Aluminum (Al) is a light metal whose compounds are widely distributed in nature. The resource of aluminum in the earth's crust is about 40-50 billion tons, second only to oxygen and silicon, ranking third. Among the metal varieties, it is the first major category of metals. Aluminum has special chemical and physical properties. It is not only light in weight, strong in texture, but also has good ductility, electrical conductivity, thermal conductivity, heat resistance and nuclear radiation resistance. It is an important basic raw material for the development of the national economy.