| 摘要 |
<p>1430409 Ceramic shell moulds MONSANTO Ltd 2 May 1974 [13 June 1973] 28181/73 Heading B5A [Also in Division C3] A process for the production of a hollow ceramic article such as a crucible or a part of a shell mould, comprises applying to a pattern having a smooth surface of a fluorocarbon polymer and a shape devoid of re-entrant features a coating of a slurry of a finely divided refractory material in a liquid binding agent, applying a stucco of a coarse refractory material to the slurry coating, setting the binding agent, applying further slurry and stucco coatings to build up the shell to the desired thickness, and, after withdrawing the pattern, firing the shell. The binding agent is preferably an acid catalysed alkyl silicate in a water miscible alcohol, the primary coating containing zircon as the refractory material and the primary stucco is calcined kaolin clay. The pattern may be either composed entirely of the fluorocarbon polymer or may be a wood or metal pattern with a fluorocarbon coating. Suitable polymers are p.t.f.e., polychlorotrifluoroethylene, copolymers of tetrafluoro ethylene and hexafluoropropylene. The pattern may be part of a composite pattern for the production of a shell mould and in this case the remainder of the composite pattern will be composed of a conventional expendable material such as wax. Specification 1,309,915 is referred to.</p> |
