Al-低Cu合金の鋳型内凝固過程の数値解析

Abstract

The purpose of the present paper is to investigate the solidification process of alloy castings by numerical calculations, using the previously derived equations on the model that the dispersed crystals grow in the melt. Al-low Cu plates were taken as the examples. An explicit finite difference method in which the first approximations are obtained regarding an equilibrium solidification process and corrected to the non-equilibrium values has been introduced.The influence of the factors of the casting operation was investigated, and it has been made clear that the increase of copper addition, the decrease of thickness of casting and the decrease of heat transfer coefficient at the mold-casting interface make a flat distribution of solids in a casting during solidification, while the increases of pouring temperature and preheat temperature of the mold have little influence on the distribution of solids but delay the time of solidification. The macrosegregations due to diffusion were too little to be confirmed experimentally. The calculated cooling curves have the same behaviors as those experimentally obtained, but the details of the curves do not agree with each other because of unknown changes of the heat tranfer coefficients during solidification. The solidus and liquidus concentrations have always higher aluminum values than the equilibrium, and the deviations from the equilibrium rapidly decrease with the progression of solidification. The variation of number or shapes of growing crystals hardly affects the calculated results.