(a)


(b)


Figure 8. The bottom filled, vertically cast, preheated (800°C) ceramic shell mold simulations show the best results for casting P900 plates. The 100°C superheat simulation (a) exhibits mold temperatures between the liquidus and solidus so there is a chance of cold shut formation even though the distribution of temperatures indicates directional solidification from the top to the bottom. The 300°C superheat simulation (b) has no indication of cold shuts or other temperature related defects. The temperature distribution also indicates directional solidification. Both simulations are the best case when compared with the bonded sand molds at their respective superheats.


(a)


(b)


Figure 9. FLUENT models of triple junctions from a (a) horizontally cast bonded sand P900 plate and a (b) vertically cast, pre-heated (800°C) ceramic shell P900 plate are compared to metallographic sections through triple junctions. Ovals indicate triple junctions.


62 International Journal of Metalcasting/Winter 10


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