Research on the Flatness Control Performance and Parameter Influence Law of Four-High Skin Pass Rolling Mill

Strip flatness is one of the important quality indicators of strip steel, and flatness control is the core technology in cold rolling. However, there is a lack of comprehensive research on the influencing factors and methods to improve the flatness of the four-high skin pass rolling mill. Therefore, a systematic study on flatness control performance of the four-high skin pass rolling mill based on a unified finite element model under multi-variate and multi-evaluation indicators was conducted in this paper. The loaded roll gap crown control domain, the lateral stiffness of the roll gap, and the flatness control efficiency curve were analyzed. Besides, the effect of important parameters on the roll gap shape and the influence of high tension on strip flatness were investigated. The results indicate that the loaded roll gap crown control domain area increases with the increase in strip width, rolling force, and bending force. This implies that the rolling mill has better flexibility in adjusting the roll gap shape, demonstrating stronger flatness control capabilities. The area of the loaded roll gap crown control domain is not affected by the roll diameter. The lateral stiffness of the roll gap gradually decreases, remains constant, or increases slightly with the increase in strip width, bending force, and roll diameter. The roll gap crown increases with the increase in strip width and rolling force. The roll gap crown decreases with the increase in bending force and roll diameter. Effective control and utilization of tension are crucial during rolling, but the loaded roll gap becomes less smooth under high tension, compromising the stability of the rolling mill. The above research contributes to enhancing the flatness control capabilities of the four-high skin pass rolling mill, providing data references and theoretical support for developing reasonable rolling process strategies and flatness control methods.