EFFECTS OF SHOT SLEEVE FILLING ON EVOLUTION OF THE FREE SURFACE AND SOLIDIFICATION IN THE HIGH-PRESSURE DIE CASTING MACHINE

High-pressure die casting (HPDC) is one of the most important manufacturing processes. The air entrapment caused by the liquid metal flow in the slow shot phase of HPDC in a horizontal cold chamber is one of the factors that contribute to the porosity defect of die castings. The pouring of molten metal into the shot sleeve of a HPDC resembles gravity pour die casting. This stage did not receive much attention in the die casting research because it is believed that it does not play a significant role. The shot sleeve filling time depends on the amount of metal being poured and is in the range of 1-8 s. Furthermore, a common foundry practice in aluminum HPDC is to let the metal settle for a few seconds, to allow for any air bubbles to escape from the melt. This paper examines the influence of shot sleeve filling on evolution of the free surface and solidification in the HPDC machine. The numerical simulation of the free surface and solidification during the two-dimensional flow of aluminum in the horizontal cylinder and mold fillings of the HPDC machine with cold chamber was developed. The developed numerical model is based on the conservation equations of mass, momentum and energy. The moving boundary condition of the plunger movement in the injection process was considered. The tracking of the free surface is ensured by the volume of fluid (VOF) method. The enthalpy method is employed to solve the phase change heat transfer problem in the solidification process. The study examines the influence of the shot sleeve filling, the fraction filling and the time of metal settle on the evolution of the interface aluminum liquid-air profile, the mass of air imprisoned, the velocity magnitude and the temperature contours versus time.