Mathematical and numerical analysis of cross-directional control for SmartCrown rolls in strip mill

The advanced SmartCrown technology, one of the Variable Crown by Axial Shifting (VCAS) technologies, can significantly enhance the cross-directional control capability of strip mill, and alleviate or eliminate complex high-order flatness defects. In this paper, the mathematical modeling for SmartCrown system including roll contour design and roll-gap profile comparison based on shape pattern recognition is implemented. The results indicate that the unloaded roll-gap morphology formed by the SmartCrown roll is affected by the contour angle in terms of the spatial frequency distribution. When the contour angle is less than 30 degrees, the SmartCrown roll contour is basically coincident with the continuous variable crown (CVC) roll contour, and its capacity to control the quartic crown is almost zero. Meanwhile, a 3D elastic-plastic finite element analysis (FEA) model of 6-high SmartCrown mill for strip rolling is established. The accuracy and convergence of the numerical model are verified by rolling force data and targeted damping application. The relative errors of roll force between the simulated result and the theoretical value are less than 5.0% even with the limitation that the exit strip thickness should not be less than 1.50 mm. The validated model is applied to investigate the cross-directional characteristics of the SmartCrown-contoured intermediate roll shifting (IMR Shifting) in terms of inter-roll pressure, thickness profile and flatness control of rolled strips with different widths.