METHOD OF GLASS MELTING IN VACUUM FURNACE Russian patent published in 2016 - IPC C03B5/225 

FIELD: metallurgy.

SUBSTANCE: glass is faced up in platinum vessel 5-50 l to volume of glass mass maximum 4/5 of its height, is held for 2-3 hours at specified melting temperature corresponding to viscosity (10-0.2) Pa·s. The glass mass is vacuumised to specified residual pressure, air is removed from vacuum furnace by minimum 4 stages as follows: first stage - to 60-75 kPa with rate 8000-40000 Pa/min, second stage - to 3000-8000 Pa with rate 250-350 Pa/min, third stage - to 100-400 Pa with rate 20-40 Pa/min, forth stage - to 50-80 Pa with rate 0.1-2 Pa/min. Total vacuum treatment time is 8-13 hours.

EFFECT: dehydration of glass mass, this corresponds to average passage in range 3-5 mcm.

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