The Key Technical Research And Process Optimization Of Squeeze Casting For Aluminum Alloy Wheel Chair Arms

Compared with the traditional casting and forging process, the squeeze casting technology has the characteristic of high efficiency, short process, high quality, accurate forming and so on, which provide unlimited probability for making high performance components. Particularly, the promotion of the automobile light weight and other related industries developed the theory and practice of squeeze casting. The Al-Si casting alloy has the characteristics of low density, high specific strength, good fluidity, which makes it one of the most commonly used materials in squeeze casting field. The squeeze castings can be heat treated so as to meet the high technical requirements of the parts. In this paper, an aluminum alloy wheelchair bracket was prepared by using squeeze casting technology. Molding mechanism and application of squeeze casting technology were thoroughly and comprehensively discussed from some aspects, including process parameters, key technology, the optimization of alloy material, the heat treatment process and so forth. Specific research and discussion as follows:(1) The squeeze casting general scheme of aluminum alloy wheelchair bracket was designed. The filling and solidification process of squeeze casting was simulated based on a finite element analysis software. The simulation results guide how to use local pressurization process to estimate shrinkage cavity and porosity. The mechanical properties of different parts of the casting were detected. The results show that the overall mechanical properties of the casting are relatively uniform. In as-cast condition, the average tensile strength value is 259.7 MPa, yield strength is 171.1 MPa, elongation is 6.46%, and the highest tensile strength value is 280.3 MPa.(2) The local pressurization technology is adopt in the thick part of the casting. The effect of different local pressurization processes on the key parts were analyzed through X-ray real-time imaging detecting system and any other methods. The mechanical properties of the local pressurization part and other parts of the castings were compared. The results show that good pressurization effect for A354 alloy can be produced when the pressure is 100 MPa, lag time is 0.5s. However, the mechanical properties of the local pressurization part is lower than the average of the casting, which may attribute to the process parameters. Both of the tensile properties of the local pressurization part and other parts were overwhelmingly increased after T6-treated. Tensile strength value reached 341.0 MPa,365.4 MPa, respectively, increased by 36.8% and 25.4% respectively as compared to as-cast condition.(3) The effect of Mg, Cu on the microstructure and properties of squeeze casting aluminum alloy was analyzed. Results indicated that the strength of Al-Si increased appreciably with increased Mg and Cu contents within limits. But at the expense of decreasing the elongation of the alloy. Heat treatment can make the Al-Si-Cu-Mg alloys obtain high strength and good toughness. The alloy has favorable comprehensive mechanical properties when the Cu/Mg value is 4. In my work, tensile strength, yield strength and elongation were 426.2 MPa,295.0 MPa and 6.3%, respectively.(4) For squeeze casting A354 alloy, the best heat treatment schedule:solution treatment process for 525℃×10h and aging treatment process for 175℃×6 h. The peak hardness value of A354 alloy is 129HB with the optimized heat treatment process.