Investigations into Roll Thermal Fatigue in Hot Rolling

In the current paper, a study into the mechanism of roll thermal fatigue crack propagation during hot rolling of long products is presented. A range of 2D implicit FEM models taking into account the complex thermal and mechanical interactions during rolling and cyclic cooling have been developed and used to predict how the stress state inside the roll contributes in a different manner to energy release at the crack tip, depending on the length of the initial crack. A stress intensity factor (SIF) approach has been used to derive the crack growth rate for a given roll material and roll cooling configuration. This work describes the methodology of predicting thermal fatigue crack growth using innovative modelling techniques and highlights the importance one needs to attach to operating conditions (roll cooling, roll coating, controlling oxide scale etc.) alongside the optimum selection of roll material for reduced surface degradation of current hot long product rolls.