Abstract: With 35MnB alloy steel as the object of study, an orthogonal test was designed with the cryogenic temperature, cryogenic time and alternating times as the independent variables and the residual stress as the dependent variable. By means of X-ray diffractometer, the distribution of residual stress on the specimen surface was measured, and the influence factors of the cryogenic process parameters on residual stress in the specimens were analyzed by range analysis method. Via scanning electron microscope, the microstructure and morphology of the specimens under different cryogenic treatment process parameters were observed, and the change of retained austenite volume fraction after cryogenic treatment was quantitatively analyzed by means of X-ray diffractometer. The mechanism of residual stress reduction was comprehensively explored from the microscopic point of view. The results show that the influencing factors of cryogenic process parameters on residual stress of the 35MnB alloy steel are as follows: cryogenic temperature>alternating times>cryogenic time, and the optimal combination is the cryogenic temperature of -160 ℃, cryogenic time of 12 h, alternating number of 1 time. After cryogenic treatment, the retained austenite is refined and transformed into new martensite. The retained austenite distributed at the martensite boundary can relax the stress concentration caused by dislocation accumulation at martensite interface, thus reducing the residual stress inside the microstructure.

Key words: 35MnB alloy steel, cryogenic treatment, residual stress, microstructure