Research On Squeeze Casting Technology Of New Energy Vehicle Motor Shell

Due to the requirement of energy saving and emission reduction, as the new energy automobile key part, the material of the motor shell has been converted from cast iron to aluminum alloy, not only reduced the weight of the vehicle, but also improved the cooling condition of the motor. However, the aluminum alloy castings manufactured by conventional casting process had much shrinkage porosity and low air-tightness. In this paper, forming method by squeeze casting instead of conventional casting, the forming quality, air-tightness and qualified rate of motor shell was improved.Based on numerical simulation and experiments analysis, the motor shell made of ADC12 aluminum alloy was manufactured by squeeze casting. The influence of process parameters on the forming quality and air-tightness of motor shell was researched by numerical simulation, X-ray detection, density analysis, mechanical properties analysis, air-tightness analysis and so on, the motor shell with excellent performance was obtained by means of optimized process parameter. The main research work of the paper are as follows:(1)Combined with the structure and performance requirements of the motor shell part, the motor shell casting model was designed, the squeeze casting equipment was chosen and the indirect squeeze casting process parameters were initially identified through process analysis and equipment parameters calculation. On the basis of motor shell casting model, the indirect squeeze casting mold with automatic cut gating system inside the mold was designed.(2)The filling and solidification of motor shell during squeeze casting were simulated by ProCAST for verifying process design rationality. The results showed that filling without turbulence and gas volumes, the directional solidification was conducive to pressure transmission. Based on the single variable method, the influence of pouring temperature and mold temperature on shrinkage porosity ofmotor shell was studied. The numerical simulation results showed that low and high pouring temperature were both go against shrinkage porosity of motor shell, the optimum pouring temperature range was about 680-700 ℃. With increasing mold temperature, the shrinkage porosity of motor shell was decreased, and the shrinkage porosity was least when the mold temperature reached 280℃. The local pressurization device could be designed to eliminate the critical region shrinkage porosity.(3)In this paper, the orthogonal experiment of three factors and three levels was designed with pressure, pouring temperature and mold temperature as the variables, and the experiment of the motor shell was carried out by indirect squeeze casting. By the internal and external quality inspection, density determination,microstructure observation, mechanical properties testing and air-tightness testing of the casting, the results revealed that at the proper pouring temperature and mold temperature, good filling quality, smooth pressure transfer, shrinkage porosity, round grain structure and excellent mechanical properties were obtained. With increasing to110 MPa in pressure, the shrinkage porosity of the casting decreased, the density and mechanical properties improved apparently. Through comprehensive analysis, the optimum process parameters of motor shell manufactured by indirect squeeze casting were acquired with pressure at 110 MPa, pouring temperature at 680 ℃,mold temperature at 280 ℃, dwell time at 30 s, injection speed at 0.1m/s. With using optimum process parameters, the air-tightness of the motor shell was examined by using self-designed device, and the qualified rate reached 86%.The motor shell made of aluminum alloy instead of cast iron satisfied lightweight requirement, and was manufactured by squeeze casting to better satisfy the forming quality, air-tightness and qualified rate requirements.