PURPOSE: To provide the composition of sand for forming a mold capable of manufacturing a casting scarce in gas defect.
CONSTITUTION: This sand composition for forming the mold is composed of reconditioned sand, binder consisting of acid hardening furan resin and phosphorus compound as hardening catalyst for the acid hardening furan resin. As the reconditioned sand, the one satisfying the following two essential condition. That is, (1) the difference between an ignition loss ratio of the reconditioned sand and the ignition loss ratio of the new sand is to be ≤4.0wt.%, (2) the phosphorus content in the reconditioned sand is to be 0.008-0.55wt.% and/or the nitrogen content is to be 0.004-0.22wt.%. Further, as the phosphorus compound, one or more kinds of the compounds selected from group composed of phosphoric acid, condensed phosphoric acid, phosphoric ester and phosphate is used.
NAKAI SHIGEO
TANAKA TSUTOMU
KATO MASAYUKI
