Abstract: Natural yellow clay-bonded green sand casting process is suitable for producing iron casting. It can avoid burnt-on sand and improve the casting surface quality, and has the comprehensive advantages of low cost, less pollution and high efficiency. The big difference between natural yellow clay bonded green sand process and usual clay bonded green sand processis that the former can form a dense sinter skin at the interface of casting and mold, which can resist the scouring and infiltration of liquid metal, and can firmly adhere to the casting surface after the liquid metal is solidified. So, elevated temperature knockout can be realized without too fast cooling of casting and too high surface hardness, thus improving production efficiency. At room temperature, it can easily shed from the casting surface, thus reducing the amount of sand-removing work. In order to understand this phenomenon in depth, the mechanical performances of sinter layer of natural yellow clay-bonded sand at elevated and room temperatures are investigated . The results show that the sinter layer sample has excellent plasticity at elevated temperature, and with the decreasing of temperature, the plasticity decreases and the compression strength increases. At room temperature, it exhibits obvious brittleness. This accounts for the agreement of the variation of mechanical performance of sinter layer with its behavior in the casting process

Key words: Burning-on sand, Casting mold, Elevated temperature property, Natural yellow clay bonded sand, Stinter skin