Numerical Simulation Of Solidification Of A Large Ductile Iron Casting And Optimization Of Its Foundry Process

Shrinkage porosity and cavity exist in the ductile iron casting because of its pastesolidification characteristics.It has been researched for a long time to find a way todeminish the shrinkage porosity and cavity. Since a large ductile iron casting has aheavy body and is of a complicate structure, it is difficult to control the expansion ofits mould, resulting in more shrinkage porosity.In this thesis, a large machine ram, where serious cavity defects exist, isresearched. Numerical simulation of its solidification and optimization of its foundryprocess are carried out.The main contents are included as:(1) Based on the analysis of morphology and chemical composition of the defectsample, the defect which leads to casting scrap is ascertained as shrinkage porosity.(2) According to the structural characteristics of casting and combined withnumerical simulation results， the cause of serious shrinkage porosity defect isanalysised: It is difficult to make sure simultaneous solidification for suchlarge-scale castings which has long and large size, complex shape and lots of horngate. To solve the shrinkage with the self-feeding of nodular cast iron is notworkable, strengthenning the feeding effect and layouting the riser and chillreasonablly to ensure the feeding channel smooth is necessary.(3) A finite element model of the casting was built. the process of numericalsimulation on each casting process is conducted with ProCAST software to forecastthe shrinkage porosity, and the simulation results were analyzed, according to theresults and combining theoretical analysis, the casting process was optimized.(4) A set of experiment scheme is determined according to the optimized process,And the optimized processing plan of experimental verification was conducted.Experimental results show that, after process optimization, shrinkage porosity defectis effectively decreased,and successfully solved the production problem of suchlarge-scale ductile iron castings.In summary,this research successfully completed the optimization of the largeductile iron casting process using the numerical simulation technology., ensured theunobstructed feeding channel of casting solidification process, and has solved theengineering practical problems. the clew of the processing design of such large-scale ductile iron castings is presented,and also has certain reference significance for thecasting process optimization combined with numerical simulation technique.