Patent RU 2731764
Quartz glass melting method
Summary:
The invention relates to a method of crucible, vacuum compression melting of extremely pure quartz glass ingots with low internal friction, achieved due to the high structural perfection of the glass volume. According to the method, the tank with sand is filled with especially pure oxygen, warmed up at a temperature of 1400 ° C, then cooled below 50 ° C, evacuated to 10*-4 Pa, the tank with high-purity sand is amputated under vacuum, the ampoule is wrapped in a carbon graphite cloth in 1-2 layers, inserted into a graphite crucible installed in an inductor of a high-frequency vacuum compression melting furnace, the chamber of which is first evacuated to 10*-2 - 10*-3 Pa, then filled with a gas mixture of argon and helium to a pressure of (1-2)10*4 Pa, ampoule with sand melts at a temperature of 1800 ° C, the set time is maintained at this temperature, the glass melt is homogenized, at the final stage the melt is compressed with a gas mixture of argon and helium at a pressure of (1.5-2) MPa, then the temperature of the furnace heat node decreases to 1650 ° C, the gas mixture is removed, the temperature in the heat node decreases at a rate of (5 ± 2) ° C /min up to 1200 ° C, then the furnace heater is turned off and the glass ingot is cooled at speed below 50 ° C, the residual gas mixture is pumped out of the melting chamber, the chamber is filled with atmospheric air, the crucible with a quartz glass ingot is removed from the furnace. The technical result is the melting of a quartz glass ingot of high chemical purity, with low absorption of optical radiation from the infrared to the ultraviolet region of the wavelengths of light, homogeneous and perfect.
