It has the characteristics of strength and rigidity and neat appearance. It has certain strength and rigidity, can resist large external force, has neat appearance and smooth surface, and the plastic steel pipe can well adapt to the use conditions such as bending, compression and stretching. It has the characteristics of corrosion resistance, wear resistance and reliable quality. Square steel tube with round steel tube is a kind of square or other polygonal steel tube made of round steel tube by cold bending process. It can change the shape of steel pipe without changing its physical and chemical properties, and can be used in vehicle manufacturing, construction engineering, factory layout and furniture making, which is helpful to make better use of space and improve work efficiency.