PRODUCTION OF OPAQUE QUARTZ GLASS RING

摘要

PROBLEM TO BE SOLVED: To provide a process for easily producing an opaque quartz glass ring which is uniformly dispersed with air bubbles, is excellent in high-temp. viscosity and heat shieldability and is useful as a blank of the flange parts of the furnace core tubes of various kinds of heat treatment devices in semiconductor production. SOLUTION: The process for producing the opaque quartz glass ring having an apparent density of 1.70 to 2.15 kg/cm<3> , an average air bubble size of 10 to 100μm and an air bubble quantity of 5×10<4> to 5×10<6> pieces/cm<3> , in which a power mixture composed of crystalline silica powder of 10 to 500μm in average particle size and 0.001 to 0.05 pt.wt. silicon nitride powder per 100 pts.wt. crystalline silica powder is packed into heat resistant molds of an annular shape in the in-mold space and thereafter, the molds are installed in an electric furnace and the powder mixture is held for >=1 hour at >=1400 to <=1650 deg.C at least once in a heating up process of heating the powder mixture from room temp. in a vacuum atmosphere and is subsequently heated to the temp. at which the powder mixture melts or above to <=1900 deg.C, by which the powder mixture is vitrified.