Controlling green sand properties with environmentally beneficial phosphate additives

摘要

The addition of phosphate-based and hydroxide-based chemicals to green sand from a Cu-base foundry has demonstrated the effectiveness of maintaining or improving sand molding properties and reducing the concentration of metals within the sand, asmeasured by the Toxicity Characteristics Leaching Procedure (TCLP).A study of the effect of numerous additives to green sand, during mulling, has demonstrated their ability to maintain and, in some cases, improve the properties of the sand with slight additional moisture demand. Leachable metals in the sand areeffectively stabilized. Compactibility, compressive strength and shear strength properties can be controlled within desired operating ranges.Green sand amended with either triple super phosphate (TSP), magnesium hydroxide, or a proprietary blend of TSP and magnesite provided a green sand control operating window in which compactibility, permeability and compressive strength could be maintained and shear strength maintained or improved. Subsequent TCLP analysis indicated that these additives stabilized the leaching of heavy metals from the green sand to well below hazardous limits.