Effect of Friction on Tandem Cold Rolling Mills Chattering

Chatter phenomenon in the rolling mills is the undesired mechanical vibrations which reduces the productivity and quality of the products. Many studies have led to the point that friction is one of the most effective factors incurring chatter. In this paper, a chatter simulation model for the tandem cold rolling mills based on the well-known Coulomb and the Tresca friction models is proposed. By considering the effects of the material strain-hardening and the elastic deformation of the work roll, the model relaxes certain assumptions. The simulation results are verified by comparing to experimental data obtained from Mobarakeh Steel Company. In addition, a numerical method is developed to introduce a relationship between the Tresca friction factor and the Coulomb friction coefficient. A parametric study on the effects of friction coefficients of the two stand rolling mill on the chatter critical speed is conducted. The results show that an optimal setting of friction coefficients improves the process efficiency. Under the operating conditions stated in this paper, the friction coefficient of the second stand should be increased as much as possible in order to get closer to its optimum point. The optimum friction coefficient of the first stand depends on the friction coefficient of the second stand.