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.

An active method suppressing rolling mill vibration: disturbance estimation and compensation algorithm

The rolling mill vibration not only seriously causes the strip thickness heterogeneity, but also damages the rolling mill equipment and its electrical components. Existing vibration suppression methods are passive and mainly tune mechanical, hydraulic, electrical and rolling process parameters. A new active vibration suppression method was thus proposed using the disturbance estimation and compensation algorithm. Firstly, the hydraulic-mechanical coupling model of the rolling mill vibration was established, and an active vibration suppressor was designed based on the extended state observer. Then, through the numerical simulation, it is found that the vibration energy is reduced by 35.3% using the vibration suppressor, and the vibration suppressor is valid when the vibration frequency is lower than 60 Hz Finally, the vibration suppressor was applied to the in-site manufacturing, and the expected vibration suppression was obtained. The method makes the produced steel strip have more uniform thickness and further significantly increases the finished product ratio.

Influence of mill modulus control gain on vibration in hot rolling mills

The rolling mill vibration is characterized by the coupling effects among mechanical,electrical,hydraulic and interfacial subsystems.The influence of the mill modulus control gain in automatic gauge control on the vibration in hot rolling mills was investigated.Firstly,an experiment related to the mill modulus control gain was carried out in the hot rolling mill process,and it was found that the rolling mill vibration increases with the mill modulus control gain.Then,based on the Sims rolling force method,the coupling dynamic model was established to explain this phenomenon.Finally,the influence of mill modulus control gain on the vibration was analyzed numerically on the basis of the coupling dynamic model.Moreover,the agreement between the experimental results and the simulation results was confirmed and the measure reducing the mill modulus control gain was obtained to relieve mill vibration.