Abstract
Pure nickel is used in vacuum tubes as lead wires. In the stem making process or glass sealing processes, they often become brittle by heating in city gas. This brittlness is generally considered as an effect of impurities included in nickel. In this experiment the brittleness of several specimen wires, namely, Inco nickel, Mond Nickel, Falconbridge nickel, Driver Harris nickel and Domestic nickel wires were examined and it was clarified that the brittleness observed in these specimens are due to micro cracks formed along the grain boundaries by the gas attack. When heated in a gas purified through a NaOH and P2O5 tower and a hot copper furnace, the brittleness was not observed. An addition of some alloying elements, i,e, Mg, Si, Cr, Ti, Al and Mn was found very useful for the prevention of brittle fracture in pure nickel.
