At present, the effective method to produce the driven spiral bevel gear blank of automobile rear axle at home and abroad is the ring rolling process. The ring rolling process of spiral bevel gear blank is the deformation accumulation of the ring blank through continuous local pressure, and finally realize the purpose of overall deformation. The production process of driven spiral bevel gear blank has many advantages. Due to local deformation, the deformation force is low, and the tonnage of production equipment is small, the production cost investment is small, the production efficiency is high, and the materials and energy are saved, which has high benefits.
At present, researchers at home and abroad have conducted in-depth research on this technology. Wang Aizhen compares the advantages and disadvantages of the traditional forming process of spiral bevel gear blank with the ring rolling forming process. Finally, it is concluded that the previous open and closed die forging has the defects of high material consumption, large vibration and high material cost. The ring rolling forming process has the advantages of small equipment tonnage, high material utilization rate, good labor environment and high forging quality and precision. Song Jinsheng studied the process of forging and ring rolling to produce driven spiral bevel gear blank. Forging process flow: blanking, heating, blank making, punching and connecting skin, secondary heating, forging and forming, punching and connecting skin; Ring rolling process: blanking, heating, blank making, punching and skin, secondary heating (can also be cancelled), ring rolling forming. Through comparison, it can be concluded that the ring rolling process can save energy, save materials, shorten working hours, improve productivity, improve production environment and improve the service life of molds. The research results show that the following key problems should be paid attention to in the ring rolling process of spiral bevel gear blank: the dimensional accuracy of preform should be strictly restricted, that is, the thickness of preform, the coaxiality of preform outer circle and inner hole.
Taking the driven spiral bevel gear forging of EQ140 automobile rear axle as an example, Hualin et al. Studied the advantages of ring rolling process, and studied several key problems in the forming process of ring rolling process from three aspects: spiral bevel gear blank design and manufacturing, rolling hole design and process operation. Finally, three conclusions are drawn: first, in order to optimize the final result of ring rolling process, the inclination design is adopted for the bottom surface of small hole of ring blank, so as to ensure that the workpiece has no tension crack and warpage in the process of ring rolling; Second, the shape of the forging determines the cross-sectional size and shape of the rolling hole. A reasonable spiral bevel gear blank can produce a ring that meets the requirements of all aspects through one pass; Third, the heating of spiral bevel gear blank and the feed speed of ring rolling have a great impact on the quality and accuracy of formed forgings.
Mamalis has been doing in-depth research on the ring rolling process. Through the research on the widening deformation test of rectangular section ring, the metal flow trend inside and on the surface of the ring is analyzed. The results show that there will always be “fishtail” phenomenon in the plastic deformation process of the ring. In addition, he also made an experimental study on the forming of T-shaped section ring in rectangular hole. The experimental results found that with the increase of feed rate, the ring will leave the surface of driving roller, which is called “cavity”. This phenomenon is related to the ring blank size, the pass shape of the forming die and the feed speed. Mamalis has also done relevant research on the influence of the pressure in the ring rolling process on the formed ring parts. He has installed pressure measuring needles on the core roll and drive roll of the forming die respectively. Through the ring rolling test on the ring parts with different materials and different pass types, the results show that the pressure just entering the deformation zone increases rapidly and then decreases slowly. There will be two maxima at the connecting line of the driving roll in the whole process. This is very different from the unit pressure forming law of flat plate. The unit pressure of flat plate rolling is large in the middle and downward on both sides. His findings are consistent with the conclusions of Utsunomiya, Hiroshi, Saito and others.