US1345441A - Process of drawing refractory metal - Google Patents

Description

UNITED STATES PATENT OFFICE.

JUNZO HISAMOTO, OF NAGOYA CITY, JAPAN, ASSIGNOR TO TOYO-KAGAKU-YAKIN-KA- BUSIKI-KAISHA (THE ORIENTAL CHEMICAL METALLURGIC COMPANY, LIMITED),

OF TOKYO, JAPAN.

PROCESS OF DRAWING REFRACTORY METAL.

No Drawing.

To all whom it may concern:

Be it known that I, JUNzo HIsAMo'ro, a subject of the Emperor of Ja an, residing at 22 Miyademachi, Nagoya ity, Aichiken, Japan, have invented certain new and useful Improvements in Processes of Drawing Refractory Metal, of which the following is a specification.

This invention relates to a method of drawing wire made of refractory metals which are liable to become contaminated with carbon while being drawn or during annealing of the same, and has for its object the prevention of such contamination and the production of uniform filamentary wires suitable as illuminants for electrical incandescent lamps.

tion, I insert them in a tube or cylinder of metal having about the same hardness as the slugs. This tube may be a metal such as malleable nickel or an alloy of nickel and chromium or may be of steel although I do not confine myself to such metals for even silver will be found serviceable in some cases. The tube may be somewhat larger than the slug of refractory metal so that I may pack therein a small quantity of some metallic oxid powder such as thoria or magnesia, or ceria, or zirconia or other substance capable of being drawn down and annealed without clogging the tube or cylinder. The material selected for the filling of the tube should be in fine powder and must be tightly packed with the slug in the tube and any air or moisture may be pumped or drawn out or a rupture of the metal of the tube might be caused during the later stages of the draw-' ing down of the wire.

The cylinder, when properly packed, is then treated as though made of solid metal in the manner of drawing tungsten wire and can be readily reduced to filamentary size.

When drawn to the desired diameter the,

Specification of Letters Patent.

Patented July 6, 1920.

Application flied April 24, 1919. Serial No. 292,405.

compound wire may then be cut into lengths suitable for incandescent lamps and the inner metal drawn out of the inclosing tube, or the tube may be dissolved in acid or other solvents and thus leavethe wire clear. Another way of removing the tube metal from the refractory wire is to cut it in lengths suitable for lamp filaments, place them in a flashing jar, connecting them with electrical terminals and after exhausting the turning on a proper current on the tube and contents snfficient to melt the tube from the contained wire but not enough heat to injure the wire.

In using this invention it may be proper in some cases to insert the refractory slug in a cylinder or tube without using the oxid filling and this is particularly so where it is found better to remove the tube metal by means of acids or other solvents or by meltin" the tube from the wire.

It will be proper to so regulate the diameter of the tube to the diameter of the slug so that the tube will be strong enough to allow of its being drawn down the entire distance with the slug and yet have it thin at the finishing dies.

In the method hereinbefore described the refractory slugs are set forth as being hammered and worked before placing in the tube or cylinder but they may instead be placed in t e tube before being worked and then be hammered or forged after being'inserted in the tube.

In place of using one tube I may in some cases use a double tube, for instance, a tube of some ductile metal such as, for example, copper, silver or nickel, may receive the slug of refractory metal and this tube be placed in an outer tube the tubes then being drawn or rolled in the same manner as already herein set forth. A steel tube is preferably em )loyed as the outer cylinder.

After the drawing operation the outer tube is removed by dissolving it in hydrochloric acid or sulfuric acid. There then remains on the drawn Wire a thin coating or shell of the material of the inner tube. Lastly the thin coating can be removed by melting it or by dissolving it in acid. The refractory oxid may be packed in the inner tube as hereinbefeore described.

This invention is characterized by that a refractory metal which is poor in its malleability and inserted in the metal tube made of a malleable metal is subjected to an elongation by means of operating said metal tube, so that whenever the metal tube is operated to an appropriate size. the metal wire inserted therein can be made very fine compared to the size of the tube; according to this process. there is no necessity to employ the accurate and expensive diamond dies in the case when dies are required to operate such metal wire as the inexpensive copper dies which have larger holes are sufiicient to accomplish the purpose; furthermore, according to this improved process, the metallic oxidation caused by a high temperature of metal when it is drawn through die holes is utterly avoided, and a metallic filament in any small size can easily be obtained by adjusting the diameter of the outer tube to be employed, so that the incandescent filaments are economically produced by this process, and the outer tube dissolved in this method is utilized to make some salts as a by-product of this process, thereby not causing any loss in an economy.

What I claim is;

1. The method of drawing refractory metal to a filamentary diameter which consists in surrounding a refractory slug of metal with a refractory oxid, placing these evenly in a metal tube, drawing the tube and contents to a filamentary size and removing the tube and oxid from the inclosed refractory metal.

2. The method of drawing refractory metal to a filamentary diameter which consists in surrounding a refractory slug of tungsten with a refractory oxid, placing these in a metal tube, exhausting theair therefrom, hammering and working the tube and contents at a heated temperature, drawing it to a filamentary size and removing the tube metal and oxid from the inclosed tungsten.

In testimony whereof I have aflixed my signature in the presence of two witnesses.

J UNZO HISAMOTO.

lVitnesses lucnom RoJIMA, TAFUIIOHI NAKAYAMA.