Rolling mill abnormality determination system and rolling mill abnormality determination method

Abstract

To provide an abnormality determination system of a rolling machine which can detect an abnormality generated, especially, in a rolling device, as an abnormality of a rolling machine, in an early period.SOLUTION: An abnormality determination system of a rolling machine includes: a rolling machine having a rolling part having a pair of work rolls arranged so as to face each other, and a rolling device for adjusting an interval of the pair of work rolls; and a control mode switching part for switching a control mode of the rolling machine to any one of a first control mode and a second control mode, according to the positional information of a weld point of a steel strip. The abnormality determination system of the rolling machine includes: a load detector for detecting a detection load in the rolling machine; a load setting part for setting the rolling load of the rolling machine as a transition target load, in a target load change period during which the control mode is switched; and a determination part for determining an abnormality of the rolling machine, on the basis of the detection load in an evaluation period including the target load change period, and deviation data in operation time generated on the basis of the transition target load.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rolling mill abnormality determination system and a rolling mill abnormality determination method. [Background technology]

[0002] In the manufacturing process of thin steel sheets, a rolling mill having a pair of rolls is used to apply a load to a steel strip. Specifically, the pair of rolls is arranged so that the distance between them is narrower than the thickness of the steel strip, and the steel strip is passed between the pair of rolls to ensure the dimensional accuracy of the thin steel sheet and to adjust the material properties of the thin steel sheet by applying an appropriate reduction.

[0003] The reduction device of the rolling mill controls the distance between a pair of rolls, i.e., the roll gap, to an appropriate value during rolling of the steel strip. For example, the reduction device controls the roll gap so that the elongation rate or reduction rate applied to the steel strip is a predetermined value, and so that the rolling load applied to the steel strip is a predetermined value.

[0004] Therefore, it is important to maintain the normal condition of the reduction device of the rolling mill in order to maintain the appropriate rolling condition of the steel strip. Various proposals have been made as a method for detecting the abnormal condition of the rolling mill. For example, Patent Document 1 discloses a method for determining the abnormal condition of a load detector in a rolling mill equipped with a hydraulic reduction device. Specifically, the abnormal condition of the load detector is determined by comparing the load calculation value calculated based on a pressure gauge provided in the hydraulic cylinder and the load measurement value measured by the load detector over time.

[0005] Patent Document 2 discloses an anomaly determination system that monitors equipment driven by an electric motor and determines an anomaly in the equipment. In Patent Document 2, the equipment driven by an electric motor includes, for example, a rolling mill using an electric screw-down device. Patent Document 2 discloses that the correlation of variables based on data such as the torque current performance of the electric motor during normal operation is defined as the normal average behavior, and an anomaly in the equipment is determined based on the degree of deviation from the normal average behavior for the correlation of the variables acquired during operation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-177203 A [Patent Document 2] Patent No. 5991042 Summary of the Invention [Problem to be solved by the invention]

[0007] According to the method of determining an abnormal state of a load detector in Patent Document 1, it is possible to determine an abnormality in a load detector (load cell). However, if the load detector is normal, there is a problem that other abnormalities, such as an abnormality in the screw down device, cannot be detected.

[0008] Furthermore, when the abnormality judgment system described in Patent Document 2 is applied to the reduction device of a rolling mill, it is necessary to obtain time-series data regarding the torque current of the motor that drives the reduction device and the movement speed and movement amount of the backup roll displaced by the reduction device.

[0009] However, there is a problem that the abnormality determination system cannot be directly applied to a hydraulic screw down device that does not generate a torque current of an electric motor.In addition, it becomes necessary to install equipment that is not provided in a normal rolling mill, such as an equipment for measuring the torque current of an electric motor, and there is room for improvement in terms of increasing equipment costs.

[0010] The present invention has been made to solve the above problems, and has an object to provide an abnormality judgment system and an abnormality judgment method for a rolling mill that can detect abnormalities in a rolling mill, particularly abnormalities occurring in the reduction-down device, at an early stage and can detect abnormalities regardless of the type of reduction-down mechanism of the reduction-down device. [Means for solving the problem]

[0011] [1] a rolling mill having a rolling section having a pair of work rolls arranged opposite to each other and a reduction device for adjusting the gap between the pair of work rolls; a load detector that detects a rolling load of the steel strip by the rolling unit as a detection load; a position information acquisition unit for acquiring position information of the welding point of the steel strip; A control mode switching unit that switches a control mode of the rolling mill to either a first control mode or a second control mode according to the position information of the welding point, a period information acquisition unit that acquires a target load change period, which is a period from one of the first control mode and the second control mode to the other control mode, and an evaluation period, which includes the target load change period and is a period during which the rolling load of the rolling unit is evaluated; a load setting unit that sets a first rolling load set in the first control mode, a second rolling load set in the second control mode and different from the first rolling load, and a transition target load that is set during the target load change period and is used until the first rolling load or the second rolling load is changed to the other rolling load, in the rolling mill; a screw-down control unit that controls the screw-down device so that the detected load approaches the transition target load during the evaluation period; a deviation data generating unit that generates, during the evaluation period, operational deviation data that is an integral value of a deviation between the transition target load and the detected load corresponding to the transition target load; a determination unit that determines an abnormality in the rolling mill based on the operation-time deviation data. [2] the deviation data generating unit generates the operational deviation data when the rolling mill operates normally as normal deviation data, The abnormality determination system for a rolling mill according to [1], wherein the determination unit uses the normal state deviation data as a reference and determines that there is an abnormality in the rolling mill when a deviation degree of other operational deviation data different from the normal state deviation data from the reference is greater than a preset threshold value. [3] The abnormality judgment system for a rolling mill described in [1] or [2], wherein the evaluation period includes the target load change period and an additional period equivalent to the period from when the control mode switching is started to when the detection load corresponding to the control mode switching is detected. [4] A method for determining an abnormality in a rolling mill, the method including switching a control mode of the rolling mill having a rolling section with a pair of work rolls arranged opposite to each other and a screw down device for adjusting a gap between the pair of work rolls, the control mode of the rolling mill being switched to either a first control mode or a second control mode in accordance with position information of a welding point of a steel strip, the method comprising: a period information acquisition step of acquiring a target load change period, which is a period from one of the first control mode and the second control mode to the other control mode, and an evaluation period, which includes the target load change period and is a period during which the rolling load of the rolling section is evaluated; a load setting step of setting a first rolling load set in the first control mode, a second rolling load set in the second control mode and different from the first rolling load, and a transition target load set during the target load change period and for changing from one of the first rolling load and the second rolling load to the other rolling load, in the rolling mill; a roll-down control step of controlling the roll-down device so that the rolling load of the rolling portion is a detection load and the detection load approaches the transition target load during the evaluation period; a load detection step of detecting the load; a deviation data generating step of generating, during the evaluation period, deviation data during operation that is an integral value of a deviation between the transition target load and the detected load corresponding to the transition target load; and a determination step of determining whether or not an abnormality exists in the rolling mill based on the operational deviation data. [5] In the deviation data generating step, the operational deviation data when the rolling mill operates normally is generated as normal deviation data; The method for determining an abnormality in a rolling mill according to [4], wherein, in the determination step, the normal state deviation data is used as a reference, and it is determined that there is an abnormality in the rolling mill if a deviation degree of other operational deviation data different from the normal state deviation data from the reference is greater than a preset threshold value. [6] The method for determining an abnormality in a rolling mill described in [4] or [5], wherein the evaluation period includes the target load change period and an additional period equivalent to the period from when the control mode switching is started to when the detection load corresponding to the control mode switching is detected. Effect of the Invention

[0012] According to the rolling mill abnormality judgment system and rolling mill abnormality judgment method of the present invention, it is possible to detect abnormalities in the rolling mill, particularly abnormalities occurring in the reduction device, at an early stage. This makes it possible to improve the yield of thin steel sheets. Furthermore, the rolling mill abnormality judgment system and rolling mill abnormality judgment method of the present invention can be applied regardless of the type of reduction mechanism of the reduction device, making it possible to increase versatility. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a conceptual diagram showing a configuration of an abnormality determination system for a rolling mill. [Diagram 2] FIG. 2 is a front view showing the front of the rolling mill in FIG. [Diagram 3] FIG. 2 is a side view of the rolling mill of FIG. [Figure 4] FIG. 2 is a block diagram showing functional blocks of the abnormality determination system for a rolling mill. [Diagram 5] FIG. 11 is a flow chart for determining an abnormality in a rolling mill. [Figure 6] FIG. 4 is an explanatory diagram showing a manner in which the settings of a first rolling load and a second rolling load are switched. [Figure 7] FIG. 11 is an explanatory diagram showing the state of the detection load when the settings of the first rolling load and the second rolling load are switched. [Figure 8] FIG. 11 is an explanatory diagram showing the state of the detection load and the deviation load when the settings of the first rolling load and the second rolling load are switched. [Figure 9] 13 is a graph showing an integral value of a deviation load with respect to a change amount of a load setting value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 1 shows the configuration of an abnormality determination system 100 that determines an abnormality in a rolling mill 10. The rolling mill 10 is disposed, for example, in a steel strip production line, more specifically, downstream of a continuous annealing line.

[0015] The continuous annealing line has a furnace body (not shown) including, for example, a heating zone, a soaking zone, and a cooling zone. At the inlet side of the continuous annealing line, the front end and rear end of the steel strip are connected to other steel strips by welding or the like, and continuous heat treatment is performed in the furnace body.

[0016] The continuous annealing line has a facility for performing continuous temper rolling on the steel strip that has been heat-treated in the furnace body. The rolling mill 10 is disposed in the facility for performing continuous temper rolling. Therefore, the steel strip that has been heat-treated in the furnace body is continuously rolled by the rolling mill 10 disposed downstream thereof.

[0017] As shown in Fig. 1, an entry-side bridle roll BR1 and an entry-side tension meter TM1 are disposed on the upstream side (entry side) of the rolling mill 10. An exit-side tension meter TM2 and an exit-side bridle roll BR2 are disposed on the downstream side (exit side) of the rolling mill 10.

[0018] The entrance bridle roll BR1 and the exit bridle roll BR2 are rolls for applying an appropriate tension to the steel strip SS.

[0019] The tension meter TM1 is provided between the rolling mill 10 and the inlet bridle roll BR1. The tension meter TM1 measures the tension of the steel strip SS on the inlet side of the rolling mill 10.

[0020] The tension meter TM2 is provided between the rolling mill 10 and the exit bridle roll BR2. The tension meter TM2 measures the tension of the steel strip SS on the exit side of the rolling mill 10.

[0021] The rolling mill 10 has a rolling section 11 that rolls the steel strip SS, and a reduction device 12 that adjusts some of the rolling conditions of the rolling section 11.

[0022] The rolling section 11 has a pair of work rolls 11a, 11b arranged to face each other. The pair of work rolls 11a, 11b are supported by a pair of backup rolls 11c, 11d. The pair of work rolls 11a, 11b are arranged with a gap between them in the vertical direction.

[0023] Therefore, the pair of work rolls 11a, 11b contact the steel strip SS, which is the material to be rolled, and apply pressure to the steel strip SS by passing the steel strip SS between them. In addition, the backup rolls 11c, 11d support the pair of work rolls 11a, 11b from above and below, suppressing deflection of the work rolls 11a, 11b.

[0024] The rolling mill 10 is not limited to the four-high rolling mill shown in FIG. 1, but may be a six-high rolling mill.

[0025] The reduction device 12 adjusts the arrangement interval of the pair of work rolls 11a, 11b, i.e., the roll gap, so that the rolling load applied to the steel strip SS becomes a predetermined value. Therefore, the steel strip SS is given the predetermined reduction adjusted by the reduction device 12 by passing between the pair of work rolls 11a, 11b.

[0026] The load detector 20 (load cell) detects the load applied to the steel strip SS of the rolling mill 10.

[0027] Fig. 2 shows a front view of the rolling mill 10. Fig. 3 shows a side view of the rolling mill 10. As shown in Figs. 2 and 3, the rolling mill 10 has a pair of housings 13 constituted by an integral frame having a substantially rectangular frame shape. The pair of housings 13 may be constituted by a frame-shaped structure constituted by columnar members.

[0028] The pair of housings 13 are disposed opposite each other. An opening 13a is formed on the opposing surface of the housing 13, the opening 13a being open across the height of the housing 13. The opening 13a is formed penetrating the pair of housings 13 in the opposing direction.

[0029] A bearing box 14a (backup roll chock) supporting the backup roll 11c is accommodated in the upper portion of the opening 13a of each housing 13. In this embodiment, the bearing box 14a is provided in the housing 13 so as to be slidable in the vertical direction within the housing 13. The backup roll 11c is journaled to the housing 13 by the bearing box 14a so as to be rotatable about its axis.

[0030] A support portion 15a for supporting the upper work roll 11a is provided below the bearing box 14a of each housing 13. A support portion 15b for supporting the lower work roll 11b is provided below the support portion 15a. The work rolls 11a, 11b are journalled to the housing 13 by the support portions 15a, 15b so as to be rotatable about their axes.

[0031] A bearing box 14b (backup roll chock) supporting the backup roll 11d is provided at the bottom of the opening of each housing 13. The backup roll 11d is journaled to the housing 13 by the bearing box 14b so as to be rotatable about its axis.

[0032] Each of the work rolls 11a, 11b has an end connected to a coupling or reducer (not shown) and a driving motor (not shown) via supports 15a, 15b, so that when the driving motor is operated, the work rolls 11a, 11b rotate about their axes.

[0033] The driving motor for rotating the work rolls 11a, 11b may be configured to rotate either one of the pair of work rolls 11a, 11b. Also, it may be configured to rotate the backup rolls 11c, 11d instead of the work rolls 11a, 11b. This is because when the torque required for rolling the steel strip SS is relatively small, such as in a temper rolling mill, a large torque is not required.

[0034] A screw down device 12 is provided on the upper part of each housing 13. Either an electric or hydraulic screw down mechanism may be used as the screw down device 12. The screw down device 12 adjusts the roll gap, which is the arrangement distance between the work rolls 11a, 11b, by connecting to a bearing housing 14a of the backup roll 11c.

[0035] For example, when the screw-down mechanism uses a hydraulic screw-down device 12, a hydraulic cylinder may be connected to the bearing housing 14a of the backup roll 11c. The screw-down device 12 can move the bearing housing 14a of the backup roll in the vertical direction of the housing 13 by controlling the hydraulic pressure of the hydraulic cylinder.

[0036] Furthermore, when the rolling mechanism uses an electric rolling device 12, a rolling screw that rotates about its axis in response to the driving of the electric motor may be connected to the bearing housing 14a of the backup roll 11c. Therefore, the rolling device 12 can displace the bearing housing 14a of the backup roll in the vertical direction of the housing 13 by controlling the driving of the electric motor.

[0037] The screw down device 12 only needs to be able to adjust the distance between the pair of work rolls 11a, 11b, i.e., the roll gap. The screw down device 12 only needs to be able to move at least one of the backup rolls 11c, 11d in the vertical direction of the housing 13. Therefore, the screw down device 12 may, for example, displace the backup roll 11d in the vertical direction from the lower part of the housing 13, or may displace both the backup roll 11c and the backup roll 11d in the vertical direction.

[0038] Each screw down device 12 is adjusted, for example, so that the vertical positions (displacement amounts) of the housings 13 of the pair of bearing housings 14a are approximately the same. Note that each screw down device 12 may be adjusted by so-called leveling so that the vertical positions of the housings of the pair of bearing housings 14a are different from each other.

[0039] In addition, a load detector 20 is provided below the bearing box 14b of the housing 13. Therefore, when the steel strip SS is rolled by the work rolls 11a, 11b, the load detector 20 is pressed down by the bearing box 14b to detect the actual value of the load (rolling load) applied to the steel strip SS.

[0040] The load detector 20 is not limited to being disposed below the bearing box 14b in the lower part of the housing 13 as long as it can detect the rolling load of the steel strip SS. The load detector 20 may be disposed, for example, in the upper part of the housing 13, between the screw down device 12 and the bearing box 14a.

[0041] Also, the load detector 20 may be disposed on the same side as the screw down device 12 in the up-down direction of the housing 13, at the upper or lower part of the housing 13. Furthermore, the load detector 20 may be disposed on each of the left and right housings 13. When the load detector 20 is disposed on each of the left and right housings 13, the detected value of the rolling load (detected load) may be the sum of the values ​​detected by the left and right load detectors 20.

[0042] 4 shows functional blocks of a rolling mill abnormality determination system 100. The rolling mill abnormality determination system 100 includes a rolling mill 10 that rolls a steel strip SS, a load detector 20 that detects the load of the rolling mill 10, a position measurement unit 30 that measures the positions of welding points of the steel strip SS, and a control unit 40 that controls the operation of the rolling mill 10.

[0043] The rolling mill 10, the load detector 20, and the position measuring unit 30 are communicatively connected to a control unit 40.

[0044] The load detector 20 (load cell) is a sensor that converts force into an electrical signal. Detectors of magnetostrictive type, electrostatic capacitance type, strain gauge type, etc. can be used as the load detector 20. When the load detector 20 (load cell) detects a force, it transmits an electrical signal corresponding to the force to the control unit 40.

[0045] The position measuring unit 30 detects the position of the welding point of the steel strip SS by known means such as an optical means, a mark detection means, a load fluctuation detection means, etc. The position measuring unit 30 transmits the detection information detected by these position detection means to the control unit 40.

[0046] The control unit 40 is configured by a general-purpose device such as a personal computer or a workstation having a CPU, ROM, and RAM (not shown). The ROM stores a control program for executing the plate thickness control method according to the embodiment of the present invention, and a processing program and processing data for controlling the operation of the entire abnormality determination system 100. The CPU controls the operation of the entire abnormality determination system 100 according to the control program and processing program stored in the ROM. The RAM temporarily stores the processing program and processing data related to the processing executed by the CPU, and functions as a working area for the CPU.

[0047] The ROM stores various setting information such as line speed information. The ROM also stores a target load change period, which is the period from the first control mode to the second control mode until the control mode is changed to the other control mode. The ROM also stores an evaluation period, which includes the target load change period and is the period during which the rolling load of the rolling unit 11 is evaluated. The ROM also stores detected load data transmitted from the load detector 20 as time-series data.

[0048] The position information acquiring unit 41 tracks the welding points based on the line speed and the like of the detection information transmitted from the position measuring unit 30. The tracking information tracked by the position information acquiring unit 41 is stored in the ROM.

[0049] The tracking of the welding points is performed, for example, based on the position information of the welding points and the line speed for transporting the steel strip SS. The position information of the welding points is obtained by providing the above-mentioned position detection means for detecting the position of the welding points on the upstream side of the production line.

[0050] The control mode switching unit 42 switches the control mode of the rolling mill 10 between a first control mode and a second control mode according to the position information of the welding point. More specifically, the control mode switching unit 42 sets the control mode to the first control mode based on the tracking information when rolling a steel strip SS other than the welding point (hereinafter also referred to as a steady portion), and sets the control mode to the second control mode when rolling a steel strip SS in the vicinity of the welding point.

[0051] In the first control mode, for example, when temper rolling of the steel strip SS is performed using the rolling mill 10, elongation rate control is performed to roll the steel strip SS after the annealing process at a predetermined elongation rate. In this embodiment, a case where elongation rate control is adopted to keep the elongation rate of the steel strip SS constant will be described as an example of the first control mode.

[0052] Here, the elongation rate is the elongation rate of the steel strip SS before and after rolling. The elongation rate is defined, for example, as the length of the steel strip SS after the temper rolling process relative to the length of the steel strip SS before the temper rolling process, that is, the increase rate. The elongation rate can be measured, for example, by the difference in peripheral speed between the entrance bridle roll BR1 and the exit bridle roll BR2.

[0053] In addition, under conditions where the elongation rate is small, the rolling reduction rate, which is the rate of change in plate thickness, and the elongation rate tend to be approximately the same value. Therefore, in controlling the elongation rate, the rolling reduction rate may be used instead of the elongation rate.

[0054] In this embodiment, a case will be described in which the welding point passing control, in which the rolling load applied to the steel strip SS is kept constant, is adopted as an example of the second control mode.

[0055] The welding point passage control is executed by switching from the elongation rate control in accordance with the timing when the welding point reaches the rolling mill 10. In other words, the control mode switching unit 42 switches between the elongation rate control and the welding point passage control based on the tracking information.

[0056] The load setting unit 43 sets a rolling load corresponding to the elongation rate control, the welding point passing control, and the target load change period to the rolling mill 10. Specifically, the load setting unit 43 sets a first rolling load to the rolling mill 10 in the elongation rate control, which is the first control mode.

[0057] As described above, in the elongation rate control, the elongation rate of the steel strip SS is controlled to be kept constant. Moreover, the elongation rate of the steel strip SS differs depending on the composition, size, etc. of the steel strip SS. Therefore, the first rolling load is a value that can vary depending on the composition, size, etc. of the steel strip SS.

[0058] In the second control mode, ie, welding point passing control, the load setting unit 43 sets a second rolling load, which is different from the first rolling load, to the rolling mill 10. In this embodiment, the second rolling load is set lower than the first rolling load. Specifically, at the entry side of the production line, a preceding material and a following material are joined by lap welding such as seam welding to form a steel strip SS. At the welding point of the steel strip SS, the preceding material and the following material overlap each other. Therefore, the welding point of the steel strip SS has a thicker plate thickness than the preceding material and the following material.

[0059] Therefore, when a rolling load is applied to the weld point at the first rolling load set in the elongation rate control, there is a risk of defects occurring on the surfaces of the work rolls 11a and 11b. If rolling is performed with defects on the surfaces of the work rolls 11a and 11b, the defects are transferred to the surface of the steel strip SS, resulting in surface defects in the steel sheet product.

[0060] In the weld point passing control, in order to prevent the occurrence of such surface defects, the rolling load is once reduced before the weld point of the preceding material reaches the rolling mill 10, and the weld point is passed at this light load. Therefore, the second rolling load is necessarily set lower than the first rolling load.

[0061] During the target load change period, the load setting unit 43 sets a transition target load for the rolling mill 10 until the rolling load is changed from one of the first rolling load and the second rolling load to the other rolling load.

[0062] The transition target load may be set, for example, to have a proportional relationship with the target load change period. In other words, the transition target load may be set to decrease or increase at a constant rate during the period from one rolling load to the other rolling load. By setting the transition target load in this manner, it is possible to improve the accuracy of determining whether or not there is an abnormality in the rolling mill 10, which will be described later.

[0063] The roll down control unit 44 controls the roll down device 12 with a gap between the pair of work rolls 11a, 11b according to the first rolling load, the second rolling load, and the transition target load.

[0064] Specifically, the reduction control unit 44 adjusts the vertical positions of the pair of bearing housings 14a in the housing 13 by controlling each of the reduction devices 12. For example, the reduction control unit 44 sets an arbitrary position in the vertical direction of the housing 13 as a reference point and adjusts the roll gap by using the relative position from the reference point as the reduction amount of the bearing housings 14a.

[0065] The roll gap control unit 44 can obtain the vertical position of the backup roll, for example, by providing a displacement meter (not shown) in the housing 13. The roll gap control unit 44 may adjust the roll gap by using, for example, an average value of the relative positions of the pair of bearing housings 14a as the roll gap amount.

[0066] In the elongation rate control, the roll down control unit 44 controls the operation of the roll down device 12 of the rolling mill 10 so that the measured elongation rate approaches a predetermined elongation rate.

[0067] Here, the elongation rate of the steel strip SS differs even with the same roll gap depending on the thickness, width, deformation resistance, etc. of the steel strip SS being rolled. For example, when the preceding material and the following material are different in size or steel type, the reduction control unit 44 sets different roll gaps for the steady portion of the preceding material and the steady portion of the following material. By setting the roll gap in this manner, the rolling load differs between the steady portion of the preceding material and the steady portion of the following material, but the elongation rate of both can be made constant.

[0068] Furthermore, in the welding point passing control, the roll down control unit 44 controls the operation of the roll down device 12 of the rolling mill 10 so that the detected load approaches the second rolling load.

[0069] In the welding point passing control, the roll reduction control unit 44 reduces the rolling load to pass the welding point by making the roll gap larger than that in the elongation rate control in accordance with the timing at which the welding point passes through the rolling mill 10.

[0070] Furthermore, during the target load change period, the roll gap control unit 44 controls the operation of the roll gap device 12 of the rolling mill 10 so that the detected load approaches the transition target load.

[0071] The period information acquisition unit 45 acquires the target load change period and the evaluation period. Specifically, the period information acquisition unit 45 reads and acquires the target load change period and the evaluation period from the ROM. The target load change period and the evaluation period are set by the deviation data generation unit 46, which will be described later, and are stored in the ROM in advance.

[0072] The period information acquisition unit 45 may set a target load change period and an evaluation period based on tracking information, and acquire the set target load change period and evaluation period.

[0073] The deviation data generating unit 46 generates, during the evaluation period, deviation data during operation that is an integral value of the deviation between the transition target load and the detected load corresponding to the transition target load.

[0074] The judgment unit 47 judges an abnormality of the rolling mill 10 based on the operational deviation data. The judgment unit 47 outputs the result of the judgment as to whether or not there is an abnormality in the rolling mill 10 to a notification means (not shown). Examples of the notification means include a screen display on a display, and a voice or buzzer sound from a speaker. The notification means may be one of these, or a combination of two or more.

[0075] A method of determining whether or not an abnormality occurs in the rolling mill 10 using the abnormality determination system 100 for determining whether or not an abnormality occurs in the rolling mill 10 described above will be described.

[0076] Fig. 5 shows a flow of determining an abnormality in the rolling mill 10 by the abnormality determination system 100. As shown in Fig. 5, the process of determining an abnormality in the rolling mill 10 is started, for example, by being triggered by the execution of switching control for changing the control mode of the rolling mill 10.

[0077] Specifically, the position information acquiring unit 41 performs welding point tracking on the production line and generates information (tracking information) on the positions of the welding points. The control mode switching unit 42 executes switching control according to switching from one of the first control mode and the second control mode to the other control mode based on the tracking information.

[0078] The control mode switching unit 42 switches from elongation rate control to welding point passage control when the welding point reaches a preset position (e.g., 3 to 5 m upstream of the rolling mill 10) on the upstream side of the rolling mill 10 with reference to the tracking information. The control unit 40 detects this control mode switching and executes a process of determining whether or not there is an abnormality in the rolling mill 10.

[0079] The period information acquisition unit 45 acquires period information by reading out the target load change period and the evaluation period from the ROM (step S01).

[0080] The load setting unit 43 sets a transition target load according to switching from one of the first control mode and the second control mode to the other control mode (step S02).

[0081] Specifically, when the control mode switching unit 42 executes control to switch the control mode, the load setting unit 43 recognizes the other control mode and sets a transition target load according to switching to the other control mode.

[0082] When the transition target load of the screw down device 12 is set, the screw down control unit 44 controls the roll gap of the screw down device 12 so that the detected load approaches the predetermined transition target load (step S03). Specifically, the screw down control unit 44 monitors the detected load by successively acquiring it, and controls the roll gap so that the detected load follows the transition target load from moment to moment.

[0083] The load detector 20 detects the rolling load of the rolling mill 10 during the evaluation period (step S04). The control unit 40 stores the detected load data detected during the evaluation period in the ROM as time-series data.

[0084] The deviation data generating unit 46 generates, during the evaluation period, deviation data during operation that is an integral value of the deviation between the transition target load and the detected load corresponding to the transition target load (step S05).

[0085] The judgment unit 47 judges an abnormality of the rolling mill 10 based on the operational deviation data (step S06). The judgment unit 47 outputs the result of the judgment as to whether or not there is an abnormality in the rolling mill 10 to a notification means (not shown).

[0086] Fig. 6 shows a state in which the control mode is switched from the elongation rate control to the welding point passing control. As shown in Fig. 6, when the control mode is switched from the elongation rate control to the welding point passing control, the load setting unit 43 sets the rolling load to be set in the rolling mill 10 to the second rolling load.

[0087] Specifically, the load setting unit 43 sets the rolling load from the rolling load of the preceding material applied in the elongation rate control (first rolling load) to the rolling load in the welding point passage control (second rolling load). At that time, the load setting unit 43 sets a transition target load in the target load change period.

[0088] The left side of Fig. 6 shows the transition target load during the target load change period from the first rolling load to the second rolling load. In this case, the transition target load can be expressed as a reduction speed (load reduction rate) which is the rate at which the rolling load is reduced per unit time.

[0089] The second rolling load is set, for example, at 500 to 1500 kN. The load reduction rate is preferably set, for example, at -1500 kN / s.

[0090] In the center of Fig. 6, the welding point passage control is executed and the second rolling load is maintained. The holding time during which the second rolling load is maintained in the welding point passage control is the time from when the rolling load set in the rolling mill 10 reaches the second rolling load to when the control mode is switched.

[0091] The holding time can be determined, for example, according to the position of the welding point where the control mode was switched, the length of the welding point in the flow direction of the line, and the line speed. The holding time is not limited to this embodiment, and may be determined, for example, by the time required for the welding point to pass through the rolling mill 10. The holding time can be set appropriately according to the line speed, but is preferably set to, for example, 3 to 5 seconds.

[0092] On the right side of Fig. 6, the transition target load during the target load change period is shown, from the second rolling load to the first rolling load. In this case, the transition target load can be expressed as an increase speed (load increase rate) which is the rate at which the rolling load is increased per unit time. The load increase rate is set to, for example, 1500 kN / s.

[0093] The reduction speed (load reduction rate), the increase speed (load increase rate), and the holding time may be set in advance and stored in the ROM. That is, the load setting unit 43 stores the transition target load thus set in the ROM as time-series data.

[0094] As shown in FIG. 6, the target load change period includes the period from when the control mode is switched from elongation rate control to welding point passing control until the rolling load set in the rolling mill 10 reaches the second rolling load, and the period from when the control mode is switched from welding point passing control to elongation rate control until the rolling load set in the rolling mill 10 reaches the first rolling load corresponding to the succeeding material.

[0095] FIG. 7 shows an example of time series data of the transition target load and time series data of the detected load when the control mode is switched from the elongation rate control to the welding point passing control.

[0096] When the control mode is switched from the elongation rate control to the weld point passage control, the screw down control unit 44 issues a screw down command to the screw down device 12 so that the detected load detected by the load detector 20 approaches the transition target load.

[0097] As shown on the left side of FIG. 7, when such control is performed by the screw-down control unit 44, the detected load also decreases so as to follow the transition target load.

[0098] When the control mode is switched from the weld point passage control to the elongation rate control, the screw down control unit 44 issues a screw down command to the screw down device 12 so that the detected load detected by the load detector 20 approaches the transition target load.

[0099] As shown on the right side of FIG. 7, when such control is performed by the screw-down control unit 44, the detected load also increases so as to follow the transition target load.

[0100] The target load change period and the evaluation period are set based on, for example, the time series data of the transition target load and the detected load. Specifically, the deviation data generating unit 46 sets the target load change section from the acquired time series data of the transition target load and the detected load, and stores it in the ROM.

[0101] For example, if the target load change period is the period required for switching from a first rolling load to a second rolling load, the deviation data generating unit 46 sets the target load change period as the period from time A when the switching of the load set in the rolling mill 10 shown in Figure 7 begins to time B when the switching of the setting is completed.

[0102] In addition, if the target load change period is set to the period during which the second rolling load is switched to the first rolling load, the deviation data generating unit 46 sets the target load change period to the period from time A' when the switching of the load set in the rolling mill 10 shown in Figure 7 begins to time B' when the switching of the setting is completed.

[0103] Incidentally, the setting of the target load change period by the deviation data generating unit 46 is not limited to this manner, and may be performed, for example, by acquiring a switching signal between the elongation rate control (first rolling load) and the welding point passage control (second rolling load) from the load setting unit 43 and based on this signal.

[0104] Fig. 8 shows an example of the deviation load in the evaluation period when the control mode is switched from the elongation rate control to the welding point passing control. The deviation data generating unit 46 sets the evaluation period based on the target load change period and stores the evaluation period in the ROM. As shown in Fig. 8, the evaluation period includes the target load change period and is set so as to extend the end point of the target load change period in response to the time delay of the detected load relative to the transition target load.

[0105] Specifically, the evaluation period includes a target load change period (times A to B and A' to B') and an additional period (times B to C and B' to C') corresponding to the period from when the control mode switching starts to when the detected load corresponding to the control mode switching is detected. This makes it possible to identify the behavior related to the deviation of the detected load from the transition target load, and makes it easier to determine an abnormality in the screw down device 12.

[0106] The response speed of the screw down device 12 differs depending on the screw down mechanism. Specifically, the response speed of the electric screw down device 12 to a screw down command from the screw down control unit 44 is slower than that of the hydraulic screw down device 12. For this reason, the electric screw down device 12 tends to have a larger deviation between the transition target load and the detected load than the hydraulic screw down device 12.

[0107] The deviation data generating unit 46 may set the evaluation period taking into consideration the screw down mechanism of the screw down device 12. When the screw down mechanism of the screw down device 12 is of a hydraulic type, the evaluation period is preferably set to, for example, 100 to 400 ms, and when it is of an electric type, the evaluation period is preferably set to 200 to 1000 ms.

[0108] The deviation data generating unit 46 generates operation time deviation data, which is an integral value of the deviation between the transition target load and the detected load, during the evaluation period specified as described above. The time interval for the integral calculation of the time series data during the evaluation period may be set arbitrarily to a time longer than the sampling time of the detected load. The sampling time of the detected load refers to the data acquisition period during which the control unit 40 acquires the detected load data from the load detector (load cell) 20. The sampling time of the detected load is set to, for example, 10 to 200 ms.

[0109] However, it is preferable to set the time interval in the integral calculation to be at least 10 points or more within the evaluation period. That is, the integral calculation is performed by taking the sum of the product of the detection load data and the time interval within the evaluation period. Therefore, if the time interval is less than 10 points within the evaluation period, it becomes difficult to specify the behavior related to the deviation of the detection load from the transition target load.

[0110] The judgment unit 47 judges an abnormality in the rolling mill 10 based on the generated operational deviation data. The function of the deviation data generation unit 46 will be described below.

[0111] The judgment unit 47 judges an abnormality in the rolling mill 10 based on the operational deviation data generated by the deviation data generation unit 46 . The judging unit 47 judges that an abnormality has occurred in the screw down device 12 of the rolling mill 10 when the magnitude (absolute value) of the operational deviation data becomes larger than that in a normal state.

[0112] For example, if an abnormality occurs in the reduction device 12 of the rolling mill 10, the operation of the reduction device 12 will be delayed in response to a reduction command from the reduction control unit 44, causing the magnitude (absolute value) of the operational deviation data to be larger than normal.

[0113] Furthermore, when an abnormality occurs such that the operation of the screw down device 12 stops, the change in the detected load is smaller than the change in the transition target load. Therefore, the magnitude (absolute value) of the deviation data during operation becomes larger than that during normal operation.

[0114] Therefore, the determining unit 47 determines that an abnormality has occurred in the screw down device 12 of the rolling mill 10 when the magnitude (absolute value) of the operational deviation data exceeds the threshold value compared to normal times.

[0115] Here, the reason why the judgment unit 47 uses the magnitude (absolute value) of the operational deviation data generated during the evaluation period is as follows: In the first control mode in which the steady portion of the preceding or succeeding strip is rolled, the elongation rate and reduction rate of the steel strip SS are controlled to predetermined values.

[0116] However, in the elongation rate control and the reduction rate control performed in the first control mode, the reduction device 12 operates so that the elongation rate and the reduction rate applied to the steel strip SS are constant. Therefore, in the first control mode, the rolling load may constantly change. Therefore, in the first control mode, it is difficult to determine whether such a change in the detected load is normal or abnormal. Therefore, even if the detected load detected by the load detector 20 is monitored, it is difficult to determine an abnormality in the reduction device 12.

[0117] On the other hand, when switching from either the first control mode or the second control mode to the other control mode, a transition target load is set by the load setting unit 43. Therefore, by observing the deviation between the set transition target load and the detected load, it becomes possible to easily determine an abnormality in the screw down device 12.

[0118] For example, when a measurement error occurs in the load detector 20, the second control mode, ie, the welding point passing control, controls the load detected by the load detector 20 with the error to approach the target load. Therefore, if there is no abnormality in the load detector 20, the operational deviation data does not change significantly from the normal state.

[0119] In other words, the method of Patent Document 1 does not detect the load that accompanies the operation of the screw down device 12, so it is difficult to determine whether there is an abnormality in the screw down device 12. In contrast, the rolling mill abnormality determination system 100 of the present invention determines an abnormality in the rolling mill 10 based on the detection load when switching from one of the first control mode and the second control mode to the other control mode. That is, during the evaluation period, the transition target load set from the first rolling load to the second rolling load varies from moment to moment. The roll gap is controlled by the reduction device 12 in response to the change in the transition target load. Therefore, when the reduction device 12 is operating normally, the detection load also varies following the change in the transition target load. The rolling mill abnormality determination system 100 of the present invention can determine an abnormality in the reduction device 12 by using the detection load when the roll gap is controlled by the reduction device 12 to determine an abnormality in the rolling mill 10.

[0120] Specifically, the rolling load applied to the steel strip SS in the elongation rate control is about 3000 to 5000 kN, whereas the second rolling load is about 500 to 1500 kN.

[0121] Therefore, during the target load change period, a larger change in the detected load is observed compared to the change in the detected load while the elongation rate control is being executed for the same steel strip SS. Accordingly, the change in the reduction amount by the screw down device 12 during the period also becomes larger. As a result, the difference between the target load and the detected load when an abnormality occurs in the screw down device 12 also becomes larger, so that it becomes easier to determine the abnormality of the screw down device 12.

[0122] For example, if there is an abnormality in the screw down device 12, when the control mode is switched from the first control mode to the second control mode, the transition target load decreases, but the roll gap is not appropriately controlled, so the detection load of the first control mode is maintained.

[0123] Since the judgment unit 47 cannot detect the tracking of the detected load accompanying the switching of the control mode, that is, since peculiar data different from that during normal operation is detected in the deviation data during operation, it becomes possible to detect that an abnormality has occurred in the screw down device 12.

[0124] It is preferable that the judgment unit 47 makes the judgment based on normal state deviation data, which is the integral value of the deviation between the target load and the detected load during the evaluation period, acquired when the rolling mill 10 is operating normally.

[0125] Specifically, the judgment unit 47 uses the normal deviation data as a standard and judges that there is an abnormality in the rolling mill 10 if the deviation of other operational deviation data, which is different from the normal deviation data, from the standard is greater than a preset threshold value.

[0126] The normal state deviation data can be generated in the same manner as the operational state deviation data. The state in which the rolling mill 10 is operating normally refers to a state in which no abnormality occurs in the reduction device 12 of the rolling mill 10.

[0127] Specifically, it can be determined that the rolling mill 10 is in a state where the elongation rate and reduction rate of the steel strip SS rolled by the rolling mill 10 are controlled within a predetermined range, and there is no abnormality in the dimensional quality and material properties of the steel sheet product. In addition, after maintenance and inspection of the reduction device 12 of the rolling mill 10, it can be considered that no abnormality has occurred in the reduction device 12 for at least about one day of operation. This is because it is empirically known that abnormalities in the reduction device 12 occur several days after maintenance and inspection.

[0128] That is, the normal-state deviation data can be the operational deviation data acquired when the screw down device 12 is in a normal state. Specifically, the integral value of the deviation between the transition target load and the detected load during the evaluation period acquired in a normal state can be used as the normal-state deviation data.

[0129] Fig. 9 is a plot of the relationship between the change in the load setting value of the transition target load and the integral value of the deviation load of the normal state deviation data. Specifically, in Fig. 9, the period during which the control mode is switched from the first control mode to the second control mode is set as the target load change period, and the detected load and normal state deviation data are acquired.

[0130] As shown in FIG. 9, the integral value of the load deviation in the normal data group tends to increase according to the amount of change in the transition target load, and the value falls within a certain range.

[0131] In contrast, when operational deviation data acquired when an abnormality occurs in the screw down device 12 is plotted, the data falls outside the distribution range of normal deviation data.

[0132] In this manner, the determination unit 47 can easily determine an abnormality in the screw down device 12 by identifying the behavior from which the operational deviation data deviates based on the normal deviation data.

[0133] The degree of deviation from the standard can be calculated by identifying correlations between variables under normal conditions through principal component analysis of the normal deviation data, and then using Q statistics.

[0134] Principal component analysis is an analysis that synthesizes a small number of uncorrelated variables, called principal components, which best represent the overall variability, from a large number of correlated variables, and includes a calculation to calculate the projection of observed data onto a space formed by preset principal component vectors.

[0135] Specifically, N (N≧2) pieces of normal-state deviation data may be acquired, and k principal components of the normal-state deviation data acquired by principal component analysis may be used to calculate the deviation degree in the principal component space for the operational deviation data.

[0136] In this case, the k principal components are determined as major principal components whose cumulative contribution ratio is equal to or greater than a preset value (e.g., 0.8). This allows the k principal components and outlier components, which are principal components lower in rank than the k principal components, to be calculated for the operational deviation data.

[0137] The Q statistic can be obtained from the residue calculated in this manner, and if the Q statistic is treated as the deviation and is greater than a preset threshold, it is determined that there is an abnormality in the rolling mill.

[0138] The deviation threshold can be set, for example, by calculating the Q statistic of the normal deviation data and setting it to about 3 to 10 times the Q statistic of the normal deviation data.

[0139] In addition, the judgment unit 47 may be configured to count the number of times it is judged that there is an abnormality in the screw down device 12 of the rolling mill 10, and judge whether or not the screw down device 12 needs repair by thresholding the counted number in a specified period of time with a specified threshold value.

[0140] This is because, in cases where an abnormality gradually occurs in the movable parts of the screw down device 12 due to gradual wear or the like, the degree of deviation gradually increases, and the number of times the threshold value is exceeded may increase.

[0141] The deviation of the operational deviation data from the normal deviation data may be calculated using the k-nearest neighbor algorithm. The k-nearest neighbor algorithm is a classification method based on the closest training example in a feature space. Specifically, a plurality of normal deviation data are acquired and plotted in a model space (vector space), and the distance (Euclidean distance) in the model space from the operational deviation data acquired during operation is calculated. Then, k pieces of data (k≧1) with close distances are acquired, and the distances (Euclidean distances) from the operational deviation data are calculated, and the average distance is calculated. This is a method for determining that there is an abnormality in the rolling mill 10 if the calculated average distance is greater than a preset threshold value.

Claims

1. a rolling mill having a rolling section having a pair of work rolls arranged opposite to each other and a reduction device for adjusting the gap between the pair of work rolls; a load detector that detects a rolling load of the steel strip by the rolling unit as a detection load; a position information acquisition unit for acquiring position information of the welding point of the steel strip; A control mode switching unit that switches a control mode of the rolling mill to either a first control mode or a second control mode according to the position information of the welding point, a period information acquisition unit that acquires a target load change period, which is a period from one of the first control mode and the second control mode to the other control mode, and an evaluation period, which includes the target load change period and is a period during which the rolling load of the rolling unit is evaluated; a load setting unit that sets a first rolling load set in the first control mode, a second rolling load set in the second control mode and different from the first rolling load, and a transition target load that is set during the target load change period and is used until the first rolling load or the second rolling load is changed to the other rolling load, in the rolling mill; a screw-down control unit that controls the screw-down device so that the detected load approaches the transition target load during the evaluation period; a deviation data generating unit that generates, during the evaluation period, operational deviation data that is an integral value of a deviation between the transition target load and the detected load corresponding to the transition target load; a determination unit that determines an abnormality in the rolling mill based on the operation-time deviation data.

2. the deviation data generating unit generates the operational deviation data when the rolling mill operates normally as normal deviation data, 2. The rolling mill abnormality determination system according to claim 1, wherein the determination unit determines that the rolling mill has an abnormality when the normal state deviation data is used as a reference and a degree of deviation of the other operational deviation data different from the normal state deviation data from the reference is greater than a preset threshold value.

3. 3. The rolling mill abnormality determination system according to claim 1 or 2, wherein the evaluation period includes the target load change period and an additional period corresponding to a period from when the switching of the control mode is started to when the detection load corresponding to the switching of the control mode is detected.

4. A method for determining an abnormality in a rolling mill, the method including switching a control mode of the rolling mill having a rolling section with a pair of work rolls arranged opposite to each other and a screw down device for adjusting a gap between the pair of work rolls, the control mode of the rolling mill being switched to either a first control mode or a second control mode in accordance with position information of a welding point of a steel strip, the method comprising: a period information acquisition step of acquiring a target load change period, which is a period from one of the first control mode and the second control mode to the other control mode, and an evaluation period, which includes the target load change period and is a period during which the rolling load of the rolling section is evaluated; a load setting step of setting a first rolling load set in the first control mode, a second rolling load set in the second control mode and different from the first rolling load, and a transition target load set during the target load change period and for changing from one of the first rolling load and the second rolling load to the other rolling load, in the rolling mill; a roll-down control step of controlling the roll-down device so that the rolling load of the rolling portion is a detection load and the detection load approaches the transition target load during the evaluation period; a load detection step of detecting the load; a deviation data generating step of generating, during the evaluation period, deviation data during operation that is an integral value of a deviation between the transition target load and the detected load corresponding to the transition target load; and a determination step of determining whether or not an abnormality exists in the rolling mill based on the operational deviation data.

5. In the deviation data generating step, the operational deviation data when the rolling mill operates normally is generated as normal deviation data; 5. The method for determining an abnormality in a rolling mill according to claim 4, wherein, in the determination step, the normal state deviation data is used as a reference, and it is determined that an abnormality exists in the rolling mill when a degree of deviation of the other operational deviation data different from the normal state deviation data from the reference is larger than a preset threshold value.

6. 6. The method for determining an abnormality in a rolling mill according to claim 4 or 5, wherein the evaluation period includes the target load change period and an additional period corresponding to a period from when the switching of the control mode is started to when the detection load corresponding to the switching of the control mode is detected.

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