Patent GB-1215384-A (GB)
Title: Process for explosively bonding together metal layers
IPC: F42B1/00
Filed: 1968-06-27
Abstract: 1,215,384. Welding by pressure. E. I. DU PONT DE NEMOURS & CO. 27 June, 1968 [29 June, 1967], No. 30725/68. Heading B3R. [Also in Division F3] In a process for explosively bonding metal layers, in which a layer of explosive is placed on the outer surface of at least one metal layer, the or each explosive layer 8 is initiated by detonation of a primer 1 which is embedded in the explosive layer with its longitudinal axis perpendicular to the explosive layer, that end portion of the primer which is closest to the metal layer 7 bearing the explosive in which it is embedded being of smaller cross-section normal to the longitudinal axis than the remoter portion of the primer, detonation of the primer being initiated at the end of the remoter portion. The primers are preferably constructed so that detonation along their peripheral portion precedes detonation along their longitudinal axes whereby an annular impulse followed by an axial impulse are sequentially applied to the metal layer. The term layer includes a planar or a curvilinear e.g. tubular, body. Preferably, the primer has a higher detonation velocity than the layer of explosive in which it is embedded. The peripheral shape of the primer may be circular, oval, rectangular, triangular or other polygonal. In one embodiment (Fig. 1, not shown), the primer has a cylindrical portion (1b) and a lower frusto-conical portion (1a) comprising e.g. cast or extruded plastics explosive (2) surrounded, at its cylindrical portion (1b) with a different explosive sheath (3) which also forms a thin disc (4) over the end of the cylindrical portion (1b), the centre of the disc (4) having a blasting cap (5) affixed thereto. The sheath (3) may have a higher detonation velocity than the body of the primer. In a second embodiment (Fig. 2, not shown), the primer has a cylindrical body (2), a sheath (3) and a disc (4) of such area that the primer has a smaller cross-section portion at the end which will be adjacent the metal, i.e. the end opposite that covered by the disc. Alternatively, the disc may have the same area as the end of the cylinder and additional explosive may be wrapped or otherwise formed about the disc. In a further embodiment (Fig. 3, not shown) the primer has a body (2) of frusto-conical shape having an inert (e.g. wood) block (6) inserted at its larger end so as to provide a narrow circumferential portion on a narrow end portion of explosive. In modifications (not shown), the primer may be similar to that of the second embodiment, but the disc may extend over the layer of explosive on the metal plate; the end of the primer may-be a point e.g. the apex of a cone; the primers may be of powdered explosive in a weak container e.g. cardboard. Typical explosives which may be used are PETN, TNT, RDX, HMX and other organic nitrates, nitramines, and nitro compounds, inorganic azides, and mixtures of the foregoing alone or with e.g. cast pentolite or 80/20 amatol. Instead of a blasting cap, a line wave generator can be used to initiate the primer. Protective material between the end of the primer and the metal layer may be used; the primer may be placed centrally, at an edge or at a corner of the metal layer, and a number of primers may be used. Two or more metal layers may be bonded and one or more explosive layers may be provided. In a first example a silver/copper alloy cladder plate is bonded to a copper/silver alloy backer plate; in a second example titanium cladder plates are bonded to a steel backer plate to sandwich the latter, one cladder plate being propelled by a primer as described above and the other by a conventional constant cross-section primer. The results are compared.