The invention discloses a 42CrMo deep
nitriding process, and belongs to the technical field of
metal material heat treatment. Firstly, slope heating is conducted on the gear ring, the heating speed is smaller than or equal to 60 DEG C / h, the time ranges from 8 h to 10 h, and the
heating temperature ranges from 580 DEG C to 600 DEG C; in the first stage, the temperature ranges from 580 DEG C to 600 DEG C, the Kn value is not controlled, the ventilation capacity is 24 m / h, the CO2 ventilation capacity is 0.6 m / h, and the time ranges from 40 h to 50 h; in the second stage, the temperature is reduced to 500 DEG C, strong
permeation treatment is conducted, the Kn value is 3-6, and the heat preservation time is 10 hours; in the third stage, the temperature is raised to 515 DEG C for
diffusion treatment, the Kn value is 0.8-1.0, and the heat preservation time is 15 hours; in the third stage, the gear ring is subjected to rapid cooling treatment,
ammonia gas replacement is adopted before the gear ring is cooled to 350 DEG C,
nitrogen gas replacement is adopted below 350 DEG C, and the gear ring is cooled to 120 DEG C and discharged out of the furnace; by means of the method, the total time of the 42CrMo deep
nitriding process can be effectively shortened, meanwhile, the
nitriding surface
hardness and the structure grade are guaranteed through strong nitriding and
diffusion in the rear section of the process, and the surface
hardness after nitriding can reach 630 HV1 or above.