Knowing the quenching heat treatment requirements of the gear shaft, how to determine the process flow

(1) Workpiece name: A certain gear shaft, its appearance is shown in Figure 1-128. The material used is 38CrMoAl steel.

(2) Heat treatment technical conditions. The depth of the nitriding layer is 0.3~0.4mm, the surface hardness is 700-720HV (after grinding off 0.05mm of the nitriding layer on the surface, the hardness is 700-715HV), and the bending deformation of the part is ≤0.08mm.

(3)Processing process

①Original process. Quenching and tempering treatment - mechanical processing - ordinary nitriding treatment - fine grinding - finished product.

②Improve the process. Quenching and tempering treatment - mechanical processing - ion nitriding treatment - fine grinding - finished product.

(4) Final heat treatment process specifications

① The original process is ordinary nitriding treatment: 540℃ nitriding treatment, holding time 14-16h.

②Nitriding treatment by the original Shangyi Jintong. Nitriding treatment at 540℃ and heat preservation for 14-16 hours. After the treatment is completed, the workpiece is slowly cooled in the furnace for more than 7 hours and released.

(5) Heat treatment process analysis

①The original process is ordinary nitriding treatment. Originally, ordinary gas nitriding treatment was used, which not only had a long production cycle, but also had a brittle surface, easy peeling, bending deformation ≥0.30mm, required one or more thermal straightening, and high production costs.

②The improved process adopts ion nitriding treatment. It can be seen from the ion nitriding effect that not only the depth and hardness of the nitriding layer meet the process requirements, but also the surface is not brittle, especially the bending deformation of the part is 0.03mm or less. For such parts, such small deformation cannot be achieved by ordinary heat treatment processes such as nitriding and gas carburizing. Therefore, ion nitriding is effective and saves both energy and time.

(6) Key points for the implementation of heat treatment process technology

① Temperature measurement method of ion nitriding furnace. In order to ensure that the hardness of the ion nitriding layer of the workpiece meets the process requirements, a photoelectric pyrometer and an IRT-3000 portable fast infrared thermometer are used to calibrate each other and combine it with "visual inspection" to make the measured temperature as close as possible to the actual temperature. The temperature is close. Tests show that the temperature measurement is more accurate.

②The determination of ion nitriding temperature and holding time is determined by empirical data.