Relation between HTC evolution, gap formation and stress analysis at the chill interface in aluminium sand casting

The effect of the interface pressure on the metal-chill Heat Transfer Coefficient (HTC) during the cooling of a A356 aluminum alloy in a gravity sand casting process is analyzed. HTCs are evaluated by inverse analysis in different processing conditions, by varying both chill material (copper, aluminum and cast iron) and size (30, 60 and 90 mm depth). All the experimental conditions are reconstructed by numerical analysis with the aim of evaluating the increase of contact pressure between casting and chill before the formation of an air gap. The experimental heat flow as determined in each experiment was used as a boundary condition for the calculations. The evaluated interface pressures were put in relation to the particular HTC evolution in the different experiments in order to point out correlations.