GB778005A - A method for casting metallic articles with covered passageways - Google Patents

Abstract

778,005. Core-materials. HILLS-McCANNA CO. May 16, 1955 [Jan. 10, 1955], No. 14063/55. Drawings to Specification. Class 83 (1). Class cores, which are chemically removed from the casting, have an outer layer of a substance which is non-volatile and which is effectively inert to the casting-metal at the casting temperatures. The core is preferably of borosilicate glass. The coating may be of oxides, fluorides or salts of metals, e.g. titanium dioxide, barium oxide, barium fluoride, borium titanate, lead oxide, lead fluoride, lead tungstate, basic lead sulphate, lead chromate, lead metaborate, bismuth trioxide, zirconium dioxide, chromic oxide, ferric oxide, and applied by dipping, spraying, dusting, painting, and sooting, mixed if required with a volatilecarrier such as a low-boiling alcohol which, after application of the mix, may be driven off by heating. Alternatively metallic coatings which are the same as, or inert to reaction with the cast metal, e.g. magnesium, aluminium and alloys thereof, may be used and applied by spraying, painting, dusting or plating. To enable the complete removal of the glass core, after casting, to be verified by radiography, a coating may be selected to be of high radiographic-density with respect to the casting- metal and the glass core. Some of the materials may react with the cast-metal and such coatings, after application to the core, are coated with an inert coating-material. In a modification, radioactive-material, e.g. a radioactive isotope of zirconium, is mixed with the coating- material, e.g. a suspension of titanium dioxide in ethyl alcohol, or the radioactive-material is applied to the core and then coated with an inert material. Removal of all core and coating- material is then ensured when the radiation count measured from the outer surface of the casting reaches a prescribed minimum. The core may be removed by hydrofluoric acid pumped therethrough.