Abstract
In order to get small bubbles dispersed in the muddy mold materials (=slurry), the small amount of bubbling powder was added into the slurry mixture of refractory materials colloidial silica with basic or acid gelatinizer as a binder. The mold was made by pouring the molding materials the small bubbles dispersed into the pattern, and was kept to be hardened, The pattern was removed while the mold was still in plastic condition. The mold has to be kept more to be hardened. Many small cracks were grown between these small bubbles on leaving, and less dimension change occured, It is known that the common muddy material have big cracks on hardening by absence of bubbles and big dimension change occured. In show process mold dimension is kept constant owing to the number of cracks produced in impact heating. However, this method gave many small cracks spontaneously. Many small bubbles in the mold was effective not only for the accurate dimension of the mold, but to prevent from the heterogeneous state of mold caused by the difference of grading and gravity of the refractory materials and improve the fluidity of it. It was possible to get the smooth casting surfaces of mold if the unti-bubble reagent with seperating effect was dressed on the pattern.
