Experimental evaluation of the heat transfer coefficient in gravity die casting with air-gap formation

Phenomena occurring during early stages of solidification of molten metal into a mould, play an important role concerning the capacity of exchanging heat though the surfaces that are in mutual contact. During the cooling phase, molten metal shrinks, solidify and generates the latent heat according to the solid fraction evolution. The formation of air-gaps leads to a relevant variation in the heat flux, which is controlled for several parameters (i.e. the contact pressure and surface roughness during perfect contact; air-gap dimensions during incomplete contact). Present paper shows an experimental activity aimed at obtaining a relevant air-gap formation during solidification for a sample-casting and at correlating the gap with the exchanged heat. Several thermocouples were used in order to measure the temperature inside the mould and the casting. The exchanged heat was calculated by means of an inverse method and then the Heat Transfer Coefficient, HTC, was calculated. This problem has been examined for the case of aluminium gravity die casting