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Rolling and Metal Science
ArticleName Study of causes of vibrations in a continuous cold rolling mill
DOI 10.17580/chm.2022.03.09
ArticleAuthor V. A. Pimenov
ArticleAuthorData

Novolipetsk Iron and Steel Works, Lipetsk, Russia:

V. A. Pimenov, Cand. Eng., Head of Technological Projects of the Directorate for Development of New Process Technologies, e-mail: pimenov_va@nlmk.com

Abstract

Abstract: A retrospective review of studies of the problem of vibrations (chatter) during highspeed cold rolling at the five-stand mill 2030 of the Novolipetsk Iron and Steel Works, as well as the results of operation of vibration diagnostics and speed control systems at the mill, is presented. As part of the continuation of research on the 2030 mill, a series of experimental rolling of thin strips with chatter provocation was carried out, a statistical analysis of the dynamics of technological parameters and vibration accelerations of the roll chocks in time and frequency (spectral) representations was performed. It is shown that the reason for the development of the chatter is the mutual synchronization of vibrations of stands at the frequency corresponding to the natural frequency of the vertical vibrations of the housing posts stretching. The dynamics of the oscillations phases ratio of the stands has been studied and it has been established that when the frequencies are synchronized and the phases of neighboring stands coincide, the amplitudes of their oscillations increase sharply, indicating the beginning of the chatter. A criterion for violation of the stability of the rolling process is proposed, which makes it possible to diagnose the critical level of vibrations and the moment of occurrence of the chatter. A mathematical model of vibrations of the stand during rolling is presented, taking into account the nonlinear damping of the dynamic deformation zone, on the basis of which the dependence of the amplitude of synchronized vibrations of the stand on the magnitude of disturbances and technological parameters is obtained using the Van der Pol method. The adequacy of the relation obtained was confirmed during a series of experimental rolling with varying technological parameters, which made it possible to increase the maximum rolling speed without the chatter to 25%. The results obtained can be used to stabilize the technological process and increase the productivity of cold rolling, when creating systems for diagnosing vibrations and controlling continuous mills.

NLMK workers A. V. Morozov, N. A. Dikarev, Yu. K. Slaby, A. V. Litvinov, Yu. A. Tsukanov, M. E. Orekhov, et al took part in carrying out the experimental rolling.

keywords Cold rolling, vibrations, instability, experiment, spectral density, synchronization, mathematical model
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