Investigation of the effect of the mould temperatures on the casting-mould interface heat transfer coefficient during solidification

The heat transfer coefficient on the metal-mold interface is an important factor which determines the structural and mechanical properties of the casting, and controls the solidification rate of the casting. The heat transfer coefficient on the metal-mould interface is dependent on time. It is effected by many parameters such as surface roughness, mould material, type of alloy, direction of solidification, mould and casting temperatures, expansion of the mould, contraction of the metal, and air gap on the interface. In this study, it is aimed to investigate the change of the interfacial heat transfer coefficient with temperature of the mold, and to identify the metal-mold interfacial heat transfer the mechanisms depending on the temperature of the mold.Time-temperatures relationships were measured with copper chill having different preheat temperatures (50 oC, 100 oC and 150 oC) in upwards solidifying commercial aluminum alloy (ETIAL-220) which is poured at 750 oC. The measured temperatures have been used to determine the effect of mold temperature on the interface heat transfer coefficient.It is concluded that:1- The metal-mold interfacial heat transfer coefficient increased with increasing preheat temperature of the chill (mould).2- The heat transfer coefficient was found to be higher in 150 oC copper chill temperature than other chill temperatures due to late seperation of the metal from the mould surface.3- Maximum heat flow for 50 oC, 100 oC and 150 oC chill temperatures was determined 37 000 W/m2, 40 000 W/m2 and 45 000 W/m2, and interface heat transfer coefficients was calculated 12 000 W/m2K, 20 000 W/m2K and 25 000 W/m2K, respectively.