GB1051689A - - Google Patents

Abstract

1,051,689. Moulding processes. SOC. DES FORGES ET ATELIERS DU CREUSOT. March 18, 1964 [March 26, 1963], No. 11531/64. Heading B3F. A method of making a refractory shell mould comprises coating an expendable pattern with a contact layer, coating the contact layer with a first slurry of a refractory material to form a primary layer on the contact layer, and then coating the primary layer with one or more successive slurries of refractory material to form one or more outer layers. The grain size of the refractory material used in the slurry forming the primary layer is intermediate the grain size for the material for forming the contact and outer layers. Each of the layers is sprinkled before it is completely dry with a dry powdered fireclay containing approximately 40% by weight of alumina, the grain size of the fireclay progressively increasing from that sprinkled on the primary layer to that sprinkled on the outer layer. The slurry for coating the pattern comprises a mixture of powdered silica and aluminium silicate, a colloidal silica salt, a foam depressant and a sedimentation inhibitor. The coated pattern is invested, in an enclosure, with a pourable refractory material and the resultant assembly is dried. An example of the composition of the slurries is given.