Effects of Cooling Rate and Original Microstructure on Final Microstructure of Low-carbon and Micro-alloyed Steels

In order to investigate the effects of original warm-rolled microstructure and cooling rate on the final microstructure,a rapid heating and cooling process without pre-deforamtion were utilized in two different low-carbon steels,and a comparison about the final microstructure of different samples was employed.The results indicate that more significant effect of the warm-rolled microstructure on the final microstructure was obtained in the steel with more alloying elements.Better refinement effect and multiphase could be more easily evolved from the original warm-rolled tempered martensite.The average ferrite grain size decreased with the increase of cooling rate.Besides,bainite and martensite preferentially formed in the steel with higher content of alloying elements.The final microstructure was less sensitive to cooling rate in the steel with lower content of alloying elements.