Suppression strategies of chatter in the cold rolling by regulating interface friction based on dynamic stability analysis

In the process of cold rolling, the interfacial friction between strip and rolls is necessary and key for ensuring smooth rolling, and also one of significant factors causing chatter instability. In order to achieve high-speed and stable rolling, the issue how the friction state is reasonably set and dynamically regulated is very important, but it still lacks enough theoretical investigation and applicable supports. This paper firstly focuses on establishing a mathematical model of friction coefficient which characterizes the interfacial friction state and comprehensively takes various influencing factors into consideration, such as the surface roughness of rolled strip and rolls, rolling speed, lubrication conditions, and oil film thickness. Then, the critical friction coefficient related to chatter is calculated based on the Routh stability condition from the structure-process coupling dynamics model of rolling mill, and the stable working region is determined through exploring the relationship between critical friction coefficient and rolling speed. Finally, according to the dynamic stable region of critical friction coefficient, three friction-dependent chatter suppression strategies are presented and applied by regulating rolling speed, hybrid lubrication emulsion flow quantity, and roughness of work rolls individually. These suppression strategies provide guidance for achieving high-speed rolling and improving production efficiency in actual production.