Casting pure titanium into commercial phosphate-bonded SiO2 investment molds

Pure titanium was cast into five different phosphate-bonded SiO2 investment mold materials (at 350 degrees 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 the reacted layer differed in degree among these investments, in spite of the same phosphate-bonded SiO2-type investment. A significant correlation was obtained between the thermal expansion (at 350 degrees C) and the casting accuracy.