Study On Mould Design And Molding Process Of Magnesium Alloy Used For Electronic Control Box

Magnesium alloys have wide applications, however there are molding difficulties in thin-walled castings due to poor fluidity of magnesium melts. Electronic control boxes of a novel magnesium alloy were made by common sand casting method in this paper. The moulds design and molding process of the boxes were also conducted. Based on the analysis of the structural processing ability for electronic control boxes, castings model schemes were drawn and sand moulds were designed. The filling and solidification processes of the Electronic control box castings were simulated by AnyCasting software. The effects of two types of pouring systems were comparatively analyzed. The simulation results were experimentally verified and the pouring process parameters were optimized.The magnesium alloys smelting process for electronic control boxes is that:magnesium ingot, aluminum ingots, zinc ingots and aluminum master alloys of manganese (Al-lOMn) are melted at 720℃;magnesium ingot, aluminum ingots, zinc ingots and aluminum master alloys of manganese (Al-10Mn) are added into the melt at 750℃. magnesium ingot, aluminum ingots, zinc ingots and aluminum master alloys of manganese (Al-10Mn) at 720℃;the mixture of gases CO2, SF6 and dry air are used for protection smelting process. Refining at 750℃ and modification with spherical graphite powders can improve the melt quality. The numerical simulation of casting process predicted the position of casting defects which has implications for the design of pouring system. The experiments indicated that the unilateral pouring way with flat internal runner has good filling effect and the pouring time is approximately 14-15s. Analysis of macro-defects of casting blanks indicates that the actual pouring results are consistent with the simulation results.The electronic control boxes of the novel magnesium alloy were solid solutionized for 24 hours at 413℃ then water-quenched,finally aged for 12hours at 200℃.The tensile properties, physical properties and the microstructure of the specimens from the boxes were studied with tensile test instrument, optical metallographic microscope, scanning electron microscope (SEM), flange coaxial tester and XRD test instrument. The microstructure is composed of a-Mg matrix, a continuous reticular β-Mg17Al12 phase and A14Ce dispersed distribution of acicular phase. The specimens achieve 171.6MPa (UTS), 11.1%(elongation),70.6(HB) and 1.015×10-2S/m(electric conductivity). The energy value of electromagnetic shielding effectiveness is always higher than 60dB, which meets the requirements of the electronic control box.