Dynamic analysis of vibration stability in tandem cold rolling mill

Tandem cold rolling mills are comprehensive dynamic systems coupling with structure and rolling technology. A frequent problem is mill chatter, often occurring when rolling hard, thin materials at high speed and affecting the quality of the strip. In this paper, a dynamic increment model for chatter in a Universal Crown Control mill (UCM mill) is proposed with the considering of strip hardening, elastic deformation of the work roll, non-linear friction, transfer delay of the strip, and dynamic coupling effect of tension between adjacent stands. Mathematically, this model is based on the Taylor series expansion of the Bland-Ford-Hill rolling force equation. The comparative results of both simulation and experimental data show that this chatter model has a high accuracy. A novel, time-varying stability criterion is proposed to evaluate mill stability. Further study is provided on the optimal friction coefficient and reduction ratio required to increase the critical rolling speed and vibration stability in a tandem cold rolling mill. This mathematical criterion is validated by comparing the actual rolling speed with the calculated critical rolling speed. The present work provides a more accurate prediction of mill chatter and a basis for optimal design of rolling conditions.