GB785228A - Improvements relating to shell moulds and the casting of metal therein - Google Patents

Abstract

785,228. Making metal-casting moulds. GENERAL MOTORS CORPORATION. Jan. 28, 1955 [Feb. 18, 1954], No. 2623/55. Class 87(2). [Also in Group XXII] During casting, shell moulds are supported between a pair of refractory backup members made of an aqueous slurry comprising refractory oxides and refractory cement, and pressed inwards against the mould. The mould mix, e.g., resin-coated sand of 140 A.F.S. number containing 3 per cent phenol formaldehyde resin and ¢ cc. of liquidizer per pound of coated sand, is blown into the space between an electricallyheated pattern 10 and a member 24, and the shell 29 then pressed and cured by a heated press-head 30. The mould-halves 38, which may be glued together, and backing-members 40, are then clamped for casting between plates 44 in frames 42. Alternatively one backing- member may be mounted on a spring-loaded plate with the other carried on a pistonactuated cross-head. The backing-members are made from a slurry of ten parts of a refractory compound essentially of calcium aluminate cement, and grog of refractory oxides such as silica, alumina and magnesia, and two parts of water, which is cast on a pattern. The pattern may be a shell mould formed on the press head 30 and coated with a water-resistant coating such as shellac or varnish, or a non-shrinking material such as type-metal, plastic or rubber cast into the impression 32 of the press-head. Reference has been directed by the Comptroller to Specifications 700,989 and 761,694 [both in Group XXII]