GB922039A - A method of drawing or extruding elongated metallic workpieces - Google Patents

Abstract

922,039. Drawing; extruding; making tubes. T.I. (GROUP SERVICES) Ltd. Jan. 22, 1962 [Feb. 27, 1961], No. 7042/61. Classes 83 (2) and 83 (4). A method of making a tube or bar of round or other section comprises placing a metal workpiece 3 within an extensible metal envelope 7, 8 formed, at least in part, of longitudinally divided sections secured together to permit easy separation, heating the assembly, drawing or extruding it, and subsequently removing the envelope. The workpiece 3 may be of beryllium. A central core 4, preferably of a material having a higher expansion coefficient than the workpiece, is placed within the workpiece and a hollow liner 7 is surrounded by longitudinally divided sections 8, which may be of steel, secured together by light welding at 9 and also at 10 to end plugs 5, 6. A coating of lime is applied to these sections 8 to prevent their welding together and to the liner during the extrusion or drawing ; the sections may also be oxidized or coated with an oxalate to promote spreading of the lime. After extrusion or drawing the assembly is machined or pickled to remove the welding 9, 10, the sections 8 are detached, the liner 7 is removed by pickling and the core 4 is then stretched to facilitate its removal. The core may comprise a tube of higher expansion material and a solid inner portion. Alternatively, the core may be omitted and a fixed mandrel used. The liner 7 may be omitted when using a solid workpiece or a core.