Method of explosively welding tubes to tube plates

1,124,891. Welding by pressure; jointing by tube expanding. WESTINGHOUSE ELECTRIC CORP. 8 June, 1966 [28 June, 1965], No. 25454/66. Headings B3J, B3Q and B3R. In explosively welding an open-ended metal tube to a metal plate having a planar surface, an opening is provided in the plate in which an end portion of the tube is inserted with the open end of the tube in juxtaposition with the planar surface and an explosive charge enclosed in a body of deformable material positioned in the end of the tube is detonated to weld an annular portion of the tube to the plate. A heat exchanger tube plate 12 comprising a body 17 of mild steel and an outer layer 18 of nickelchromium-iron alloy has openings 13 therethrough receiving open-ended tubes 15 of hairpin shape also of nickel-chromium-iron alloy. The outer ends of the openings 13 are counterbored at 21 and prior to insertion of the tubes the inside of the opening, the counterbore 21 and the tube ends are degreased, wire brushed and blown with dry air. With the tube end slightly beyond the planar surface S of the plate an explosive charge 25 is placed within the tube end with an electric detonator 26 and the charge 25 embedded in deformable filler material 27 of paraffin, polypropylene, polyethylene, nylon etc. The charge of TNT of PETN in disc form is parallel to the plate surface S and when detonated expands the tube end into the counterbore where a weld 29 is effected. The end of the tube above the surface S is explosively sheared away. The clearance between the end of the tube and the bore may be obtained by swaging or otherwise reducing the diameter of the tube end portion. The preparation for all the joints may be made concurrently.