1) The initial forging temperature is high, the holding time is long, the gear grain is coarse and overheated; If the final forging temperature is low or the temperature of the blank gear itself has dropped very low during forging, micro cracks will occur in the gear, which has a great impact on the subsequent heat treatment. Solution: control the initial forging temperature and final forging temperature according to the material, and strictly implement the forging process.
2) The interval between the gear forged at the beginning of heat preservation in the same furnace and the gear forged at the end is long, resulting in long heat preservation time, coarse structure and overheating of the gear forged after heat preservation, and the deformation of post-processing will increase. Solution: formulate the charging amount and holding time for forging blank gears.
3) Forging blank gear normalizing purpose. ① Refine grain, uniform structure, improve internal structure and prepare for quenching. ② Improve cutting performance and mechanical properties. ③ Eliminate internal stress, stabilize part size, and avoid or reduce deformation and cracking in subsequent heat treatment processes such as carburizing and quenching.
4) Excessive charging of blank gear, uneven charging and impervious heating will cause incomplete elimination of organizational stress and thermal stress, which will cause deformation or cracking of gear in subsequent heat treatment. Solution: the blank gear shall be evenly bulk in the furnace, and the furnace loading and holding time shall be well controlled. Pre heat treatment is a very important heat treatment process, which can not be ignored. It is an important basis to ensure the mechanical performance and quality of gears.