ROLL-BITE DEFORMATION DURING THE HOT-ROLLING OF STEEL STRIP

Heat transfer and deformation during the hot rolling of steel strip has been analysed with the aid of a coupled finite-element model based on the flow formulation approach. Sliding friction is assumed to prevail along the arc of contact and the effect of roll flattening on the roll radius has been incorporated. The model has been verified by comparing the predicted temperature rise at the centre due to deformation with measurements on a test sample in the laboratory. The model has shown that the deformation in the roll bite is inhomogeneous with the strain rate reaching values approximately 5-10 times the nominal strain rate just beneath the surface due to redundant shear. The maximum rate is attained at the entrance to the roll bite just beneath the rolls. The corresponding strain distribution through the thickness is also non-uniform, and the effective strain is equal to the nominal strain only in the central two-thirds of the strip and increases toward the surface. When strain hardening is explicitly allowed for in the constitutive equation it decreases the computed strain rates and strains. The model-predicted roll forces have been compared with measured values.