GB744313A - The production of tubular steel junction pieces - Google Patents

Abstract

744,313. Making composite tubes. CHESTERFIELD TUBE CO., Ltd., and UNITED STEEL CO'S., Ltd. Feb. 25, 1954 [March 2, 1953], No. 5775/53. Classes 83 (2) and 83 (4). Extruding.-A tubular junction piece between tubular members of austenitic and ferritic steel respectively is made by inserting two heated slugs 1, 2 of the respective steels, assembled face to face and sealed together at their exposed mating surfaces, in a die or container 4 and extruding them by a plunger 6 into tubular form thereby to force the trailing slug 2, Fig. 2, into the leading slug 1 and thus produce a joint in which a tapering length of one steel surrounds a complementary tapering length of the other steel. The slug 1 is of austenitic steel containing 18 per cent chromium, 12 per cent nickel 1 per cent niobium and 0.1 per cent carbon; the slug 2 is of ferritic steel containing 2.25 per cent chromium, 1 per cent molybdenum and 0.1 per cent carbon. The slugs are welded together at 3 to prevent oxidation at their contacting surfaces and are heated to 2150‹ F. The slugs are then extruded between the outlet of the die 4 and a mandrel 5 to form a tubular junction piece which may be drawn down to a smaller wall thickness and then machined inside and outside to the desired diameters. This junction piece is butt welded in position between austenitic and ferritic steel tubes 22, 23, Fig. 5 (not shown). In order to prevent migration of carbon, a barrier layer of nickel, applied as an electrolytic coating or as a thin sheet, is disposed between the two slugs. A number of pairs of austenitic and ferritic steel slugs 1, 2, Fig. 6, welded together at 3 as a unit or in pairs, may be extruded in one operation to form a tube which is subsequently cut into individual junction pieces. These slugs are solid and are pierced by a piercing mandrel 10 before extruding. In another embodiment, Fig. 7, a pair of slugs 1, 2 are extruded rearwardly by a punch 11 to form a composite closed-ended cylinder which is subsequently drawn through dies 17, 18, Fig. 10 (not shown), and the closed end is then removed. Punch guides 14, 15 and an ejector 13 are provided.