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A Rapid-set Cement Suitable as a Molding Sand Binder for Small Ferrous Castings.
Sanders-SD; Scott-ED; Sullivan-GV
MISSING :16 pages
The Tuscaloosa Research Center investigated using rapid-set cement as a suitable molding sand binder for small ferrous castings; currently petroleum-based binders are used. Substitution of a rapid- set cement would eliminate organic vapors associated with the petroleum-based binders; these vapors constitute occupational hazards and environmental pollutants. A binder containing 60 percent white portland cement (wpc) and 40 percent calcium aluminate (ca) would be an acceptable and economic substitute for petroleum- based binders where the foundry requirements are compatible with its limitations. It produced a set time and a pattern strip time of less than 1 hour. Cement, sand, and water mixtures developed compressive strengths from about 40 to 75 psi after 2 hours and from 120 to 130 psi after 24 hours. Tensile strengths of 18 to 22 psi were obtained after 2 hours, increasing to 30 to 35 psi after 24 hours. The addition of about 1 percent polyphosphate to the sand- cement-water mixture doubled the compressive strength and increased the tensile strength about 50 percent after 4 hours, but also increased the set time from 30 minutes to 1 to 1-1/2 hours. Polyvinylacetate (pva) resin latex additions resulted in rapid strength development. When castings were poured into the cement- bonded molds, the surface finish was fair to good on gray iron castings, but some areas of burn-on were present on steel castings. Using a graphite wash on the cement-bonded molds produced good surfaces on gray iron castings.
IH; Report of Investigation;
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division