Vibrations of tandem cold rolling mill: coupled excitation of rolling force and variable stiffness of fault-free back-up roll bearing

Vibration issues of a five-stand tandem cold rolling mill were found in the steel production practice, and the experimental observation and numerical analysis indicated that the vibrations were related to the back-up roll bearing. The results were validated by replacing the back-up roll bearing with the new bearing resulting in 30% decline in vibration amplitude. Models describing the four-row cylindrical roller bearing and the vertical system of the cold rolling mill including the bearing were established. Moreover, the mechanisms of periodic excitation and amplified vibrations of fault-free bearing were explained theoretically, along with the analysis of bifurcation behaviors of the motion states of the roller bearing and rolling mill system. It is found that the energy transmitted between vibrations with different frequencies if multiple excitation frequencies in the rolling mill system were close.