| 摘要 |
Glass envelopes for tungsten-halogen lamps and glasses suitable for these are described which have properties favorable for this purpose of use and which can be drawn in a high-speed-draw process. Their properties and composition are characterised in that they contain essentially, in % by weight on an oxide basis 60.0 +/- 1.5 SiO2, 17.0 +/- 1.0 Al2O3, 5.0 +/- 0.8 B2O3, 11.4 +/- 0.8 CaO, 7.5 +/- 0.8 MgO, the SiO2:Al2O3 weight ratio is 3.3-3.8 and the CaO:MgO weight ratio is 1.3-1.8, and as regards their properties, they have a relaxation temperature of at least 670 DEG C, a coefficient of thermal expansion at 0-300 DEG C of 42-45.10<-7>/ DEG C, a liquidus temperature of less than 1150 DEG C, and a viscosity at the liquidus temperature of more than 2.10<4> poise.
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