Circular tubes have certain limitations, such as being less bend-resistant than square or rectangular tubes when subjected to plane bending. Therefore, square and rectangular tubes are commonly used in the frames of agricultural machinery and steel-wood furniture. Different applications may require special-shaped steel tubes with various cross-sectional shapes.

1. Seamless steel tubes (GB/T 8162-2008) used for structural and mechanical structures.

2. Seamless steel tubes for fluid conveyance (GB/T 8163-2008) are general-purpose seamless steel tubes used for transporting fluids such as water, oil, and gas.

3. Seamless steel tubes for low and medium pressure boilers (GB3087-2008) are hot-rolled and cold drawn (rolled) seamless steel tubes made from carbon structural steel, used for manufacturing various structural low and medium pressure boiler superheated steam pipes, water-tube boilers, locomotive boiler superheated steam pipes, large flue pipes, small flue pipes, and arch brick tubes.

4. Seamless steel tubes for high-pressure boilers (GB5310-2008) are carbon steel, alloy steel, and stainless heat-resistant steel seamless tubes used for the heating surfaces of water-tube boilers for high pressure and above.

5. High-pressure seamless steel pipes for fertilizer equipment (GB6479-2000) are carbon structural and alloy steel seamless pipes suitable for chemical equipment and pipelines operating at temperatures of -40~400℃ and pressures of 10~30Ma.