Abstract: The strippable sinter layer, which is produced during sintering of natural clay-bonded sand, can eliminate the burn-on defects and improve the surface quality of steel castings. A series of sintering experiments are carried out with different size and weight ratio of silica sands to find a proper formula of molding sand under different sinter temperatures. The molding sand, which is composed of natural clay and diameter 0.15-0.30 mm (50/100 mesh) silica sands with mixing ratio of 3∶7, is used in the pouring experiment of steel casting sample. The mechanical performances of natural clay-bonded sand at elevated and room temperatures are also investigated. A compact layer of burn-on sands appeared between the surface of sand mould and steel casting, which is easy to be peeled from the casting surface. The results indicated the moderate sinter layer can be generated under different pouring temperature by changing the components of molding sand; The sinter layer has excellent plasticity at elevated temperature to resist the scouring and infiltration of liquid metal. After the liquid metal is solidified, the sinter layer can firmly adhere to the casting surface. At room temperature, it exhibited obvious brittleness and is easy to be stripped. The steel casting with high surface quality can be acquired after the peeling of sinter layer.

Key words: Burn-on defects, Natural clay-bonded sand, Sinter layer, Steel castings