Assessment of Metal/Mould Interfacial Heat Transfer during Solidification of Cast Iron

Abstract

The problem of heat transfer between a ferrous alloy and a sand mould/chill has been investigated. An inverse technique has been used to measure the heat flow at the metal/mould interface during solidification of cast iron in dry sand and graphite moulds. In the case of sand moulds, the Fourier heat conduction equation was modified to take into account the packed bed nature of the sand mould, the effect of convection of the gases and the evolution and absorption of heat due to mould reactions. The interfacial heat transfer coefficient and interfacial heat flux were estimated from measured temperatures inside the mould during the solidification of the cast iron. The temporal variation of the heat flux transients during the early stages of the experiment was explained on the basis of the formation of an initial solid skin and the nucleation of an air gap resulting from the combined action of the movement of the solid shell away from the mould wall and mould dilation. At later times the interfacial heat transfer from the cast iron casting was found to be dominated by radiation which accounted for as much as 80% of the overall heat flux.