Chatter of the stands of the cold Rolling tandem mill 2000 of the Magnitogorsk Iron and Steel Works

Abstract

One of the problems of cold rolling of thin strips is self-excited chatter vibrations, which lead to the appearance of various defects. High-frequency self-oscillations can lead to defects related to surface quality, low-frequency ones with high amplitude levels can lead to gusts of thin bands or even severe accidents of the rolling mill itself. As a rule, self–oscillations occur suddenly at high rolling speeds, more than 20 m / s and thin strips, the thickness is usually around 300-700 microns. For the normal operation of the rolling mill, it is necessary to use special systems for monitoring the vibration state and preventing the occurrence of self-oscillations. The control system for exceeding the critical vibration level generates signals from the automated control system of the mill to eliminate self-oscillations. The critical vibration level is determined by the spectral composition using the fast Fourier transform (FFT). When self-oscillations occur, lowfrequency components from 5 to 20 Hz prevail, frequencies in the range of the third octave from 100 to 200 Hz and frequencies of the fifth octave from 400 to 800 Hz. The cold rolling mill 2000 of the Magnitogorsk Iron and Steel Works combines a tandem five-cell mill and a continuous etching unit. There is no regular vibration monitoring system at the mill, warning and elimination of self-oscillations occurs in manual mode. With the use of research vibration equipment, experimental studies have been conducted on the possibility of using technological parameters to control and prevent the occurrence of self-oscillations. The moment of occurrence of self-oscillations can be controlled by the vibrations of the hydraulic tensioning device (GNU) of the mill. Processing of the vibration displacement signal of the measuring channel of the GNU FFT