GB821579A - Manufacture of hollow turbine blades - Google Patents

Abstract

821,579. Making turbine blades by extrusion. COMPTOIR INDUSTRIEL D' ETIRAGE ET PROFILAGE DE METAUX. April 11, 1957 [May 7, 1956], No. 11953/57. Classes 83 (2) and 83 (4). A method of making a hollow turbine blade having longitudinal cooling passages comprises providing a billet of steel or refractory alloy with longitudinal passages of circular crosssection arranged with their centres on one or more straight lines, filling the passages with cylindrical rods of ordinary mild steel, heating the billet to extrusion temperature and extruding it, using a lubricant, in a container of rectangular cross-section through a die having the same cross-section as the desired blade root; cutting the thus-extruded bar into lengths each equal in volume to that of the desired blade and partly extruding each length, if necessary after re-heating, in a container of the same cross-section as the root through a die having the cross-section of the desired blade portion, and finally removing the filler. A vitreous lubricant such as window-glass is used during the extrusion. In the final extruded blade portion the original circular holes 2, 3 are deformed into oval section 21, 31. The cylindrical steel filler rods may be oxidized to prevent their adherence to the billet or they may be covered with stainless steel. In addition they may be coated with a composition made from silicate of soda, alumina or chromium chloride and water. The rods are finally removed by circulating nitric acid at 70‹ C. The final extrusion die may be open or it may be a closed frusto-conical die formed in sections, which imparts taper and longitudinal twist to the blade portion. In the final extrusion operation a ram may be used having in its marking surface a tapered recess for forming a tapered root on the blade. Specifications 739,499, 762,214 and 814,569 are referred to.