A high temperature of the unbonded sand used to produce the molds in the lost foam casting (LFC) process heats the ceramic coating and the foam pattern. This in turn influences the velocity of the metal front during mold filling, the metal-foam-coating interface behavior and the severity of any defects that may occur in the casting. Several tests were performed in which the sand temperature was an important variable. A preliminary test showed that a thin expandable polystyrene (EPS) pattern heated quickly when hot sand was used during compaction; the velocity of the metal front increased substantially as a result of the hotter sand, coating and pattern. In a second, more detailed, test, four sets of four EPS flange patterns were coated and poured at different times over a several month period using what was hoped to be identical conditions. This provided an indication of the reproducibility that could be obtained in measuring metal velocities and casting defects. One of the four sets used hot sand. The higher temperature sand increased metal velocity and, in addition, more blisters and folds were observed. The higher temperature sand did reduce the number of internal pores that were found. In a final test, EPS flange patterns were used with 26℃ to 50℃ sand temperatures, two pouring temperatures and two coatings. Higher sand temperatures increased metal velocity but, perhaps because a low-density foam pattern and an empty sprue were used, little effect of sand temperature on pyrolysis defects was noted.
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