Thermal stresses and kinetics of phase transformation on the run-out table after hot strip rolling of low-carbon steels

A thermo-elastic analysis coupled with a phase change model is employed to evaluate thermal stresses as well as progress of austenite decomposition after hot strip rolling operations. The thermo-mechanical finite element analysis is utilized to assess the distributions of temperature and thermal stresses during cooling while at the same time, a model based on the additivity rule is used to determine the rate of austenite to ferrite decomposition. The proposed model is applicable to multi-pass rolling schedules while the effects of different process parameters including the rolling speed and cooling configuration of the run-out table can be taken into account. In order to verify the predictions, the measured and predicted temperature-time diagrams are compared and a reasonable agreement is observed. The results show that significant variations occur in the thermal stresses in the period of austenite to ferrite transformation owing to changes in the thermo-physical properties such as the thermal expansion and Young modulus during continuous cooling.