The invention relates to a sub-temperature
carburizing heat treatment method for reducing heat treatment deformation of a thin-wall gear. The method comprises the following steps of S1, pre-sub-temperature normalizing; S2,
slow speed shot blasting; S3, sub-temperature carburization, specifically, gradient heating is adopted to a sub-temperature
carburizing temperature, a two-stage
carburizing method is adopted in the sub-temperature carburizing process, the first stage is a strong carburizing stage, and the second stage is a
diffusion stage; S4, gradient
slow cooling quenching, specifically, firstly, gradient
slow cooling is carried out on a carburized thin-wall gear
forging to 840-860 DEG C, heat preservation is carried out for about 1h, then the
slow cooling is continuously carried out to 815-825 DEG C, the heat preservation is carried out for about 1h, the
carbon potential in the furnace is controlled to be 0.5-0.05%, and then
quenching is carried out in a
polyvinyl alcohol solution; and S5, low-temperature
tempering. According to the method, the deformation degree of a gear workpiece can be greatly reduced, the production qualification rate can be obviously improved, meanwhile,
crystal grains can be effectively refined, the
hardness and strength of a gear can be improved, the service life of the gear can be obviously prolonged, and in addition, the refined
crystal grains can obviously improve the carburizing speed, reduce the
process time and reduce the
energy consumption.