Plastic clay binder for foundry sand mixt. - is cold setting and used with a rapid setting portland cement

摘要

Cold setting inorganic binder is used for a foundry sand mixt. which allows removal of the pattern without delay and hardening being effected after the removal. The mixt. comprises sand, modified rapid setting Portland cement, water, and plastic clay as binder. The clay provides sufficient plasticity and time for the prodn. of the mould while hardening of the cement occurs only after the mould has been formed. Pref. the sand mixt. is composed of 7-10 bulk % modified rapid setting Portland cement, 2-4 bulk % plastic clay, 5-10 bulk % water, balance quartz sand. The foundry sand mixt. may be composed of 7-10 bulk % modified rapid setting Portland cement (i.e. low dicalcium silicate content), 5-10 bulk % water, balance sand which contains plastic clay with or without addn. of sand which does not contain a binder. The binder also contains a C-contg. substance forming lustrous carbon at the temp of liquid iron. Use of the inorganic binder eliminates heath bazards usually associated with synthetic resin binders, and provides a high strength moulding sand at low cost.