| 摘要 |
<p>1,253,284. Strengthened glass. CORNING GLASS WORKS. 15 April, 1969 [19 April, 1968], No. 19129/69. Heading C1M. A lithium or sodium aluminosilicate glass sheet of thickness 0À060-0À105", and having a flexural strength of above 15,000 p.s.i., has potassium ions substituted for the original Li or Na ions in a surface layer to create a surface compressive stress layer, the ratio of the depth of the surface compressive stress layer to the maximum interior (tensile) stress being greater than 0À004##/kg./mm.<SP>2</SP> for lithium glass and greater than 0À005"/kg./mm.<SP>2</SP> for sodium glass. The strengthened glass may be produced by immersing the glass in a molten potassium salt bath (e.g. 87% by weight KNO 3 +13% by weight K 2 SO 4 ) operating preferably at 575- 595‹ C., for at least 3 hours for the sodium glass and for at least 12 hours for the lithium glass. A suitable sodium aluminosilicate glass comprises, by weight, 1-15% Na 2 O; 15-25% Al 2 O 3 ; and 55-56% SiO 2 , these constituents totalling at least 90% by weight of the composition. A suitable lithium aluminosilicate glass comprises 2-6% by weight Li 2 O, 5-10% Na 2 O, 15-25% Al 2 O 3 , and 60-70% SiO 2 , these constituents totalling at least 95% by weight of the composition.</p> |
