Abstract: Heat treatment process and properties of the 34CrNi3MoV steel box were analyzed and compared. The results show that the pre-heat treatment adopts double normalizing, which can homogenize the microstructure, refine the grain, cut off the structure inheritance, and remove hydrogen to prevent white spots. After the pre-heat treatment, the microstructure of the 34CrNi3MoV steel is ferrite matrix with dispersed granular or spheroidal carbides, which realizes the microstructure preparation for the quenching and tempering treatment. The selection of quenching temperature is mainly based on the transverse impact property. When the tempering temperature is set at 605 ℃ and the quenching temperature is set at 850-870 ℃, the transverse impact property is acceptable. When the 34CrNi3MoV steel is quenched and tempered, its microstructure and properties change significantly with the change of tempering temperature. When the quenching temperature is 860 ℃ and the tempering temperature is 605 ℃, the hardness, tensile and impact properties at room temperature meet the requirements, and the comprehensive properties are the best.

Key words: 34CrNi3MoV steel box, heat treatment process, mechanical properties