Aluminum alloy with low melting point, good casting performance, and low pressure casting, gravity casting products are widely used in automobiles, motorcycles, electrical, communications, hardware tools, and other fields; In particular, large wall thick products have more applications. It can also better avoid the casting of secondary processing in the pore. Gravity casting refers to the process of injection of molten metal under the gravity of the earth, also known as gravity casting. The generalized gravity casting includes sand casting, metal casting, melt casting, die casting, mud mould casting, etc. The gravity casting of the narrow sense is mainly a metal casting.