Taking a certain type of automobile rear axle spiral bevel gear as the research object, taking the product part drawing as the starting point, the process flow is pushed back, and a set of feasible casting forging compound forming process scheme for manufacturing spiral bevel gear is explored through numerical simulation. The research and development of casting and forging composite forming process of spiral bevel gear of automobile rear axle provides a new processing idea for the production of spiral bevel gear and similar gears. This composite process breaks through the limitations of traditional processing methods, helps to reduce the production cost of domestic auto parts and improve the competitiveness of domestic auto parts market. The closed hot die forging and cold precision forging process of spiral bevel gear are simulated and analyzed by using the finite element analysis software DEFORM-3D of metal volume forming, and the casting process of coated sand of spiral bevel gear is numerically simulated by using the casting process simulation software AnyCasting. The simulation results and conclusions are as follows:
- The tooth shape and size of cold precision forging preform have an important influence on the cold precision forging steps of spiral bevel gear. Two schemes of uniform diffusion tooth profile and non-uniform diffusion tooth profile are proposed, and the corresponding mathematical models are established. The simulation results of DEFORM-3D software show that the preform with non-uniform diffusion tooth profile scheme has relatively good tooth profile quality when the cold precision forging amount of tooth profile is 0.2mm, but the cold precision forging effect is not obvious because the cold precision forging amount is too small; For the preform with non-uniform diffusion tooth profile scheme, when the maximum cold precision forging amount of tooth profile is 0.6mm, the forming load is reasonable and there is no metal accumulation at the large end of tooth profile, and the forming quality of tooth profile is the best. Thus, the optimized tooth shape and size of cold precision forging preform of spiral bevel gear are determined.
- The tooth shape and size of hot die forging preform and the taper of spiral bevel gear have an important influence on the closed hot die forging step of spiral bevel gear. In this paper, based on the shunting theory, an approximate trapezoidal tooth shape scheme is proposed to leave a certain shunting space at the tooth top of the preform in the process of hot die forging, so as to promote the rational flow of metal and fill the cavity; Adjust the taper of the spiral bevel gear blank to make it less than the taper of the tooth die, so that the small end of the spiral bevel gear blank first contacts with the die and begins to form, which is conducive to adjusting the material flow condition and completing the hot die forging of the spiral bevel gear blank at the same time. The numerical simulation results show that the forming effect is the best when the taper of spiral bevel gear blank is 3 ° smaller than that of hot die forging tooth shape die and the approximate trapezoidal tooth shape height is 5.8mm. Thus, the optimized tooth shape and taper of spiral bevel gear closed hot die forging preform are determined.
- According to the material characteristics of 20CrMoH and the structural characteristics and output of spiral bevel gear casting, the coated sand casting process is determined, and a new type of quartz sand based high temperature resistant coated sand is introduced as the coated sand material. The central top pouring scheme and the common Pouring Scheme of pouring and riser are designed, and the dimensions of each component of the pouring system and riser are calculated. The results of simulation analysis show that although the common Pouring Scheme of pouring and riser has simple shape, because the gating system has no slow flow effect, the impact of liquid metal on the mold is too large, and it is very easy to produce shrinkage defects; The pouring scheme of central top injection mold has stable and orderly filling process, the castings are solidified in sequence, the riser feeding is good, and the casting defects are very few, which is more suitable for the production of spiral bevel gear castings.
- The effects of pouring temperature and pouring speed on the forming quality of 20CrMoH gear blank casting are studied and analyzed: in a certain temperature range (1510 ~ 1640 ℃), the higher the pouring temperature, the less shrinkage defects of spiral bevel gear blank casting; The optimum pouring temperature is 1640 ℃; The pouring speed has a great influence on the distribution of residual air on the upper surface of the casting. When the pouring speed is 0.8m/s (the corresponding pouring time is 2.97s), the residual air content on the upper surface of the casting is the smallest and the forming quality is the best.