Abstract
A tensile break-up experiment of green mold sands was undertaken. The green mold sands were prepared using various kinds of bentonite as a binder under different conditions of composition, mixing ratio, moisture content and aging period. On the basis of the data obtained, the molding and flowage properties of green mold sands were examined. The following are the results obtained.
1. A large tensile strength was obtained from the green mold sands that contained a binder mixed with activated bentonite by exchange of Ca cation with Na ion or a binder mixed with Ca- and Na-bentonite. This may indicate a higher molding property.
2. Prolongation of the aging period of Na-bentonite containing green mold sands produces high compaction of green mold sands and higher flowage.
3. By addition of approximately 70% uncalcined bentonite, used mold sands regain tensile strength almost as high as that of new green mold sands.
4. The tensile strength of green mold sands varies more with the amount of bentonite (binder) than with moisture content. The tensile strength in high-pressure molding also varies with the effect of the amount of bentonite.
