Patent GB-547813-A (GB)
Title: Improved method of and apparatus for electric arc welding
IPC: B23K9/00
Filed: 1941-07-11
Abstract: 547,813. Electric arc welding. BRITISH  THOMSON-HOUSTON CO., Ltd. July 11, 1941, No. 8810. Convention date, July 12, 1940 [Class 39 (iii)] [Also in Group XXII] An atomic hydrogen welding apparatus applicable to silicon steel sheets comprises a clamp consisting of jaws 11, 12 and pole pieces 13, 14, between which thin plates 10 which are to be welded are held. The pole pieces 13, 14, controlling the arc are separated by a high reluctance gap formed by a strip of non-magnetic material 16 spaced slightly below the edges of the sheets. The clamp jaws are closely spaced so that they conduct heat away from the sheets, except at the edges, and they are provided with passages 17 for cooling water. The jaws are secured to box beams 18, 19 extending lengthwise of the machine, and the pole pieces 13, 14 are attached to a non-magnetic member 22 supported by cylinders 23 which rest on superposed sections of fire nose 24. The cylinders act as guides, and are supplemented by brackets 26 carried by the electromagnet and engaging the outer walls of a beam 25, parallel to, and attached to beams 18, 19. The seam between the sheets is welded by an atomic hydrogen torch as described in Specification 400,675. The torch, with its controls, is supported on a carriage travelling along a track supported by members 20. The electromagnet is provided with a plurality of coils 39 in series, on cores extending between the pole pieces. The supply circuit includes an inductance 41, variable resistances 40, 42, and variable inductance 43. The supply leads 44 are also connected through a variable inductance 45 to the electrodes 46. The phase relationship between the current supplied to the arc and to the electromagnet is adjusted by varying the relative values of resistance 42 and inductance 43. The torch carries a switch 35 actuated by contact with cams 38, by means of which portions of resistance 42 are cut out when the torch approaches the ends of its travel. The magnetic flux across the seam gap and the self generated flux inside the arc loop act to pull the arc down to the seam and position it immediately over the seam. If the magnetic flux is reversed, the arc is blown away from the seam, and the phase relationship may thus be used to control the heating effect, so that full heat is not applied at beginning and end of a weld. Additional heat control is obtained by variable resistance 40 controlling the flux intensity, or by variable inductance 45 controlling the arc current supply. If non-magnetic sheets are being welded, the seam requires more accurate alignment over the pole gap. The weld may be annealed by traversing the torch along it at a rate which raises it to red heat. The apparatus is applicable to arc welding otherwise than with an atomic hydrogen torch. Other forms of electromagnet may be used, or the field about a conductor extending lengthwise of the seam may be used. Alternatively, the electromagnet may be connected directly in the welding circuit, or through a series transformer so that the field varies with the welding current or the current to the electromagnet may be controlled without material change in the welding current. Alternatively, the magnetic field may be produced by direct current, so that alternate attraction and repulsion of the arc take place. Specification 439,644 also is referred to.