Abstract: Effect of Mn and Cr content on the microstructure and properties of SWRCH45K steel was studied. The steel was quenched by heating at 860 ℃+oil or water cooling, in addition, the hardness after quenching was simulated by using simulation software. The results show that with the increase of Mn and Cr content, the tensile strength of the tested steel is increased. The oil quenching microstructure of the tested steel consists of ferrite+troostite, with the ferrite fraction is slightly higher in the core of the specimen. The water quenching microstructure near the surface of the tested steel consists of martensite+a little troostite, while the troostite in the core of the specimen decreases with the increase of Mn and Cr content. The hardness of the tested steel after oil quenching changes slightly along the diameter direction, and the tested steel specimens with 0.70%Mn-0.04%Cr have the lowest hardness which is within 22-24 HRC and markedly lower than that of other specimens. The near-surface hardness difference among the water quenched specimens is relatively small, while the core hardness decreases obviously. It is found from comparison that the simulation hardness values are in good agreement with the near-surface hardness of the quenching specimens.

Key words: SWRCH45K steel, alloy elements, microstructure, properties