The 4000 series aluminum alloy is an aluminum alloy with silicon as the main alloying element. Most of its alloys are heat-treated non-strengthened aluminum alloys. Only alloys containing Cu, Mg and Ni, and welding heat-treated strengthened alloys can absorb certain elements. It can be strengthened by heat treatment. Due to the high silicon content, low melting point, good melt fluidity, easy feeding, and no brittleness of the final product, this series of alloys are mainly used to manufacture aluminum alloy welding additives, such as brazing plates, welding rods and Welding wire, etc. In addition, due to the good wear resistance and high temperature performance of some of this series of alloys, they are also used to make pistons and heat-resistant parts. The alloy containing about 5% of silicon is black-gray after anodizing and coloring, so it is suitable for building materials and manufacturing decorative parts.