| Due to the rapid development of automobile industry and the demand for energy saving and emission reduction,aluminum alloy parts are gradually replacing steel parts with superior performance.The semi-solid rheo-extrusion casting of aluminum alloy instead of other manufacturing processes can effectively balance the cost and efficiency,and improve the quality of the products greatly.However,the process is still in the transition stage from experimental research to actual production in China,so it cannot reach the large-scale production of high-performance parts.In this paper,the flow extrusion casting technology of Al Si7 Mg aluminum alloy was studied by taking the wheel hub as a typical automobile structural part and taking the Al Si7 Mg aluminum alloy as the research object.The influence of different technological parameters on the quality and performance of the hub was studied by means of simulation and production trial production,X-ray inspection,metallographic inspection,tensile test and tensile fracture scanning,and the optimal combination of technological parameters was analyzed.The specific work content of this paper is as follows:(1)According to the structural characteristics of the automobile wheel hub,the overall design and analysis of the rheological extrusion casting process of the wheel hub was carried out,and the rheological extrusion casting mold of the wheel hub was designed.(2)Anycasting simulation software was used to numerically simulate the casting process of semi-solid rheological extrusion for aluminum alloy hub,and the influence rules of injection velocity,casting temperature and preheating temperature of mold on the filling and solidification process of semi-solid slurry were studied.The results show that within the appropriate parameters(injection velocity 0.04?0.09m/s,casting temperature 585?595?,preheating temperature 200?250?),airflow and turbulence can be effectively avoided,the shrinkage of semi-solid slurry can be ensured,and the solidification time can be reduced,which is beneficial to the microstructure and mechanical properties of casting.(3)According to the simulation of casting defects in the casting process optimization design,and Using Anycasting simulation software,the orthogonal test of three factors and three levels was established by taking three factors of injection velocity,casting temperature and preheating temperature of mold.The results show that the injection rate and pouring temperature have the greatest influence on the filling and solidification process of slurry,while the preheating temperature of mold is the least.The optimum process parameters were obtained: injection velocity 0.07m/s,casting temperature 595?,preheating temperature225?,and the minimum residual melt modulus was 0.9649.(4)In order to verify the numerical simulation results,this paper adopts the production trial production method to test and verify the flow extrusion casting technology of the hub.Qualitative and quantitative data of microstructure and mechanical properties of castings were obtained by means of various testing methods.The influences of different process parameters on microstructure and mechanical properties of castings were analyzed and summarized.The order and significance of each index factor were calculated by means of range calculation.Results show that the injection speed 0.07m/s,mould preheating temperature 225?,the pouring temperature of 595? and extrusion pressure 140 MPa rheological under the optimal process parameters combination of squeeze casting wheel casting organization density,grain size small rounded,casting on the mechanical property after T6 heat treatment can achieve the tensile strength of 328 MPa and 259 MPa plastic elongation of 0.2% of the yield strength,elongation rate of 10.3%. |
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