Understanding the foam-metal interface. (Lost Foam).

Through the Lost Foam Div.'s nine presentations, a clear goal was to increase the understanding of the foam pattern-molten metal interface.

In a presentation (02-101) on the degradation of expanded polystyrene (EPS) patterns, T.V, Molibog and H.E. Littleton, Univ. of Alabama at Birmingham, discussed experiments conducted on EPS patterns containing additives used to reduce the molecular weight of the liquid Formed from pattern degradation. The ultimate goal of theses additives is to increase the efficiency of the removal of the pattern from the casting cavity.

The conclusions from the experiments included:

* the effect of the additives on gas friction only was observed at temperatures greater than 1256-1310F (680-710C) when the additive-treated EPS had a lower gas fraction than the untreated patterns;

* pattern degradation resistance pressure for all EPS was found to be a function of temperature and feed speed as the resistance pressure decreased at higher temperatures and at lower recession rates;

* the molecular weight of liquid residue from the additive-treated patterns was 40-80% lower than the molecular weight of residue from the patterns without additives.

In a presentation (02-011) on the real time X-ray investigations of lost foam filling, W.L. Sun, Littleton and G.E. Bates, Univ. of Alabama at Birmingham, examined how variations in the casting process altered mold fill and EPS pattern degradation.

The revelations from the X-ray investigation included:

* patterns with low fusion filled up to five times faster with significantly more converging metal lines than normally fused patterns;

* normal fusion patterns coated with a low permeability coating filled slowly with smooth metal profiles while the same type of pattern with high permeability coating filled three times faster with irregular metal front profiles and bubbles.

Other presentations from the division looked at lost foam gating and sand compaction.