GB1327733A - Process and apparatus for triple-electrode mig welding - Google Patents

Abstract

1327733 Welding by fusion MITSUBISHI JUKOGYO KK 14 Feb 1972 [24 Feb 1971] 6783/72 Heading B3R In flat position, open-square, butt MIG welding of thick plates 10, each of a plurality of weld metal layers is effected by three wire electrodes 5A-5C which are moved together relative to the plates 10, the electrodes 5A, 5C leading and acting in a clip transfer mode to effect fillet welding at the weld groove sides, and the electrode 5B following and acting in a spray-transfer mode to fill in between the fillet weld beads. The electrodes 5A-5C are arranged at the corners of a scalene or isosceles triangle, and may be of the same or different sizes, e.g. the electrodes 5A, 5C may be of small diameter (e.g. 1 mm.) and the electrode 5B of larger diameter. The electrodes 5A-5C are fed by devices 14C-14C from reels 8A-8C through contact tubes 4A-4C housed in a shielding gas cup 2 and located by an insulating spacer (3). The contact tubes 4A, 4C are angled outwardly (e.g. 45 degrees) at the ends, and the contact tube 4B is straight. Cooling water tubes (7A-7C) are disposed in contact with the contact tubes. Welding transformers 6A-6C feed current to the electrodes. Pre- and post-heating may be dispensed with, the electrodes (15A), (15C) effecting pre-heating for the bead laid by the electrode (15B) and the electrode (15B) effecting post-heating for beads laid by the electrodes (15A), (15C). The workpiece weld preparation edges need only be flame-cut.