Determination and verification of the gap dependent heat transfer coefficient during permanent mold casting of A356 aluminum alloy

In complex castings, the heat transfer across the casting / mold interface depends on the local gap size and contact pressure. Thus, an experimental setup is constructed to measure and evaluate the air‐gap dependent heat transfer coefficient during solidification of an A356 permanent mold casting. In order to evaluate the heat transfer coefficient, the temperature gradient and air gap development is measured at the casting / mold interface. This allows the interface temperatures and the time‐dependent heat flux across the gap to be calculated as a function of the measured gap size. Furthermore, the heat transfer coefficient and gap size are correlated to the interface temperature of the casting. The experimental setup and the evaluation procedure provide consistent and reproducible results. The heat transfer coefficient thus evaluated is employed to simulate the experimental setup. The temperatures measured are well reproduced. The results of the present work are compared to simulations using two heat transfer coefficient functions found in literature. This comparison shows a substantial improvement over the state of the art. This improvement is due to the exact knowledge of gap formation and the corresponding values of the heat transfer coefficient.