GB798358A - Improvements in or relating to the production of castings with internal passages - Google Patents

Abstract

798,358. Casting composite articles. BRISTOL AERO ENGINES, Ltd. Nov. 1, 1954 [Nov. 5, 1953], No. 30636/53. Class 83 (1). A group of internal passages in a casting are produced by a metal-core composed of two sheet-metal parts, each constituting one part of the wall of each of the passages of the group, and a flange part on each side of and running the whole length of each wall part, and said sheetmetal parts being joined together with the flange parts of one overlying the flange parts of the other to form the core. A segment of nozzle-guide blading for a gas-turbine, Figs. 1 and 2, is made by the lost-wax process, stainless steel cores 23, 24, which may be chromiumplated, being supported in the mould, and cobalt-base-alloy being cast at a temperature of 1500-1550‹ C. Refractory plugs may be inserted in the core-passages to prevent collapse. Alternatively, the segment may be cast from nickel-chrome alloys at a a temperature of 1550-1600‹ C., the cores then being cooled by air flowing through pipe 15 and outlets 12. Alternatively molten-metal such as lead, aluminium, copper or brass may be passed through the core, or heat-absorbing plugs placed in the core-passages. The cooling may be so regulated that an outer superficial layer of the core is fused to assist bonding with the cast-metal, or the core may be coated with a metal such as copper which will melt and promote bonding, or a flux. In a modification for making a blade, a mild-steel core is supported between the halves of a shell-mould. The core is made from two sheet-metal portions to form a manifold passage system comprising a header 27 in the root-portion 40 of the blade, Figs. 6 and 7, and passages 30-33 through the portion 41 of the blade. Cast-metal keys into holes in the portions 37 of the core between the passages The cores may have a varying cross-section throughout their length. To prevent chilling of the cast-metal, e.g. aluminium alloy, a removable plug comprising an electric heating element may be inserted in each core-passage.