GB139065A - Process of drawing refractory metal - Google Patents

Abstract

139,065. Hisamoto, J., and Toyo-Kagaku - Takin Kabushiki - Kaisha. April 23, 1919. Wire.-Relates to a method of drawing wire for electric-lamp filaments made of metal which is liable to become contaminated with carbon while being drawn or annealed, and consists in placing a slug or bar of refractory metal, surrounded by a refractory oxide, in a metal tube, drawing the assembly to filamentary size and removing the casing material. A slug of tungsten, tantalum, thorium, zirconium or of an alloy, consisting partly of one of the refractory metals, or of a suitable refractory composition consisting of a refractory metal and a non-metallic substance such as boron or silicon, is placed in a tube of either nickel, an alloy of nickel and chrome, steel, copper, or silver. A space is left between the slug and the tube, and is packed with thoria, magnesia, ceria or zirconia. The slug may be hammered or worked before or after being placed in the tube. The cylinder is drawn in the usual way. The compound wire is then cut into lengths, and the outer tube drawn, dissolved, or melted off. In the latter case the lengths may be placed in a flashing jar connected to electrical terminals. The jar is then ehausted, the current passed, and the tube melted from the wire. A double tube may be used comprising a copper, silver, or nickel tube in an outer steel case. The tube after drawing is dissolved off by hydrochloric or sulphuric acid and the last thin coating may be melted off.