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An Investment Mold for Titanium Casting.
MISSING :35 pages
The Bureau of Mines conducted research on an alternate mold material that has commercial potential for titanium investment casting. Using variations of the conventional lost wax molding process, investment shell molds were formed entirely of fused, calcia- stabilized zro2 and a zro2-forming binder. Optimization of binder/slurry properties, stucco grain size and distribution, and curing practices resulted in a structurally sound investment shell that was distortion free and thermally stable. Small titanium castings, weighing up to 10 pounds, were prepared in unheated molds by both static and centrifugal casting techniques. Microstructural examination of the castings revealed that mold fill and surface quality were enhanced by centrifugal casting, although good results also were obtained from the statically poured molds. Microstructural and electron microprobe examinations showed that excessive, brittle case formation could be avoided by curing the dried shell molds in air for at least 2 hours at 1,400 deg. C. Increasing curing temperature and time above these levels yielded added benefits. Molds fired in vacuum at 1,500 deg. C for 4 hours yielded castings essentially free of case formation. The tensile properties of as-cast test specimens (no surface conditioning performed) and the chemical composition of representative metal samples showed that castings produced were comparable to grades c-1 and c-2 unalloyed titanium. This indicated that no significant degradation of metal properties resulted from mold/metal interaction.
IH; Report of Investigation;
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division