ES354541A1 - Eliminating patterns from and hardening of shell molds - Google Patents

Abstract

Refractory shell moulds are formed on a fusible pattern and soaked with a flammable liquid, and then by burning the liquid, the pattern melts and flows from the mould, the mould then being fired to the desired hardness without cooling after the burning of the liquid. A pattern of wax, thermoplastic composition &c. may be dip-coated with a slurry comprising a refractory and a silica-containing binder, e.g. hydrolysed ethyl or isopropyl silicate which may be gelled with ammonia or bonded with colloidal silica, and the pattern is then dusted with coarse refractory. After repeating these steps to the desired thickness, the mould is soaked with a flammable liquid by dipping, spraying &c. The liquid may be petrol, hexane, acetone or alcohol, or if a silicate binder is used, the flammable liquid may be siliciferous, e.g. acetone or ethanol-based hydrolysed ethyl silicate or ethanol-based hydrolysed isopropyl silicate. The liquid is then ignited and burning may be continued in an oven, e.g. at 1500 F., to remove all wax and carbonized deposits thereof and to strengthen the mould until its full high temperature strength is reached.