Measurement of interfacial heat transfer coefficient for the evaporative pattern casting of A356 aluminium alloy

In this study, the interfacial heat transfer coefficient between the casting and the mould, h, for the evaporative pattern casting (EPC) of A356 aluminium alloy is measured. The data obtained, which present h as functions of time and/or casting temperature at the interface, is very important for mathematical modelling of the solidification phenomena of evaporative pattern casting. A unidirectional heat transfer system for the evaporative pattern casting of A356 aluminium alloy is designed and fabricated. Temperature measurements are conducted using thermocouples aligned in the casting and the binder-free sand mould, which is rather difficult to achieve in EPC. An Inverse Method is then employed to analyse the measured temperatures and obtain the interfacial heat transfer coefficient. The measured h is then verified by comparing the calculated temperature of the checkpoint with the obtained h and the measured temperature at the same checkpoint, where the measured temperature is not used in the inverse program to calculate h. The measured values of h can be categorised into three ranges with reference to the surface temperature of casting. The value of h is approximately 588 W/m(2) K (0.014 cal/s cm(2)degreesC) for temperatures above the liquidus temperature, 610degreesC. The value is dropped to around 336 W/m(2) K (0.008 cal/s cm(2) degreesC at 600degreesC. Then, it gradually decreases to around 252 W/m(2) K (0.006 calls cm(2) T) at the temperature of 475degreesC.