GB358934A - - Google Patents

Abstract

Leads to be sealed vacuum tight into glass are made of alloys of iron with nickel, cobalt and manganese, such alloys being particularly suitable for sealing into borosilicate glasses. For such glasses alloys of from 28-34 per cent nickel, 5-20 per cent cobalt and 0-1 per cent manganese, the remainder being iron, are employed. Specific examples of alloys for sealing into particular glasses are given. For borosilicate glasses with expansivities between 3,0 and 5,5 x 106 cm. per cm. per degree alloys containing 23-28 per cent of nickel, 17-23 per cent of cobalt, 0-0,5 per cent of manganese, and 0-0,3 per cent of carbon are employed. Generally the percentages should be connected by the relationship % nickel + 2,5 (% manganese) + 18 (% carbon)/% iron = 0,50-0,60. For lead glass, alloys containing 23-45 per cent of nickel, 5-23 per cent of cobalt, and 0-1 per cent of manganese may be employed. To improve the adhesion of the metal to the glass the alloy may be annealed in vacuo or in a bath of fused sodium nitrate or other salt which readily dissolves the metallic oxides. Excess of carbon may be removed from the alloy by heating in hydrogen or in a fused salt bath containing 15 per cent sodium chloride and 85 per cent barium chloride.