Modelling heat transfer coefficient at cast/chill interface to account for effects of metal head

The evolution of heat transfer coefficient (HTC) in the sand casting of A357 aluminium alloy against aluminium chills is evaluated with different metal heads to study the effect of pressure on the HTC. Inverse modelling techniques based on Beck's analysis were used to determine the experimental evolution of HTC as a function of time, casting temperature and chill temperature. The experiments were reconstructed by means of numerical analyses to determine the best way to fit the experimental data. Two approaches were considered: in the first, a simple thermal analysis of the solidification was carried out with the HTC depending on both the interface casting temperature and the effective metal head as determined from the experiments; in the second, a coupled thermal stress analysis was performed with the HTC dependent on the interface pressure.