GB765747A - Improvements in or relating to method of precision casting - Google Patents

Abstract

In shell moulds made by packing a wet moulding mixture comprising a finely divided refractory material and an aqueous dispersion or solution of a water-dispersable or soluble heat hardenable synthetic resin binder into a moulding cavity preferably truly water-soluble resins are used such as urea-, melamine- and phenol formaldehyde, and water soluble polyesters. In a specific example the mix comprises 100 lb. silica sand 100 A.F.S. fineness 4 lb. phenolic resin containing a curing catalyst, 3 lb. water, 0.5 lb. kerosene and 0.01 lb. oleic acid and is suitable for cast iron, malleable iron, brass, steel, aluminium and bronze. For casting higher melting point steel alloys, the mix is 100 lb. silica sand 90 A.F.S., 1 lb. silica flour 200 mesh, 0.5 lb. iron oxide 200 mesh, 0.5 fire clay 200 mesh, 1 lb. dextrine powder 200 mesh, 4 lb. phenolic resin containing a curing catalyst, 0.2 lb. kerosene, 4 lb. water, 0.25 lb. isopropanol, 0.1 lb. oleic acid. For casting magnesium and its alloys the mix is 100 lb. silica sand 120 A.F.S., 4 lb. urea formaldehyde resin, 0.5 lb. powdered sulphur, 0.25 boric acid, 0.25 lb. potassium fluorborate, 0.5 lb. dextrine powder, 0.1 lb. kerosene, 3 lb. water, 0.5 lb. diethylene glycol, 0.4 lb. kerosene, and 0.02 lb. oleic acid are added after mixing.