MATHEMATICAL MODELING OF CASTING FLUIDITY

Abstract

The present study is an attempt to analyse the heat and fluid flow associated with casting fluidity, which is an important engineering parameter in foundries. When the molten metal is poured in a mould, it flows into the gate of mold cavity under the metallostatic head of the sprue and cup. As the metal flows into the fluidity channel it looses heat to the mold by heat transfer through mold-metal interface and also, there is evolution of heat due to solidification. Grids have been set up in the molten metal filled fluidity channel and the number of grids increases as the metal flows over longer distances with time. Heat balance has been carried out in each grid by considering inflow and outflow of molten metal from a given grid and solidification of metal around the mold surface progressing with time. There is also heat loss to the mold controlled by heat transfer coefficient. Heat balance in grids at a given times yields temperature distribution in the molten metal along the fluidity channel at that time. Time evolution of temperature distribution is determined to find the time when the temperature of a grid reaches the melting point of the liquid metal and the distance metal has flown in the channel at that time is taken as fluidity length. The fluidity length increases almost linearly with superheat but nonlinearly with heat transfer coefficients and section size. The fluidity lengths obtained for pure aluminum for different degree of superheat are similar to those obtained by the expression proposed by Fleming earlier