Patent GB-1438653-A (GB)
Title: Explosive welding
IPC: B23K20/08
Filed: 1972-07-26
Abstract: 1438653 Welding by pressure UNITED KINGDOM ATOMIC ENERGY AUTHORITY 25 July 1973 [26 July 1972 17 Nov 1972] 34952/72 Heading B3R In welding a first component to a second component an explosive charge is detonated adjacent the first component to impact it against the second component while an anvil is positioned adjacent that side of the second component remote from the first, the anvil being so shaped and dimensioned and of such mass that it supports the second component against the forces generated by the explosion and is caused to fly completely away from the second component by the energy stored in the anvil after the weld is completed. In an embodiment a pipe 1a, Fig. 1, is welded underwater to a surrounding pipe 1 by placing an explosive charge 2 in the bore of pipe la adjacent its end, which is spaced somewhat from the pipe 1. A segmented anvil 3 is assembled around the pipes with initial restraint, inflatable bags are positioned in the pipes away from the charge 2, the water is pumped from the space between the bags and air is fed into the space. A rubber sleeve is assembled outside the pipes to prevent the passage of water into or through the joint and the charge 2 is detonated. The compression shock wave travels radially through the anvil until, when the charge is substantially half burnt, it reaches the free surface 5 so that the anvil is fully compressed. The compression in the anvil is relieved as a rarefaction or tensile wave extending inwardly from the surface 5, the surface 5 moves away from the explosion and the anvil starts to expand to its original size. When the rarefaction wave reaches the interface 4 between the anvil and the pipe 1 the anvil overcomes its restraint and is accelerated away from the pipe. An anvil for use in the explosive welding of two pipes to an external sleeve overlapping the butt joint comprises eight abutting segments which may be hollow and filled with water, held in place initially by two wire bands and one or more braking masses may be provided in the flight path of each segment. The segments may be loosely restrained initially by frangible couplings, shear pins, rubber bands, magnetic clamps or adhesives. Instead of employing abutting segments thin slivers 14 Fig. 9 may be used held in place by a hoop or band of wire or rubber and in a further modification each member may be in two parts 16, 17 Fig. 11 with the inner member held by a band 21 and the outer members by a band 22, as shown, the part 16 may be provided with a broaching tool 20 which just contacts the part 17 and which on the extension of the part 16 does work on the part 17. Shear pins may alternatively be located in the path of the moving end of part 16. Instead of holding the tool 20 in contact with the part 17 spacing may be provided so that impact is involved. In a further embodiment a resilient pad is located between the parts 16, 17. In a modification the anvil parts may be decelerated by a hydraulic or penumatic shock absorber, each outer anvil part being connected to a push rod carrying a piston operating in a cylinder, and the cylinder being carried on an annular yoke. Springs may replace the shock absorbers. The welding may take place, not only in water, but in air in other gases or in other liquids and the components being welded need not be pipes. An annular segmented anvil may be arranged between two segmented annular side plates.