Patent GB-763141-A (GB)
Title: Improvements in the production of metallic bodies
Inventor: PFEIL LEONARD BESSEMER
IPC: B21C23/16
Filed: 1953-03-27
Abstract: 763,141. Extruding; piling; destructible cores. WIGGIN & CO., Ltd., H. June 28, 1954 [March 27, 1953], No. 8575/53. Classes 83 (2) and 83 (4). [Also in Group XXVI] Making turbine blades.-In a process for making a metallic body with holes in it; a heated billet having transverse holes occupied by filler material is hot worked by extrusion, forging or otherwise so as to be elongated axially and reduced in cross-section. The filler material may be porous or preferably it is subsequently removed. In the manufacture of a gas turbine blade, a hollow billet 2, Fig. 2, having radially drilled holes 1 occupied.by the filler material 4 is extruded through a die 30 by a punch 7 with a mandrel extension 8 to form a tube 5. The latter is then cold drawn to the desired blade profile 9, Fig. 3, and the filler is then removed. The billet may alternatively be formed by a plurality of annular discs 24, 25, Fig. 12, in which the discs 25 have radial slots 10, Fig. 4 (not shown). The discs 24 may be unslotted or they may be slotted in which case the slots in alternate discs are staggered. Alternatively discs having various patterns of punched holes, Figs. 7-11 (not shown), may be piled to form a billet. The discs may be frusto-conical, Fig. 6 (not shown), instead of flat. The billet is preferably heated in an atmosphere having reduced oxygen content so as to prevent appreciable surface oxidation of the discs which would prevent them welding together during extrusion. If the discs are of a chromium containing alloy they are preferably coated with nickel by electrodeposition. Nickel coated discs 24, 25, Fig. 12, of nickel-chromium alloy may be consolidated into a solid billet before extrusion by clamping them together with a bolt 26 of metal having a lower co-efficient of expansion than the disc metal. The billet is then sprayed externally with nickel and is heated to 850‹ C. in a furnace whereby the bolt will pull the discs together. Glass may be used as a lubricant during extrusion. The filler may be of low-melting point metal whereby it may be subsequently removed by melting out or it may be dissolved by an acid or disintegrated by inducing intergranular corrosion. If the filler is of molybdenum or graphite it is removed by oxidation. Alternatively the filler may be of a refractory material which will be disintegrated during the hot working and subsequently removed by jets of air or water. Making filter plates.-In the manufacture of a perforated plate for use as a filter or for subsequent fabrication into a flame tube for a gas turbine, a billet having longitudinal holes occupied by filler material is elongated by extrusion to form a strip 20, Fig. 15 (not shown), which is cut into lengths. The latter 21 are then put face to face in a billet container 22, Fig. 17, with the filler disposed transversely. The composite billet is then extruded to form a single sheet, Fig. 18 (not shown), from which the filler is removed thereby leaving perforations. Alternatively the starting billet may be formed as described in Specification 745,655. Specification 619,634 also is referred to.