JP2019206028A - Method for detecting abnormal vibration in cold rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormal vibration detection method in cold rolling capable of accurately detecting abnormal vibration caused by a drive system or a drive shaft of a small-diameter roll that causes chatter marks in cold rolling. SOLUTION: An abnormal vibration detecting method in cold rolling includes a vibration detecting step (step S1) for detecting a vibration speed of each small diameter roll 16 and 17, and a roll rotation for detecting a rotation speed of each small diameter roll 16,17. A speed detection step (step S2), a frequency analysis step (step S3) for performing frequency analysis of vibration speeds of the small diameter rolls 16 and 17, and a basic frequency caused by a drive system of the small diameter rolls 16 and 17 are calculated. When the result of the fundamental frequency calculation step (step S4) and 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 of the small diameter rolls 16 and 17, An abnormal vibration determination step (step S5, step S6) of determining abnormal vibration is included. [Selection diagram] Figure 2

Description

  The present invention relates to an abnormal vibration detection method in cold rolling suitable for detecting chattering that occurs during cold rolling of a metal sheet in a cold rolling mill.

  In general, steel sheets used for automobiles, beverage cans, and the like are subjected to continuous casting, hot rolling, and cold rolling, and after annealing and plating processes, processing according to each shape is performed. Here, the cold rolling process is a final process for determining a steel plate thickness as a product. In recent years, the thickness of the plating has been made thinner, and the surface of the steel sheet before plating determines the surface of the final product after plating, so the cold rolling process also requires a function to prevent surface defects. It has been.

One of surface defects generated in the cold rolling process is a chatter mark. This chatter mark is a pattern in which linear marks extending in the width direction of the metal strip appear periodically along the longitudinal direction of the metal strip, and are mainly vibrations of a cold rolling mill (hereinafter referred to as chattering). It is supposed to be caused by. An extremely light chatter mark is not found by visual inspection after rolling or sheet thickness measurement, but is found for the first time after the plating process, which is a factor that greatly hinders product productivity. In particular, it is known that thin materials such as steel plates for cans and electromagnetic steel plates impede production due to the phenomenon that the plate breaks due to sudden fluctuations in the plate thickness and tension caused by chattering.
For this reason, conventionally, many chattering detection methods and prevention methods 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 in each part of the rolling mill to detect vibrations in each part of the rolling mill during operation, and chattering of the rolling mill is detected from the vibrations detected in each part of the rolling mill. In the method, the natural frequency of the mill, the poor meshing of the gear, the bearing failure, the backlash of the coupling between the spindle and the roll, and the specific vibration frequency generated from the roll saddle are calculated and used as the fundamental frequency for each cause of chatter mark. The vibration displacement, vibration speed or vibration acceleration of each part of the rolling mill is detected, and frequency analysis of the detected vibration displacement, vibration speed or vibration acceleration of each part is performed, and tension, rolling torque, rolling speed, rolling load, plate thickness variation When the result of frequency analysis of the measured values of rolling parameters exceeds the set value at a frequency that is an integral multiple of the basic frequency for each cause of chatter mark occurrence, It determines that Yataringu generation, chattering detection method of a rolling mill to identify the cause of the fundamental frequency are disclosed.

  Patent Document 2 discloses a vibration signal collecting step for collecting vibration signals detected by at least one small-diameter roll among the small-diameter rolls between the stands of the cold rolling mill or the cold rolling mill outlet, The frequency analysis of the fast Fourier transform method is performed on the vibration signal, and the frequency component included in the vibration signal and its spectrum value are obtained. Of the frequency components obtained in the FFT frequency analysis execution step and the FFT frequency analysis execution step, A vibration abnormality detection method in cold rolling having a vibration abnormality determination step that determines that a vibration abnormality has occurred when the spectrum value of the same frequency component as the string vibration frequency of the steel sheet exceeds a preset threshold value. It is disclosed.

  Further, Patent Document 3 discloses a steel plate having a chord length between the natural frequency of the cold rolling mill, and the final stand of the cold rolling mill and a small diameter roll that first contacts the steel plate on the cold rolling mill exit side. A method for preventing chatter marks on a steel sheet is disclosed in which the frequency of the string vibration of the steel sheet is not matched and the bending strain generated on the surface of the steel sheet is such that the steel sheet does not undergo plastic deformation.

Japanese Patent No. 2996487 Japanese Patent Laid-Open No. 2006-153138 Japanese Patent No. 6102835

However, in the chattering detection method of a rolling mill shown in Patent Document 1, 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 following problems are present. there were.
That is, in the case of the chattering detection method of a rolling mill shown in Patent Document 1, attention is paid only to vibrations generated by the rolling mill body, and angles set to the entrance side and the exit side of each rolling stand are equal to or greater than a certain value. In this case, it is impossible to cope with vibration caused by a drive system of a small-diameter roll around which a metal band is wound.

The inventors' research has revealed that the vibration of the small-diameter roll as described above affects the chatter mark. Further, it has also been found that vibrations generated in the rolling mill main body cannot be detected by a vibration meter installed in a housing or the like in the rolling mill main body, and can often be detected by vibration of a small diameter roll.
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 steel sheet shown in Patent Document 3, the occurrence of vibration due to string vibration can be suppressed. Generation of chatter marks due to vibration caused by the drive system or drive shaft of a small-diameter roll disposed on the exit side of the rolling stand and wound with a metal strip at an angle of a certain value or more cannot be prevented.

  Therefore, the present invention has been made to solve these conventional problems, and its purpose is to arrange chatter marks in cold rolling and between the rolling stands and on the exit side of the final rolling stand. An object of the present invention is to provide an abnormal vibration detection method in cold rolling, which can accurately detect abnormal vibration caused by a drive system or drive shaft of a small-diameter roll around which a metal strip is wound at an angle of a certain value or more.

  First, as a result of various investigations by the cold rolling equipment 100 that is a tandem rolling mill as shown in FIG. 12, the present inventors have increased the number of false detections in the conventional method (method according to Patent Document 1). I found out. That is, it has been found that many examples with high vibration values occur even though they do not appear as surface defects after rolling or plating. This is presumed that the tandem rolling mill is affected by the surrounding noise because there are many peripheral facilities, and the vibration value becomes large in a specific frequency band. It has also been found that if the threshold value is set high in order to reduce false detections, abnormal vibration cannot be detected under the condition that chatter marks are generated.

  Therefore, first, the present inventors investigated a vibration source of abnormal vibration that causes chatter marks. As a result, it has been found that although the natural vibration of the cold rolling mill and the engagement of the gear stored in the gear box 103 always generate large vibrations, chatter marks due to the vibrations do not occur. In addition, as a factor that has a great influence on the chatter mark, it is disposed between the rolling stands 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 is above a certain value. It has been found that the vibration caused by the drive system or drive shaft of the roll 104 (hereinafter referred to as a small-diameter roll) around which the metal strip is wound at the angle is affected. This is presumed that the small-diameter roll 104 directly makes a mark because the small-diameter roll 104 is in direct contact with the metal band.

  Therefore, in order to achieve the above object, an 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 mill having one or more rolling stands. A vibration detection method, comprising vibration detectors installed at at least one location of each rolling stand, and between each rolling stand and on the exit side of the final rolling stand, wherein the metal strip is wound at an angle of a certain value or more. A vibration detecting step for detecting vibration displacement, vibration speed or vibration acceleration of each part of each rolling stand and each small diameter roll by means of 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 for detecting the rotation speed of each small-diameter roll by a speed detector installed on the roll, and the vibration detection step. A frequency analysis step for performing frequency analysis of vibration displacement, vibration speed or vibration acceleration of each part of each rolling stand and each small diameter roll, and vibration displacement, vibration speed or vibration acceleration of each small diameter roll detected in the vibration detection step and the above Based on the rotation speed of each small-diameter roll detected in the roll rotation speed detection step, a basic frequency calculation step for calculating a basic frequency caused by the drive system or drive shaft of each small-diameter roll, and the result of the frequency analysis step are An abnormal vibration determination step for determining abnormal vibration when a threshold is exceeded in a 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 calculated in the basic frequency calculation step; Inclusion is included.

The vibration caused by the drive system and the like includes vibration due to abnormality of the gear used for the drive shaft, vibration due to the universal joint of the drive shaft, and vibration due to bearing abnormality.
Moreover, as a small diameter roll, in addition to the thing without an external force drive, the thing with an external force drive like a shape meter roll etc. is contained.

  According to the abnormal vibration detection method in the cold rolling according to the present invention, the chatter mark is generated in the cold rolling, arranged between the rolling stands and on the exit side of the final rolling stand, and the metal strip is at an angle of a certain value or more. It is possible to provide an abnormal vibration detection method in cold rolling that 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 schematic structure of the cold rolling equipment which can apply the abnormal vibration detection method in the cold rolling which concerns on 1st Embodiment and 2nd Embodiment of this invention. It is a flowchart for demonstrating the flow of the process performed with 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 speed of the small diameter roll between rolling stands ST3-ST4 by the method which concerns on the comparative example 1. FIG. It is a graph which shows the result of having performed the frequency analysis of the vibration speed of the small diameter roll between rolling stands ST3-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 speed of the small diameter roll between rolling stands ST3-ST4 by the method which concerns on the comparative example 2. FIG. It is a graph which shows the result of having performed the frequency analysis of the vibration speed of the small diameter roll between rolling stands ST3-ST4 by the method which concerns on Example 2 of this invention. The rolling stand subject to vibration detection is the final rolling stand ST5 and the preceding rolling stand ST4, and the small diameter roll subject to vibration detection in the vibration detecting step is the final rolling stand ST5 and the preceding rolling stand. A small-diameter roll installed between the stand ST4 and the exit side of the final rolling stand ST5, and the vibration speed of the small-diameter roll between the final rolling stand ST5 and the preceding rolling stand ST4 by the method according to Comparative Example 3. It is a graph which shows the result of having performed frequency analysis. The rolling stand subject to vibration detection is the final rolling stand ST5 and the preceding rolling stand ST4, and the small diameter roll subject to vibration detection in the vibration detecting step is the final rolling stand ST5 and the preceding rolling stand. A small-diameter roll installed between the stand ST4 and the exit side of the final rolling stand ST5, and the vibration of the small-diameter roll between the final rolling stand ST5 and the preceding rolling stand ST4 by the method according to Example 3 of the present invention. It is a graph which shows the result of having performed frequency analysis of speed. The rolling stand subject to vibration detection is the final rolling stand ST5 and the preceding rolling stand ST4, and the small diameter roll subject to vibration detection in the vibration detecting step is the final rolling stand ST5 and the preceding rolling stand. A small-diameter roll installed between the stand ST4 and the exit side of the final rolling stand ST5, and the vibration of the small-diameter roll between the final rolling stand ST5 and the preceding rolling stand ST4 by the method according to Example 4 of the present invention. It is a graph which shows the result of having performed frequency analysis of speed. The rolling stand subject to vibration detection is the final rolling stand ST5 and the preceding rolling stand ST4, and the small diameter roll subject to vibration detection in the vibration detecting step is the final rolling stand ST5 and the preceding rolling stand. Frequency analysis of the vibration speed 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 using a small-diameter roll installed between the stand ST4 and the outlet side of the final rolling stand ST5. It is a graph which shows the result of having performed. The rolling stand subject to vibration detection is the final rolling stand ST5 and the preceding rolling stand ST4, and the small diameter roll subject to vibration detection in the vibration detecting step is the final rolling stand ST5 and the preceding rolling stand. A small diameter roll installed between the stand ST4 and the exit side of the final rolling stand ST5 is used, and the frequency analysis of the vibration speed of the small diameter roll (low tension roll) of the final rolling stand ST5 is 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 schematic structure of the principal part of the general cold rolling equipment used for 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 between elements, the ratio of elements, and the like may be different from actual ones. Even between the drawings, there are cases in which parts having different dimensional relationships and ratios are included.

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

Further, a tension meter roll 16 and a pass line roll 17 are disposed 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. The metal band 12 is wound around the tension meter roll 16 and the pass line roll 17 at an angle (for example, 5 ° or more) greater than a certain value. 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 provided on each small-diameter roll 16, 17. Is installed. Each vibration detector 18 detects vibration displacement, vibration speed, or vibration acceleration of the mill housing 11 of each rolling stand STi. Further, each vibration detector 19 detects the vibration displacement, vibration speed, or vibration acceleration of each gear box 15. Further, each vibration detector 20 detects vibration displacement, vibration speed, or vibration acceleration of each small-diameter roll 16, 17.

Furthermore, the work roll 13 of the final rolling stand ST5 on the exit side of the cold rolling facility 10 has a speed detector 21 that detects the rotation speed of the small diameter rolls 16 and 17 by detecting the rotation speed of the work roll 13. is set up.
The vibration displacement, vibration speed or vibration acceleration of the mill housing 11 of the rolling stand STi, the vibration displacement, vibration speed or vibration acceleration of each gear box 15, the small diameter rolls 16, 17 detected by the vibration detectors 18, 19, 20. The vibration displacement, vibration speed, or vibration acceleration is input to the vibration signal processing computer 22 as a vibration detection signal.

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.
The vibration signal processing computer 22 individually performs abnormal vibration detection processing on the vibration detection signals collected at a 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 includes, for example, a CPU, a ROM, a RAM, and the like as main components.

(First embodiment)
Next, for the abnormal vibration detection method in cold rolling according to the first embodiment, see the flowchart for explaining the flow of processing executed by the vibration detector, speed detector and vibration signal processing computer shown in FIG. To explain.
Each vibration detector 18, 19, 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 that is a frequency analysis step, step S4 that is a basic frequency calculation step, and steps S5 and S6 that are abnormal vibration determination steps.

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

In step S3, the vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of the rolling stand STi, vibration displacement, vibration speed or vibration acceleration of each gear box 15 detected by the vibration detectors 18, 19 and 20 are detected. The vibration displacement, vibration speed, or vibration acceleration of each small-diameter roll 16, 17 is input to the vibration signal processing computer 22 as a vibration detection signal.
In step S3, the rotational speeds of the small-diameter rolls 16 and 17 detected by the speed detector 21 are input.

In step S3, the vibration signal processing computer 22 executes frequency analysis, and inputs the vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi, vibration displacement and vibration of each gear box 15. Frequency analysis of speed or vibration acceleration and vibration displacement, vibration speed or vibration acceleration of each of the small diameter rolls 16 and 17 is performed.
In this frequency analysis step, vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi within a specific time t1, vibration displacement, vibration speed or vibration acceleration of each gear box 15, and each small diameter roll 16, A plurality of results of frequency analysis of 17 vibration displacements, vibration speeds or vibration accelerations are held. In performing the 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. For example, when the sampling frequency is 2 kHz or more, the specific time t1 is preferably 0.15 sec or more.

And the continuous specific time from which the rotational speed of each small diameter roll 16 and 17 is in a specific range (speed deviation small so that it may be recognized with respect to an operation speed, for example, 30 m / sec) among the results hold | maintained in multiple numbers. A plurality of data measured within t2 (for example, 10 sec) is selected, and the amplitudes of the same frequency of the selected plurality of data are averaged.
Next, in step S4, the vibration signal processing computer 22 inputs the vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi, vibration displacement of each gear box 15, vibration speed or vibration acceleration, and Based on the vibration displacement, vibration speed or vibration acceleration of each small diameter roll 16, 17 and the input rotational speed of each small diameter roll 16, 17, the basic attribute caused by the drive system or drive shaft of each small diameter roll 16, 17 Calculate the frequency.

  In step S5, the vibration signal processing computer 22 determines the vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi, vibration displacement of each gear box 15, vibration speed or vibration acceleration, and each small diameter roll. The vibration frequency centering on the integral multiple of the fundamental frequency resulting from the drive system or drive shaft of each small-diameter roll 16, 17 is obtained as a result of frequency analysis of vibration displacement, vibration speed, or vibration acceleration of 16, 17 It is determined whether or not a threshold value has been exceeded in the region. Here, it is preferable to use a different threshold value for each frequency. This is because, depending on the structure of the small-diameter rolls 16 and 17 and the characteristics of the vibration measuring elements constituting the vibration detectors 18, 19, and 20, there are frequencies that are likely to appear in vibrations and frequencies that are unlikely to appear. Furthermore, if the hardness of the metal strip 12 is large, chatter marks tend not to appear, so it is preferable to change the hardness depending on the hardness.

In this determination, when the following three conditions are satisfied, it is determined that the frequency analysis result has exceeded the threshold value, the determination result is YES, and after step S6, the determination result is NO and processing is performed otherwise. finish.
1. The amplitude of the same frequency of a plurality of selected averaged data, which is the result of frequency analysis, is an integral multiple of the fundamental frequency due to the calculated drive system or drive shaft of each small-diameter roll 16, 17. When the threshold is exceeded in the center vibration frequency range.
2. When the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the above threshold is 10 Hz or less.
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 small-diameter roll 16, 17 exceeding the aforementioned threshold.
In step 6, the vibration signal processing computer 22 determines that the vibration is abnormal and ends the process.

  Thus, according to the abnormal vibration detection method in the cold rolling according to the first embodiment, the vibration displacement, vibration speed or vibration of the mill housing 11 of each rolling stand STi, each part of the gear box 15 and each of the small diameter rolls 16 and 17. The acceleration is detected, the rotational speed of each small-diameter roll 16, 17 is detected, and the frequency analysis of the vibration displacement, vibration speed, or vibration acceleration of each mill stand 11 of each rolling stand STi, each part of the gear box 15 and each small-diameter roll 16, 16 is detected. Based on the vibration displacement, vibration speed or vibration acceleration of each small-diameter roll 61, 17 and the rotational speed of each small-diameter roll 16, 16, the fundamental frequency due to the drive system or drive shaft of each small-diameter roll 16, 17 is determined. The frequency analysis result is calculated on the drive system or drive shaft of each of the small diameter rolls 16 and 17 calculated in the basic frequency calculation step. When the threshold is exceeded in the vibration frequency range centered at integer multiples of the fundamental frequency of factors, it determines that abnormal vibration.

Thereby, driving of small-diameter rolls 16 and 17 that are arranged between the respective rolling stands STi and on the exit side of the final rolling stand ST5 and generate the chatter mark in the cold rolling and the metal strip 12 is wound at an angle of a certain value or more. Abnormal vibration caused by the system or the drive shaft can be detected with high accuracy.
Further, in the abnormal vibration determination step, the amplitude of the same frequency of a plurality of selected data that is averaged as a result of the frequency analysis is applied to the calculated drive system or drive shaft of each small-diameter roll 16, 17. When a threshold value is exceeded in the vibration frequency region centered on an integral multiple of the resulting fundamental frequency, it is determined as abnormal vibration. Therefore, the noise ratio in the frequency signal can be reduced, and the abnormal vibration can be detected more accurately. .

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

Further, in the abnormal vibration determination step, the average amplitude of the selected plural data averaged as a result of the frequency analysis is applied to the calculated driving system or driving shaft of each small-diameter roll 16, 17. When the above-mentioned threshold value 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 value is 10 Hz or less In addition, since the abnormal vibration is determined, the abnormal vibration connected to the chatter mark can be detected with higher accuracy.
In other words, the present inventors have found that abnormal vibrations that lead to chatter marks have sharp peaks in the frequency analysis results even at frequencies due to the drive systems or drive shafts of the small-diameter rolls 16 and 17, and broadly conversely. We found that vibrations with different frequency bands do not appear as chatter marks. Therefore, the average amplitude of the same frequency of a plurality of selected data that is the result of the frequency analysis is an integer of the fundamental frequency that is derived from the calculated drive system or drive shaft of each small-diameter roll 16, 17. In the case where the above threshold value is exceeded in the vibration frequency region centered on the double, it is determined that the vibration is abnormal 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. I tried to do it.

The amplitude value used for the above-described determination is not limited to 70%, and may be set within a range of 50 to 90%. Further, when the frequency width is not limited to 10 Hz or less and is a certain value or less, abnormal vibration is detected. You may make it determine.
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 a plurality of selected and averaged data as a result of the frequency analysis exceeds the aforementioned threshold value. If there are at least two frequencies that are integral multiples of the fundamental frequency due to the above, it is determined that the vibration is abnormal. Therefore, an error due to external vibration other than vibration caused by the drive system or drive shaft of the small-diameter rolls 16 and 17 is detected. Detection can be prevented with high accuracy.

  That is, vibration generated from an external power source, a lubricant pump, a fan, or the like may appear in the vibration detector as very strong noise at a specific frequency. Usually, measures such as cutting these frequencies with a band stop filter are taken. However, 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 external vibration described above. Thus, abnormal vibrations caused by the drive system or drive shaft of the small-diameter rolls 16 and 17 cannot be detected. Therefore, the inventors of the present invention have not only the fundamental frequency but also an integral multiple, particularly about 10 times, of the vibration caused by the drive system or drive shaft of each small-diameter roll 16, 17 that generates abnormal vibration leading to chatter marks. Paying attention to the fact that a plurality of vibration peaks having the above-mentioned frequencies are generated simultaneously at the frequencies up to and including a plurality of frequency peaks that are an integral multiple of the basic frequency due to the drive system or drive shaft of each small-diameter roll 16, 17. When detected, it is determined as 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, an abnormal vibration detection method 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 abnormal detection method in cold rolling according to the first embodiment, but the object of vibration detection in the vibration detection step (step S1). The rolling stand STi and the small diameter rolls 16 and 17 are different from the abnormality detection method in the cold rolling according to the first embodiment in that the rolling stand STi and the small diameter rolls 16 and 17 are limited as follows.
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 preceding rolling stand ST4, 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 preceding rolling stand ST4 and on the exit side of the final rolling stand ST5.

  The present inventors have found that abnormal vibrations that occur in the front stand, specifically, the rolling stands ST1 to ST3 that do not have a final sheet thickness, appear as a variation in sheet thickness at a level that does not cause a problem in the product. We focused on the fact that many marks do not appear. Therefore, the rolling stand STi that is the object of vibration detection in the vibration detection step (step S1) is narrowed down to the rear stage stand to be the final rolling stand ST5 and the preceding rolling stand ST4, and vibration is detected in the vibration detection step (step S1). The small-diameter rolls 16 and 17 to be detected were small-diameter rolls 16 and 17 installed between the final rolling stand ST5 and the preceding rolling stand ST4 and on the exit side of the final rolling stand ST5.

As mentioned above, although embodiment of this invention has been described, this invention is not limited to this, A various change and improvement can be performed.
For example, if the noise ratio in the frequency signal does not matter much, in the frequency analysis step (step S3), the vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi within a specific time t1, A plurality of results of frequency analysis of vibration displacement, vibration speed or vibration acceleration of each gear box 15 and vibration displacement, vibration speed or vibration acceleration of each small-diameter roll 16, 17 are held. 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 to average the amplitude of the same frequency of the selected plurality of data. Is not necessarily.

  In this case, in the abnormal vibration determination step (step S5), the vibration signal processing computer 22 performs vibration displacement, vibration speed or vibration acceleration of each mill housing 11 of each rolling stand STi, vibration displacement and vibration of each gear box 15. The results of frequency analysis of the speed or vibration acceleration and the vibration displacement, vibration speed or vibration acceleration of the small diameter rolls 16 and 17 are the drive systems of the small diameter rolls 16 and 17 calculated in the basic frequency calculation step (step S4) or It suffices to determine whether or not the threshold value is exceeded in the vibration frequency region centered on an integral multiple of the fundamental frequency caused by the drive shaft. In the abnormal vibration determination step (step S5), the result of the frequency analysis step is averaged. The small-diameter rolls 16, 1 calculated in the fundamental frequency calculation step (step S4) Condition is determined whether exceeds a threshold value in the vibration frequency range centered at integer multiples of the fundamental frequency due to the driving system or the drive shaft is not necessary.

Further, in the abnormal vibration determination step (step S5), the drive system of each of the small-diameter rolls 16 and 17 in which the amplitude of the same frequency of the plurality of selected data averaged as a result of the frequency analysis is calculated. Alternatively, when the above-mentioned threshold value is exceeded in the vibration frequency region centered on an integral multiple of the fundamental frequency due to the drive shaft, the amplitude value is 50% to 90% of the amplitude value at the frequency exceeding the above-described 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 abnormality is not necessarily required.
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 plurality of selected data averaged as a result of the frequency analysis exceeds the aforementioned threshold value. Alternatively, the condition for determining abnormal vibration is not always necessary when there are at least two frequencies that are an integral multiple of the fundamental frequency due to the drive shaft, and even if there is one such frequency, it may be determined that there is abnormal vibration. Good.

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

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 Invention Examples 1 to 5.
(First embodiment)
The experiment is performed on the rolling equipment shown in FIG. 1, that is, a tandem rolling mill including five rolling stands ST1 to ST5. A vibration detector 18 including a piezoelectric element is provided in the mill housing 11 of each rolling stand STi, and a reduction gear. A vibration detector 19 made of a piezoelectric element is placed in each gear box 15 storing the vibration, and a vibration detector 20 made of a piezoelectric element is placed on each of the small-diameter rolls 16 and 17 disposed between the rolling stands and on the exit side of the final rolling stand ST5. Attached.

The test material is made of low carbon steel, a plurality of ones having an entrance side thickness of 2.9 mm for the rolling stand ST1, an exit side thickness of 0.8 mm for the rolling stand ST5, and a steel plate width of 1240 mm are used, and the rolling speed is 10 m / sec. It was.
In the first example, the vibration abnormality detection method according to Comparative Examples 1 and 2 and the vibration abnormality detection method according to Invention Examples 1 and 2 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 in which a uniform threshold is provided for a frequency component due to abnormality in each bearing or the like). Yes, frequency analysis of the vibration speed of the small-diameter roll between the rolling stands ST3 to ST4 was performed.

  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 the frequency analysis of the vibration speed 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 seconds, and a plurality of results of frequency analysis of the vibration speed of the small diameter rolls 16 and 17 between the rolling stands ST3 to ST4 within the specific time t1 = 10 seconds are held. Among a plurality of the results held, a plurality of rotation speeds of the small-diameter rolls 16 and 17 measured within a specific range (± 15 m / sec with respect to the operation speed) are measured within a continuous specific time t2 (10 sec). Data was selected, and the amplitude of the same frequency of the selected data was averaged. When the abnormal vibration is determined, the amplitude of the same frequency of the selected plurality of data averaged as a result of the frequency analysis is calculated as the drive system or drive shaft of each of the small-diameter rolls 16 and 17. When the threshold value was exceeded in a vibration frequency region centered on an integer multiple of the fundamental frequency caused by the vibration, it was determined as abnormal vibration.

  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 the frequency analysis of the vibration speed of the small-diameter rolls 16 and 17 between the rolling stands ST3 to ST4 was performed. When performing this frequency analysis, the amplitude of the same frequency of a plurality of selected averaged data, which is the result of the frequency analysis, is based on the drive system or drive shaft of each of the small-diameter rolls 16 and 17. When the threshold value is exceeded in the vibration frequency region centered on an integer multiple of the frequency, the abnormality determination is performed when the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the above-described threshold value is 10 Hz or less. It was.

  In the evaluation of abnormal vibration, whether vibration is detected and determined as abnormal vibration, or after taking a rolled steel sheet about 500 mm and measuring the thickness with a contact-type thickness gauge, the fluctuation of the thickness of the corresponding frequency To what extent the pitch was generated, and after the alloying zinc plating, a grinding stone inspection was performed, and a chatter mark having a pitch of the corresponding frequency was visually evaluated. The evaluation results are shown in Table 1.

  In Table 1, “x” in the evaluation results indicates that vibration was detected and an abnormality was determined, the plate thickness variation was 1 μm or more, the chatter mark was clearly visible, and Δ was the plate thickness variation was less than 1 μm. The chatter mark appears thin, ○ indicates that no vibration was detected and an abnormality was not judged, and the chatter mark could not be confirmed.

FIG. 3 shows the result of the frequency analysis of the vibration abnormality detection method according to Comparative Example 1, FIG. 4 shows the result of the frequency analysis of the vibration abnormality detection method according to Example 1 of the present invention, and FIG. 4 shows the vibration abnormality detection method according to Comparative Example 2. FIG. 5 shows the result of the frequency analysis, and FIG. 5 shows the result of the frequency analysis of the vibration abnormality detection method according to Example 2 of the present invention. In FIG. 3 to FIG. 5, an integer multiple pitch of the outer ring flange frequency of the bearing is indicated by arrows.
Referring to FIG. 3, in the vibration abnormality detection method according to Comparative Example 1, since the noise N exceeds the threshold, vibration was detected and abnormality was determined as shown in Table 1, but chatter marks could be confirmed. First, false detection was caused by noise N. In the vibration abnormality detection method according to Comparative Example 1, there are many noise components in vibration, and if the threshold value is set high, chatter marks 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 averaged vibration speed amplitude, which is the result of the frequency analysis, is an integer multiple pitch (4 In the frequency region of 2 times and 5 times), the abnormal vibration caused by the drive system or drive shaft of each small-diameter roll 16, 17 was detected. Referring 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 judged, so the chatter mark could be clearly confirmed.
In the vibration abnormality detection method according to Example 1 of the present invention, since the data is averaged, noise components other than abnormal vibration can be reduced as shown in FIG. Abnormal vibration can be detected.

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 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 chatter marks could not be confirmed, resulting in false detection.
On the other hand, in the vibration abnormality detection method according to Example 2 of the present invention, as shown in FIG. 5, the frequency width of the amplitude value of 70% of the amplitude value at the frequency exceeding the threshold is 50 Hz. Not excluded. For this reason, as shown in Table 1, the vibration was not detected and the abnormality was not determined. In addition, the chatter mark could not be confirmed, and it was possible to accurately determine that the vibration was not abnormal.

(Second embodiment)
The experiment is performed in the rolling equipment shown in FIG. 1, but the rolling stand that is the target of vibration detection is the final rolling stand ST5 and the preceding rolling stand ST4, and the small diameter roll that is the target of vibration detection is The small diameter rolls 16 and 17 are provided between the final rolling stand ST5 and the preceding rolling stand ST4 and on the exit side of the final rolling stand ST5. And the tension | tensile_strength between all the rolling stands STi was 120 Mpa or more, and was 50 Mpa on the exit side of final rolling stand ST5.
The test material is made of low carbon steel, a plurality of ones having an entrance side thickness of 2.9 mm for the rolling stand ST1, an exit side thickness of 0.8 mm for the rolling stand ST5, and a steel plate width of 1240 mm are used, and the rolling speed is 10 m / sec. It was.

In the second example, the vibration abnormality detection method according to Comparative Examples 3 and 4 and the vibration abnormality detection method according to Invention Examples 3 to 5 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 in which a uniform threshold is provided for a frequency component due to abnormality in each bearing or the like). Frequency analysis of the vibration speed of the small-diameter rolls 16 and 17 between the rolling stands ST4 to ST5 and 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 technique of Patent Document 1 is applied to a small-diameter roll, and a small-diameter roll (roll having a high tension of 120 MPa or more) between the rolling stands ST4 to ST5 and the exit side of the final rolling stand ST5. Frequency analysis of the vibration speed of a small-diameter roll (a roll having a low tension of less than 120 MPa).

The vibration abnormality detection method according to Example 3 of the present invention is the abnormal vibration detection method according to the second embodiment, and vibrations of the small-diameter rolls 16 and 17 between the rolling stands ST4 to ST5 and the exit side of the final rolling stand ST5. Frequency analysis of speed was performed. When performing this frequency analysis, it is caused by 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 a plurality of selected averaged data that is the result of the frequency analysis exceeds a threshold value. When there are at least two frequencies that are integral multiples of the fundamental frequency to be detected, it is determined that the vibration is abnormal.
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 vibrations of the small-diameter rolls 16 and 17 between the rolling stands ST4 to ST5 and the exit side of the final rolling stand ST5. Frequency analysis of speed was performed. When performing this frequency analysis, it is caused by 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 a plurality of selected averaged data that is the result of the frequency analysis exceeds a threshold value. When there are at least two frequencies that are integral multiples of the fundamental frequency to be detected, it is determined that the vibration is abnormal.

Furthermore, the vibration abnormality detection method according to Example 5 of the present invention is the same as the abnormal vibration detection method according to the second embodiment, in which the small-diameter rolls 16 and 17 to be subjected to frequency analysis are wound around the metal band 12 at an angle equal to or greater than a certain value. Of the small-diameter rolls 16 and 17 attached, the small-diameter rolls 16 and 17 between the rolling stands ST4 to ST5 in which the tension of the metal strip 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. The rolls 16 and 17 (the tension is less than 120 MPa and low) are excluded from the frequency analysis target.
In the evaluation of abnormal vibration, about 500mm of steel sheet after rolling is detected or the rolled steel sheet is collected, and the thickness is measured with a contact-type thickness gauge. Also, after the alloying zinc plating, a grinding wheel inspection was performed, and a chatter mark having a pitch of the corresponding frequency was visually evaluated. The evaluation results are shown in Table 2.

  In Table 2, “x” in the evaluation results indicates that vibration was detected and an abnormality was determined, the plate thickness variation was 1 μm or more, the chatter mark was clearly visible, and Δ was the plate thickness variation was less than 1 μm. The chatter mark appears thin, ○ indicates that no vibration was detected and an abnormality was not judged, and the chatter mark could not be confirmed.

  Further, FIG. 7 shows the frequency analysis result of the vibration abnormality detection method according to Comparative Example 3 (result of the frequency analysis of the small diameter roll between the rolling stands ST4 to ST5), and FIG. 7 shows the frequency analysis of the vibration abnormality detection method according to Example 3 of the present invention. 8 (result of frequency analysis of small diameter roll between rolling stands ST4 to ST5), FIG. 8 shows the result of frequency analysis of vibration abnormality detection method according to Example 4 of the present invention (frequency of small diameter roll between rolling stands ST4 to ST5). FIG. 9 shows the results of analysis), FIG. 10 shows the results of frequency analysis of the vibration abnormality detection method according to Comparative Example 4 (results of frequency analysis of the small diameter roll on the outlet side of the final rolling stand ST5), and FIG. FIG. 11 shows the result of frequency analysis of the vibration speed 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, an integer multiple pitch of the outer ring flange frequency of the bearing is indicated by arrows.

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

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 a plurality of selected averaged data that is the result of frequency analysis has a threshold value. As shown in Table 2, there are at least four (2 times, 3 times, 4 times, and 5 times) frequencies that are integral multiples of the fundamental frequency due to the drive system or drive shaft of each small-diameter roll 16, 17 Furthermore, vibration was detected with a small-diameter roll between the rolling stands ST4 to ST5, and it was determined as abnormal vibration. Chatter marks were confirmed, and 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, the amplitudes of the same frequency of a plurality of selected averaged data that are the results of frequency analysis exceed a threshold value. There is only one (three times) frequency that is an integral multiple of the fundamental frequency due to 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 to ST5. The vibration could not be detected and the vibration was not determined. The chatter mark was not confirmed, and it was possible to accurately determine that the vibration was not abnormal.

  Further, in the vibration abnormality detection method according to Comparative Example 4, as shown in FIG. 10, despite the low tension (less than 120 MPa) of the metal strip 12 wound around the small-diameter roll on the exit side of the final rolling stand ST5. The amplitude of vibration at a frequency that is an integral multiple (10 times) of the fundamental frequency due to the drive system or drive shaft of each small-diameter roll 16, 17 exceeds the threshold value, and as shown in Table 2, the final rolling stand ST5 The vibration of the small roll on the side was detected and determined as abnormal vibration. However, the chatter mark was not confirmed at this time, and it was a false 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 strip 12 wound on 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. Thus, even if 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 small-diameter roll 16, 17 exceeds the threshold value, 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 strip 12 is not less than a certain level (for example, 120 MPa or more), the metal wound around the small-diameter roll on the outlet side of the final rolling stand ST5. When the tension of the belt 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 detected. , Not determined as abnormal vibration. Moreover, 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 Band 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 (6)

An abnormal vibration detection method in cold rolling in which a metal strip is rolled by a cold rolling mill having one or more rolling stands,
Vibration detectors installed at at least one location of each rolling stand, and each small-diameter roll that is placed between each rolling stand and on the exit side of the final rolling stand, and in which the metal strip is wound at an angle of a certain value or more And a vibration detection step for detecting vibration displacement, vibration speed or vibration acceleration of each part of each rolling stand and each small diameter roll,
A roll rotation speed detection step for detecting a rotation speed of each small diameter roll by means of a speed detector installed on the small diameter roll or the rolling roll of the rolling stand,
Frequency analysis step for performing frequency analysis of vibration displacement, vibration speed or vibration acceleration of each part of each rolling stand and each small diameter roll detected in the vibration detection step;
Based on the vibration displacement, vibration speed 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, due to the drive system or drive shaft of each small-diameter roll A fundamental frequency calculating step for calculating a fundamental frequency to be performed;
Abnormal vibration when the result of the frequency analysis step exceeds a threshold in a 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. The abnormal vibration detection method in cold rolling characterized by including the abnormal vibration determination step which determines. 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 held, and a plurality of results are held. Among the results of the frequency analysis, a plurality of data selected in a continuous specific time in which the rotation speed of each small-diameter roll obtained in the roll rotation speed detection step falls within a specific range is selected, Average the amplitude of the same frequency in the data of
In the abnormal vibration determination step, the averaged amplitude as a result of the frequency analysis step is centered on an integral multiple of the fundamental frequency derived from the drive system or drive shaft of each small-diameter roll calculated in the fundamental frequency calculation step. The method for detecting abnormal vibration in cold rolling according to claim 1, wherein an abnormal vibration is determined when a threshold value is exceeded in the vibration frequency region.   In the abnormal vibration determination step, the averaged amplitude as a result of the frequency analysis step is set to the threshold value in a 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. If the frequency width of a specific amplitude value set within a range of 50 to 90% of the amplitude value at a frequency exceeding the threshold value is less than a certain value when it exceeds the threshold value, it is determined that the vibration is abnormal. The method for detecting abnormal vibration in cold rolling according to claim 2.   In the abnormal vibration determination step, the averaged amplitude as a result of the frequency analysis step exceeds the threshold value, and the basic frequency caused by the drive system or drive shaft of each small-diameter roll calculated in the basic frequency calculation step. The method for detecting abnormal vibration in cold rolling according to claim 3, wherein when there are at least two frequencies that are integer multiples, the vibration is determined as abnormal vibration.   The rolling stand subject to vibration detection in the vibration detecting step is a final rolling stand and the preceding rolling stand, and the small diameter roll subject to vibration detection in the vibration detecting step is the final rolling stand and its The abnormal vibration in cold rolling according to any one of claims 1 to 4, wherein the roll is a small-diameter roll installed between the previous rolling stand and the exit side of the final rolling stand. Detection method.   The small-diameter roll that is the target of frequency analysis in the frequency analysis step is limited to the small-diameter roll in which the tension of the metal band is equal to or greater than a certain value among the small-diameter rolls in which the metal band is wound at an angle of a certain value or more. The method for detecting abnormal vibration in cold rolling according to any one of claims 1 to 5, wherein:

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