Abstract
The properties of molding sand changed as it was repeatedly used. It was caused partly due to the change in the properties of organic additives such as starch and coal flour mixed with molding sand. Starch was gelatinized after the repetition of using molding sand. The gelatinization of starch resulted in increase in hot compression strength of sand mold at 200°C. Coal flour was changed to tar, which increased the compression strength of green sand mold. As a result of experimets, it was known that starch and coal flour thus changed had preferable effect upon reducing scab defects.
