Optimizing the preheating temperature of hot rolled slab from the perspective of the oxidation kinetic

Decreasing the preheating temperature is an effective step to control the energy consumption in the hot rolling process. In order to obtain the lowest preheating temperature to prepare enough thickness of oxide scale in the hot rolling process, the oxidation resistance of commercial steel samples with different Al and Si contents were investigated in this paper. The results indicate that both Al and Si based oxides form at the steel-oxides interface as diffusion barrier but Al provide stronger diffusion resistance than Si in the diffusion-controlling oxidation region. Meanwhile, a three-dimensional oxidation kinetic model has been adopted to depict the oxidation behavior of four types of commercial steel. The oxidation process of automotive steel sample containing with low alloy elements is kinetically determined by interface chemical reaction. Its activation energy is 55.2 ± 6.9 kJ/mol. As for silicon steel containing with relative high alloy elements, its controlling process is determined by diffusion step at low temperature and controlled by chemical reaction rate at high temperature. In order to obtain enough thickness of oxide scale, the lowest preheating temperature of different types steel range from high to low should be the steel with high content of Al (1180 °C), the steel with high content of Si and low content of Al (1130 °C) and the steel with high contents of Si and Al (1030 °C).