Abstract
Sand mold bonded with dicalcium silicate and sodiun silicate has more advantages than other sand molds, but there is a disadvantage in that the mold bonded by them has the great tendency of sand burning on the surface of steel casting. The interrelationship between sintering point or refractoriness and sand burning have already been studied, so a study was conducted to clarify how the sintering point or refractoriness is influenced by the amount of commercial dicalcium silicate, sodium silicate or mol-ratio of sodium silicate added to silica sand. Dicalcium silicate ranged from 0 to 5.0% and sodium silicate ranged from 3.0 to 7.0% with mol-ratio of 2.7 and 3.2. As sand grain flineness influences the sintering point, sand grains of a unit mesh ranging from 35 to 150 mesh were used in the sintering test. The more the dicalcium silicate was added, the higher the sintering point became which later dropped. The highest sintering points were proved within the range from 0.5 to 0.8% dicalcium silicate. In the refracoriness test, there was roughly the same tendency. The more the sodium silicate was added, the higher the sintering point became which late dropped. The highest sintering points were proved within the range from 5.0 to 6.0% sodium silicate. The higher the mol-ratio of sodium silicate was, the higher the sintering point or refractoriness. The finer the grain size of sand, the higher was the sintering point. Hence, the burnig on the surface of sttel casting seems to be improved by using finer grains with addition of dicalcium silicate ranging from 0.5 to 0.8% and sodium silicate ranging from 5.0 to 6.0%.
