Tempering of Cold-Rolled Martensite in Mild Steel and Elucidating the Effects of Alloying Elements

The martensite thermomechanical process was applied to the st37 steel and a modified version of this steel containing micro-addition of Cr and Mo. It was found that the presence of Cr and Mo can result in the retardation of softening during tempering of cold-rolled sheets, where the hardness of the modified steel at each tempering time was much higher compared to that of the st37 steel. Accordingly, the characteristic hardness fall (related to the occurrence of continuous recrystallization) was postponed effectively. The development of fine ferrite/carbide aggregate via martensite process resulted in the enhancement of tensile properties compared to the as-received ferrite/pearlite microstructure. The micro-addition of Cr and Mo was also found to be conducive to grain refinement during tempering of cold-rolled martensite.