GB738757A - Improvements in or relating to methods of casting metals - Google Patents

Abstract

738,757. Casting processes. BRISTOL AEROPLANE CO., Ltd. July 21, 1953 [Aug. 20, 1952], No. 20952/52. Class 83 (1). In a method of casting metals in a porous mould, such as a sand or wax - investment mould, an inert gas is caused to pass through the pores of the mould and into the mould space to expel air entrapped in the pores and also in the mould space, and the casting metal is poured into the mould while it is impregnated and filled with the inert gas. An investment mould 10, Fig. 1, for turbine blades, is covered by a member 16 clamped against an asbestos mat 21 supported over a furnace, the mould space communicating with the atmosphere through the pouring gate 13, 14. Inert gas, e.g. argon, is supplied under pressure through a pipe 19 and after a period of time sufficient to ensure the expulsion of the air from the pores of the mould and the mould space, the metal is poured by inverting the mould and furnace assembly, the flow of inert gas being maintained meanwhile and after casting while the metal is allowed to cool sufficiently to solidify. After solidification the mould on a base 23, Fig. 2, is covered by a vessel 26 with a valve 30, and propane under pressure supplied to the chamber 27. The gas jet is lit before the vessel 26 is placed in position, to prevent an explosion. Ducts 31, which may be formed by passing a wire through the mould, ensure that argon penetrates to the mould space remote from the pouring gate. Nitrogen may be used instead of argon.