A Stydy about Investment for Titanium Alloy.

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Pure titanium was cast into five different phosphate-bonded SiO_2 investment mold materials (at 350^ﾟC) with an argon-arc melting and pressure casting machine. The mesh castability, the fit of the MOD inlay castings, and the Knoop hardness and the micro-structure in cross-sections of castings were examined. The setting and thermal expansion, the compressive strength, and the x-ray diffraction analysis of the investments were also measured. The castability, the fit, and the thickness of reacted layer differed in degree among these investments, in spite of the same phosphate-bonded SiO_2-type investment. This result may be related to the cristobalite/quartz ratios of these investments, as estimated from the thermal expansion curves. Quartz-type and cristobalite-type phosphate-bonded investments were made. Molten titanium reacted more severely with the cristobalite-type than with the quartz-type investment molds.