The objective of this project was to perform research that leads to molding media and practices that are less costly and more environmentally compatible with the use of silica. The research started from the fundamental premise that the attrition experienced by silica sand grains when exposed to the molten metal, sand reclaiming and sand handling systems of a foundry could be eliminated by substituting a pulverizing-resistant granular medium.
Various alternative media were identified and tested for their pulverization resistance.
Three of the alternative media had significantly improved resistance to pulverization over silica sand -- high alumina proppant, low bulk density proppant and fused brown aluminum oxide. (These media are 10 to 24 times more costly than silica sand on a volumetric basis.)
A cost model was developed to determine if the initial cost difference between silica sand and the various alternative media was significant when compared on a total life cycle basis that includes disposal costs.
The cost model showed that operating costs are not strongly affected by the initial cost of the particular granular medium used in green sand, whether it be silica sand or one of the alternative media. The cost per ton of castings shipped did not change greatly across the various scenarios tested. Therefore, the application of alternative media into green sand foundries that use sand reclaiming systems is a question of initial cost, not feasibility and not operating cost.