Abstract: A practical software for two-dimensional simulation of casting solidification and its implementation was developed on IBM PC/AT microcomputer. This paper proposed a changeable timestep calculation method for numerical heat transfer calculation. Its application shows that this method can increase the simulation speed by more than two or three times and the error derived from this method is less than 2% by comparing with the normal calculation method, here we take the changeable timestep coefficient q=0.5.A further discussion was made for the shrinkage cavity and porosity prediction method and was proposed to be taken as the prediction parameter for the occurrence of porosity. Another, by considering the solidification shrinkage of castings, this paper took the critical fluid solid fraction curve method to predict the size, shape and position of shrinkage cavity of castings. The calculations for three plans of a practical steel casting were compared with the experimental results, the calculations and experiments coincided well with each other. So the practicability of the software and the shrinkage cavity and porosity prediction method was verified for a practical problem.

Key words: 凝固模拟, 缺陷预测, 铸件辅助设计