Hot and cold composite precision forging forming method of great-modulus high-thickness straight-tooth cylindrical gear

Abstract

The invention provides a hot and cold composite precision forging forming method applied to a great-modulus high-thickness straight-tooth cylindrical gear, and belongs to the technical field of metal plastic processing. The hot and cold composite precision forging forming method adopts the following steps of: baiting, upsetting after heating, hot die forging, annealing middle treatment, cold forward extrusion, center hole processing, annealing middle treatment and cold finishing, wherein the deformation quantity is reasonably distributed in three forming work procedures, certain tooth shapes are formed by the hot die forging work procedure, then, the cold forward extrusion process is adopted for further forming complete tooth shapes, and better surface quality is formed through radial and axial material flowing. Through the center hole processing work procedures, the stress concentration phenomenon during the closed cold finishing can be effectively reduced, and the service life of a mold is improved. Through the cold finishing work procedure, the tooth surface precision can be further improved, simultaneously, the defect of imperfect gear sectional surface filling generated in the cold extrusion work procedure is eliminated, and finally, the tooth-shaped surface of a forge element can directly reach gear hobbing and gear milling precision.

Description

technical field [0001] The invention relates to a compound precision forging forming method, in particular to a hot-cold compound precision forging forming method of a spur gear with a large modulus and high thickness, and belongs to the technical field of metal plastic processing. Background technique [0002] Spur gears are important transmission parts widely used in automobiles, aerospace, machinery and other industries. Their shapes are complex, and their materials, dimensional accuracy, surface quality, and mechanical properties have high requirements. In order to improve the utilization rate of materials and the mechanical properties of gear parts, forging is now used in China to produce gear forgings, which are then machined into gear parts. For small-sized spur gears, some domestic manufacturers have realized the cold precision forging process, and the tooth profile surface can be realized with little or no machining. There are currently two main methods for produci...

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Problems solved by technology

Although the investment in hot forging equipment is low and the mold is simple, the shortcomings of low material utilization, low production efficiency, and high energy consumption cannot be overcome. In addition, because the heating temperature of the material is high during hot forging, defects such as scale on the surface of the forging are obvious, and it is necessary to reserve Larger machining allowance is required, and in order to fill the forgings full, reduce the forming force, and improve the life of the die, it is often necessary to increase the initial forging temperature of the blank. Higher heating time and temperature will deepen the decarburization layer on the surface of the forging. Affects the performance of the final part

In recent years, some enterprises and research institutions have begun to adopt the compound forming method of hot forging and closed cold finishing to trial-produce large-scale spur gears. However, the cold finishing process of large-scale spur gears requires a large forming force, and The increase of the load will reduce the life of the cold finishing core and increase the production cost. Moreover, for the high-thickness spur gear with a large height-to-diameter ratio, the filling of the corner part of the tooth profile is from top to bottom in the axial direction of the gear. That is, the metal material first fills the tooth-shaped corner of the upper end of the mold and then starts to fill the lower end of the mold. It is easy to cause the stress concentration of the tooth-shaped mold at the upper end of the mold, resulting in cracking and damage to the mold. Therefore, hot forging plus closed cold The finishing compound forming method to manufacture large-scale spur gears is still in the experimental stage and has not been applied in batches

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