A study on the microshinkage control of the investment cast diesel valve seal ring

摘要

Quality of casting is dependent on the degree ofcasting defecets such as shrinkage, porosity, segregation, and etc.In this study, the sensitivity analysis was carried out to investigatethe effect of casting parameters on the thermal history of thecasting. Prediction of microshrinkage formation within theinvestment cast diesel valve seal ring was also made by computersimulation using ProCAST. The calculated thermal history wasutilized to get the thermal gradient, the cooling rate, and thesolidification velocity of the whole casting during solidification.In sensitivity analysis, the solidification time of the casting waslargely dependent upon the metal pouring temperature and thethermal conductivity of the mould. The microshrinkage formationwas closely related to the lower thermal gradient region in theStellite alloy casting. The G/R value, called Niyama criterion,successfully predicted the distribution of microshrinkage in theactual investment casting and the critical G/R value formicroshrinkage formation in Stellite alloy casting was found asmin.1/2cm for the diesel valve seal ring.