Evaluation of roll surface temperature and heat transfer in the roll gap by temperature measurements in the rolls

Background: In hat rolling, roll consumption represents a significant part of the processing cost. Thermal fatigue is the most important wear factor, but even in rolls mainly subjected to abrasive wear, the temperature rise of the roll surface determines the wear. Methods: A heat transfer model was derived, and a simple formula for heat conductance is presented. Rolling trials were carried out. The temperature was measured inside the rolls and the coefficient of heat conductance was calculated and compared to the theoretical values. Results: From the experiments, the theoretical formula for coefficient of heat conduction was verified. However the theoretical model slightly underestimates the heat transfer. The breaking of the oxide layer due to the reduction creates virgin areas in the contact with the roils, and scattering surface temperature. The non-balanced heating and cooling increases the base temperature of the rolls that makes the evaluation of the measurements theoretically correct during the first healing cycle only. Conclusions: By the combination of a theoretical analysis and experimental work, the coefficient of heat conduction can be simply estimated by the derived equation, using a constant G of the order of 1900 when conventionally cast iron rolls are used. (C) Munksgaard, 1997.