Abstract
The purpose of this paper is to clarify the softening temperature of porcelain for metal-ceramics. Thermal expansion curves were investigated and softening temperature under load and flow rate were measured. Following results were obtained. 1. The temperature in which the thermal expansion coefficient decreased or shrinkage initiated on the thermal expansion curve was not softening temperature of porcelain. It seemed to be firing shrinkage. 2. Softening temperature under load from 1, 000kgf/cm2 to 20kgf/cm2 was above 600℃ and stress relaxation due to flow of porcelain was not produced below 600℃. 3. The viscosities of opaque porcelains were calculated from flow rate as a function of temperature. Softening temperature and strain temperature were determined comparing with the viscosity of typical glass. Softening temperatures of opaque porcelains were about 861℃ in Jelenko, about 900℃ in Ceramco, and about 846℃ in Vita. Strain temperatures of opaque porcelain were about 527℃ in Jelenko, about 497℃ in Ceramco, and about 526℃ in Vita.
