GB659015A - Improvements in method of welding aluminium - Google Patents

Abstract

659,015. Uniting by fusion. AIR REDUCTION CO., Inc. July 18, 1949, No. 18873. Convention date, July 28, 1948. [Class 83 (iv)] A method of welding aluminium and aluminium alloys comprises feeding an aluminium or aluminium alloy wire 5 to a point adjacent and spaced from the workpiece 18, maintaining an electric arc between the wire and the workpiece and surrounding the arc with an inert gas. The wire 5 is withdrawn from a reel 6 by rolls 9 driven by a motor 10 and passes through a current pick-up shoe 11 in an electrode holder 12 which has a gas chamber 13 and a nozzle 14 for discharging the gas around the wire electrode 5. The pick-up shoe 11 and the workpiece 18 are connected by cables 15 and 17 to a welding machine 16. A cylinder 19 delivers the gas, preferably argon, through a valve 20 to a pressure gauge 24 then to a pressure-reducing valve 21 and via a pressure gauge 25 to a pipe 22 controlled by a valve 23 leading to the chamber 13. The delivery rate of the gas must ensure a laminar flow and that the arc atmosphere contains not more than 2 per cent by volume of impurities and not over ¢ per cent of atmospheric impurities. The workpiece is used as the cathode so that the oxide film on the work is removed by electron emission and positive ion bombardment at the weld puddle. The current may range from 75 to 1050 amperes at 14 to 30 volts. Aluminium or aluminium alloy plates above three-eighths of an inch in thickness can be welded in a single pass at high speeds with 480 amperes D.C. reverse polarity at sixteen inches per minute with no edge preparation _ other than sawing. Preheating for heavy sections is reduced from 400‹ to 150‹ F. or lower. Helium and the inert atmospheric gases of greater atomic weight than argon, or mixtures thereof, may be used. The wire 5 is preferably uncoated but may have a wash coating of any suitable material to aid the stabilization of the arc.