Patent GB-1087304-A (GB)
Title: Hot compression process and applications of said process to the bonding of metal parts
Inventor: LACROIX ROGER
IPC: B23K20/22
Filed: 1965-05-13
Abstract: 1,087,304. Welding by pressure. COMPTOIR LYON-ALEMAND, LOUYOT & CIE. May 13, 1965 [May 29, 1964], No. 20324/65. Headings B3A and B3R. In a hot compression process which may be used for bonding metal parts or for densification of metal parts obtained by the compression of powders, the parts to be compressed, for example plates 23, 24 and 25, 26, are put between jaws 28 and clamped in an outer jacket 29 made of a material having a lower coefficient of expansion than that of the jaws 28 so that upon subsequent heating the plates 23, 24 and 25, 26 are forced together by pressures generated by virtue of the differences in expansion. The bonding of plates, which may be subsequently drawn or rolled, may be either in solid phase or by means of brazing or soldering compounds and plates not required to be bonded are separated by a layer 27 of, for example, asbestos, graphite, magnesia, alumina or a sheet of paper which is reduced to a carbon deposit after heating. The outer jacket 29 may be a continuous tubular member which is force fitted or shrunk on to the jaws 28, or may be in wire or strip form which is wound helically on the jaws. The jaws 28 may be hollowed out to accommodate heating sources. The heating may be carried out in a vacuum or a suitable protective atmosphere and may be by low frequency induction means. In examples described gold alloy is overlaid on cupro-nickel plates for subsequent rolling or die-stamping; gold alloy is overlaid on bronze in a protective atmosphere of nitrogen containing a small proportion of hydrogen; gold alloy foil is overlaid in a vacuum to a ferritic stainless steel after first electro-plating the steel with a layer of silver; electrical contacts are formed by bonding phosphor bronze edges to a silver plate and rolling the plate to obtain a thin strip from which the contacts are cut out; a silver strip is inlaid in a plate of bronze; and contacts containing 60% silver and 40% tungsten carbide are bonded on a copper base obtained by powder metallurgy in an atmosphere of cracked ammonium. In disclosures of prior art pairs of plates are enclosed in a box 1, Fig. 1 (not shown), holding a neutral or reducing atmosphere and the whole assembly is heated in a furnace and rapidly thrust beneath a press; a pressure plunger (6), Fig. 2 (not shown), and a heating coil (11) are arranged within a chamber (8) so that the plates (10) can be heated and then pushed on to a bottom plate (7) and have pressure applied; the plates to be bonded are held under pressure by a press (16), Fig. 3 (not shown), before being heated by a furnace (13); plates (17), Fig. 4 (not shown), may be welded at their edges before heating and hot-rolling; a tube (21), Fig. 5 (not shown), having a coefficient of expansion less than that of a part (20) may be bonded thereto by pressure generated by differential expansion on heating, or if the coefficient of expansion of the tube (21) is greater than that for the part (20), then a force-fitted or shrunk-on casing (22), Fig. 6 (not shown) of low coefficient of expansion is arranged on the tube (21) before heating.