NUMERICAL SIMULATION AND OPTIMIZATION OF LIQUID METAL FLOW IN THE SHOT SLEEVE OF COLD CHAMBER DIE CASTING PROCESS

摘要

The air entrapment caused by the liquid metal flow in the slow shot phase of high-pressure die casting in a horizontal cold chamber is one of the factors that contribute to the porosity defect of die castings. In this paper, a three-dimensional numerical model was developed and used to simulate the metal in the injection chamber. The moving boundary condition of the plunger movement in the injection process was considered. Gas entrapments of different slow shot velocity profiles were simulated and the results show that there exists a critical plunger velocity under which no gas entrapment will appear in the shot sleeve. Based on the numerical simulation results, optimal slow shot velocity schemes were proposed. Experimental studies were carried out to compare the gas porosities of die-cast parts under different slow shot velocity profiles and the results show that the proposed optimal slow shot velocity schemes can be applied to practical die casting process to minimize the gas porosity in die castings.