JPH0635004B2 - Method for detecting chattering in cold rolling mill - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a chattering detection method in a cold rolling mill.

In a cold rolling mill, abnormal vibration (this is called chattering) occurs in the rolling mill during high-speed rolling of thin and hard materials,
It causes tension fluctuation and gauge fluctuation. As a result, quality and yield are deteriorated due to gauge fluctuation, and further, a strip breakage accident occurs.

Therefore, as a method for detecting this abnormal vibration, for example, Japanese Patent Laid-Open No. 50-84445 has been proposed. In this system, a vibration acceleration detector is attached to a backup roll chock, a work roll chock, etc., and abnormal vibration is detected when the detected value exceeds a certain value. However, this method is often disturbed by noise caused by damage to the roll bearing, rattling between the chock and the housing, and the like. Further, the occurrence of chattering is related to the natural vibration of the rolling mill, and its frequency is generally within the range of 100 to 200 Hz, and there is a problem that the acceleration detection of vibration is not necessarily suitable for the frequency within this range. is there.

In the first place, chattering is self-excited vibration that oscillates at the natural frequency of the roll system including rolling work rolls, backup rolls, stands, etc. It is considered to be a neutral shift. Therefore, the phenomenon is different from the chatter mark in which the roll system is vibrated due to scratches on the backup roll, imbalance of the roll drive system, or the like.
The inventor has further studied and analyzed the above-mentioned known contents, and the chattering is represented by the vibration model shown in FIG. 3 and is in its first-order mode.

The vibration equation in this case is m + kx = Fo + Fsinωt where x: Vertical displacement Fo: Rolling load Fsinωt: Exciting force due to poor lubrication, etc.
The natural frequency of the roll system does not change significantly,
It is approximately 100 to 200 Hz. It was found from a modal analysis that when chattering occurs, the amplitude of vibration is relatively large in the horizontal direction near the stand pass line.

On the other hand, as is clear from the above vibration equation, it is considered that chattering can be detected not only as a vibration phenomenon but also as an apparent change in rolling load. In fact, a proposal based on this idea is shown in, for example, Japanese Examined Patent Publication No. 54-38912. However, the change due to chattering of the rolling load and rolling speed proposed here is practically difficult to detect as shown in Fig. 4 (a) and (b), even if only the frequency band is focused. In addition, since harmonic components (second order 100 or 120 Hz, third order 150 or 180 Hz) of the power supply frequency (50 or 60 Hz) and the like come in as noise, for example, the chattering frequency band is focused and this change is expanded. Even so, there is a problem that the noise is also magnified at the same time, and the judgment is very ambiguous in reality.

According to the present inventor, the apparent load fluctuation due to chattering is rather remarkable in the tension between the stands (Fig. 4 (c)). This tension fluctuation increases the horizontal vibration of the stand in combination with the above findings. , And found that it facilitates detection of chattering due to vibration in this direction.

Further, in the case of comparative analysis of such low or intermediate frequency vibrations of about 100 to 200 Hz, it is preferable to detect the vibration velocity as shown in FIG. 7, and even if the vibration acceleration is detected, the vibration velocity is detected. It is preferable to convert to and compare.

It is an object of the present invention to provide a chattering detection method capable of solving the above-mentioned problems based on the above knowledge.

A feature of the chattering detection method of the present invention is that a vibration velocity sensor is attached to a housing of a cold rolling mill, a signal of this sensor is passed through a filter that passes only a signal in a natural vibration band of the rolling mill, and an output signal passed through this filter is passed. The chattering is detected by.

An embodiment of the present invention will be described below with reference to the drawings. Reference numeral 2 in the figure denotes a sensor attached to the rolling mill housing 1 for detecting a horizontal vibration velocity. It is best to detect the horizontal vibration when viewed from the vibration mode of the housing 1 during chattering, but the vertical vibration may be detected by the vibration speed sensor 2 '.

The vibration waveform of the vibration sensor 2 is widened by the widening device 3.

The amplified signal is passed through a filter 4 that passes only the signal in the natural frequency band of the rolling mill. This is done by paying attention to chattering occurring in the natural frequency band of the rolling mill, and this frequency is generally in the range of 100 to 200 Hz. The natural frequency of the rolling mill of this embodiment is 120 to 130H.
It was z. The signal waved by the bandpass filter 4 is rectified by the rectification circuit 5 and further smoothed by the smoothing circuit 6. The smoothed signal is sent to the arithmetic circuit 7. This arithmetic circuit 7
Is a microcomputer, for example, which compares the digitized chattering vibration signal with a preset reference value to issue an alarm or an automatic deceleration command.

A vibration acceleration sensor may be used instead of the vibration speed sensor, and the speed may be integrated and corrected to the speed, and similarly, the amplification and band-pass filtering may be performed.

The chattering detection method of the present invention is as described above, and the vibration speed sensor is attached to the housing, and the chattering is detected through the filter that passes the detection signal only in the natural frequency band of the rolling mill. It is possible to detect chattering with high accuracy without affecting the operation.

An example of chattering detection by this method is shown in FIG. Each detected amount is a waveform after passing through a band filter of 100 to 200 Hz. As shown in the figure, not only the level of vibration velocity changes clearly when chattering occurs, but also the symptoms appear before it occurs, which is an effective method that can be reflected in the actual operation.

Also, as is clear from this case, a remarkable change is observed in the fluctuation of the tension between the stands. Therefore, it may be considered that this is the detected amount, but it often changes due to factors other than chattering, and there is a difference from the reliable detected amount in which a clear change such as the vibration speed of the stand stably occurs.

Looking further at the relationship with the roll rotation speed, as shown in FIG. 6, it is completely unrelated, that the frequency is constant regardless of the size of the rotation speed, and fluctuations that agree with the rotation cycle are recognized. It was not confirmed that it was confirmed that it was a phenomenon different from Chatamark.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a mounting state of a vibration speed sensor on a rolling mill housing, and FIGS. 2 (a) and 2 (b) are explanatory views showing an example of a detection signal processing system and waveforms at respective stages, FIG. 3 is an explanatory diagram of a vibration model, FIGS. 4 (a), (b), and (c) are explanatory diagrams showing changes in rolling load, rolling speed, and tension between stands due to chattering, and FIG. FIG. 6 is an explanatory diagram showing the state of chattering detection based on the vibration speed of the method of the present invention in comparison with the change in tension between stands, rolling load, and rolling speed, and FIG. 6 shows the relationship between the roll rotation speed and the chattering vibration frequency. FIG. 7 is an explanatory diagram showing the frequency characteristic of the basic vibration amount. 1 ... Housing, 2, 2 '... Vibration speed sensor, 4 ... Band filter, 7 ... Arithmetic circuit.

Claims (1)

[Claims] 1. A vibration velocity sensor is attached to a housing of a cold rolling mill, a signal of this sensor is passed through a filter which passes only a signal in a natural frequency band of the rolling mill, and chattering is detected by an output signal passed through this filter. A method for detecting chattering in a cold rolling mill, comprising: