Modelling the investment casting process: a novel approach for view factor calculations and defect prediction

Abstract

A rigorous simulation of the investment casting process (including view factor calculations) is tedious and time consuming. During the initial simulation stage, one needs to analyze quickly a large number of process designs to select the most promising ones for more rigorous analysis. Toward this end, a new model was developed for the solidification heat transfer analysis of investment castings. The model is based on an approach that considers the geometric as well as the solidification parameters that dominate the heat transfer and the sequence of solidification and takes into account the radiation heat losses from the mold surface. A new and efficient scheme is developed for the calculation of view factor distribution on the mold surface, which governs the radiation loss. This scheme is generally applicable for models with finite difference representation. The model is capable of predicting the solidification time profile in the casting and can be used for quick estimation of defects like hot spots which lead to macroporosities. Although the proposed model is approximate, it makes only a modest sacrifice in accuracy while making tremendous savings in computation time. The model has been validated by comparison with experimental results as well as analytical solutions obtained from the literature.