Heat-resistant glass composition

Abstract

A heat-resistant glass composition which comprises, in % by weight; 56 to 68% of SiO.sub.2, 0.2 to 5% of Al.sub.2 O.sub.3, 0 to 6.4% of ZrO.sub.2, 0 to 0.5% of Li.sub.2 O, 0.2 to 8% of Na.sub.2 O, 2.5 to 14% of K.sub.2 O, 1 to 7% of MgO, 2 to 12% of CaO, 0 to 12% of SrO, 0 to 13% of BaO, 0 to 2% of ZnO, 0 to 1% in total of SO.sub.3 and Sb.sub.2 O.sub.3, and 0 to 3% of TiO.sub.2, with the proviso of the total amount of Na.sub.2 O and K.sub.2 O being 7 to 17%, the total amount of MgO and CaO being 7 to 15%, the total amount of SrO and BaO being 4 to 18%, the total amount of MgO, CaO, SrO, and BaO being 15 to 27%, and the total amount of SiO.sub.2, Al.sub.2 O.sub.3, and ZrO.sub.2 being 58% or more, and which has an average thermal expansion coefficient of 75.times.10.sup.-7 to 100.times.10.sup.-7 /K at 50 to 350.degree. C. and a strain point of 530.degree. C. or more. The heat-resistant glass composition has substantially the same thermal expansion coefficient as that of a soda-lime glass used as a window pane of buildings and a strain point than that of the soda-lime glass.