Patent GB-259590-A (GB)
Title: Improvements in and relating to methods of and apparatus for fusing metals by the electric arc process
IPC: B23K28/02
Filed: 1926-10-07
Abstract: 259,590. British Thomson-Houston Co., Ltd., (Assignees of Alexander, P. P.). Oct. 7, 1925, [Convention date]. Addition to 257,955. Lathe and like tools; dies.-In a process of electric arc welding in a gaseous medium consisting of nitrogen and hydrogen as described in the parent Specification, for depositing an alloy known under the registered Trade Mark as stellite on backing pieces for providing a wearing or cutting surface for a die or tool, the gaseous medium is produced by dissociating ammonia or a compound of the ammonia series such as trimethylamine. Liquid compounds of the ammonia series may be vapourized before supplying to the arc. The ammonia may be dissociated by the arc or may be previously dissociated and the resulting mixture compressed and stored for future use. The mixture may be preheated in the welding tool or other place to about 300‹ C. to increase its volume. Ammonia from a tank 1 containing liquid ammonia, under pressure may be passed over a dissociator 3 containing a catalytic agent consisting of iron filings heated to redness by a bunsen burner, the resulting mixtura being conveyed to a hood 4 with an open top, in which the parts 5 a,re welded by an arc struck from an iron or carbon electrode 6. The gases burn for a short distance above the openmg. In Fig. 2 the mixed gases or the ammonia are passed through a flexible tube 15 into an annular member, 11, preferably of copper, and of any geometric configuration, provided with two series of staggered holes 12 and an asbestos cover 13. The holes of one row project downwardly and those of the other row upwardly so as to prevent admixture of atmospheric air. If the member is to serve as a dissociater it is filled with iron filings and provided with a heating element insulated therefrom and consisting of a wire of an alloy known under the registered trade mark as nichrome. In an automatic or semi-automatic machine the ammonia is passed from a tank 1. Fig. 3, through a dissociater 3 consisting of a receptacle containing porous iron or iron filings 18 in which is embedded a tube 16 containing a heated nichrome wire 17 from which emerges a tube 20 to convey the mixed gases to the welding tool 21. The receptacle is encased in asbestos. In a further form, Fig. 4, the mixture from the dissociater 3 passes through a needle valve 28 into a heat insulated burner 27. In order to increase the nitrogen content of the mixture, air is drawn in through a valve 29 and the oxygen burnt, the mixture being conveyed to the arc. The gases may be ignited by sparking electrodes or by a tube 31 surrounded by a " nichrome " heater 30. The water vapour may be eliminated by passing the mixture through a finned tube 32 and finned condenser 33 provided with a water gauge 35 and overflow valve 36, the hydrogen and nitrogen mixture being conveyed to the arc through the pipe 37. The mixed gases may be stored in containers inserted in the pipe lines 20 or 37. When using dissociated trimethylamine &c. the resulting carbon is converted into carbon monoxide by mixing therewith carbon dioxide or water vapour, this gas being delivered to the arc together with the hydrogen and nitrogen. Specifications 184,141 and 272,067, [both in Class 83 (iv), Metals, Working], are referred to. The Specification as open to inspection under- Sect. 91 (3) (a) states that the mixture may also be produced by burning air in an excess of hydrogen or other gaseous medium which combines with oxygen. This subject-matter does not appear in the Specification as accepted.