Influence of Work Roll Surface Oxide Scale on Interface Thermal Transfer

Abstract

In hot rolling processes, an accurate prediction of thermal expansion of work rolls is necessary because it affects profile of strips. A precise calculation of thermal expansion requires an accurate heat transfer coefficient between the roll and the strip, and the oxide scale on the surface of the work roll (mill scale) is one of the important factor that affects the heat transfer coefficient. Although clear relation between the mill scale and the heat transfer coefficient is required, it has not clarified because forming mill scale in a laboratory is difficult. In this study, first, we developed a generating method of the mill scale of hot rolling mill in a laboratory. Uniaxial compression contact experiments are used to simulate the contact between the work roll and the strip during the hot rolling. An oxide scale layer that simulates the mill scale was obtained on the surface of punch. The thickness of mill scale which was generated from the different kinds of strips material was measured. Second, the interface heat transfer coefficient for various thickness of mill scale are measured. Heat transfer coefficient is obtained from comparing the measured temperature of punch and the results of computer simulation by FEM. From these results, the relation between the thickness of mill scale and the heat resistance is clarified.