GB1131031A - Improvements in overlay welding - Google Patents

Abstract

1,131,031. Welding by fusion. ARCOS CORP. 1 Oct., 1965 [2 Dec., 1964; 24 June, 1965 (2)], No. 41780/65. Heading B3R. [Also in Division C7] In overlay welding on a base-plate, each bead is formed by the fusion of the edge of an adjacent bead, the upper surface of the base-plate, a barrier in the form of a layer of powder or a strip of metal deposited on the base-plate near the adjacent bead, and a consumable strip electrode located generally transverse to the welding direction. In this way a plain carbon or low alloy steel plate may be coated with a plain carbon or a chromium nickel stainless steel, a nickel alloy, e.g. 76% Ni, 16% Cr, 8% Fe or 67% Ni, 30% Cu, copper or cobalt alloy. The barrier serves to reduce dilution of the overlay. The strip electrode may be skewed in either direction, and is ¢ to say 12 inches wide and 0À02-0À25 inch thick. A barrier strip may be of similar dimensions and may be fed at the same or a faster rate than welding speed and have one edge flanged. The barrier strip may be spot or seam welded to the base or may be adhered by coating the base with 7% nitrocellulose and 3% aluminium in butyl acetate or a mixture of ethyl acetate and toluol, which coating serves as a deoxidizer, or by using an adhesive flux coating consisting of one of boric acid, ammonium chloride or lithium chloride in a solvent of water or alcohol. Where the baseplate is a high carbon steel the surface is decarburized by heating in wet hydrogen at 1200- 1400‹ F., by flame treating to scale the surface with iron oxide or by adhering the barrier strip using a decarburizing flux, e.g. 10% Cr 2 O 3 , 10% Fe 3 O 4 in sodium silicate solution and baking prior to welding. A photo-electric cell may be used to indicate if the gap between the barrier and the adjacent bead is excessive, and the process may be stopped automatically if the barrier ceases to be fed. Other adhesive fluxes that may be used are aluminium or magnesium powder; 95% calcium fluoride, 5% manganese; 98% calcium fluoride, 2% aluminium; with in each case a binder of sodium silicate. Submerged arc welding may be used with deposition of granular flux of the same or different composition in front of and behind the electrode. Alternatively arc welding using as a shielding gas carbon dioxide, argon or helium, may be used, with no flux or with flux in one or both of the electrode and the barrier. An overlay of 0.049% C, 0À89% Mn, 0.85% Si, 18.02% Cr, 9.4% Ni, balance Fe is produced using a powder barrier of 0.019% C, 0À65% Si, 18.15% Cr, 10.10% Ni, balance Fe, an electrode of 0.035% C, 1.14% Mn, 0.68% Si, 18À21% Cr, 9.53% Ni, balance Fe and the following submerged arc flux, 25% fluorspar, 15% aluminium silicate, 2% clay, 3% Mn, 6% Cr, 1% Al and a sodium silicate binder. A hard surface of 0.3% C, 5.4% Mo, 2.7% Ni, 24% Cr, 58% Co, balance substantially Fe is produced using a cobalt electrode a powder barrier of 24 parts Cr, 3 parts high (10%) carbon Cr, 3 parts Ni, 6 parts Mo and the above submerged arc flux. The barrier powder may be fed from a plurality of valve controlled sources. The barrier is usually thicker than the electrode. The welding supply may be A.C. or D.C. of either polarity. The electrode and/or the barrier may be compacted or sintered powder which includes flux, or may be a plain metal strip or a strip with a layer of such powder or a sandwich with the powder compact in the centre. The metal strip may be fluxcored. In a machine for automatically welding with a powder barrier, the barrier 66<SP>5</SP>, Fig. 35, is deposited from a hopper and levelled by a scraping plate. Granular flux is deposited behind the scraping plate and also from a nozzle 94 behind the strip electrode 56. The electrode is fed by rolls and guided by edge rolls 61 to a contact device comprising spaced steel members 70, 71 and an intervening copper shoe 72 on one side and a steel member 69 on the other side. The shoe 72 is mounted on the upper member 70 and is spring-loaded. The feeding and contact arrangement is adjustable about a vertical axis. In a modification for overlaying the inside of a cylinder, the machine is mounted on a boom 40<SP>1</SP>, Fig. 1a, and carries a reel 66<SP>2</SP> of barrier strip 66 and a spring-loaded roller 106 or guide fingers for pressing the strip 66 against the base-plate. The axis of the cylinder is tilted at ¢-10 degrees so that the weld pool tends to run to the adjacent bead, and welding takes place at a location spaced “-3 degrees back from the vertical plane. Where shielding gas is used it is fed from a nozzle adjacent the electrode or into an enclosure surrounding the weld zone. The work or the machine may be stationary.