Effect of Pouring Conditions and Gating System Design on Air Entrainment During Mold Filling

摘要

Air entrainment during mold filling is a major source of oxide inclusion formation in metal casting. A model was recently developed by the authors to predict the volumetric air entrainment during pouring of metal castings. In the course of validating the model with experimental data for plunging liquid jets, it was shown that the air entrainment rate during mold filling depends fundamentally on the velocity and diameter of the jet formed by the pouring stream. In this study, the effect of more complex pouring conditions and gating system design on air entrainment is examined. Simulations are performed investigating the air entrainment characteristics of castings filled without a gating system, and with bottom-gated and side-gated filling systems. Results indicate that reducing the head height and pouring time, and the addition of a nozzle extension significantly reduces the air entrainment. In addition, using an offset pouring basin with a stopper and pressurizing the gating system further reduces the volume of entrained air. Simulation results also show that the generation of vortex flows inside the filling system is beneficial in reducing free surface turbulence, which results in less air entrainment and oxide inclusion formation during mold filling.