Rapidly curing foundry sand compsn. - contains gypsum as binder

摘要

The amt. of gypsum used is 5-20 wt.% (10-15) (based on total compsn.). A curing retarder may be added as required. Gypsum is cheaper than furan resins and other known organic cpds. and the compsn. cures faster than cement. Less water is evolved than when sand is used to make the mould entirely and the mould retains some gas permeability.