Statically determinate characteristics of microdisplacement in a four-high mill

Contemporary high-speed four-high mills are statically indeterminate structures because of microdisplacement of their components. This displacement involves movement of the chock in the stand window. In this paper, regular micro-scale dynamic cross between the work roll and the back-up roll is discussed. This dynamic cross results in excessive axial force and causes frequent burning loss of the end-thrust bearing of the work roll. A gyroscopic effect and a propelling mechanism due to friction force are proposed as the causes of the dynamic cross. Experiments confirmed the existence of micro-scale dynamic cross throughout the whole rolling process. To prevent dynamic cross between the rolls, a roll system that is a statically determinate structure has been designed. This markedly decreases burning loss of the end-thrust bearing.