| 摘要 |
Hard glass fire retardant glasses can be tempered in a conventional air tempering plant having heat transmission values of approximately 200-500 W/(m2xK) yielding in the tempered state a fire resistance period of at least 30 minutes according to DIN 4102 and the safety properties according to DIN 1249 (safe break). In order to achieve the combination of fire resistance period and safety properties, the glasses must have a coefficient of thermal expansion alpha 20/300 of between 3 and 6x10-6 K-1, a specific thermal stress phi of between 0.3 and 0.5 N/(mm2xK), a glass transition temperature Tg of between 535 DEG and 850 DEG C., a product of specific thermal stress phi multiplied by (Tg -20 DEG C.) of between 180 and 360 N/mm2, an upper annealing temperature (temperature at a viscosity of 1013 dpas) of over 560 DEG C., a softening temperature (temperature at a viscosity of 1077.6 dpas) of over 830 DEG C. and a working temperature (temperature at a viscosity of 104 dpas) of below 1300 DEG C.
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