GB580794A - Improvements in and relating to fusion welding - Google Patents

Abstract

580,794. Uniting by fusion. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 6, 1944, No. 17014. Convention date, Sept. 13, 1943. [Class 83 (iv)] In a method of fusion welding, particularly of parts of magnesium, aluminium or their alloys which are readily oxidisable to form over the molten portion a refractory oxide skin, the parts which have or are bevelled on their upper sides to obtain contacting joining edges about #" thick, have the contacting edges smoothed and the lower halves thereof bevelled so that they are separated from one another by an amount sufficient to permit the edge portions of the parts at the joining edges, when fused, to drop down to form a reinforcement along the bottom edges without coming into contact with each other, heat being applied to the top surface of the edge portions to melt them and form a gap between the parts which is then filled with molten metal to complete the weld. Complete fusion at the bottom of the weld is thus obtained without excessive dropping down of the molten edges. Edges of about #" thick have contacting portions 20 and bevelled lower portions 21, the widest parts of which may be about 0.005-0.025" apart or the bevel may be up to an angle of 90 degrees. When thicker parts are being welded, the upper portion is first bevelled to bring down the thickness to about #" and the upper bevelled portion, after welding the other portion as previously described, is filled with weld metal in a series of passes. Welding may be effected by flame or by the electric arc, in the latter case in an atmosphere of helium or argon as described in Specifications 273,297 and 273,705, [both in Class 83 (iv)]. A tungsten electrode 10 surrounded by a gas chamber and a nozzle arranged at an angle of at least 60 degrees with respect to the electrode and through which a filler metal rod 17 of the same metal as the work is fed, are traversed along the line of weld. Welding of a #" sheet of an alloy containing 6 per cent of aluminium, 0.7 per cent of zinc, 0.2 per cent of manganese and the rest magnesium, may be effected with a 65 amp. current at 16¢ volts at a rate of 13" per minute. The parts may be held on supports 22, 23 with their bottom edges unsupported or arranged over a grooved backing member such as of stainless steel with a wide groove.