GB784484A - Improvements in or relating to the manufacture of hollow fluid conducting members - Google Patents

Abstract

784,484. Making pipes and heat exchangers, casting composite ingots, stamping. REVERE COPPER & BRASS, Inc. March 9, 1956 [March 9, 1955; June 29, 1955], No. 7529/56. Classes 83 (1), 83 (2) and 83 (4). A method of making metal strip having one or more longitudinal slits which can be expanded by fluid-pressure to form tubular passages, e.g. for heat-exchangers, comprises casting a billet around one or more rods of friable material capable of being crushed to a weld-preventing powder and rolling the billet to the required thickness thereby crushing the rods and forming slits filled with the weldpreventing material. The rods 3 are preferably of rectangular-section but could be of round, oval or tubular form and are made of graphite, soapstone, china clay, magnesia or alumina. After rolling, the sheets are clamped between die plates such as 59, 61, Fig. 16, and the slits 7 expanded by fluid-pressure to form such shapes as those shown in Figs. 7 to 10. Before the expansion the ends of each of the slits is opened out mechanically, a plug 41, Fig. 14, is inserted at one end and a nozzle 35 at the other. The billet may contain several rows of rods to give sheets with slits arranged as shown in Figs. 24, 26 or 31, which may be expanded as shown in Figs. 25, 27, 32, 51, 54. The sheets may be slit longitudinally to form single tubes, or a billet may be cast around a single rod and the tubes thus formed, after expansion, may have marginal portions by which it can be fixed to a surface, e.g. Figs. 46 and 47. In addition the walls of the tube may be formed with corrugations, Fig. 49. The sheets may be of aluminium, zinc, copper, brass, bronze, nickel silver, stainless steel or carbon steel. Casting. The billets are cast in a mould comprising a vertical chamber, Figs. 34, 36, with side walls 77 engaged by water-cooled castings 87, 89, end walls 79 formed by water-cooled castings 91, and a bottom 81 formed by a watercooled casting 93, the elements being secured together by bolts. The rod inserts are held in position in the mould by upper refractory horizontal plates 111, 113, preferably of graphite and by lower refractory plates 127, 129 which clamp the rods to prevent them from rising due to buoyancy when the molten metal is poured through an upper pouring-box 121. In a modification, the inserts are built up from a number of interengaging sections 285, Fig. 59, threaded on rods or wires 279 which are secured within the mould. Alternatively, the billets may be formed by continuous casting.