Simulation of the TNT-based melt-cast explosive charging process using hot mandrel assisted solidification

The melt-cast charging process, widely used in warheads for its adaptability, cost efficiency, and automation, requires optimization to minimize defects such as shrinkage cavities and porosity that compromise explosive quality, destructive power, and safety, particularly in large-volume munitions. The hot mandrel technique, by providing localized heating during solidification, helps maintain an open feeding channel, thereby reducing defect formation and improving charge integrity. In this study, the solidification process of a TNT-based melt-cast explosive is investigated using ProCAST combined with an orthogonal test approach, focusing on the hot mandrel charging technique for a warhead. The influence of three primary process parameters—the hot mandrel length, heating time, and temperature—on the solidification process is analyzed. The results demonstrate that, compared to traditional natural solidification, the solidification process with hot mandrel assistance significantly reduces the occurrence of shrinkage cavities and porosity defects, decreases the volume of shrinkage-related flaws, and enhances the overall charge quality. Among the parameters studied, the heating time of the hot mandrel exerts the greatest influence on charge quality, followed by its temperature and length. Prolonging the heating time not only reduces shrinkage defects but also extends the solidification duration. Considering both defect reduction and solidification efficiency, the optimal process conditions within the tested range are as follows: a hot mandrel length of 350 mm, a heating time of 4000 s, and a hot mandrel temperature of 90 ${}^{\circ }$C. This study innovatively develops a numerical simulation approach using ProCAST for hot mandrel-assisted solidification, systematically investigating the effects of three critical parameters on charge quality. The proposed optimization framework balances defect control with production efficiency, providing theoretical guidance for industrial implementation.