JP6841264B2 - Abnormal vibration detection method in cold rolling - Google Patents

Description

The present invention relates to a method for detecting abnormal vibration in cold rolling, which is suitable for detecting chattering generated during cold rolling of a metal plate in a cold rolling machine.

Generally, steel sheets used for automobiles, beverage cans, etc. are continuously cast, hot-rolled, and cold-rolled, annealed, and plated, and then processed according to each shape. Here, the cold rolling process is the final process for determining the thickness of the steel plate as a product. In recent years, it has become more common to reduce the plating thickness, and since the surface of the steel sheet before plating determines the surface of the final product after plating, a function to prevent surface defects is also required in the cold rolling process. Has been done.

Chatter mark is one of the surface defects generated in the cold rolling process. This chatter mark is a pattern in which linear marks extending in the width direction of the metal band appear periodically along the longitudinal direction of the metal band, and are mainly vibrations of a cold rolling mill (hereinafter referred to as chattering). It is said that it is caused by. Very mild chatter marks are not found by visual inspection or plate thickness measurement after rolling, but are found only after the plating process, which is a factor that greatly impairs product productivity. Further, it is known that especially in thin materials such as steel sheets for cans and electromagnetic steel sheets, phenomena such as breakage of the plates occur due to sudden fluctuations in plate thickness and tension due to chattering, which hinders production.
For this reason, in the past, many methods for detecting and preventing chattering have been proposed from the viewpoint of inhibiting productivity and preventing surface defects.

For example, in Patent Document 1, vibration detectors are installed at one or more locations of each part of the rolling mill to detect the vibration of each part of the rolling mill during operation, and chattering of the rolling mill is detected from the detected vibration of each part of the rolling mill. In the method, the specific vibration frequency of the mill, poor meshing of gears, defective bearings, looseness of coupling between spindle and roll, and specific vibration frequency generated from roll flaws are calculated and used as the basic frequency for each cause of chatter mark. The vibration displacement, vibration velocity or vibration acceleration of each part of the rolling mill is detected, and the frequency analysis of the detected vibration displacement, vibration velocity or vibration acceleration of each part is performed, and the tension, rolling torque, rolling speed, rolling load and plate thickness fluctuation When the result of frequency analysis of the measured value of the rolling parameter exceeds the set value at a frequency that is an integral multiple of the basic frequency for each cause of chatter mark, it is determined that chattering has occurred and the cause is specified from the basic frequency. A method for detecting chattering of a rolling mill is disclosed.

Further, Patent Document 2 includes a vibration signal collecting step for collecting vibration signals detected by at least one small-diameter roll among the small-diameter rolls between each stand of the cold rolling mill or on the exit side of the cold rolling mill. Of the frequency components obtained in the FFT frequency analysis execution step and the FFT frequency analysis execution step, in which the frequency analysis of the fast Fourier transform method of the vibration signal is performed to obtain the frequency components contained in the vibration signal and their spectral values. A vibration abnormality detection method in cold rolling, which has a vibration abnormality determination step for determining that a vibration abnormality has occurred when the spectrum value of a frequency component having the same frequency as the string vibration frequency of the steel plate exceeds a preset threshold value. It is disclosed.

Further, Patent Document 3 describes a steel sheet having a chord length between the natural frequency of the cold rolling mill and the small diameter roll that first contacts the steel plate on the exit side of the cold rolling mill from the final stand of the cold rolling mill. Disclosed is a method for preventing chatter marks on a steel sheet so that the frequencies of the chord vibrations of the steel sheet do not match and the bending strain generated on the surface of the steel sheet is set to a size that does not cause plastic deformation of the steel sheet.

Japanese Patent No. 2964887 Japanese Unexamined Patent Publication No. 2016-153138 Japanese Patent No. 6102835

However, the chattering detection method of the rolling mill shown in Patent Document 1, the vibration abnormality detection method in cold rolling shown in Patent Document 2, and the chattering mark prevention method of the steel sheet shown in Patent Document 3 have the following problems. there were.
That is, in the case of the chattering detection method of the rolling mill shown in Patent Document 1, only the vibration generated by the rolling mill main body is focused on, and the angles above a certain value installed on the entry side and the exit side of each rolling stand. It is not possible to cope with the vibration caused by the drive system of the small diameter roll around which the metal band is wound.

The research by the present inventors has clarified that the vibration of the small-diameter roll as described above affects the chatter mark. It was also found that the vibration generated in the rolling mill main body cannot be detected by the vibrometer installed in the housing or the like in the rolling mill main body, but can be detected by the vibration of the small diameter roll in many cases.
Further, in the case of the vibration abnormality detection method in cold rolling shown in Patent Document 2 and the chatter mark prevention method of a steel sheet shown in Patent Document 3, the generation of vibration due to string vibration can be suppressed, but between each rolling stand and at the end. It is not possible to prevent the generation of chatter marks due to vibration caused by the drive system or drive shaft of a small-diameter roll that is placed on the outlet side of a rolling stand and has a metal band wrapped around it at an angle of a certain value or more.

Therefore, the present invention has been made to solve these conventional problems, and an object thereof is arranged between each rolling stand and on the exit side of the final rolling stand, which generates chatter marks in cold rolling. It is an object of the present invention to provide a method for detecting abnormal vibration in cold rolling, which can accurately detect abnormal vibration caused by a drive system or a drive shaft of a small-diameter roll in which a metal band is wound at an angle of a certain value or more.

First, as a result of various investigations by the cold rolling equipment 100, which is a tandem rolling mill as shown in FIG. 12, the present inventors have increased erroneous detection by the conventional method (method according to Patent Document 1). I found that. That is, it was found that many cases with high vibration values occur even though they do not appear as surface defects after rolling or plating. It is presumed that this is because the tandem rolling mill has a lot of peripheral equipment and is affected by ambient noise, and the vibration value becomes large in a specific frequency band. It was also found that if the threshold was set high to reduce false positives, abnormal vibration could not be detected under the condition that chatter marks occur.

Therefore, the present inventors first investigated the vibration source of the abnormal vibration that causes the chatter mark. As a result, it was found that although the natural vibration of the cold rolling mill and the meshing of the gears stored in the gear box 103 always generate a large vibration, the chatter mark due to the vibration does not occur. In addition, as a factor that has a great influence on the chatter mark, it is arranged between each rolling stand STi (i = 1 to 5) and on the exit side of the final rolling stand ST5, which is not directly related to the rolling phenomenon, and exceeds a certain value. It has been found that the vibration caused by the drive system or the drive shaft of the roll 104 (hereinafter referred to as a small-diameter roll) around which the metal band is wound at the angle of 1 is affected. This is because the small diameter roll 104 is in direct contact with the metal strip, so it is presumed that the small diameter roll 104 directly creates the mark.

Therefore, in order to achieve the above object, the abnormal vibration detection method in cold rolling according to one aspect of the present invention is an abnormality in cold rolling in which a metal strip is rolled by a cold rolling machine having one or more rolling stands. A vibration detection method in which vibration detectors installed at at least one location on each rolling stand are placed between each rolling stand and on the exit side of the final rolling stand, and the metal strip is wound at an angle of a certain value or more. A vibration detection step for detecting vibration displacement, vibration velocity or vibration acceleration of each part of each rolling stand and each small diameter roll by a vibration detector installed on each small diameter roll, and rolling of the small diameter roll or the rolling stand. A roll rotation speed detection step that detects the rotation speed of each small diameter roll by a speed detector installed on the roll, and vibration displacement, vibration speed or vibration of each part of each rolling stand and each small diameter roll detected in the vibration detection step. Based on the frequency analysis step for performing frequency analysis of acceleration, the vibration displacement, vibration velocity or vibration acceleration of each small diameter roll detected in the vibration detection step, and the rotation speed of each small diameter roll detected in the roll rotation speed detection step. The results of the basic frequency calculation step for calculating the basic frequency caused by the drive system or drive shaft of each small diameter roll and the result of the frequency analysis step are applied to the drive system or drive shaft of each small diameter roll calculated in the basic frequency calculation step. The gist is to include an abnormal vibration determination step of determining abnormal vibration when the threshold is exceeded in the vibration frequency region centered on an integral multiple of the resulting fundamental frequency.

Vibrations caused by the drive system and the like include vibrations caused by abnormal gears used in the drive shaft, vibrations caused by the universal joint of the drive shaft, and vibrations caused by bearing abnormalities.
Further, the small diameter roll includes a roll having an external force drive such as a shape meter roll in addition to a roll having no external force drive.

According to the method for detecting abnormal vibration in cold rolling according to the present invention, the metal strips are arranged between each rolling stand and on the exit side of the final rolling stand, which generate chatter marks in cold rolling, and the metal strip is formed at an angle of a certain value or more. It is possible to provide a method for detecting abnormal vibration in cold rolling, which can accurately detect abnormal vibration caused by a drive system or a drive shaft of a wound small diameter roll.

It is a system block diagram which shows the schematic structure of the cold rolling equipment to which the abnormal vibration detection method in the cold rolling which concerns on 1st Embodiment and 2nd Embodiment of this invention can apply. It is a flowchart for demonstrating the flow of processing executed by a vibration detector, a speed detector and a vibration signal processing computer. It is a graph which shows the result of having performed the frequency analysis of the vibration velocity of the small diameter roll between rolling stands ST3 to ST4 by the method which concerns on Comparative Example 1. It is a graph which shows the result of having performed the frequency analysis of the vibration velocity of the small diameter roll between rolling stands ST3 to ST4 by the method which concerns on Example 1 of this invention. It is a graph which shows the result of having performed the frequency analysis of the vibration velocity of the small diameter roll between rolling stands ST3 to ST4 by the method which concerns on Comparative Example 2. It is a graph which shows the result of having performed the frequency analysis of the vibration velocity of the small diameter roll between rolling stands ST3 to ST4 by the method which concerns on Example 2 of this invention. The rolling stand to be the target of vibration detection is the final rolling stand ST5 and the rolling stand ST4 immediately before it, and the small diameter roll to be the target of vibration detection in the vibration detection step is the final rolling stand ST5 and the rolling one before it. A small-diameter roll installed between the stand ST4 and the exit side of the final rolling stand ST5, and the vibration velocity of the small-diameter roll between the final rolling stand ST5 and the previous rolling stand ST4 by the method according to Comparative Example 3. It is a graph which shows the result of performing the frequency analysis of. The rolling stand to be the target of vibration detection is the final rolling stand ST5 and the rolling stand ST4 immediately before it, and the small diameter roll to be the target of vibration detection in the vibration detection step is the final rolling stand ST5 and the rolling one before it. Small diameter rolls installed between the stand ST4 and on the outlet side of the final rolling stand ST5, and vibration of the small diameter roll between the final rolling stand ST5 and the previous rolling stand ST4 by the method according to Example 3 of the present invention. It is a graph which shows the result of performing the frequency analysis of the speed. The rolling stand to be the target of vibration detection is the final rolling stand ST5 and the rolling stand ST4 immediately before it, and the small diameter roll to be the target of vibration detection in the vibration detection step is the final rolling stand ST5 and the rolling one before it. Small diameter rolls installed between the stand ST4 and on the outlet side of the final rolling stand ST5, and vibration of the small diameter roll between the final rolling stand ST5 and the previous rolling stand ST4 by the method according to Example 4 of the present invention. It is a graph which shows the result of performing the frequency analysis of the speed. The rolling stand to be the target of vibration detection is the final rolling stand ST5 and the rolling stand ST4 immediately before it, and the small diameter roll to be the target of vibration detection in the vibration detection step is the final rolling stand ST5 and the rolling one before it. A small diameter roll installed between the stand ST4 and the exit side of the final rolling stand ST5, and frequency analysis of the vibration velocity of the small diameter roll (roll with low tension) on the outlet side of the final rolling stand ST5 by the method according to Comparative Example 4. It is a graph which shows the result of performing. The rolling stand to be the target of vibration detection is the final rolling stand ST5 and the rolling stand ST4 immediately before it, and the small diameter roll to be the target of vibration detection in the vibration detection step is the final rolling stand ST5 and the rolling one before it. Using a small-diameter roll installed between the stand ST4 and the exit side of the final rolling stand ST5, frequency analysis of the vibration velocity of the small-diameter roll (roll with low tension) of the final rolling stand ST5 was performed by the method according to Example 5 of the present invention. It is a graph which shows the result. It is a figure which shows the schematic structure of the main part of the general cold rolling equipment used for the investigation.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, etc. may differ from the realistic ones. Even between drawings, there may be parts that differ in dimensional relationship and ratio from each other.

First, FIG. 1 shows a schematic configuration of a cold rolling facility to which the abnormal vibration detection method in cold rolling according to the first and second embodiments of the present invention can be applied. In 10, five rolling stands ST1 to ST5 are arranged in a row at predetermined intervals.
Each rolling stand STi (i = 1 to 5) supports a work roll 13 and each work roll 13 which are a pair of rolling rolls for cold rolling the metal strip (steel strip) 12 in the mill housing 11. It includes a pair of backup rolls 14.
Each work roll 13 is connected to a speed reducer (not shown) provided in the gear box 15.

Further, tension meter rolls 16 and pass line rolls 17 are arranged between the rolling stands (between ST1 and ST2, between ST2 and ST3, between ST3 and ST4 and between ST4 and ST5) and on the exit side of the final rolling stand ST5. Has been done. A metal band 12 is wound around the tension meter roll 16 and the pass line roll 17 at an angle of a certain value or more (for example, 5 ° or more). Since the tension meter roll 16 and the pass line roll 17 have a smaller diameter than the work roll 13, they are hereinafter referred to as small diameter rolls 16 and 17.
Further, a vibration detector 18 is installed on the upper part of the mill housing 11 of each rolling stand STi, a vibration detector 19 is installed on the upper part of each gear box 15, and the vibration detector 20 is also installed on each of the small diameter rolls 16 and 17. Is installed. Each vibration detector 18 detects the vibration displacement, vibration velocity or vibration acceleration of the mill housing 11 of each rolling stand STi. Further, each vibration detector 19 detects the vibration displacement, the vibration speed or the vibration acceleration of each gear box 15. Further, each vibration detector 20 detects the vibration displacement, the vibration velocity or the vibration acceleration of each of the small diameter rolls 16 and 17.

Further, on the work roll 13 of the final rolling stand ST5 on the outlet side of the cold rolling equipment 10, a speed detector 21 for detecting the rotation speed of each of the small diameter rolls 16 and 17 by detecting the rotation speed of the work roll 13 is provided. is set up.
Vibration displacement, vibration velocity or vibration acceleration of the mill housing 11 of the rolling stand STi, vibration displacement, vibration velocity or vibration acceleration of each gearbox 15, each small diameter roll 16, 17 detected by each vibration detector 18, 19, 20. The vibration displacement, vibration velocity or vibration acceleration of the above is input to the vibration signal processing computer 22 as a vibration detection signal.

Further, the rotation speeds of the small diameter rolls 16 and 17 detected by the speed detector 21 are input to the vibration signal processing computer 22 as roll rotation speed detection signals.
Then, the vibration signal processing computer 22 individually performs abnormal vibration detection processing on the vibration detection signals collected in the predetermined sampling period T1.
The vibration signal processing computer 22 is realized by an arithmetic processing device such as a personal computer or a workstation, and has, for example, a CPU, a ROM, a RAM, and the like as main components.

(First Embodiment)
Next, regarding the abnormal vibration detection method in cold rolling according to the first embodiment, refer to a flowchart for explaining the flow of processing executed by the vibration detector, the speed detector, and the vibration signal processing computer shown in FIG. I will explain.
Each of the vibration detectors 18, 19 and 20 executes step S1 shown below, which is a vibration detection step. The speed detector 21 executes step S2, which is a roll rotation speed detection step. The vibration signal processing computer 22 executes step S3 which is a frequency analysis step, step S4 which is a fundamental frequency calculation step, and steps S5 and S6 which are abnormal vibration determination steps.

First, in step S1, each vibration detector 18 detects the vibration displacement, the vibration speed, or the vibration acceleration of the mill housing 11 of each rolling stand STi. Further, each vibration detector 19 detects the vibration displacement, the vibration speed or the vibration acceleration of each gear box 15. Further, each vibration detector 20 detects the vibration displacement, the vibration velocity or the vibration acceleration of each of the small diameter rolls 16 and 17.
Further, in step S2, the speed detector 21 detects the rotation speed of the small diameter rolls 16 and 17 by detecting the rotation speed of the work roll 13 of the final rolling stand ST5 on the exit side of the cold rolling equipment 10.

Then, in step S3, the vibration displacement, vibration velocity or vibration acceleration of each mill housing 11 of the rolling stand STi, the vibration displacement, vibration velocity or vibration acceleration of each gearbox 15 detected by the vibration detectors 18, 19 and 20. The vibration displacement, vibration velocity, or vibration acceleration of each of the small diameter rolls 16 and 17 is input to the vibration signal processing computer 22 as a vibration detection signal.
Further, in step S3, the rotation speeds of the small diameter rolls 16 and 17 detected by the speed detector 21 are input.

Then, in step S3, the vibration signal processing computer 22 executes frequency analysis, and the vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi, the vibration displacement, and the vibration of each gearbox 15 are executed. Frequency analysis of velocity or vibration acceleration and vibration displacement, vibration velocity or vibration acceleration of each small diameter roll 16 and 17 is performed.
In this frequency analysis step, the vibration displacement, vibration velocity or vibration acceleration of each mill housing 11 of each rolling stand STi, the vibration displacement, vibration velocity or vibration acceleration of each gearbox 15, and each small diameter roll 16 within the specific time t1. A plurality of results of frequency analysis of vibration displacement, vibration velocity or vibration acceleration of 17 are retained. In performing frequency analysis, the resolution of the frequency appearing in the vibration data depends on the sampling period T1 and the specific time t1 of the data to be analyzed. Therefore, in order to increase the resolution and see the sharpness of the abnormal vibration, the specific time t1 is set. It is desirable to make it as large as possible, for example, when the sampling frequency is 2 kHz or more, the specific time t1 is 0.15 sec or more.

Then, among the results of holding a plurality of the small diameter rolls 16 and 17, the continuous specific time in which the rotation speeds of the small diameter rolls 16 and 17 are within a specific range (a speed deviation small enough to be recognized as a variation with respect to the operating speed, for example, 30 m / sec). A plurality of data measured within t2 (for example, 10 sec) are selected, and the amplitudes of the same frequency of the selected data are averaged.
Next, in step S4, the vibration signal processing computer 22 determines the vibration displacement, vibration velocity or vibration acceleration of each mill housing 11 of each rolling stand STi, the vibration displacement, vibration velocity or vibration acceleration of each gearbox 15, and the vibration velocity or vibration acceleration. Based on the vibration displacement, vibration velocity or vibration acceleration of each small diameter roll 16 or 17, and the input rotation speed of each small diameter roll 16 or 17, the basics caused by the drive system or drive shaft of each small diameter roll 16 or 17 Calculate the frequency.

Then, in step S5, the vibration signal processing computer 22 uses the vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi, the vibration displacement, vibration speed or vibration acceleration of each gearbox 15, and each small diameter roll. The result of frequency analysis of vibration displacement, vibration velocity or vibration acceleration of 16 and 17 is the vibration frequency centered on an integral multiple of the basic frequency caused by the drive system or drive shaft of each small diameter roll 16 and 17 calculated. Determine if the threshold has been exceeded in the region. Here, it is preferable to use a different value for each frequency as the threshold value. This is because, depending on the structure of the small diameter rolls 16 and 17 and the characteristics of the vibration transducers constituting the vibration detectors 18, 19 and 20, there are frequencies that are likely to appear in vibration and frequencies that are unlikely to appear in vibration. Further, if the hardness of the metal band 12 is large, chatter marks tend to be less likely to appear, so it is preferable to change the hardness as well.

In this determination, when the following three conditions are satisfied, it is determined that the frequency analysis result exceeds the threshold value, the determination result becomes YES, the process proceeds to step S6, and if not, the determination result becomes NO and the process is performed. finish.
1. 1. The amplitude of the same frequency of the averaged and selected data, which is the result of the frequency analysis, is an integral multiple of the fundamental frequency due to the drive system or drive axis of each of the calculated small diameter rolls 16 and 17. When the threshold is exceeded in the central vibration frequency region.
2. 2. When the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the above threshold value is 10 Hz or less.
3. 3. When there are at least two frequencies that are integral multiples of the fundamental frequency due to the drive system or drive shaft of each of the small diameter rolls 16 and 17 exceeding the above threshold value.
Then, in step 6, the vibration signal processing computer 22 determines that the vibration is abnormal and ends the processing.

As described above, according to the abnormal vibration detection method in cold rolling according to the first embodiment, the vibration displacement, vibration speed or vibration of the mill housing 11, the gearbox 15 parts and the small diameter rolls 16 and 17 of each rolling stand STi. Detects acceleration, detects rotation speed of each small diameter roll 16, 17 and frequency analysis of vibration displacement, vibration speed or vibration acceleration of each rolling stand STi mill housing 11, gearbox 15 parts and each small diameter roll 16, 17 Based on the vibration displacement, vibration speed or vibration acceleration of each small diameter roll 61, 17 and the rotation speed of each small diameter roll 16, 17, the basic frequency caused by the drive system or drive shaft of each small diameter roll 16, 17 is calculated. When the calculated frequency analysis result exceeds the threshold in the vibration frequency region centered on an integral multiple of the basic frequency caused by the drive system or drive shaft of each small diameter roll 16 or 17 calculated in the basic frequency calculation step. , Judged as abnormal vibration.

As a result, the small diameter rolls 16 and 17, which are arranged between the rolling stands STi and the exit side of the final rolling stand ST5 and around which the metal band 12 is wound at an angle of a certain value or more, which generate chatter marks in cold rolling, are driven. Abnormal vibration caused by the system or drive shaft can be detected accurately.
Further, in the abnormal vibration determination step, the amplitude of the same frequency of the averaged and selected data obtained as a result of the frequency analysis is applied to the calculated drive system or drive shaft of each of the small diameter rolls 16 and 17. When the threshold is exceeded in the vibration frequency region centered on an integral multiple of the resulting fundamental frequency, it is determined to be abnormal vibration, so the ratio of noise in the frequency signal can be reduced and the abnormal vibration can be detected more accurately. ..

That is, when looking at the frequency analysis results of short-time data, the vibration caused by the drive system or drive shaft of each of the small diameter rolls 16 and 17 may be buried in noise and may not look large. Therefore, in the frequency analysis step, the specific time Vibration displacement, vibration velocity or vibration acceleration of each mill housing 11 of each rolling stand STi in t1, vibration displacement, vibration velocity or vibration acceleration of each gearbox 15, and vibration displacement, vibration velocity or vibration velocity of each small diameter rolls 16 and 17. A plurality of results of frequency analysis of vibration acceleration are held, and among the results of holding the plurality of results, the rotation speeds of the small diameter rolls 16 and 17 are within a specific range (± 15 m / sec with respect to the operating speed). A plurality of data measured within the continuous specific time t2 are selected, and the amplitudes of the same frequency of the selected plurality of data are averaged. Then, in the abnormal vibration determination step, the amplitude of the same frequency of the averaged and selected plurality of data, which is the result of the frequency analysis, is applied to the calculated drive system or drive shaft of each of the small diameter rolls 16 and 17. When the threshold is exceeded in the vibration frequency region centered on an integral multiple of the fundamental frequency caused by the vibration, it is determined to be abnormal vibration.

Further, in the abnormal vibration determination step, the amplitude of the same frequency of the averaged and selected data obtained as a result of the frequency analysis is applied to the calculated drive system or drive shaft of each of the small diameter rolls 16 and 17. When the above-mentioned threshold is exceeded in the vibration frequency region centered on an integral multiple of the resulting fundamental frequency, and the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the above-mentioned threshold is 10 Hz or less. In addition, since it is determined to be abnormal vibration, abnormal vibration leading to the chatter mark can be detected more accurately.
That is, the present inventors have found that the abnormal vibration leading to the chatter mark has a sharp peak in the frequency analysis result even at the frequency caused by the drive system or the drive shaft of each of the small diameter rolls 16 and 17, and conversely, it is broad. It was found that vibrations with various frequency bands do not appear as chatter marks. Therefore, the amplitude of the same frequency of the averaged and selected data, which is the result of the frequency analysis, is an integer of the basic frequency due to the drive system or drive shaft of each of the calculated small diameter rolls 16 and 17. When the above-mentioned threshold is exceeded in the vibration frequency region centered on the double, and the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the above-mentioned threshold is 10 Hz or less, it is determined as abnormal vibration. I tried to do it.

The amplitude value used in the above determination is not limited to 70% and may be set within the range of 50 to 90%, and the frequency width is not limited to 10 Hz or less and is not limited to a certain value or less. It may be determined.
Further, in the abnormal vibration determination step, the drive system or drive shaft of each of the small diameter rolls 16 and 17 in which the amplitude of the same frequency of the averaged and selected data which is the result of the frequency analysis exceeds the above-mentioned threshold value. When there are at least two frequencies that are integral multiples of the fundamental frequency caused by, it is determined to be abnormal vibration. Therefore, an error due to external vibration other than the vibration caused by the drive system or drive shaft of the small diameter rolls 16 and 17 is erroneous. Detection can be prevented with high accuracy.

That is, the vibration generated from the external power supply, the lubricant pump, the fan, etc. may appear in the vibration detector as very strong noise at a specific frequency. Normally, measures such as cutting these frequencies with a band stop filter are taken, but when the frequency of abnormal vibration caused by the drive system or drive shaft of the small diameter rolls 16 and 17 matches the frequency of the above-mentioned external vibration. , Abnormal vibration caused by the drive system or drive shaft of the small diameter rolls 16 and 17 cannot be detected. Therefore, the present inventors consider that the vibration caused by the drive system or the drive shaft of each of the small diameter rolls 16 and 17 that generate the abnormal vibration leading to the chatter mark is not only the fundamental frequency but also an integral multiple, particularly about 10 times. Focusing on the fact that a plurality of vibration peaks having the frequencies described above occur at the same time, a plurality of frequency peaks that are integral multiples of the fundamental frequency caused by the drive system or drive shaft of each of the small diameter rolls 16 and 17 are generated. When it is detected, it is determined to be abnormal vibration, and erroneous detection due to external vibration other than vibration caused by the drive system or drive shaft of the small diameter rolls 16 and 17 is accurately prevented.

(Second Embodiment)
Next, the method for detecting abnormal vibration in cold rolling according to the second embodiment will be described. The abnormal vibration detection method in cold rolling according to the second embodiment has the same basic configuration as the abnormality detection method in cold rolling according to the first embodiment, but is subject to vibration detection in the vibration detection step (step S1). The rolling stand STi and the small diameter rolls 16 and 17 are limited as follows, which is different from the abnormality detection method in cold rolling according to the first embodiment.
That is, the rolling stand STi that is the target of vibration detection in the vibration detection step (step S1) is the final rolling stand ST5 and the rolling stand ST4 immediately before it, and is the target of vibration detection in the vibration detection step (step S1). The small-diameter rolls 16 and 17 are small-diameter rolls 16 and 17 installed between the final rolling stand ST5 and the previous rolling stand ST4 and on the exit side of the final rolling stand ST5.

The present inventors have stated that the abnormal vibration generated in the pre-stage stand, specifically, the rolling stands ST1 to ST3, which do not have the final plate thickness, appears at a level that does not cause a problem in the product as the plate thickness fluctuation. I paid attention to the fact that many marks did not appear. Therefore, the rolling stand STi, which is the target of vibration detection in the vibration detection step (step S1), is narrowed down to the subsequent stand to be the final rolling stand ST5 and the rolling stand ST4 immediately before it, and vibration is generated in the vibration detection step (step S1). The small-diameter rolls 16 and 17 to be detected were the small-diameter rolls 16 and 17 installed between the final rolling stand ST5 and the previous rolling stand ST4 and on the exit side of the final rolling stand ST5.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and various modifications and improvements can be made.
For example, when the ratio of noise in the frequency signal does not matter so much, in the frequency analysis step (step S3), the vibration displacement, vibration velocity or vibration acceleration of each mill housing 11 of each rolling stand STi within the specific time t1. A plurality of results of frequency analysis of the vibration displacement, vibration velocity or vibration acceleration of each gearbox 15, and the vibration displacement, vibration velocity or vibration acceleration of each of the small diameter rolls 16 and 17 are retained, and the results of the plurality of retained results are retained. Among them, it is necessary to select a plurality of data measured within a continuous specific time t2 in which the rotation speeds of the small diameter rolls 16 and 17 are within a specific range, and average the amplitudes of the same frequency of the selected plurality of data. Is not always.

In this case, in the abnormal vibration determination step (step S5), the vibration signal processing computer 22 determines the vibration displacement, vibration velocity or vibration acceleration of each mill housing 11 of each rolling stand STi, and the vibration displacement and vibration of each gearbox 15. The speed or vibration acceleration, and the vibration displacement of each small diameter roll 16 or 17, and the result of the frequency analysis of the vibration speed or vibration acceleration are the drive system of each small diameter roll 16 or 17 calculated in the basic frequency calculation step (step S4). It is sufficient to determine whether or not the threshold has been exceeded in the vibration frequency region centered on an integral multiple of the basic frequency caused by the drive shaft, and in the abnormal vibration determination step (step S5), the result of the frequency analysis step is averaged. Whether or not the amplitude exceeds the threshold in the vibration frequency region centered on an integral multiple of the basic frequency caused by the drive system or drive shaft of each of the small diameter rolls 16 and 17 calculated in the basic frequency calculation step (step S4). The condition for determining is not always necessary.

Further, in the abnormal vibration determination step (step S5), the drive system of each of the small diameter rolls 16 and 17 is calculated by calculating the amplitude of the same frequency of the averaged and selected plurality of data which is the result of the frequency analysis. Alternatively, when the above-mentioned threshold value is exceeded in the vibration frequency region centered on an integral multiple of the basic frequency caused by the drive shaft, the amplitude value of 50% to 90% of the amplitude value at the frequency exceeding the above-mentioned notation threshold value. When the frequency width is equal to or less than a certain value (for example, 10 Hz or less), the condition for determining an abnormality is not always necessary.
Further, in the abnormal vibration determination step (step S5), the drive systems of the small diameter rolls 16 and 17 in which the amplitude of the same frequency of the averaged and selected data, which is the result of the frequency analysis, exceeds the above-mentioned threshold value. Alternatively, the condition for determining abnormal vibration when there are at least two frequencies that are integral multiples of the fundamental frequency caused by the drive shaft is not always necessary, and even if it is determined that there is one such frequency, it is determined to be abnormal vibration. Good.

Further, in the abnormal vibration detection method in cold rolling according to the first embodiment and the second embodiment, the metal band 12 of the small diameter rolls 16 and 17 to be frequency-analyzed in the frequency analysis step (step S3) is constant. Of the small-diameter rolls 16 and 17 wound at an angle equal to or greater than the value, the small-diameter rolls 16 and 17 in which the tension of the metal band 12 is constant or higher (for example, 120 MPa or higher) may be limited.
The present inventors have focused on the fact that the small diameter rolls 16 and 17 directly create marks on the metal band 12, and the tension of the metal band 12 applied to the small diameter rolls 16 and 17 is less than a certain value (for example, 120 MPa). This is based on the experimental confirmation that chatter marks are less likely to occur in the case of low tension.

In order to verify the effect of the present invention, abnormality detection was performed by the method according to Comparative Examples 1 to 4 and the vibration abnormality detection method according to Examples 1 to 5 of the present invention.
(First Example)
The experiment is carried out in the rolling equipment shown in FIG. 1, that is, a tandem rolling mill composed of 5 rolling stands ST1 to ST5, and a vibration detector 18 made of a piezoelectric element is attached to a mill housing 11 of each rolling stand STi to reduce the speed. A vibration detector 19 made of a piezoelectric element is placed in each gear box 15 for storing, and a vibration detector 20 made of a piezoelectric element is placed in each of the small diameter rolls 16 and 17 arranged between the rolling stands and on the exit side of the final rolling stand ST5. I installed it.

Low carbon steel is used as the test material, and a plurality of rolling stands ST1 with an inlet thickness of 2.9 mm, a rolling stand ST5 with an outlet thickness of 0.8 mm, and a steel plate width of 1240 mm are used, and the rolling speed is 10 m / sec. And said.
In the first embodiment, the vibration abnormality detection method according to Comparative Examples 1 and 2 and the vibration abnormality detection method according to Examples 1 and 2 of the present invention were compared.
The vibration abnormality detection method according to Comparative Examples 1 and 2 is a method in which the method of Patent Document 1 is applied to a small-diameter roll (a method of determining a frequency component due to an abnormality of each bearing or the like by setting a uniform threshold value). Yes, the frequency analysis of the vibration velocity of the small diameter roll between the rolling stands ST3 and ST4 was performed.

Further, the vibration abnormality detection method according to Example 1 of the present invention is the vibration abnormality detection method according to the first embodiment, and frequency analysis of the vibration velocities of the small diameter rolls 16 and 17 between the rolling stands ST3 to ST4 was performed. When performing this frequency analysis, the specific time t1 is set to 10 sec, and a plurality of results of frequency analysis of the vibration velocities of the small diameter rolls 16 and 17 between the rolling stands ST3 and ST4 within the specific time t1 = 10 sec are retained. Among the results of holding a plurality of these, a plurality of small diameter rolls 16 and 17 measured within a continuous specific time t2 (10 sec) in which the rotation speed is within a specific range (± 15 m / sec with respect to the operating speed). Data were selected and the amplitudes of the selected data at the same frequency were averaged. Then, at the time of determining the abnormal vibration, the amplitude of the same frequency of the averaged and selected plurality of data which is the result of the frequency analysis is calculated by the drive system or the drive shaft of each of the small diameter rolls 16 and 17. When the threshold was exceeded in the vibration frequency region centered on an integral multiple of the fundamental frequency caused by the above, it was determined to be abnormal vibration.

Further, the vibration abnormality detection method according to Example 2 of the present invention is the vibration abnormality detection method according to the first embodiment, and frequency analysis of the vibration velocities of the small diameter rolls 16 and 17 between the rolling stands ST3 and ST4 was performed. When performing this frequency analysis, the amplitude of the same frequency of the averaged and selected data, which is the result of the frequency analysis, is basically caused by the drive system or the drive shaft of each of the small diameter rolls 16 and 17. When the threshold is exceeded in the vibration frequency region centered on an integral multiple of the frequency, and the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the above-mentioned threshold is 10 Hz or less, an abnormality is determined. And said.

In the evaluation of abnormal vibration, either the vibration is detected and it is judged as abnormal vibration, or the rolled steel plate is sampled about 500 mm, the plate thickness is measured with a contact type plate thickness gauge, and the plate thickness fluctuation is the corresponding frequency. A grindstone inspection was performed after alloying zinc plating to see how much the pitch was generated, and the chatter marks of the pitch of the corresponding frequency were visually evaluated. The evaluation results are shown in Table 1.

In Table 1, x in the evaluation result detects vibration and determines an abnormality, the plate thickness fluctuation is 1 μm or more, the chatter mark is clearly visible, and Δ is the plate thickness fluctuation of less than 1 μm. , The chatter mark looks faint, ○ indicates that vibration is not detected and is not judged as abnormal, and the chatter mark cannot be confirmed.

Further, the result of frequency analysis of the vibration abnormality detection method according to Comparative Example 1 is shown in FIG. 3, the result of frequency analysis of the vibration abnormality detection method according to Example 1 of the present invention is shown in FIG. 4, and the result of frequency analysis of the vibration abnormality detection method according to Comparative Example 2 is shown in FIG. The result of the frequency analysis of the above is shown in FIG. 5, and the result of the frequency analysis of the vibration abnormality detecting method according to Example 2 of the present invention is shown in FIG. In FIGS. 3 to 5, the pitch of an integral multiple of the outer ring defect frequency of the bearing is indicated by an arrow.
With reference to FIG. 3, in the vibration abnormality detection method according to Comparative Example 1, since the noise N exceeds the threshold value, vibration is detected and an abnormality is determined as shown in Table 1, but the chatter mark can be confirmed. However, it was erroneously detected due to noise N. In the vibration abnormality detection method according to Comparative Example 1, there are many noise components in the vibration, and if the threshold value is set high, the chatter mark cannot be detected, and if the threshold value is set low, many false detections occur due to noise. ..

On the other hand, in the vibration abnormality detection method according to Example 1 of the present invention, as shown in FIG. 4, the amplitude of the averaged vibration velocity, which is the result of frequency analysis, is an integral multiple pitch (4) of the outer ring defect frequency of the bearing. Abnormal vibration caused by the drive system or drive shaft of each of the small diameter rolls 16 and 17 was detected because the threshold value was exceeded in the frequency range of 2 times and 5 times). With reference to Table 1, in the abnormal vibration detection method according to Example 1 of the present invention, the vibration was detected and the abnormality was determined, so that the chatter mark could be clearly confirmed.
In the vibration abnormality detection method according to Example 1 of the present invention, since the data are averaged, noise components other than abnormal vibration can be reduced as shown in FIG. 4, and even if the threshold value is lowered to some extent. It is possible to detect abnormal vibration.

Further, referring to FIG. 5, in the vibration abnormality detection method according to Comparative Example 2, the amplitude of a specific frequency (around 500 Hz) is increased due to the influence of the fixing method of the small diameter rolls 16 and 17, and the influence of the noise N. As shown in Table 1, vibration was detected and an abnormality was determined, but the chatter mark could not be confirmed, resulting in an erroneous detection.
On the other hand, in the vibration abnormality detection method according to Example 2 of the present invention, as shown in FIG. 5, since the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the threshold value is 50 Hz, the abnormality determination is performed. Not excluded, excluded. Therefore, as shown in Table 1, the abnormality was not determined without detecting the vibration. In addition, the chatter mark could not be confirmed, and it was possible to accurately determine that there was no abnormal vibration.

(Second Example)
The rolling equipment shown in FIG. 1 is used for the experiment. The rolling stands to be detected for vibration are the final rolling stand ST5 and the rolling stand ST4 immediately before it, and the small diameter rolls to be detected for vibration are used. , Small diameter rolls 16 and 17 installed between the final rolling stand ST5 and the previous rolling stand ST4 and on the exit side of the final rolling stand ST5. The tension between all the rolling stands STi was 120 MPa or more, and 50 MPa on the exit side of the final rolling stand ST5.
Low carbon steel is used as the test material, and a plurality of rolling stands ST1 with an inlet thickness of 2.9 mm, a rolling stand ST5 with an outlet thickness of 0.8 mm, and a steel plate width of 1240 mm are used, and the rolling speed is 10 m / sec. And said.

In the second embodiment, the vibration abnormality detection method according to Comparative Examples 3 and 4 and the vibration abnormality detection method according to Examples 3 to 5 of the present invention were compared.
The vibration abnormality detection method according to Comparative Example 3 is a method in which the method of Patent Document 1 is applied to a small-diameter roll (a method of determining a frequency component due to an abnormality of each bearing or the like by setting a uniform threshold value). Frequency analysis of the vibration velocities between the rolling stands ST4 to ST5 and the small diameter rolls 16 and 17 on the exit side of the final rolling stand ST5 was performed.
The method according to Comparative Example 4 is also a method in which the method of Patent Document 1 is applied to a small diameter roll, and the small diameter roll between the rolling stands ST4 and ST5 (roll having a high tension of 120 MPa or more) and the output side of the final rolling stand ST5. The frequency analysis of the vibration velocity of the small-diameter roll (roll whose tension is less than 120 MPa and low) was performed.

Further, the vibration abnormality detection method according to Example 3 of the present invention is the abnormality vibration detection method according to the second embodiment, and the vibration between the rolling stands ST4 to ST5 and the vibrations of the small diameter rolls 16 and 17 on the exit side of the final rolling stand ST5. Frequency analysis of velocity was performed. When performing this frequency analysis, the result of the frequency analysis is due to the drive system or drive shaft of each small diameter roll 16, 17 in which the amplitude of the same frequency of the selected data selected exceeds the threshold. When there are at least two frequencies that are integral multiples of the fundamental frequency, it is determined to be abnormal vibration.
Further, the vibration abnormality detection method according to Example 4 of the present invention is the abnormality vibration detection method according to the second embodiment, and the vibration between the rolling stands ST4 to ST5 and the vibrations of the small diameter rolls 16 and 17 on the exit side of the final rolling stand ST5. Frequency analysis of velocity was performed. When performing this frequency analysis, the result of the frequency analysis is due to the drive system or drive shaft of each small diameter roll 16, 17 in which the amplitude of the same frequency of the selected data selected exceeds the threshold. When there are at least two frequencies that are integral multiples of the fundamental frequency, it is determined to be abnormal vibration.

Further, in the vibration abnormality detection method according to Example 5 of the present invention, in the abnormality vibration detection method according to the second embodiment, the small diameter rolls 16 and 17 to be frequency-analyzed are wound by the metal band 12 at an angle of a certain value or more. Of the attached small diameter rolls 16 and 17, the small diameter rolls 16 and 17 between the rolling stands ST4 and ST5 where the tension of the metal band 12 is equal to or higher than a certain level (120 MPa or higher) are limited to the small diameter on the exit side of the final rolling stand ST5. Rolls 16 and 17 (tension is low at less than 120 MPa) are excluded from the target of frequency analysis.
In the evaluation of abnormal vibration, vibration is detected, or about 500 mm of rolled steel plate is sampled, the plate thickness is measured with a contact type plate thickness gauge, and then the plate thickness fluctuation occurs at the pitch of the corresponding frequency. After the alloying zinc plating, a grindstone inspection was performed to visually evaluate the chatter marks of the pitch of the corresponding frequency. The evaluation results are shown in Table 2.

In Table 2, x in the evaluation result detects vibration and determines an abnormality, the plate thickness fluctuation is 1 μm or more, the chatter mark is clearly visible, and Δ is the plate thickness fluctuation of less than 1 μm. , The chatter mark looks faint, ○ indicates that vibration is not detected and is not judged as abnormal, and the chatter mark cannot be confirmed.

Further, the frequency analysis result of the vibration abnormality detection method according to Comparative Example 3 (the result of the frequency analysis of the small diameter roll between the rolling stands ST4 and ST5) is shown in FIG. 7, and the frequency analysis of the vibration abnormality detection method according to Example 3 of the present invention is shown in FIG. (Result of frequency analysis of small diameter roll between rolling stands ST4 and ST5) is shown in FIG. 8, and the result of frequency analysis of the vibration abnormality detection method according to Example 4 of the present invention (frequency of small diameter roll between rolling stands ST4 and ST5). The result of the analysis) is shown in FIG. 9, and the result of the frequency analysis of the vibration abnormality detection method according to Comparative Example 4 (the result of the frequency analysis of the small diameter roll on the exit side of the final rolling stand ST5) is shown in FIG. FIG. 11 shows the result of frequency analysis of the vibration velocity of the small diameter roll (roll with low tension) of the final rolling stand ST5 by the vibration abnormality detection method. In FIGS. 7 to 11, the pitch of an integral multiple of the outer ring defect frequency of the bearing is indicated by an arrow.

Referring to FIG. 7, in the vibration abnormality detection method according to Comparative Example 3, the noise N1 caused by an external vibration source other than the vibration caused by the drive system or the drive shaft of each of the small diameter rolls 16 and 17 exceeds the threshold value. As shown in 2, vibration was detected by the small diameter roll between the rolling stands ST4 and ST5, but the chatter mark could not be confirmed, and the noise N1 from the external vibration source caused an erroneous detection. In the vibration abnormality detection method according to Comparative Example 1, noise N1 from an external vibration source rides on the vibrations, and vibrations other than the vibrations caused by the drive system or drive shaft of the small diameter rolls 16 and 17 are erroneously detected as abnormal vibrations. There is.

On the other hand, in the vibration abnormality detection method according to Example 3 of the present invention, as shown in FIG. 8, the amplitude of the same frequency of the averaged and selected data, which is the result of the frequency analysis, sets the threshold value. There are at least four (2x, 3x, 4x and 5x) frequencies that are integral multiples of the fundamental frequency due to the drive system or drive shaft of each of the smaller diameter rolls 16 and 17 that exceed, as shown in Table 2. In addition, vibration was detected by a small-diameter roll between the rolling stands ST4 and ST5, and it was determined to be abnormal vibration. Then, the chatter mark was confirmed, and the abnormal vibration was detected with high accuracy.
Further, in the vibration abnormality detection method according to Example 4 of the present invention, as shown in FIG. 9, each of the averaged and selected data having the same frequency amplitude exceeds the threshold value as a result of frequency analysis. There is only one (three times) frequency that is an integral multiple of the fundamental frequency caused by the drive system or drive shaft of the small diameter rolls 16 and 17, and as shown in Table 2, the small diameter roll between the rolling stands ST4 and ST5. The vibration could not be detected and it was not judged as abnormal vibration. Then, the chatter mark was not confirmed, and it was possible to accurately determine that the vibration was not abnormal.

Further, in the vibration abnormality detecting method according to Comparative Example 4, although the tension of the metal band 12 wound around the small diameter roll on the exit side of the final rolling stand ST5 is low (less than 120 MPa), as shown in FIG. , The amplitude of vibration at a frequency that is an integral multiple (10 times) of the fundamental frequency caused by the drive system or drive shaft of each of the small diameter rolls 16 and 17 exceeds the threshold value, and as shown in Table 2, the final rolling stand ST5 comes out. The vibration of the small diameter roll on the side was detected, and it was determined to be abnormal vibration. However, at this time, the chatter mark was not confirmed, resulting in an erroneous detection.

On the other hand, in the abnormal vibration detection method according to Example 5 of the present invention, when the tension of the metal band 12 wound around the small diameter roll on the exit side of the final rolling stand ST5 is low (less than 120 MPa), it is shown in FIG. As described above, even when the vibration amplitude at a frequency that is an integral multiple (10 times) of the fundamental frequency caused by the drive system or drive shaft of each of the small diameter rolls 16 and 17, exceeds the threshold value, it is the target of frequency analysis. Since the small-diameter rolls 16 and 17 are limited to the small-diameter rolls 16 and 17 in which the tension of the metal band 12 is a certain value or more (for example, 120 MPa or more), the metal wound around the small-diameter roll on the exit side of the final rolling stand ST5. When the tension of the band 12 is low (less than 120 MPa), it is not subject to frequency analysis, and as shown in Table 2, the vibration of the small diameter roll on the exit side of the final rolling stand ST5 is not detected and is not determined to be abnormal vibration. .. In addition, no chatter mark was confirmed, and it was possible to accurately determine that there was no abnormal vibration.

10 Cold rolling equipment 11 Mill housing 12 Metal strip 13 Work roll 14 Backup roll 15 Gear box 16 Tension meter roll (small diameter roll)
17 Pass line roll (small diameter roll)
18, 19, 20 Vibration detector 21 Speed detector 22 Vibration signal processing computer ST1 to ST5 Rolling stand

Claims (3)

An abnormal vibration detection method in cold rolling in which a metal strip is rolled by a cold rolling machine having one or more rolling stands.
Vibration detectors installed at at least one location on each rolling stand, and installed on each small-diameter roll that is placed between each rolling stand and on the exit side of the final rolling stand, and the metal band is wound at an angle of a certain value or more. A vibration detection step for detecting the vibration displacement, vibration velocity or vibration acceleration of each part of each rolling stand and each small diameter roll by the vibration detector.
A roll rotation speed detection step of detecting the rotation speed of each small diameter roll by a speed detector installed on the small diameter roll or the rolling roll of the rolling stand.
A frequency analysis step for frequency analysis of vibration displacement, vibration velocity or vibration acceleration of each part of each rolling stand and each small diameter roll detected in the vibration detection step, and
Due to the drive system or drive shaft of each small diameter roll based on the vibration displacement, vibration velocity or vibration acceleration of each small diameter roll detected in the vibration detection step and the rotation speed of each small diameter roll detected in the roll rotation speed detection step. The fundamental frequency calculation step to calculate the fundamental frequency to be performed, and
When the result of the frequency analysis step exceeds the threshold value in the vibration frequency region centered on an integral multiple of the fundamental frequency caused by the drive system or drive shaft of each small diameter roll calculated in the fundamental frequency calculation step, abnormal vibration occurs. Including the abnormal vibration determination step to determine
In the frequency analysis step, a plurality of results of frequency analysis of vibration displacement, vibration speed, or vibration acceleration of each part of each rolling stand and each roll detected in the vibration detection step within a specific time are retained, and a plurality of results are retained. From the results of the frequency analysis performed, a plurality of data measured within a continuous specific time in which the rotation speed of each small-diameter roll obtained in the roll rotation speed detection step is within a specific range are selected, and a plurality of selected data are selected. Average the amplitudes of the same frequency of the data in
The abnormal vibration determining step, following a, b, when satisfying the three conditions c, abnormal vibration detection method in to that cold rolling, wherein determining that abnormal vibration.
a. The averaged amplitude resulting from the frequency analysis step is a threshold in the vibration frequency region centered on an integral multiple of the fundamental frequency due to the drive system or drive shaft of each small diameter roll calculated in the fundamental frequency calculation step. When it exceeds.
b. When the averaged amplitude resulting from the frequency analysis step exceeds the threshold in the vibration frequency region centered on an integral multiple of the fundamental frequency caused by the drive system or drive shaft of each small diameter roll, the said. When the frequency width of a specific amplitude value set within the range of 50 to 90% of the amplitude value at a frequency exceeding the threshold value is not more than a certain value.
c. The frequency at which the averaged amplitude resulting from the frequency analysis step exceeds the threshold value and is an integral multiple of the fundamental frequency due to the drive system or drive shaft of each small diameter roll calculated in the fundamental frequency calculation step is If there are at least two . The rolling stands to be detected for vibration in the vibration detection step are the final rolling stand and the rolling stand immediately before it, and the small diameter rolls to be detected for vibration in the vibration detection step are the final rolling stand and its previous rolling stand. The method for detecting abnormal vibration in cold rolling according to claim 1 , wherein the small-diameter roll is installed between the previous rolling stand and the outlet side of the final rolling stand. The small-diameter rolls to be frequency-analyzed in the frequency analysis step are limited to the small-diameter rolls in which the metal band is wound at an angle of a certain value or more and the tension of the metal band is a certain value or more. The method for detecting abnormal vibration in cold rolling according to claim 1 or 2.

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