How to control the distortion during gear heating?

　　In fact, in the heating process, not only the distortion is caused by thermal stress, but also the release of internal stress itself will also cause distortion.In the manufacturing process of high-precision gear products, the distortion of the gear heat treatment during the heating process should also be paid attention to.Taishang Precision Machinery will tell you how to control the distortion during gear heating?

　　XNUMX. Isothermal normalizing of gear blanks.Gear blanks have a large difference in structure and hardness after ordinary normalizing. The use of isothermal normalizing can first improve the uniformity of structure and hardness, and at the same time, it can also reduce the distortion caused by the uneven processing stress.In recent years, the application of isothermal normalizing of gear blanks has played a very good role in the control of gear heat treatment distortion in my country.

　　740. Preheating, stepped heating and heating.On the one hand, its purpose is to make the temperature of the surface, the inside and the parts of the workpiece more uniform, while reducing the temperature difference with the target temperature; the most fundamental thing is to reduce the temperature difference between the parts of the workpiece.Based on the effect of preheating, the US military standard on the "Heat Treatment Process of Steel" stipulates that the final processed parts should be preheated at 540°C or 650°C before heating to XNUMX°C.

　　XNUMX. Carburizing and other high-temperature heat treatments are carried out after stress relief annealing.It is equivalent to dividing the workpiece directly heated at high temperature into two heating stages. The first stage is carried out at a temperature much lower than the carburizing temperature. Due to the low heating temperature, the thermal stress is small. At the same time, the heating speed is low and the temperature gradient is small. It is not only beneficial to reduce the thermal stress, but also beneficial to the processing stress release and the slow recovery of the twisted lattice; then high temperature heat treatment such as carburizing is carried out.Therefore, it is best to put the workpiece into the high temperature carburizing furnace immediately after stress relief annealing, so as to get the best effect.In production, the existing tempering furnace can be used for this operation.