore, torque values ​​can fluctuate not only due to physical overload but also due to electrical noise, and it is difficult to capture fine behaviors such as torque fluctuations associated with torsional vibrations that occur when the drive shaft is subjected to a load. In addition, the moment of inertia of the electric motor and other drive equipment affects the motor's drive. As a result, there is a problem in that the calculated torque is larger than the actual torque being generated. Moreover, the electric motor is located at the input end of the drive system, and in many cases, malfunctions due to overload occur on the output end equipment side, where the torque is transmitted. For example, if there is a rotating roll at the output end, and the rotation of the roll is constrained for some reason, the overload is transmitted from the roll to the spindle and finally to the electric motor. Therefore, with control based on the electric motor's current value, load detection is delayed, and there are cases where the allowable torque that would destroy the spindle is exceeded by the time the motor detects the overload.

[0007] Shear pins used as protective devices, such as those described in Patent Document 1, must not break under steady-state torque, but must break under excessive torque at a load lower than the damaging load on the spindle or other drive equipment. Therefore, setting the breaking torque of the shear pin is extremely difficult, and if the shear pin breaks, there is a problem that the connection between the spindle and the motor or surrounding drive equipment is severed. If the connection is severed in the middle of the drive system, the spindle may swing due to inertia, potentially damaging surrounding equipment, and repairing the shear pin is extremely difficult. Furthermore, unintended failure may occur due to shear pin fatigue, requiring periodic replacement of the shear pin, which presents a challenge in terms of maintainability.

[0008] Furthermore, while the technology described in Patent Document 2 is easy to incorporate into newly installed equipment, there are many problems with its introduction into existing equipment. For example, introducing new components between drive units necessitates changing their respective layouts. As a result, the introduction cost, including modifications to the existing equipment, becomes a considerably high investment.

[0009] The present invention has been made in view of the above, and aims to provide a hot rolling mill that is applicable to existing equipment and has excellent protection functions with low installation costs and ease of maintenance. In addition, it provides a method for manufacturing hot-rolled steel sheets using the same equipment. [Means for solving the problem]

[0010] The inventors conducted extensive research to achieve the above-mentioned objectives and obtained the following findings: They discovered that hot rolling equipment can be protected by directly measuring actual torque and using that data to determine overload. They also found that abnormalities in torque sensors and torque meters can be detected by comparing the measured torque with the torque calculated based on the field current of the electric motor.

[0011] The hot rolling equipment according to the present invention, which advantageously solves the above problems, comprises a heating furnace, a rolling mill, and a winding machine, wherein an electric motor is connected to the rolling mill via a spindle, and at least one of the rolling mills has a torque measuring device, the torque measuring device comprises a torque sensor installed on the surface of a cylindrical body constituting the spindle, and a torque meter that supplies power to the torque sensor and collects data from the torque sensor, and is configured to transmit the measured torque value measured by the torque meter to a higher-level computer, and has determination means for constantly monitoring the transmitted measured torque value to detect abnormalities in hot rolling or abnormalities in the torque measuring device.

[0012] Furthermore, the hot rolling equipment according to the present invention is (a) While monitoring the measured torque, a first predicted torque value is calculated for each hot-rolled coil, and a first threshold value for determining an abnormality in torque is determined by adding a predetermined torque value to the calculated first predicted value, and the determination means is configured to determine that the hot rolling is abnormal and stop the hot rolling when the measured torque value exceeds the first threshold value. (b) The first predicted value is calculated as a predicted value of the torque per coil of the hot-rolled coil from the set rolling load for rolling the hot-rolled coil, the contact arc length between the rolling roll and the rolled material, and the torque arm coefficient, and the determination means is configured to determine that there is an abnormality in the hot rolling when the actual torque value exceeds the first threshold in the direction of the rolling extension of the hot-rolled coil. (c) While monitoring the measured torque, a second predicted torque is calculated based on the field current of the electric motor, and a range of a second threshold for determining torque abnormality is determined by adding or subtracting a predetermined torque value from the calculated second predicted torque, and the determination means is configured to determine that the torque measuring device is abnormal when the measured torque falls outside the range of the second threshold, and to report the abnormality of the torque measuring device. (d) The second predicted value was obtained by creating a prediction model using multiple regression analysis from past hot rolling actual values ​​of rolling load, motor current, motor field current, rolling speed, and torque, and inputting the operating results and motor field current into the prediction model. These would be more preferable solutions.

[0013] The present invention provides a method for manufacturing hot-rolled steel sheets that advantageously solves the above problems. This method involves using any of the above-mentioned hot-rolling equipment to manufacture hot-rolled steel sheets, and when transmitting the driving force of an electric motor to a rolling mill via a spindle, the torque of the spindle is directly measured and constantly monitored. When the obtained torque value exceeds a predetermined value or falls outside a predetermined range, it is determined to be a torque abnormality, and predetermined abnormality avoidance measures are taken.

[0014] Furthermore, in the method for manufacturing hot-rolled steel sheets according to the present invention, a more preferable solution is that the abnormality avoidance measure is the release of the load on the drive system from the electric motor to the rolling mill, or the repair or replacement of the torque measuring device. [Effects of the Invention]

[0015] The hot rolling equipment and hot-rolled steel sheet manufacturing method according to the present invention utilize a torque measuring device capable of measuring actual torque. Therefore, the line can be stopped before shaft breakage occurs, avoiding prolonged downtime of the production line. Furthermore, it does not require excessive equipment modifications, and in the event of a torque sensor failure, only the torque sensor needs to be replaced, without the need to remove the drive system. This makes it industrially useful in terms of introduction costs and maintainability.

[0016] Furthermore, it can also detect abnormalities in the torque measuring device, providing high accuracy, preventing prolonged line stoppages, and contributing to stable rolling operations. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic top view showing the configuration of a hot rolling mill according to one embodiment of the present invention. [Figure 2] It is a schematic conceptual diagram showing the configuration of a drive system connecting a rolling mill and an electric motor in the hot rolling equipment according to the above embodiment. [Figure 3] It is a schematic conceptual diagram showing the configuration of an abnormality avoidance measure implemented in the hot rolling equipment according to the above embodiment. [Figure 4] It is a graph showing an example of the time transition of the torque actual value of the spindle measured in the above embodiment. [Figure 5] (a) is a graph showing the frequency distribution of the difference between the torque actual value T and the first predicted value T1, and (b) is a graph showing a part of the time change of the torque actual value representing an example of the setting of an on-delay timer. [Figure 6] It is a graph showing the influence of the field current of the electric motor and the peripheral speed on the torque current. [Figure 7] It is a graph showing the relationship between the torque actual value T and the second predicted value T2.

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The following embodiments illustrate devices and methods for embodying the technical idea of the present invention, and do not specify the configuration to the following. That is, the technical idea of the present invention can be variously modified within the technical scope described in the claims.

[0019] FIG. 1 is a schematic top view showing the configuration of hot rolling equipment according to an embodiment of the present invention. FIG. 2 is a schematic conceptual diagram showing the configuration of a drive system connecting a rolling mill and an electric motor in the hot rolling equipment according to the above embodiment. FIG. 3 is a schematic conceptual diagram showing the configuration of a system for avoiding abnormalities implemented in the hot rolling equipment according to the above embodiment.

[0020] The hot rolling mill 100 shown in Figure 1 rolls a material 1 by passing it through a rolling mill 2. The hot rolling mill 100 is arranged in the order of heating furnace 20, roughing mill 2A, finishing mill 2B, and winding machine 30 in the direction FD of the material's movement. CL in Figure 1 represents the line centerline. As shown in Figure 2, in the hot rolling mill 100, the driving force of the main motor 7 is distributed vertically from the main reduction gear 6 through the lead spindle 5 to the pinion stand 4. Each driving force is transmitted to the rolling rolls of the rolling mill 2 via the universal joint spindle 3.

[0021] In this embodiment, at least one rolling mill 2 has a strain gauge 8A installed as a torque sensor on the surface of a cylindrical body constituting a universal joint spindle 3 or a lead spindle 5. Data is then transmitted non-contact from the strain gauge 8A to the torque meter 8. Power is supplied to the strain gauge 8A from the torque meter 8 non-contact.

[0022] In this embodiment, the torque meter 8 measures the actual torque value T, which is collected by a data logger 9, a measuring instrument, and transmitted to the anomaly monitoring system 10.

[0023] The abnormality monitoring system 10 evaluates abnormalities in the actual torque value T according to the configuration shown in Figure 3 and implements measures to prevent abnormalities. The abnormality monitoring system 10 is a computer composed of, for example, a CPU, ROM, and RAM. The abnormality monitoring system 10 has functions such as a main control unit, a prediction calculation unit, and an abnormality determination unit, by having the CPU execute a control program stored in the ROM.

[0024] During the hot rolling of the rolled material 1, material information and operational setting information are transmitted (S1) from the process computer 11, which acts as the computer, to the rolling control system 12, which is responsible for the rolling control sequence. The rolling control system 12 transmits a speed command (S2) to the electric motor 7 connected to the rolling mill 2. The rolling control system 12 transmits a reduction position command (S3) to the rolling mill 2.

[0025] During the hot rolling of the rolled material 1, the actual torque value T is constantly transmitted to the abnormality monitoring system 10 from a torque meter 8 installed on the universal joint spindle 3 or lead spindle 5 of the drive system.

[0026] The prediction calculation unit of the abnormality monitoring system 10 is configured to predict two types of torque values. The first predicted torque value T1 is calculated as the predicted torque value of each spindle in the drive system based on the material of the rolled material 1 and the rolling conditions. The abnormality determination unit of the abnormality monitoring system 10 adds a predetermined torque value to the first predicted value T1 and sets it as the first threshold value (T1 + ΔT). When the actual torque value T exceeds the first threshold value, the abnormality determination unit determines that there is an abnormality in hot rolling, for example, excessive torque due to bending of the rolled material 1 or jamming of two pieces. The abnormality monitoring system 10 then transmits a signal to the rolling control system 12 to issue a rapid stop command for the rolling mill 2 (S11). Upon receiving the rapid stop command, the rolling control system 12 transmits a stop signal to the electric motor 7 according to a predetermined procedure (S12).

[0027] Furthermore, the second predicted torque value T2 is calculated based on the field current of the electric motor 7. The abnormality determination unit of the abnormality monitoring system 10 adds a predetermined torque value to the second predicted value T2 and sets it as a range of the second threshold (T2 ± ΔT). The abnormality determination unit determines that the torque meter 8 is abnormal when the actual torque value T falls outside the range of the second threshold. The abnormality monitoring system 10 then notifies the operator of the abnormality of the torque meter 8 on the display unit 13 (S13). This notification of abnormality is preferably accompanied by a flashing display on the display screen or an alarm sound.

[0028] The specific method for calculating the first predicted torque value T1 will now be explained. The first predicted torque value T1 is calculated based on the material and rolling conditions of the rolled material 1, as described above. For example, it can be calculated using the following equation (1). T1 = 2 × F × Ld × γ (1) Here, T1 is the first predicted torque value, F is the rolling load set in the rolling mill 2, Ld is the contact arc length between the rolling roll and the rolled material 1, and γ is the torque arm coefficient.

[0029] Furthermore, the contact arc length Ld can be determined using the following equation (2). Ld={R·ΔH} 1 / 2 (2) Here, R is the radius of the rolling roll, and ΔH is the reduction amount. The reduction amount ΔH can be determined for rolled material 1 as the difference between the thickness of the material entering the rolling mill 2 and the thickness of the material exiting the rolling mill 2.

[0030] The torque arm coefficient γ can be expressed using predetermined theoretical or empirical formulas, depending on the characteristics of the rolling mill.

[0031] Figure 4 shows an example of the time evolution of the actual torque value T. In Figure 4, the first predicted torque value T1 was determined from the material of the rolled material 1, the rolling conditions, such as the set rolling load, the reduction amount, the contact arc length between the rolling roll and the rolled material, and the torque arm coefficient. Then, the first threshold value T1+ΔT was obtained by adding ΔT=60t·m to the first predicted value T1.

[0032] In the example shown in Figure 4, the on-delay timer is set to 0.5s. From the time the rolled material 1 became jammed until the elapsed time ta, the time during which the actual torque value T exceeded the first threshold T1+ΔT was within the time of the on-delay timer. After the elapsed time ta, the actual torque value T continued to exceed the first threshold, so the abnormality monitoring system 10 transmitted a command to the rolling control system 12 to rapidly stop the rolling mill 2, and the electric motor 7 was stopped. As a result, rolling could be continued without damaging the drive system.

[0033] Figure 5(a) shows the frequency distribution of the difference between the actual torque value T and the first predicted torque value T1 obtained for multiple rolled materials. In this example, in order to calculate the first threshold T1+ΔT, the torque value ΔT added to the first predicted torque value T1 was set to 60 t·m, which is four times the standard deviation (4σ), taking variability into consideration. It is preferable to determine the first torque threshold for determining abnormalities in hot rolling for each rolling mill.

[0034] Figure 5(b) is a graph showing the change in the actual torque value T when the leading edge of the rolled material 1 becomes engaged with the rolling rolls of the rolling mill 2. In particular, when the leading edge of the rolled material 1 becomes engaged, a high torque is detected in a short period of time, which may lead to a false detection of an abnormality in hot rolling. Therefore, by using an on-delay timer of about 0.5s, it is possible to avoid a false detection of an abnormality in hot rolling.

[0035] Figure 6 shows an example graph illustrating the effect of the motor's field current and peripheral speed on the torque current. As can be seen from Figure 6, up to a certain peripheral speed, torque control is performed based on the field current, where the torque increases uniformly with increasing field current, regardless of peripheral speed. Above that peripheral speed, weaker field control is performed so that the increase in peripheral speed affects the increase in torque. In this way, by understanding the characteristics of the motor, a second predicted torque value T2 can be calculated from the motor's peripheral speed and field current during rolling. The second predicted torque value T2 can be calculated, for example, using a prediction model based on multiple regression analysis from past hot rolling load, motor current, motor field current, rolling speed, and torque actual values.

[0036] Figure 7 shows the relationship between the second predicted torque T2 and the actual torque T, calculated by inputting the rolling conditions, motor peripheral speed, and field current into the obtained prediction model. In the example in Figure 7, considering the variation, 50 t·m was added to or subtracted from the second predicted torque T2, within the range of the second threshold T2 ± ΔT. If the actual torque T falls outside the range of the second threshold, it is determined that there is a malfunction in the torque sensor 8A or torque meter 8.

[0037] In this embodiment, the actual torque of the drive shafts (spindles 3 and 5) constituting the drive system is measured, allowing for more accurate measurement of torque fluctuation behavior compared to using the current value of the electric motor 7. In torque calculations based on equation A using the current value of the electric motor 7, the current value generated during acceleration and deceleration becomes large due to the influence of the moment of inertia of the drive system and the main motor 7 itself. Therefore, it was necessary to set the torque setting value for abnormality detection somewhat higher to avoid false detections and unnecessary stops. In this embodiment, by measuring the actual torque, the influence of the moment of inertia required for the rotation of the main motor 7 and the drive system can be ignored. Therefore, it becomes possible to set an appropriate setting value for torque abnormality detection. In addition, there is no need to set the setting value for torque abnormality detection higher as in the past. Therefore, the setting range can be made larger relative to the allowable torque. Consequently, it becomes possible to set appropriate management values ​​for drive equipment that generates a wide variety of loads.

[0038] Furthermore, in this embodiment, excessive load can be detected at an earlier stage than abnormality detection by current value measurement, and commands for abnormality avoidance processing can be issued early. Therefore, it becomes possible to release the load before the allowable torque of the drive equipment is exceeded. Normally, excessive load problems that can occur in the drive system often occur, for example, in the rolling mill 100, not on the main motor 7 side, but when foreign objects get caught in the drive roll 2. In other words, excessive load often occurs at the end of the output of the drive system, so if the main current of the electric motor 7 is measured, it will be at the position furthest from the equipment where the excessive load occurred. Therefore, by the time the excessive load reaches the main motor, the components such as the drive shaft have already been subjected to an excessive load. On the other hand, as in this embodiment, measuring the actual torque in the middle of the drive system makes it possible to detect the occurrence of torque abnormalities closer to the source of the excessive load. Therefore, it becomes possible to issue commands for abnormality processing, such as emergency stop, to the electric drive equipment earlier than if detection were done by the current of the electric motor 7.

[0039] Furthermore, this embodiment has the advantage of requiring almost no modification to existing equipment and not worsening the maintainability of the drive equipment. Safety devices such as the device described in Patent Document 2 require modification of the arrangement and dimensions of the existing drive system, resulting in very high installation costs. While shear pins have lower installation costs than the above safety devices, they have the following problems: Setting the release torque is extremely difficult, resulting in high design and study costs. There is a high risk of accidental release during operation. Even if it operates normally and shears properly, the raised spindle may swing around and damage the surrounding area. Removing and repairing the shear pin is extremely difficult. Therefore, shear pins have very poor maintainability. In comparison to these, the actual torque monitoring technology according to this embodiment does not require any modification to existing equipment, especially by introducing a torque measuring device. If the strain gauge, which is the torque sensor, is damaged, it is only necessary to replace the strain gauge on the cylindrical surface of spindles 3 and 5. Therefore, there is no need to modify or change other devices in the drive system, and it exhibits excellent effects in terms of installation costs and maintainability.

[0040] When introducing measured actual torque data into an operational anomaly detection system for continuous monitoring, it is preferable to set the torque threshold value for determining an anomaly (the torque threshold for determining a torque anomaly) to be greater than or equal to the normal operating torque and less than or equal to the allowable torque of the weakest part of the protected object, for example, the fracture stress. More preferably, it should be set to 180% or less of the maximum normal operating torque. There is no particular lower limit for the maximum normal operating torque, but it should be set within a range that does not misidentify the normal torque as an anomaly, for example, 50% or more of the maximum normal operating torque is preferable. However, this does not apply if 180% of the normal operating torque exceeds the fracture stress of the weakest part of the drive system.

[0041] Pulsating noise may be introduced during torque measurement. On the other hand, pulsed loads due to instantaneous impacts, such as the impact when the rolled material 1 is jammed in the rolling mill 2, can exceed 1.5 times the normal torque, depending on the equipment structure and operating conditions. To avoid classifying these torque values ​​as abnormal, it is preferable to classify an abnormality only when a high torque value persists for a predetermined period. For example, it is preferable to classify an abnormal torque value when it persists for more than 0.5 seconds. If the duration for classifying an abnormality is too long, excessive torque may occur for an extended period, delaying the activation of protective actions and potentially leading to equipment damage. Therefore, it is preferable to determine an appropriate value based on operating conditions and equipment tolerances. Even more preferable is to calculate the torque increase rate over a certain period and classify an abnormality by setting a control value for the increase rate.

[0042] When manufacturing hot-rolled steel sheets using the hot-rolling equipment 100 according to this embodiment, it is preferable to follow the following steps. When the driving force of the electric motor 7 is transmitted to the rolling mill via the spindles 3 and 5, the torque of the spindles 3 and 5 is directly measured and constantly monitored. When the obtained actual torque value T exceeds a predetermined value or falls outside the range of the predetermined value, it is preferable to determine that there is a torque abnormality and take predetermined abnormality avoidance measures. It is preferable that the abnormality avoidance measures are the release of the load on the drive system from the electric motor 7 to the rolling mill 2, or the repair or replacement of the torque sensor 8A or torque meter 8.

[0043] For example, if an abnormality is detected in the torque sensor 8A or torque meter 8, the abnormality in hot rolling may be determined by comparing the second predicted torque value based on the motor's field current, etc., with the first predicted torque value until the repair or replacement of the abnormal part is completed. [Industrial applicability]

[0044] The technology according to the present invention is industrially useful because it eliminates the need for excessive equipment modifications, only requires replacing the torque sensor in the event of a torque sensor failure, does not require removing the drive system, and is superior in terms of introduction cost and maintainability. [Explanation of Symbols]

[0045] 100 Hot rolling equipment 1 Rolled material 2. Rolling mill (rolling rolls, drive rolls) 2A rough rolling mill 2B Finishing Rolling Mill 3 (Universal Joint) Spindle 4. Pinion Stand 5 (Lead) Spindle 6 Main reducer 7 Main engine (electric motor) 8 Torque meter 8A Strain Gauge (Torque Sensor) 9. Measuring Instruments (Data Loggers) 10 Anomaly Monitoring System 11. Process computer (higher-level computer) 12. Rolling control system (control sequence) 13 Display device 20 Furnace 30 Winder FD (direction of movement of rolled material) CL center

Claims

1. Equipped with a heating furnace, a rolling mill, and a winding machine, The rolling mill is a hot rolling mill in which an electric motor is connected via a spindle, At least one rolling mill has a torque measuring device, The torque measuring device, A torque sensor is installed on the surface of the cylindrical body constituting the spindle, The system comprises a torque meter that supplies power to the torque sensor and collects data from the torque sensor, The torque meter is configured to transmit the measured torque value to a higher-level computer. A hot rolling mill having a determination means for continuously monitoring transmitted torque measurements to detect abnormalities in hot rolling or abnormalities in the torque measuring device.

2. While monitoring the measured torque values, a first predicted torque value is calculated for each hot-rolled coil. A first threshold value for determining torque abnormalities is determined by adding a predetermined torque value to the calculated first predicted value. The hot rolling equipment according to claim 1, wherein the determination means is configured to determine that the hot rolling is abnormal when the measured torque exceeds the first threshold value and to stop the hot rolling.

3. The first predicted value is calculated as a predicted value of the torque per coil of the hot-rolled coil from the set rolling load for rolling the hot-rolled coil, the contact arc length between the rolling roll and the rolled material, and the torque arm coefficient. The hot rolling equipment according to claim 2, wherein the determination means is configured to determine that there is an abnormality in hot rolling when the actual torque value exceeds the first threshold value in the direction of pressure extension of the hot rolling coil.

4. While monitoring the measured torque, a second predicted torque value is calculated based on the field current of the electric motor. A range for determining a torque anomaly is determined by adding or subtracting a predetermined torque value to the calculated second predicted value. The hot rolling equipment according to claim 1, wherein the determination means is configured to determine that the torque measuring device is abnormal when the measured torque value falls outside the range of the second threshold, and to report the abnormality of the torque measuring device.

5. The hot rolling equipment according to claim 4, wherein the second predicted value is obtained by creating a prediction model using multiple regression analysis from past hot rolling actual values ​​of rolling load, motor current, motor field current, rolling speed, and torque, and inputting the operating results and motor field current into the prediction model.

6. When manufacturing a hot-rolled steel sheet using the hot-rolling equipment described in any one of claims 1 to 5, When transmitting the driving force of an electric motor to a rolling mill via a spindle, The torque of the aforementioned spindle is directly measured and continuously monitored. When the obtained torque value exceeds a predetermined value or falls outside the predetermined range, it is determined that there is a torque anomaly. A method for manufacturing hot-rolled steel sheets, which includes taking prescribed measures to prevent abnormalities.

7. The method for manufacturing a hot-rolled steel sheet according to claim 5, wherein the abnormality avoidance measure is the release of the load on the drive system from the electric motor to the rolling mill, or the repair or replacement of the torque measuring device.

Images