Patent GB-245090-A (GB)
Title: Improvements in and relating to methods of and apparatus for electric arc welding
IPC: B23K9/173
Filed: 1925-12-10
Abstract: 245,090. British Thomson-Houston Co., Ltd., (Assignees of Alexander, P. P.). Dec. 26, 1924, [Convention date]. Heating by electricity.-In welding sheets, plates, cast iron &c. by an electric arc maintained between a pool of molten metal on the work and a carbon or metal electrode, the arc is surrounded by hydrogen so as to reduce oxides, remove occluded oxygen, and exclude atmospheric air and so effect a ductile weld, the hydrogen burning in contact with the surrounding air. The critical arc voltage is about 38 and a striking voltage of not less than 120 is used, preferably from 180 to 200 volts with direct current and up to 300 volts with alternating current, and the heating effect and thus the speed of welding is increased. A current of from 20 to 250 amperes mav be used. A wide arc is produced having a white incandescent core 20, Fig. 1, enveloped in a thin red sheath and a series of white streamers 21. An automatic, semi-automatic or hand welding apparatus may be used with carbon electrodes, with or without a filler or with bare or fluxed metal electrodes and work up to 1" in thickness may be welded without bevelling the edges. The arc voltage may vary from 40-100, which produce arcs of different lengths, all of which are effective when welding in hydrogen, the speed of deposition depending on the arc length and being greatest with an arc length of about <3>/16". When using alternating current and a fluxed electrode an arc voltage of 80 may be used, and with direct current and a fluxed electrode as described in Specification 167,399 a striking voltage of 130 to 180 may be used, and for bare metal electrodes 180 to 200. The current may be supplied from a constant voltage source through a series stabilizing resistance or from a regulated source of either the variable or constant current type such as a generator described in Specification 159,374, or the striking voltage may be obtained from an auxiliary source, the remainder of the current being supplied from a source at lower voltage. The hydrogen may be ignited before the arc is struck. In Fig. 1, the arc is controlled by apparatus as described in Specification 184,141. The electrode wire 1 passes from the flexible guide tube 7 through a tube 12 passing through a perforated plug 13, which closes the end of a chamber 15 supplied with hydrogen under pressure through a valve 18. A nozzle 16 is secured to the plug and a member 19 to the tube 12 and the size of the gas orifice is varied by adjusting the member 19. In Fig. 2, The hydrogen passes into a member 22 secured to a member 23 and to the nozzle 24. In Fig. 3, the flexible guide tube 7 and current carrying conductor 27 are enclosed in a rubber or like flexible insulating tube 26 serving as the chamber for the hydrogen which passes to the work by way of a body 28 and nozzle 29 provided with heatradiating ribs. In another form the nozzle may be surrounded by an asbestos hood, provided with a quartz inspection cover, the nozzle being preferably provided also with lateral openings to assist in filling the hood with hydrogen. In a hand welding apparatus, Fig. 5, the electrode 1<1> is inserted through the open top of an asbestos hood 39, above which the hydrogen, supplied through the tube 41, burns. The current may be supplied from a direct current generator having a shunt exciting winding 43 and a series cumulatively wound winding 44 which is connected to the electrode through a stabilizing resistance 45 and reactance 46 so that a low voltage only is produced when the welding circuit is open. Specifications 27714/04 and 8641/07 are also referred to. The Specification as open to inspection under Sect. 91 (3) (a) states that the size of the gas orifice may be varied by adjusting the nozzle 16 on the plug. This subject-matter does not appear in the Specification as accepted.