Simulation of mold filling and prediction of gas entrapment on practical high pressure die castings

Element parameters including volume filled ratio, surface dimensionless distance, and surface filled ratio for DFDM (direct finite difference method) were proposed to describe shape and location of free surfaces in casting mold filling processes. A mathematical model of the filling process was proposed specially considering the mass, momentum and heat transfer in the vicinity of free surfaces. Furthermore, a method for gas entrapment was established by tracking flow of entrapped gas. The model and method were applied to practical ADC1 high pressure die castings. The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts. The comparison shows validity of the proposed model and method. The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.