Chatter Marks and Vibration Analysis in a S6-High Cold Rolling Mill

S6-high rolling mill is an advanced mode to work the steel: it allows the use of very small work rolls laterally guided by individually adjustable side support rolls, which are supported by two rows of roller bearings mounted in cassettes. In this paper the vibrations generated in a S6-high cold rolling mill are analyzed with the aim to investigate the problem of skid marks generation. Such marks are regular, parallel marking across the width of strip metal that not only significantly affects the mill performance, but also reduces surface quality of the strip steel. The defects of the strip are the consequence of insurgence of vibrations, generically denominated ‘chatter’. The analyzed rolling mill has six rolls able to roll steel strip coming directly from hot rolling mill train. The purpose of the present work is to identify the reason of the excitation in order to limit the problem. A solution based on empirical observations, vibration analysis and considerations of a model is proposed.