Physical sand properties developed with non-seacoal carbonaceous materials were equal to or superior to seacoal at significantly lower additive levels. Gilsonite and asphalt mixes appeared to improve physical properties of density, water requirements and green, dry, baked and hot strengths. An even greater improvement in foundry sand green, baked, and hot strength was obtained by increasing the fineness of grind of the Gilsonite. It is postulated the finer material provides better sand coating. The higher strength may be attributed to improved sand wetting by the thermoplastic asphalt materials.
Gilsonite as a Carbonaceous Foundry Sand AdditiveThe gas evolution curve indicated Gilsonite and asphalt reacted more rapidly than seacoal but had far less total gas volume. Gilsonite and asphalt at one third the level of seacoal had the same total volatiles at one third the seacoal additive level.
A foundry research study showed casting finish with Gilsonite was equal to seacoal and better than most other substitutes. Another study with system sand confirmed the laboratory results of this research on new sand mixes with respect to sand properties and casting finish.
Through the years there has been extensive research and many technical papers writ ten on carbonaceous additives used in foundry molding sands. The majority of this research and publication concerned the effect of various carbonaceous materials on casting quality, gas evolution rates, lustrous carbon(1), clay activity and volatile compos ition.
It was the object of this research to compare the effect of several commonly used carbonaceous materials on foundry sand properties. This data was compared to available information on system sand performance with respect to properties and casting fi nish.
Five foundry grade carbonaceous sand additives were evaluated. They were:
A) Seacoal (ground, dustless, bituminous coal).
B) Pitch (coal tar pitch).
C) Petroleum asphalt (weathered residue from petroleum cracking towers).
D) Gi lsonite (natural U.S. asphaltite).
E) Blown asphalt (air - purged asphalt).
The dry and wet - screen analysis of each of these carbonaceous materials is shown in Table I. Two Gilsonite products of different AFS fineness numbers were evaluated in this program. The finer material is typical of that marketed by AGC.
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