Numerical simulation of low pressure die casting of magnesium wheel

摘要

The application of magnesium in the automotive industry contributes to reduced fuel consumption and CO2 emissions. Nowadays, most magnesium components in automobiles are manufactured by die casting. In this paper, simulation of the low pressure die casting process of a magnesium wheel that adopts FDM (finite difference method) is presented. Through calculating the temperature and velocity fields during filling and solidification stages, the evolution of temperature and liquid fraction is analyzed. Then, potential defects including gas pores in the middle of the spokes, shrinkage at the top of the rim and the rim/spokes junctions are predicted. The reasons for these defects are also analyzed and the solutions to eliminate them are presented. The air gas pores and shrinkage at the top of the rim are eliminated effectively by reducing the pouring velocity. Furthermore, the cooling capacity at the rim/spokes junctions is also investigated in the paper. Through analysis of the shrinkage defects generated in various cooling modes, it is proven that the cooling pipe system set in the side mould alone is a valid way to enhance the cooling capacity at the rim/spoke junction areas. Finally, the strength analysis is carried out for further verification of the effectiveness of the new cooling method.