Patent GB-498838-A (GB)
Title: Electrical welding process
IPC: B23K11/00
Filed: 1937-07-14
Abstract: 498,838. Uniting by fusion. MONOTHERM VERSCHMELZAPPARATE KONSTRUCTIONSUND VERWERTUNGS-GES. July 14, 1937, Nos. 19577 and 19578. Convention dates, July 14, 1936 and Nov. 9, 1936. [Class 83 (iv)] In electric welding, a heater body, the resistance of which is such that the welding temperature is maintained solely by the heat developed in the body by the passage of the current, is brought into contact with the work, the body being so composed or heated as to influence or modify the character of the welded metal. The process may be used for welding metal alloys containing chromium such as stainless steel, for welding aluminium or other metals oxidizable at welding temperatures, or for welding powdered hard metals to metallic surfaces to form a mechanically resistant surface. In welding aluminium sheets, the heater body is heated to temperatures in the region of 2050‹ C. so as to melt the aluminium oxide formed during welding, the electrode in this case consisting of carbon or graphite annealed in an electric furnace. For welding aluminium and other metals which form solid oxide coatings during welding the heater body is preferably heated to a temperature only a little above the melting point of the coating so that only the parts of the coating under the electrodes are melted. Instead of using high temperatures for the removal of the oxides or slags, the electrode may contain substances for reducing the slags, such as titanium, metals of the chromium group or of the alkaline earth group or their carbides or silicides. Carbides or silicides may be used with or without carbon or graphite. In such cases the final product formed by the reduction should have a boiling point lower than the welding temperature so that they escape in the form of a gas or vapour. As an example, for welding aluminium alloys the electrode may consist of graphite with the addition of 10-20 per cent of silicon carbide. For welding alloys containing chromium, such as stainless steel, the carbon electrode may contain titanium carbide. Carbides of manganese, molybdenum, and tungsten together with graphite may be used. If desired, the carbides or silicides may be formed during welding by using an electrode with a metal or carbide core covered with a layer of metals, carbides or silicides. An electrode may also be formed by sintering a mixture of powdered molybdenum or tungsten or carbides thereof and carbon. To weld mechanically resistant substances on to a surface the heater body may have one or more channels through which the powdered hard metal &c. is blown by a stream of inert gas. The Specification as open to inspection under Sect. 91 states that nitrides or borides of titanium &c. may be used, or substances to produce hydrogen, and platinum or palladium to convert the hydrogen into its atomic state. Also a metal or carbide core mav be coated with carbon, or a carbon core may be coated with a layer of metals, carbides or silicides. To increase the carbon or silicon content of the joint the electrode may contain such substances and to reduce the carbon content the electrode may contain substances reacting therewith. The electrode may have a profile so as to smooth the joint as it traverses it. For this purpose it may have a bevelled or sharpened end or it may be of stream-line shape or may consist of a cylinder, wheel or roller. The electrode need not exert any considerable pressure on the work. The edges of an aluminium sheet may be flanged to engage the electrode. This subject-matter does not appear in the Specification as accepted.