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Abstract
Based on the model of microstructure formation of spheroidal graphite iron (SGI) casting which includes continuous nucleation and growth of graphite nodules, carbides and austenite, a method was proposed to calculate the feeding flow during solidification processes by considering mass conservation and using Darcy's laws. The method takes into account liquid shrinkage as well as shrinkage and expansion caused by different phase formation, and can calculate the flow in liquid and mushy regions. According to calculation of the flow, macro porosity formation could be described through treating free surfaces and boundary of the regions. The proposed method has been applied to an automotive wheel hub SGI casting with two different processing cases. The feeding flow during the casting solidification with two cases, especially in isolated regions, was investigated and discussed. With the flow calculation, expansion or shrinkage of liquid or mushy regions might be judged, which could offer important information for evaluating formation of macro porosity. The results of macro porosity prediction were compared with results of practical castings. It is indicated that two results were in quite good agreement, and the method could predict macro porosity formation more accurately.