Spatial variation of heat flux at the metal-mold interface due to mold filling effects in gravity die-casting

Most of the research work pertaining to metal-mold heat transfer in casting solidification either assumes no spatial variation in the air gap formation or limits the study to only those experimental systems in which air gap formation is uniform. However, in gravity die-casting, filling effects induce variation in thermal field in the mold and casting regions. In this paper, we show that this thermal field variation greatly influences the time of air gap initiation along a vertical mold wall, which subsequently leads to the spatial variation of air gap and in turn, the heat flux at the metal-mold interface. In order to study the spatial variation of heat flux at the metal-mold interface, an experimental setup that involved mold filling was devised. A Serial-IHCP (inverse heat conduction problem) algorithm was used to estimate the multiple heat flux transients along the metal-mold interface. The analysis indicates that the fluxes at different mold segments (bottom, middle, and top) of the metal-mold interface reaches the peak value at different time steps, which shows that the initiation of air gap differs along the mold wall. The experimental and numerical results show that the heat transfer in the mold is two-dimensional during the entire period of phase change, which is initially caused by the filling effects and further enhanced by the spatial variation of the air gap at the metal-mold interface. (c) 2007 Elsevier Ltd. All rights reserved.