According to the shape characteristics of spur bevel gear forgings and the current status of forming technology, the closed precision die forging process is designed, and then the forming process is simulated and analyzed by finite element method.
The technological analysis of forgings mainly considers the geometric dimension, material, surface quality, dimensional accuracy and production equipment of forgings.
1). Forging material and treatment
In closed die forging, the materials are under high hydrostatic pressure, which is conducive to improving the plasticity of materials. Therefore, any material used for open precision die forging can be closed precision forged, and even some materials that cannot be closed precision die forged can be closed precision die forged.
The studied differential planetary gear parts are made of 45 steel. Before forging, normalizing treatment is adopted to reduce the hardness of the materials, thus reducing the deformation force, which is conducive to the die life and the selection of equipment with appropriate tonnage.
2). Forging shape and its demoulding
Whether the forgings can be successfully drawn out of the die has important guiding significance for whether the parts can be produced by forging method. If the die can not be smoothly drawn and the forming is ideal, the scheme will not work. The geometry of spur bevel gear has a certain taper from small end to large end, so it is easy to get out the die by open die forging; If closed die forging is adopted, the lower ejection mechanism shall be considered, and the die ejection slope shall be designed at the upper and lower punching connection to meet the basic requirements of closed precision die forging.
3). Dimensional accuracy and surface quality of forgings
There are many and complicated factors that affect the dimensional accuracy and surface quality of forgings, so it is difficult to calculate accurately in theory. According to the general law of cold precision forging, under the premise of strict control of various factors, the dimensional accuracy of forgings is 1-2 levels lower than that of die bore. If the precision of straight bevel gear is required to be grade 7, the it5-6 gear die can be manufactured by using the numerical control machining method, so the dimensional accuracy of the gear can be guaranteed. At the same time, the surface roughness of cold precision forging can achieve R α 0.8-0.2 μ m. It can also meet the actual surface quality requirements of gears in this subject.
The forging process analysis of spur bevel gears is only a general analysis from the aspects of material, forging shape and its demoulding, dimensional accuracy and surface quality. The process related to shape filling and surface quality is also related to the specific forming process, In the subsequent numerical simulation and analysis of the forming process, specific analysis should be carried out.
Select a common differential planetary gear as the research object, use UG to carry out the three-dimensional design of parts. At the same time, according to the requirements of the selected closed forming process and the forging drawing design criteria, carry out the forging drawing design and the die design for simulation analysis and modeling. The technological process and relevant technological parameters of closed precision die forging for spur bevel gears were established.