Modelling of air entrainment during pouring of metal castings

Air entrainment during mould filling is major source of oxide inclusions in metal castings. A model is developed to predict the location and rate of air entrainment as part of a standard mould filling simulation. The local air entrainment rate is calculated as a function of the turbulent kinetic energy and the magnitude of the normal velocity gradient of the liquid metal at the liquid–air interface. The model is validated through comparisons with experimental air entrainment measurements for a plunging water jet. It is then applied to study the effect of gating system design and pouring parameters on air entrainment in steel casting. Air entrainment is found to be reduced for a metal stream from the ladle that is centred above the pouring cup or the use of an offset step pouring basin, low head heights, high flow rates, a pressurised gating system and bottom ingates.