GB1185994A - Improvements relating to Tube Welding - Google Patents

Abstract

1,185,994. Welding by fusion. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 7 March, 1968 [20 March, 1967], No. 13022/67. Heading B3R. Tube to tube plate and like joints are welded internally by a gas-shielded consumable electrode arc-welding gun having a head 2 rotated to guide the electrode 3<SP>1</SP> around the joint X. The head 2 has a body 1, to which the electrode 3<SP>1</SP> is guided by a tube 4, and an insert 11 fitting into a slot in the body 1. A groove 12 in a curved surface of the insert 11 serves to direct the electrode 3<SP>1</SP> to the joint. The body 1 has an insulating coating or insulating spacers. Gas is fed through apertures 6 to the welding zone. In a modification the body 1 is in the form of a curved electrode guide tube which may be surrounded by a curved gas nozzle. The electrode provides about 60% of the weld deposit. Carbon steel workpieces are welded using an electrode providing a weld of lower carbon content, e.g. 0À08-0À12% C. Austenitic stainless steel workpieces are welded, using an electrode which provides a weld containing 2-15% ferrite. Reference is also made to workpieces of killed, semi-killed and rimming steel, creep-resistant steels, e.g. 1% Cr, ¢% Mo; 2“% Cr, 1% Mo; 5% Cr, ¢% Mo, and 12-14% Cr steel, aluminium, titanium, nickel, copper and their alloys. Welding may be by dip transfer using carbon dioxide or 80% argon, 20% carbon dioxide, argon-shielded spray transfer or argon-shielded pulsed arc. Reverse or straight polarity may be used. The workpieces are spaced and a gas backing at a desired controlled pressure or a non-consumable backing in the form of a ring, which may be split, of ceramic or ceramic coated steel, is used. A tube plate may be formed with stub tubes or annular recesses serving to locate rings 62, Fig. 6, serving to support the backing ring and to align the tube 8 with the plate 7. A shoulder 61 on the tube or a detachable gauging ring or clamp may contact the end of the supporting ring 62 which thereby ensures the correct welding gap. Alternatively, a thin consumable aligning insert 151, Fig. 15, may be used. The supporting ring 62 may be dispensed with and the backing ring 182, Fig. 17, may be shaped to engage and align the workpieces and to form a weld fillet where the adjacent parts of the tube 8 and tube plate 7 are of different dimensions or to shape the back of the weld to form a rounded bead.