GB1353731A - Welding processes - Google Patents

Abstract

1353731 Welding by fusion NATIONAL RESEARCH DEVELOPMENT CORP 19 April 1971 [31 Oct 1969] 53576/69 Heading B3R Workpieces welded by laser or electron-beam techniques have a material having sealing or adhesive properties located in contact with the faces to be joined or astride the joint. In Fig. 1 sealant 13 between the workpiece joint faces permites the use of an open-ended electron beam vacuum chamber 14 with inflatable seals 15, 16. Reduced pressure may be provided on the opposite side of the joint. In another form (Fig. 2, not shown), an additional layer of sealant is placed behind the joint and supported by a backing bar. Variations of this form are described (Figs. 3 and 4, not shown). The process may be applied to the peripheral internal or external welding together of cylinders. For external welding (Figs. 5 and 6, not shown) an annular backing bar comprised of arcuate segments supports a layer of sealant behind the joint, the joint also incorporating sealant. For internal welding (Fig. 8) a similar external backing bar 25 is used, and the interior region of the cylinders, including the joint area, is enclosed by diaphragms 28, 29 which define a chamber 30 which is evacuated through conduit 32, (about which the electron beam device orbits), or otherwise. The process may be applied to welding a closure in a pipe end (Fig. 2, not shown), or a tube to a tube plate (Fig. 10). In both cases the electron beam is provided in a glow-discharge technique in which positively-charged ions from a plasma formed inside a solid concave cathode strike the cathode with the emission of a beam of secondary electrons. The beam chamber is sealed to the workpiece by 0-ring seals. In welding the tube 40 to a tube plate 41 using sealant 35, the tube bore is sealed with an adjustable bung 42. The material applied to the joint area may serve merely to hold the workpieces in proper alignment for welding, or may act as a vehicle for a filler material. A number of materials are specified. The filler may contain a corrosion inhibitor, or an isotope or fluorescent material for pre-programmed or pre-weld location of the joint or to assist post-weld detection and inspection. The filler may modify the chemical and/or metallurgical composition of the joint, and may contain deoxidants and an extrusion agent. The laser beam process may employ a CO 2 laser, and the material and beam wavelength are arranged so that the material is preferentially heated by the laser beam to assist degassing.