| 摘要 |
A transparent, surface-crystallized, glass article having a modulus of rupture of at least 40,000 lb/square inch has a composition comprising on the oxide basis in mol. per cent 56-73% SiO2, 4-7% TiO2, 8.5-20% total of at least one alkali metal oxide selected from Li2O, Na2O, and K2O, the ratio Li2O: R2O being not more than 0.9, and 11-24% Al2O3, the ratio Al2O3: R2O being at least 1.0 but not more than 1.5, and the total of SiO2, TiO2, alkali metal oxide, and Al2O3 comprising at least 96% of said glass. The article is made by shaping a molten batch of the above composition, the shaped product then being subjected to a heat treatment at 600 DEG C.-750 DEG C. for a time between 5 minutes and 5 hours, and contacted with a molten lithium salt-containing material at 800 DEG -900 DEG C. for a sufficient time, e.g. 5 minutes to 1 hour, to attain the surface crystallization. Specification 786,951 is referred to. |
