Study On Warm Forging Prosess Of 45 Steel Asymmetric Gear

Gear is a mechanical transmission component commonly used in the mechanical structure. It has been widely used in all areas of industrial production because of its stable transmission and reliable performance. Asymmetric gear is one kind of new gears in order to improve the bending strength, which is characterized by two different pressure angles, corresponding to two mutually asymmetrical involutes. The advantages of this gear are small size, light weight and large carrying capacity. The gear processing methods are divided into machining and plastic forming. Using plastic forming process to produce gear can improve the utilization of raw materials and production efficiency, increase the mechanical properties of gears. As a consequence, exploring the plastic forming process of asymmetric gear has wide application prospects.Asymmetric gear has complex structure, so using plastic forming technology to process the gear has problems of large forming load, short die life, bad tooth filling, and so on. To solve these problems, this paper presents a radial warm extrusion process of asymmetric gear. Optimizing the parameters of warm forging and mold structure to reduce the forming load and improve the filling in the toothed corner portion by numerical simulation and physical experiments.Studying the influence rules of billet temperature, mold temperature, forming speed and the friction coefficient on the maximum forming load through the four factors and four levels orthogonal experiment. The billet temperature has the greatest impact on forming load, and friction coefficient has the least impact on forming load. The optimal forming parameters: billet temperature is 800 oC, mold temperature is 250 oC, the forming speed is 30 mm / s, and the friction coefficient is 0.15.Optimizing the design of forming mold based on the study of the metal flow and deformation law in the process of asymmetric gear forming. Using lead bricks forming experiments to verify the optimization results. The results showed that the use of optimized mold can significantly reduce the forming load and improve the filling in the toothed corner portion. According to the elastoplastic mechanics, designing the combined matrix instead of solid die to protect the mold. Using the new mold and No. 45 steel to conducting forming experiments can obtain the complete asymmetric gear with better surface and tooth filling.Asymmetric gears’ microstructure analysis and mechanical testing showed that the small grain evenly distributed in the region near the addendum circle with high strength; the area near the central portion of the gear had a coarse grain size, uneven distribution and low strength.Significant metal flow lines at the corner part of the gearindicated that a large number of late-forming metal flowed `into the tooth cavity filling the corner portion. The numerical simulation of metal flow and deformation also proved it.