JP2964887B2 - Method for detecting chattering in rolling mills - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting chattering of a rolling mill for preventing the occurrence of a striped flaw called a chatter mark generated due to the vibration of the rolling mill.

[0002]

2. Description of the Related Art Generally, in a rolling mill for a thin steel sheet, surface damage of a backup roll, excessive or insufficient lubrication of rolling oil,
A kind of resonance phenomenon called chattering occurs due to fluctuations in the plate surface temperature of the strip, and chatter marks may be formed on the strip. Chatter marks generated in a rolling mill are, as shown in FIG. 17, product flaws of the striped pattern 102 generated in the surface width direction of the strip 101, the pitch P of the striped pattern 102 is 5 to 3000 mm, and the thickness variation is 1 μm. From the following fine objects, in the worst cases, up to the breakage of the strip 101. For this reason, when chattering starts to occur, it is necessary to immediately take measures such as reducing the rolling speed, and if this measure is delayed, the strip will be broken or the quality will be deteriorated. Detection is extremely important.

[0003] Conventionally, as a method of preventing chatter marks, vibration detectors are installed at one or more locations of each part of a metal rolling mill to detect the vibrations of each part of the rolling mill during operation, and to measure the acceleration of the vibrations of each part. Alternatively, a method of detecting the presence or absence of abnormal vibration of each part of the rolling mill by generating an abnormal signal when the vibration energy or both of them exceeds a certain value (Japanese Patent Publication No. 57-4440)
No. 8 publication), on the cold rolling mill exit side, at intervals of substantially half the pitch of the thickness variation occurring in the longitudinal direction of the material to be rolled by chattering, at least in the longitudinal direction of the material to be rolled
A method of detecting the occurrence of chattering when the sheet thickness is measured simultaneously at two locations and the difference between the measured thicknesses at each location is equal to or greater than a preset value.
No. 25) has been proposed.

[0004]

According to the method disclosed in Japanese Patent Publication No. 57-44408, the vibration of the rolling mill is dominant as shown in FIG. 19 and the minute chatter mark as shown in FIG. When it is composed of vibrations of small amplitude that cause the above, the actual vibration has a composite waveform as shown in FIG. In the vibration shown in FIG. 21, the fine vibration component causing the chatter mark shown in FIG. 20 is hidden by the dominant vibration shown in FIG.
Vibration components that could cause chatter marks could not be detected.
Even if chatter marks with a thickness variation of ± 50 μm or more for a thickness of 0.2 mm as shown in Fig. 18 can be detected, chatter marks with a thickness variation of ± 1 μm or less for a thickness of 0.5 mm as shown in Fig. 25 can be detected. It is difficult to detect the mark. In addition, Tokiko Sho 57-444
Since the method disclosed in Japanese Patent Publication No. 08 is a method of counting the peak value of the expected frequency, the vibration of the rolling mill is dominant vibration as shown in FIG. 22, and the chatter mark as shown in FIG. When composed of the causal vibration, the actual vibration has a composite waveform as shown in FIG. The frequency of the peak value of the vibration shown in FIG. 24 does not match the frequency of the vibration component causing the chatter mark shown in FIG. 23, and it is difficult to detect the occurrence of the chatter mark. Furthermore, the method disclosed in Japanese Patent Publication No. 57-44408 does not specify the cause of chatter marks, so the expected period is not clear, and it is difficult to specify the cause of chatter marks. .

[0005] The method disclosed in Japanese Patent Publication No. 5-87325 discloses a method in which chatter marks are generated when two or more thickness gauges are installed in the longitudinal direction of a cold rolling mill and the thickness difference exceeds a set value. The measurement accuracy of the X-ray thickness gauge is 1
%, And the measurement accuracy of a plate material having a product thickness of 0.5 mm is 5 μm, making it impossible to measure a thickness variation of ± 1 μm.

SUMMARY OF THE INVENTION An object of the present invention is to detect a chattering phenomenon that causes a minute thickness variation such as a chatter mark having a thickness variation of ± 1 μm or less with a product thickness of 0.5 mm, which cannot be detected conventionally, and its chattering. It is an object of the present invention to provide a method of detecting chattering in a rolling mill, which can specify the cause of occurrence of rolling.

[0007]

Means for Solving the Problems The present inventors have intensively studied and studied to achieve the above object. As a result, by analyzing the analog waveform of the vibration sensor attached to each part of the rolling mill and the frequency analysis of rolling parameters such as tension, rolling torque, rolling speed, etc., it is possible to decompose the vibration into sine wave, and if the rolling is normal, the roll will rotate. A peak value is seen at the frequency corresponding to the cycle, but when roll flaws, coupling play, mill natural frequency, bearing failure, gear meshing failure occur, a peak appears at the frequency corresponding to each chattering occurrence cause. By setting a threshold value for the peak value, occurrence of chattering can be detected.
It has been found that the frequency of chattering caused by each chattering occurrence can be obtained by calculation, and the present invention has been achieved.

Namely this application onset bright, by installing a vibration detector in more than one place in the rolling mill each unit detects the vibration of the mill each part in the operation, the chattering detection method of the rolling mill from the detected vibration of the respective parts , Mill natural frequency, gear biting
Poor fit, bad bearing, spindle and roll
Pulling backlash, inherent vibration-frequency generated from the roll scratches
Calculate the number and calculate the basic cycle for each chattering cause.
With the wave number, the frequency analysis of the vibration displacement, vibration speed or vibration acceleration of each part detected is performed , and the frequency analysis of the rolling parameters of the rolling mill, the rolling torque, the rolling speed , the rolling load, and the rolling parameter of the sheet thickness variation is performed . And rolling parameters
The result of frequency analysis of the measured values of
When exceeding the set <br/> value in an integral multiple of the frequency of the fundamental frequency of each grayed cause, it is determined that chattering, the originating
A chattering detection method for a rolling mill , wherein a raw cause is specified from the fundamental frequency .

[0009]

[Function] Causes of chatter marks in a rolling mill include:
As shown in FIG. 15, in addition to equipment factors such as mill natural vibration, bearing failure, roll flaw, gear meshing failure, coupling play, and changes in rolling parameters such as rolling speed, plate thickness, rolling load, tension, etc. There are various factors such as schedule, raw sheet, rolling oil and the like. Even if the analog waveform of the vibration detector attached to each part of the rolling mill is as shown in FIG. 21, by performing frequency analysis of this analog waveform, it can be decomposed into the sine wave vibration shown in FIGS. 19 and 20. Can be.
Graphs in which the vibration level of the sine wave is plotted on the vertical axis and the frequency is plotted on the horizontal axis are shown in FIGS. In a normal rolling state as shown in FIG. 3, a peak value is found at a frequency corresponding to the roll rotation cycle, but roll flaws (FIG. 4), coupling play (FIG. 5), and a natural frequency of the mill (FIG. 6) ), Bearing failure
When a gear meshing failure (FIG. 8) occurs (FIG. 7), a peak appears at a frequency corresponding to each chattering occurrence cause . A threshold value is provided for each peak value, and when the peak value exceeds the threshold value, it can be determined that chattering has occurred.

Further, by analyzing the frequency of the analog waveform of each rolling parameter such as the tension, rolling torque, and rolling speed of the rolling mill, the frequency analysis of the analog waveform of the vibration detector attached to each section of the rolling mill is performed. A peak appears at a frequency corresponding to each chattering occurrence cause . That is, FIGS. 9 to 14 are schematic diagrams of the frequency analysis result of the analog waveform of each vibration sensor and the frequency analysis result of the analog waveform of each rolling parameter when a gear meshing failure occurs in the rolling mill. The vibration level of the work roll vibration shown in FIG. 9, the transmission vibration shown in FIG. 10, and the mill housing vibration shown in FIG.
A clear peak is seen in the gear meshing frequency. Also,
The tension vibration shown in FIG. 12, the rolling torque shown in FIG. 13, and the vibration of the rolling speed shown in FIG. 14, since each parameter is converted into an electric signal, the vibration level cannot be compared,
Compared with the output of the vibration sensor at each part of the rolling mill, the white noise (disordered noise such that the energy per unit bandwidth is constant for all frequencies) is large, but the peak is found in the gear meshing frequency. Can be seen. Therefore, a peak appears at the frequency corresponding to the cause of chattering also by the frequency analysis of the analog waveform of each rolling parameter, so a threshold is set for the peak value, and chattering occurs when the peak value exceeds the threshold. Can be determined to be.

[0011] In the present application onset Akira, mill natural frequency, formic
A) Poor meshing, bad bearing, spindle and low
Inherent in rattle coupling play and roll flaws
Calculate the vibration frequency for each chattering cause
The fundamental frequency of the, the vibration displacement of each part of the rolling mill, vibration speed or vibration acceleration is detected, the detected vibration displacement of each part,
Perform frequency analysis of vibration velocity or vibration acceleration,
Rolling machine tension, rolling torque, rolling speed , rolling load, plate thickness
Perform frequency analysis of rolling parameters of fluctuation , vibration and rolling
The result of frequency analysis of the measured values of the parameters is
Integer multiple of the fundamental frequency for each chattering cause
When exceeding a set value in the determination and chattering
However, by specifying the cause of the occurrence from the fundamental frequency , the occurrence of chattering and the cause of the chattering can be specified, and the thickness of the product, which was conventionally undetectable, is 0.
It is possible to detect chattering that causes a minute thickness variation such as a chatter mark with a thickness variation of ± 1 μm or less at 5 mm.

In the present invention, each part of the rolling mill on which the vibration detector is installed includes, for example, a mill housing, an upper and lower backup roll chock, an upper and lower work roll chock,
One or more places such as a gear box and a bearing of the drive motor can be mentioned. As the vibration detector according to the present invention, a vibration sensor such as a resistance strain gauge, a semiconductor strain gauge, a piezoelectric acceleration pickup, a servo acceleration pickup, an electrokinetic velocity pickup, and an eddy current pickup can be used. In addition, the frequency analysis of rolling parameters such as vibration displacement, vibration speed, vibration acceleration or tension, rolling torque, and rolling speed is performed by Fast Fourier Transform (Fast Fourie Transform).
It is common to use a frequency analyzer of the (r Transform, FFT) type.

Generation of chatter marksCauseRoll flaw,
Coupling backlash, mill natural frequency, bearing failure,
When the gear meshing failure occurs, as shown in FIGS.
And each chattering occursCauseTo a frequency equivalent to
Appears. They occurCauseThe resulting chattering
The frequency can be calculated using the following formula.
You. Roll flaw: f₁= fo Coupling play: f_Two= 2 ・ fo Bearing inner ring flaw: f_Three= 1/2 (1 + d / D ・ cosα) ・ Z ・ fo Bearing outer ring flaw: f_Four= 1/2 (1-d / D ・ cosα) ・ Z ・ fo Gear engagement cycle: f_Five= Z_G・ Fo Mill natural frequency: For example, in the case of a 6-high rolling mill,
Calculate the natural frequency by replacing the vibration model with 6 degrees of freedom such asf
_6i (i = 1-6)Is calculated. Where fo: work roll rotation speed f₁~f _6i :OutbreakCauseBasic frequency of chattering for each d: Shaft inner diameter D:axisOuter diameter Z: Number of rolling elements in bearings Z_G: Number of gear teeth α:CircleWorking angle of tapered roller bearing

[0014]

Embodiment 1 The details of the method of the present invention will be described below with reference to FIG. 1 showing an embodiment. FIG. 1 is a schematic explanatory view showing the configuration of an apparatus in an embodiment of the method of the present invention applied to a final six-fold cold rolling mill in a cold rolling line consisting of five stands. In FIG. 1, 1 is a mill housing, 2 and 3 are upper and lower backup rolls, 4 and 5 are upper and lower intermediate rolls, 6 and 7 are upper and lower work rolls, 8 and 9 are upper and lower work roll chocks, 10 and 11 are driving motors, 12 Is a gear box, which is configured so that when the drive motors 10 and 11 are driven, the upper and lower work rolls 6 and 7 are driven.

Reference numeral 13 denotes a fixed vibration sensor provided on the mill housing 1, reference numeral 14 denotes a fixed vibration sensor provided on the gear box 12, and reference numerals 15 and 16 denote replacement when work rolls provided on the upper and lower work roll chocks 8 and 9 are replaced. Vibration energy detected by each of the vibration sensors 13 to 16 is a possible magnet type vibration sensor, and the vibration energy is 17, 18, 19, 20 respectively
After being converted to an analog signal via the A / D converter 21
Is input to the chattering monitoring device 23 having the fast Fourier transform type frequency analyzer 22. Further, the chattering monitoring device 23 receives an analog signal 25 of rolling parameters such as tension, rolling torque, and rolling speed from a rolling mill control unit 24 that controls a rolling mill in a cold rolling line. The chattering monitoring device 23 converts an analog signal of vibration energy from each of the vibration sensors 13 to 16 input through each of the vibration meters 17, 18, 19, 20 into a digital signal by the A / D converter 21, An analog signal 25 of each rolling parameter such as tension, rolling torque, and rolling speed input from the rolling mill control unit 24
Is converted to a digital signal by the A / D converter 21 and the frequency analyzer 2
By performing frequency analysis in step 2, it is converted into a vibration level of a fundamental frequency that causes chatter marks.

[0016] The chattering monitoring device 23, chattering
With basic frequency for each grayed cause it is calculated and set, the threshold for determining the chatter marks occur at each vibration each sensor 13 to 16 and the rolling parameters is set in advance, the measured value If the vibration level based on the threshold exceeds the threshold, it is determined that chatter marks have occurred, and the alarm 26
At the same time as issuing an alarm to the operator to warn the operator, and at the same time, outputting an inspection instruction sheet 27 recording which part of the rolled steel sheet has chatter marks, and an index for inspecting chatter marks in the next process And Further, the chattering monitoring device 23 outputs chatter mark generation information 28 to the rolling mill control unit 24, and the rolling mill control unit 24 to which the chatter mark generation information 28 is input performs deceleration, increase of the rolling oil amount, and rolling. The apparatus is configured to take measures to prevent chatter marks such as an increase in oil temperature and an increase in rolling oil concentration. Moreover, chattering monitoring device 23, in contrast to basic frequency for each cause of chattering, roll flaws, coupling backlash, mill natural frequency, bearing failure, the chatter marks by equipment factors such as poor intermeshing gears occurs When it is determined that the inspection has been performed, the apparatus is configured to output an inspection / maintenance command for the equipment, not shown.

As a method of determining the occurrence of chatter marks, when the vibration level of two or more of the vibration sensors 13 to 16 attached to each part of the rolling mill exceeds a set value, or when tension, rolling torque, Among rolling parameters such as rolling speed, an AND method of determining that chatter marks occur when the vibration level of two or more frequency analysis exceeds a set value, and among the vibration sensors 13 to 16 attached to each part of the rolling mill. If any vibration level exceeds the set value, or if at least one of the vibration parameters of the frequency analysis among the rolling parameters such as tension, rolling torque, and rolling speed exceeds the set value, it is determined that chatter marks have occurred. There is an OR method to do. AND
The method improves the detection accuracy of chatter mark occurrence, and the OR method can completely detect the occurrence of chatter mark.Do you want to improve the detection accuracy of chatter mark occurrence, or do you want to completely detect and suppress the occurrence of chatter mark occurrence? Can be selected depending on the situation.

With the above configuration, the final
When chatter marks occur during rolling in a six-fold cold rolling mill, vibration sensors 13 attached to each part of the rolling mill are used.
The vibration energies detected by
After being converted into an analog signal via 7, 18, 19, and 20, the signal is input to the chattering monitoring device 23. The chattering monitoring device 23 converts an analog signal of vibration energy from each of the vibration sensors 13 to 16 input through each of the vibration meters 17, 18, 19, 20 into a digital signal by the A / D converter 21, By converting the analog signal 25 of the rolling parameters input from the rolling mill control unit 24 into a digital signal by the A / D converter 21 and performing a frequency analysis by the frequency analyzer 22,
It converts to the vibration level of the fundamental frequency that causes chatter marks.

In the chattering monitoring device 23, a vibration level based on the actual measurement value converted into a vibration level of a fundamental frequency causing a chatter mark is set in advance for each of the vibration sensors 13 to 16 and each of the rolling conditions. When the set value is exceeded,
It is determined that chatter marks have occurred, an alarm command is output to an alarm 26 to issue an alarm, and an operator is alerted, and at the same time, an inspection instruction 27 which records which part of the rolled steel sheet has chatter marks is output. . In the next step, the surface of the rolled steel sheet is inspected based on the inspection instruction 27 to confirm the presence or absence of chatter marks, thereby preventing outflow of defective products having chatter marks.

The chattering monitoring device 23 outputs chatter mark occurrence information 28 to the rolling mill control unit 24, and the rolling mill control unit 24 to which the chatter mark occurrence information 28 has been input
Take measures to prevent chatter marks such as deceleration, increase in the amount of rolling oil, increase in rolling oil temperature, and increase in rolling oil concentration. Moreover, chattering monitoring device 23, by comparing the vibration level of the fundamental frequency and basic frequency of each chattering caused based on the measured value, the roll scratches, coupling backlash, mill natural frequency, bearing failure, gear meshing defect If it is determined that chatter marks have been generated due to equipment factors such as the above, an inspection and maintenance command for the equipment is output. Therefore, it is possible to detect a chattering phenomenon that causes a minute variation in the thickness, and at the same time, it is possible to specify a cause of the chatter mark, thereby preventing the occurrence of the chattering at an early stage.

Example 2 Cold rolling speed 0 to 1200 m / min, product thickness 0.14 to 2.3 mm, width 600 to 1270 mm, final rolling of a six-high rolling mill using a synthetic ester lubricant as rolling oil Example 1 with 5 stands
To install the chatter mark diagnostic device described in the above, to evaluate the performance of the chatter mark diagnostic method, for ultra-thin material 100 coil with a plate thickness of 0.2 mm or less where chattering easily occurs,
Inspection is performed in the next process based on the inspection instruction sheet 27 output from the chattering monitoring device 23, and the coil which the chatter mark diagnosis device determines that chatter mark has occurred is determined by the AND method and the OR method of the chatter mark generation determination method. In contrast, the ratio of the number of coils in which chatter marks did not actually occur was determined as the false alarm rate of chatter mark diagnosis.
Find the ratio of the number of coils where chatter marks actually occurred,
The correct answer rate was determined as the oversight rate for chatter mark diagnosis. The result is shown in FIG.

As shown in FIG. 2, when the chatter mark occurrence determination method is the AND method, the miss rate of chatter mark diagnosis by the chatter mark diagnosis device is 10%, and in the OR method,
The false alarm rate of chatter mark diagnosis was 13%. In addition, when the chatter mark diagnosis apparatus determines that chatter marks have occurred and the cause of occurrence has been specified, the correct answer rate is almost 100%, and the occurrence of chatter marks has been eliminated by solving the cause of occurrence.

[0023]

As described above, according to the method of the present invention, it is possible to monitor chattering phenomena causing minute fluctuations in sheet thickness, to specify the cause of chatter marks, and to report the chattering occurrence status to the mill control unit. The chattering prevention countermeasures can be taken immediately after the output, and the chattering occurrence location is recorded, and a work instruction book for the next process is prepared, thereby preventing the steel sheet with the chatter mark from leaking outside.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a configuration of an apparatus in an embodiment of a method of the present invention.

FIG. 2 is a graph showing a determination result of chatter mark generation in a second embodiment.

FIG. 3 is a schematic diagram of a vibration level and a vibration frequency in a normal rolling state.

FIG. 4 is a schematic diagram of a vibration level and a vibration frequency when a roll flaw occurs.

FIG. 5 is a schematic diagram of a vibration level and a vibration frequency when a coupling flaw occurs.

FIG. 6 is a schematic diagram of a vibration level and a vibration frequency when a natural vibration of the mill is generated.

FIG. 7 is a schematic diagram of a vibration level and a vibration frequency when a bearing failure occurs.

FIG. 8 is a schematic diagram of a vibration level and a vibration frequency when a gear meshing failure occurs.

FIG. 9 is a schematic diagram of a vibration level and a vibration frequency of a work roll when a gear meshing failure occurs in a rolling mill.

FIG. 10 is a schematic diagram of a vibration level and a vibration frequency of a speed reducer when a gear meshing failure occurs in a rolling mill.

FIG. 11 is a schematic diagram of a vibration level and a vibration frequency of a mill housing when a gear meshing failure occurs in a rolling mill.

FIG. 12 is a schematic diagram of a vibration level and a vibration frequency of tension when a gear meshing failure occurs in a rolling mill.

FIG. 13 is a schematic diagram of a vibration level and a vibration frequency of a rolling torque when a gear meshing failure occurs in a rolling mill.

FIG. 14 is a schematic diagram of a vibration level and a vibration frequency of a rolling speed when a gear meshing failure occurs in a rolling mill.

FIG. 15 is a characteristic factor diagram showing chatter mark generation factors.

FIG. 16 is a schematic diagram of a model for calculating a natural frequency of a mill of a six-high rolling mill.

FIG. 17 is an explanatory diagram showing an outline of chatter marks generated in a rolling mill.

FIG. 18 is a graph showing a relationship between a strip length of a chatter mark and a plate thickness which can be detected by a conventional technique.

FIG. 19 is a graph showing a relationship between time and amplitude of a main vibration example of a rolling mill.

FIG. 20 is a graph showing the relationship between time and amplitude of a vibration example that causes chatter marks.

21 is a graph showing a relationship between a time and an amplitude of a combined vibration of the vibration example of FIG. 19 and the vibration example of FIG. 20;

FIG. 22 is a graph showing a relationship between time and amplitude of another main vibration example of a rolling mill.

FIG. 23 is a graph showing the relationship between time and amplitude of another example of vibration that causes chatter marks.

24 is a graph showing a relationship between a time and an amplitude of a combined vibration of the vibration example of FIG. 22 and the vibration example of FIG. 23;

FIGS. 25 (a), (b) and (c) are graphs showing the relationship between the strip length and plate thickness of chatter marks which cannot be detected by the conventional method.

[Explanation of symbols]

 1 Mill housing 2 Upper backup roll 3 Lower backup roll 4 Upper intermediate roll 5 Lower intermediate roll 6 Upper work roll 7 Lower work roll 8 Upper work roll chock 9 Lower work roll chock 10, 11 Driving motor 12 Gear box 13, 14, 15, 16 Vibration sensor 17, 18, 19, 20 Vibrometer 21 A / D converter 22 Frequency analyzer 23 Chattering monitor 24 Rolling mill control unit 25 Analog signal 26 Alarm 27 Inspection instruction 28 Chatter mark generation information 101 Strip 102 Chatter mark

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B21B 37/00 B21C 51/00

Claims (1)

(57) [Claims] [Claim 1] detects the vibration of the mill each part during operation by installing a vibration detector in more than one place of the mill each part, the chattering detection method of the rolling mill from the detected vibration of the various parts, mill-specific Vibration frequency, poor gear engagement, bare
Failure, spindle and roll coupling play,
Calculate the specific vibration frequency generated from roll flaws
And a fundamental frequency of chatter marks occur each cause, vibration displacement of the units to detect the vibration velocity or vibration acceleration, vibration displacement of each portion the detected, performs frequency analysis of the vibration velocity or vibration acceleration, Tsutomu Cho, rolling torque, the rolling speed, rolling load, performs frequency analysis of the rolling parameters of thickness variation, the frequency analysis of the measured values of vibration and rolling parameters
When the result obtained exceeds a set value at a frequency that is an integral multiple of the fundamental frequency for each of the chatter mark occurrence causes , it is determined that chattering has occurred, and the cause of the occurrence is determined as the fundamental frequency.
Chattering detection method of the rolling mill, characterized by identifying from.