Abstract: The thermal simulator Gleeble 1500D was used to investigate the microstructure evolution of hot rolled low alloy steel during cooling and reheating. The effect of reheating process on microstructure was studied in the conditions of different cooling temperature， quenching and normalizing heat treatments， respectively. The results showed that the effect of the reheating process after rolling on the quenched steel sample is more remarkable than on normalized sample. When the deformed steel is cooled to twophase region， the reheating process improves the uniformity of temperature distribution， affects the phase transformation of ferrite and precipitation of carbonitrides， prompts the growth of grains， and effectively improves and controls the microstructure and mechanical properties of the quenched steels.

Key words: induction heating, microstructure, thermal simulation, hot rolling, heat treatment