The work principles, failure modes, material selection, heat treatment process of rotary forging dies are researched in this paper. When working, the dies not only bears great pressure and long time high temperature, but also bears alternating stress caused by repeated heating and cooling which can easily lead to heat fatigue crack. Selecting proper die material and using appropriate heat treatment can improve the strength and toughness, and improve its dies life. Straight bevel gear is common part in mechanical equipments, and high precision tooth can be directly obtained by rotary forging technology. The rotary forging parts have reasonable distribution of metal fiber and its material is strengthened during the process, which not only greatly improve the gear fatigue strength, comprehensive mechanical properties, high dimensional accuracy and surface roughness, but also avoid forging various defects caused by heating. The technology saves energy, materials, reduces processing time, and it can overcome the too large deformation resistance of traditional cold forging and low dies life shortcomings. By FEM (finite element analysis) on straight bevel gear rotary forging process, the rotary forging process variation with both sides under stress, the impact of feed rate on the die failure mode and the main reason of tooth root fracture are revealed, which provide guidance for selection and optimization of process parameters in bevel gear rotary forging process.
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