Effects of tempering process on microstructure and mechanical properties of ZG30Mn

Through microstructure analysis, hardness testing, tensile and impact tests, the effects of tempering process on the microstructure and mechanical properties of ZG30Mn were studied. The results show that the microstructure of ZG30Mn treated by different tempering processes is tempered sorbite. When the holding time is 60 min, with the increasing of the tempering temperature, the hardness and strength gradually decrease, and the elongation and impact energy gradually increase. When the tempering temperature is 600 °C, the hardness and strength of ZG30Mn gradually decrease with the prolongation of holding time, while the elongation and impact energy increase first and then decrease. According to the analysis, as the tempering temperature increases, the recovery and recrystallization of α-phase occurs and dispersed fine cementite gradually grows and spheroidizes, resulting in a decrease in hardness and strength, and an increase in elongation and impact energy. With the prolongation of holding time, the aggregation growth of alloy cementite results in the decrease of the elongation and the impact energy.