Effect of Quenching and Partitioning Process on Microstructure and Mechanical Properties of 60Si2Mn Spring Steel

60Si2Mn spring steel was treated by quenching and partitioning (Q&P) at different quenching temperatures (140,160,180 ℃). The microstructure and mechanical properties of the steel after Q&P treatment were investigated, and compared with those after traditional quenching and tempering (Q&T) treatment. The results show that the microstructure of 60Si2Mn spring steel after Q&P treatment consisted of retained austenite and martensite, and the volume fraction of retained austenite was more than 12%. The microstructure of the steel after Q&T treatment was tempered troostite/tempered sorbite. The strength and hardness of the steel after Q&P treatment decreased with increasing quenching temperature, and the percentage elongation after fracture, impact energy and product of strength and elongation increased, which were all larger than those after Q&T treatment. The comprehensive performance of the spring steel after Q&P treatment was better than that after Q&T treatment because of the transformation-induced plasticity effect caused by the restained austenite during deformation.