JP7632393B2 - Rolling mill abnormality determination system and rolling mill abnormality determination method - Google Patents

Description

The present invention relates to a rolling mill abnormality determination system and a rolling mill abnormality determination method.

In the manufacturing process of thin steel plates, a rolling mill with a pair of rolls is used to apply a load to the steel strip. Specifically, the pair of rolls is positioned 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 plate and to adjust the material properties of the thin steel plate by applying an appropriate reduction.

The reduction device of a rolling mill controls the distance between a pair of rolls, i.e., the roll gap, to an appropriate value while rolling 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.

Therefore, maintaining the normal condition of the reduction device of the rolling mill is important in order to maintain the proper rolling condition of the steel strip. Various proposals have been made for detecting abnormal conditions in the rolling mill. For example, Patent Document 1 discloses a method for determining an 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 calculated load value calculated based on a pressure gauge installed in the hydraulic cylinder and the measured load value measured by the load detector over time.

Patent Document 2 also discloses an anomaly determination system that monitors equipment driven by an electric motor and determines whether the equipment is abnormal. In Patent Document 2, the equipment driven by an electric motor includes, for example, a rolling mill that uses 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 treated as the average behavior under normal conditions, and an anomaly in the equipment is determined based on the degree to which the correlation of the variables obtained during operation deviates from the average behavior under normal conditions.

JP 2017-177203 A Patent No. 5991042

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 the load detector (load cell). However, if the load detector is normal, there is a problem in that other abnormalities, such as an abnormality in the screw-down device, cannot be detected.

In addition, when applying the abnormality determination system described in Patent Document 2 to the reduction device of a rolling mill, it is necessary to obtain time-series data on the torque current of the motor that drives the reduction device, and the movement speed and amount of movement of the backup roll displaced by the reduction device.

However, there is a problem that the abnormality determination system cannot be directly applied to hydraulic reduction devices, which do not generate torque current from the electric motor. In addition, it becomes necessary to install equipment that is not provided in normal rolling mills, such as equipment to measure the torque current of the electric motor, which increases equipment costs and leaves room for improvement.

The present invention has been made to solve the above problems, and aims to provide a rolling mill abnormality determination system and method that can detect abnormalities in a rolling mill, particularly abnormalities occurring in the reduction device, at an early stage and can detect abnormalities regardless of the type of reduction mechanism of the reduction device.

[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 in accordance with 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 operation-time deviation data different from the normal state deviation data from the reference is greater than a preset threshold value.
[3]
The abnormality determination system for a rolling mill according to [1] or [2], wherein the evaluation period includes the target load change period and an additional period corresponding 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 when a deviation degree of the 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 according to [4] or [5], wherein the evaluation period includes the target load change period and an additional period corresponding to the period from when the control mode switching is started to when the detection load corresponding to the control mode switching is detected.

The rolling mill abnormality determination system and rolling mill abnormality determination method of the present invention can detect rolling mill abnormalities, particularly abnormalities occurring in the reduction device, at an early stage. This makes it possible to improve the yield of thin steel plates. Furthermore, the rolling mill abnormality determination system and rolling mill abnormality determination 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.

FIG. 1 is a conceptual diagram showing a configuration of an abnormality determination system for a rolling mill. FIG. 2 is a front view showing the front of the rolling mill of FIG. 1 . FIG. 2 is a side view of the rolling mill of FIG. 1 . FIG. 2 is a block diagram showing functional blocks of the abnormality determination system for a rolling mill. FIG. 11 is a flow chart for determining an abnormality in a rolling mill. FIG. 4 is an explanatory diagram showing a manner in which settings of a first rolling load and a second rolling load are switched. 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. FIG. 10 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. FIG. 13 is a graph showing an integral value of a deviation load with respect to a change amount of a load setting value.

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

The continuous annealing line has a furnace body (not shown) that includes, for example, a heating zone, a soaking zone, and a cooling zone. At the entry side of the continuous annealing line, the front and rear ends 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.

The continuous annealing line has equipment that performs continuous temper rolling on the steel strip that has been heat treated in the furnace body. The rolling mill 10 is arranged in the equipment that performs continuous temper rolling. Therefore, the steel strip that has been heat treated in the furnace body is continuously rolled by the rolling mill 10 that is arranged downstream.

As shown in FIG. 1, an entry bridle roll BR1 and an entry tension meter TM1 are arranged on the upstream side (entry side) of the rolling mill 10. An exit tension meter TM2 and an exit bridle roll BR2 are arranged on the downstream side (exit side) of the rolling mill 10.

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

The tension meter TM1 is installed between the rolling mill 10 and the entry bridle roll BR1. The tension meter TM1 measures the tension of the steel strip SS on the entry side of the rolling mill 10.

The tension gauge TM2 is installed between the rolling mill 10 and the exit bridle roll BR2. The tension gauge TM2 measures the tension of the steel strip SS at the exit of the rolling mill 10.

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.

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.

The pair of work rolls 11a, 11b therefore come into contact with the steel strip SS, which is the material to be rolled, and apply pressure to it 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.

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

The reduction device 12 adjusts the spacing between the pair of work rolls 11a, 11b, i.e., the roll gap, so that the rolling load applied to the steel strip SS is 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.

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

Figure 2 shows the front of the rolling mill 10. Figure 3 shows the side of the rolling mill 10. As shown in Figures 2 and 3, the rolling mill 10 has a pair of housings 13 formed of an integral frame having a substantially rectangular frame shape. The pair of housings 13 may be formed of a frame-shaped structure made of columnar members.

The pair of housings 13 are arranged facing each other. The opposing surfaces of the housings 13 have openings 13a that open across their height. The openings 13a are formed to penetrate the pair of housings 13 in the opposing direction.

A bearing box 14a (backup roll chock) that supports the backup roll 11c is housed in the upper part of the opening 13a of each housing 13. In this embodiment, the bearing box 14a is provided in the housing 13 so that it can slide vertically within the housing 13. The backup roll 11c is supported by the bearing box 14a on the housing 13 so that it can rotate freely around its axis.

Below the bearing box 14a of each housing 13, a support part 15a is provided to support the upper work roll 11a. Also, below the support part 15a, a support part 15b is provided to support the lower work roll 11b. The work rolls 11a and 11b are supported on the housing 13 by the support parts 15a and 15b so that they can rotate freely around their axes.

At the bottom of the opening of each housing 13, a bearing box 14b (backup roll chock) that supports the backup roll 11d is provided. The backup roll 11d is supported on the housing 13 by the bearing box 14b so that it can rotate freely around its axis.

The ends of each of the work rolls 11a, 11b are connected to a coupling or reducer (not shown) and a drive motor (not shown) via supports 15a, 15b. Therefore, when the drive motor is operated, the work rolls 11a, 11b rotate around their axes.

The driving motor that rotates 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 to roll the steel strip SS is relatively small, such as in a temper rolling mill, a large torque is not required.

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 for the screw-down device 12. The screw-down device 12 adjusts the roll gap, which is the arrangement distance between the work rolls 11a and 11b, by connecting to the bearing housing 14a of the backup roll 11c.

For example, if the rolling mechanism uses a hydraulic rolling device 12, a hydraulic cylinder may be connected to the bearing housing 14a of the backup roll 11c. The rolling 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.

When the rolling mechanism uses an electric rolling device 12, it is preferable to connect a rolling screw that rotates around its axis in response to the drive of the electric motor to the bearing box 14a of the backup roll 11c. Therefore, the rolling device 12 can displace the bearing box 14a of the backup roll in the vertical direction of the housing 13 by controlling the drive of the electric motor.

The reduction device 12 only needs to be able to adjust the spacing between the pair of work rolls 11a, 11b, i.e., the roll gap. The reduction 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 reduction 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.

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 boxes 14a are approximately the same. Note that each screw-down device 12 may be adjusted by a method known as leveling so that the vertical positions of the housings of the pair of bearing boxes 14a are different from each other.

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.

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.

The load detector 20 may also be arranged on the same side as the screw-down device 12 in the up-down direction of the housing 13, either at the top or bottom of the housing 13. Furthermore, the load detector 20 may be arranged on each of the left and right housings 13. When a load detector 20 is arranged 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.

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

The rolling mill 10, the load detector 20, and the position measurement unit 30 are communicatively connected to the control unit 40.

The load detector 20 (load cell) is a sensor that converts force into an electrical signal. The load detector 20 can be a magnetostrictive type, a capacitance type, a strain gauge type, or other type of detector. When the load detector 20 (load cell) detects a force, it transmits an electrical signal corresponding to that force to the control unit 40.

The position measurement unit 30 detects the position of the welding point of the steel strip SS by known means such as optical means, mark detection means, and load fluctuation detection means. The position measurement unit 30 transmits the detection information detected by these position detection means to the control unit 40.

The control unit 40 is composed of 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 that executes the plate thickness control method according to an embodiment of the present invention, and a processing program and processing data that control the operation of the entire abnormality determination system 100. The CPU controls the operation of the entire abnormality determination system 100 in accordance with 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.

The ROM stores various setting information, including 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 section 11 is evaluated. The ROM also stores the detected load data transmitted from the load detector 20 as time-series data.

The position information acquisition unit 41 tracks the welding points based on the detection information sent from the position measurement unit 30, such as the line speed. The tracking information tracked by the position information acquisition unit 41 is stored in the ROM.

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 upstream of the production line.

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 when rolling the steel strip SS other than the welding point (hereinafter also referred to as the steady portion) based on the tracking information, and sets the control mode to the second control mode when rolling the steel strip SS near the welding point.

In the first control mode, for example, when temper rolling of 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, we will explain the case where elongation rate control is adopted to keep the elongation rate of the steel strip SS constant as an example of the first control mode.

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 increase rate, i.e., 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. 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.

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 roughly the same value. For this reason, when controlling the elongation rate, the rolling reduction rate may be used instead of the elongation rate.

In addition, in this embodiment, we will explain the case where welding point passing control is adopted as an example of the second control mode, in which the rolling load applied to the steel strip SS is kept constant.

The welding point passing control is switched from the elongation rate control depending on 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 passing control based on the tracking information.

The load setting unit 43 sets a rolling load to the rolling mill 10 according to the elongation rate control, the welding point passing control, and the target load change period. 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.

As described above, in the elongation rate control, control is performed so that the elongation rate of the steel strip SS is maintained constant. Furthermore, 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.

In the second control mode, ie, welding point passing control, the load setting unit 43 sets a second rolling load, 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, the preceding material and the following material are joined by lap welding such as seam welding to form the 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 plate thickness greater than that of the preceding material and the following material.

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

In the weld point passing control, in order to prevent the occurrence of such surface defects, the rolling load is temporarily 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.

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 either the first rolling load or the second rolling load to the other rolling load.

The transition target load may be set, for example, to have a proportional relationship to the target load change period. In other words, the transition target load may be set so that it decreases or increases at a constant rate between when one rolling load is changed to the other rolling load. By setting the transition target load in this way, it is possible to improve the accuracy of determining whether there is an abnormality in the rolling mill 10, which will be described later.

The reduction control unit 44 controls the reduction device 12 to adjust the spacing between the pair of work rolls 11a, 11b according to the first rolling load, the second rolling load, and the transition target load.

Specifically, the reduction control unit 44 adjusts the vertical position of the housing 13 of the pair of bearing boxes 14a by controlling each of the reduction devices 12. For example, the reduction control unit 44 sets an arbitrary vertical position 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 boxes 14a.

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

In elongation rate control, the reduction control unit 44 controls the operation of the reduction device 12 of the rolling mill 10 so that the measured elongation rate approaches a predetermined elongation rate.

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, which is the material being rolled. For example, when the sizes or steel types of the preceding and following materials are different, 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 way, 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 kept constant.

In addition, during the welding point passing control, the reduction control unit 44 controls the operation of the reduction device 12 of the rolling mill 10 so that the detected load approaches the second rolling load.

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

Furthermore, during the target load change period, 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 transition target load.

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 advance in the ROM.

In addition, the period information acquisition unit 45 may set the target load change period and evaluation period based on the tracking information, for example, and acquire the set target load change period and evaluation period.

The deviation data generating unit 46 generates operational deviation data, which is the integral value of the deviation between the transition target load and the detected load corresponding to the transition target load, during the evaluation period.

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.

A method for determining abnormalities in the rolling mill 10 using the abnormality determination system 100 for determining abnormalities in the rolling mill 10 described above will be described.

Figure 5 shows a flow for determining an abnormality in the rolling mill 10 by the abnormality determination system 100. As shown in Figure 5, the process for determining an abnormality in the rolling mill 10 is started, for example, by the execution of switching control that changes the control mode of the rolling mill 10.

Specifically, the position information acquisition unit 41 performs welding point tracking on the production line and generates information (tracking information) related to 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.

The control mode switching unit 42 refers to the tracking information and switches from elongation rate control to welding point passing control when the welding point reaches a preset position upstream of the rolling mill 10 (e.g., 3 to 5 m upstream of the rolling mill 10). The control unit 40 detects this control mode switch and executes a process to determine an abnormality in the rolling mill 10.

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

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

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 corresponding to switching to the other control mode.

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

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.

The deviation data generating unit 46 generates operational deviation data, which is the integral value of the deviation between the transition target load and the detected load corresponding to the transition target load during the evaluation period (step S05).

The judgment unit 47 judges whether or not there is an abnormality in 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).

Figure 6 shows how the control mode is switched from elongation rate control to welding point passing control. As shown in Figure 6, when the control mode is switched from elongation rate control to welding point passing control, the load setting unit 43 sets the rolling load to be set on the rolling mill 10 to the second rolling load.

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

The left side of Figure 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.

The second rolling load is set, for example, to 500 to 1500 kN. The load reduction rate may be set, for example, to -1500 kN/s.

In the center of FIG. 6, the welding point passing 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 passing 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.

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 speed of the line. The holding time is not limited to this embodiment, and may be determined, for example, by the time it takes 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.

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 the 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.

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

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.

Figure 7 shows an example of time series data of the transition target load and time series data of the detected load when switching the control mode from elongation rate control to welding point passing control.

When the control mode is switched from elongation rate control to welding point passing control, the reduction control unit 44 issues a reduction command to the reduction device 12 so that the detected load detected by the load detector 20 approaches the transition target load.

As shown on the left side of Figure 7, when this type of control is performed by the roll-down control unit 44, the detected load also decreases so as to follow the transition target load.

When the control mode is switched from the welding point passing control to the elongation rate control, the reduction control unit 44 issues a reduction command to the reduction device 12 so that the detected load detected by the load detector 20 approaches the transition target load.

As shown on the right side of Figure 7, when this type of control is performed by the roll-down control unit 44, the detected load also increases to follow the transition target load.

The target load change period and evaluation period are set, for example, based on 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 interval from the acquired time series data of the transition target load and the detected load, and stores it in the ROM.

For example, if the target load change period is the period during which the first rolling load is switched to the second 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 FIG. 7 begins to time B when the switching of the setting is completed.

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 FIG. 7 begins to time B' when the switching of the setting is completed.

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, based on a switching signal obtained from the load setting unit 43 for switching between elongation rate control (first rolling load) and welding point passage control (second rolling load).

Figure 8 shows an example of the deviation load in the evaluation period when switching the control mode from elongation rate control to 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 ROM. As shown in Figure 8, the evaluation period includes the target load change period, and is set 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.

Specifically, the evaluation period includes the target load change period (times A to B and A' to B') and an additional period (times B to C and B' to C') that corresponds to the period from when the control mode switching begins to when the detected load corresponding to the control mode switching is detected. This makes it possible to identify the behavior of the detected load relative to the transition target load, making it easier to determine an abnormality in the screw-down device 12.

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.

The deviation data generating unit 46 should set the evaluation period taking into consideration the screw-down mechanism of the screw-down device 12. If the screw-down mechanism of the screw-down device 12 is hydraulic, the evaluation period is preferably set to, for example, 100 to 400 ms, and if it is electric, the evaluation period is preferably set to 200 to 1000 ms.

The deviation data generating unit 46 generates operational deviation data, which is the integral value of the deviation between the transition target load and the detected load, during the evaluation period identified 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.

However, it is preferable to set the time intervals in the integral calculation to at least 10 points within the evaluation period. In other words, the integral calculation is performed by taking the sum of the product of the detected load data and the time interval within the evaluation period. For this reason, if the time interval is less than 10 points within the evaluation period, it becomes difficult to identify the behavior related to the deviation of the detected load from the transition target load.

The judgment unit 47 judges abnormalities in the rolling mill 10 based on the generated operational deviation data. The function of the judgment unit 47 in relation to the deviation data generation unit 46 is explained below.

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 judgment 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.

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.

In addition, if an abnormality occurs that causes the screw down device 12 to stop operating, the change in the detected load will be smaller than the change in the transition target load. Therefore, the magnitude (absolute value) of the operational deviation data will be larger than under normal circumstances.

Therefore, the judgment unit 47 judges that an abnormality has occurred in the reduction 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.

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. That is, in the first control mode in which the steady part of the preceding or following material is rolled, the elongation rate and reduction rate of the steel strip SS are controlled to predetermined values.

However, in the elongation rate control and reduction rate control performed in the first control mode, the reduction device 12 operates so that the elongation rate and reduction rate applied to the steel strip SS are constant. For this reason, in the first control mode, the rolling load may constantly change. Therefore, in the first control mode, it is difficult to determine whether such fluctuations in the detected load are normal or abnormal. For this reason, 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.

In contrast, when switching from either the first control mode or the second control mode to the other control mode, the 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 easier to determine an abnormality in the screw-down device 12.

For example, if a measurement error occurs in the load detector 20, in the second control mode, the welding point passing control, the load detected by the load detector 20 where the error occurs is controlled 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 normal times.

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.

Specifically, the rolling load applied to the steel strip SS during elongation rate control is approximately 3000 to 5000 kN, while the second rolling load is approximately 500 to 1500 kN.

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 elongation rate control is being performed on the same steel strip SS. Accordingly, the change in the amount of reduction by the reduction device 12 during that period also becomes larger. As a result, the deviation between the target load and the detected load in the event of an abnormality in the reduction device 12 also becomes larger, making it easier to determine whether or not the reduction device 12 has an abnormality.

For example, if there is an abnormality in the screw down device 12, when switching 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.

The judgment unit 47 cannot detect the tracking of the detected load when the control mode is switched, i.e., peculiar data different from normal data is detected in the operational deviation data, making it possible to detect that an abnormality has occurred in the screw-down device 12.

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

Specifically, the judgment unit 47 may use the normal deviation data as a standard and judge 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.

The normal deviation data can be generated in the same manner as the operational 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.

Specifically, it can be judged as normal when 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 are no abnormalities in the dimensional quality or material of the steel plate product. In addition, after maintenance and inspection of the reduction device 12 of the rolling mill 10, it can be considered that no abnormalities have 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.

In other words, the operational deviation data acquired when the screw down device 12 is in a normal state can be used as the normal deviation data. 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 deviation data.

Figure 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 deviation data. Specifically, in Figure 9, the period during which the control mode switches from the first control mode to the second control mode is set as the target load change period, and the detected load and normal deviation data were obtained.

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

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

In this way, the judgment unit 47 can easily judge an abnormality in the screw-down device 12 by identifying the behavior that deviates from the operational deviation data based on the normal deviation data.

The degree of deviation from the standard can be determined by identifying correlations between normal variables through principal component analysis of normal deviation data, and then using Q statistics to calculate the degree of deviation from the normal deviation data.

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

Specifically, N (N≧2) pieces of normal state deviation data are acquired, and the deviation degree in the principal component space for the operational state deviation data is calculated using k principal components of the normal state deviation data acquired by principal component analysis.

In this case, the k principal components are determined as the major principal components whose cumulative contribution rate 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.

The Q statistic can be calculated from the residual calculated in this way, 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.

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

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

If the moving parts of the screw-down device 12 gradually become abnormal due to wear or other reasons, the deviation gradually increases, and the number of times the threshold is exceeded may increase.

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 feature space. Specifically, multiple 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, the distances (Euclidean distances) from the operational deviation data are calculated, and the average distance is calculated. This method determines that there is an abnormality in the rolling mill 10 if the calculated average distance is greater than a preset threshold value.

Claims (6)

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 in accordance with 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. 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. 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 the period from when the control mode switching is started to when the detection load corresponding to the control mode switching is detected. 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. 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. 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 the period from when the control mode switching is started to when the detection load corresponding to the control mode switching is detected.

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