| Gears are important components in mechanical systems that are widely applied in the transmission and speed regulation, and its performance plays an important role. Currently, the material of gears is mostly steel, resulting in larger forging force and lower die life for harsh working conditions. Aluminum alloys with the advantages of low density, high strength, good thermal conductivity, good appearance and surface treatment are widely used in the fields of aerospace and automobile. Therefore, aluminum alloys instead of steel without affecting its performance can promote the product with lighter weight, more stable structure, less energy consumption. The plastic of forging aluminum alloys is relatively good, but its hot workability and formability are poor for its worse mobility and narrow forming temperature, so, isothermal forging is always used for aluminum forming. Gears manufactured by isothermal forging have better quality and precision, but the isothermal forging technology has not been widely used for the difficulty of heating and heat preservation system and the lower productivity.In this paper, the spur bevel gear with 7075 forging aluminum and open die were used for studying the forging process and parameters optimization. The 3D models of forging dies and billet were achieved through UG from the part drawings, so the FEM model was established by DEFORM-3D, then the velocity fields, loads changes and forging quality were researched during simulation process. For the defects and loads, the orthogonal test and single variable were used to optimize the critical parameters (temperature, skin location, skin thickness, radius, edge thickness, punch velocity, friction factor) during the forming process. Make the forging gear with no defects and filled completely under the premise that the loads is minimum as optimized goal, the significant of different parameters on loads and optimal parameters of isothermal forging were obtained.In the forging process of gear, dies would occur some elastic deformation for the force of billet, the gear would also appear some elastic recovery, which would both affect the precision of forging gear that couldn’t be ignored. The FEM models of elastic deformation of dies and elastic recovery of billet were established by DEFORM-3D, the radial deformation of dies and gear were both obtained, the total radial deformation were also achieved by superposition. Then the total radial deformation would be removed based on the original die size by using invers compensation method to realize the precise design of die cavity finally.In the precision forging process of gears, the dies are important tools to guarantee the precision. The dies are wore seriously for the poor working conditions, resulting in the precision of dies negatively, even scrapped. The parameters of forging and heat treatment of dies were studied respectively to reduce the wear and improve the die life. Firstly, the analysis of wear depth of dies were conducted with different parameters (hardness, temperature, punch velocity, friction factor) of isothermal forging. We got the regularity between the wear depth and parameters. Secondly, the parameters were optimized(quenching temperature, cooling temperature of oil, first tempering temperature, second tempering temperature) during the heat treatment process, make the minimum wear depth of the die as the optimized goal, the significant of different parameters on wear depth and optimal parameters of heat treatment process of H13 dies were obtained.Finally, the experimental mold and device were designed, and the experiment of isothermal forging for gear of aluminum alloys. The correctness of numerical simulation was verified though the forging shape between experiment and simulation. |
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