Seamless steel pipes are long steel products with a hollow cross-section and no seams along their periphery. Due to their hollow cross-section, seamless steel pipes can be used as conduits for transporting fluids, such as oil, natural gas, coal gas, water, and certain solid materials. Compared to solid steel products such as round bars, seamless steel pipes are lighter in weight while offering equivalent bending and torsional strength, making them an economical choice for structural and mechanical components. They are widely used in the manufacture of structural members and mechanical parts, such as oil drilling pipes, automotive drive shafts, bicycle frames, and steel scaffolding in construction. Manufacturing ring-shaped parts from seamless steel pipes improves material utilization, simplifies manufacturing processes, and saves on materials and machining time. Examples include rolling bearing rings and jack sleeves, which are now widely produced using steel pipes. Steel pipes are also an indispensable material for various conventional weapons; gun barrels and cannon barrels, for instance, are manufactured from them. Steel tubes can be classified into round tubes and shaped tubes based on the shape of their cross-sectional area. Since a circle has the largest area for a given circumference, round tubes can convey more fluid. Furthermore, a circular cross-section distributes stress more evenly when subjected to internal or external radial pressure; consequently, the vast majority of steel tubes are round. However, round tubes have certain limitations. For instance, under planar bending conditions, their bending strength is inferior to that of square or rectangular tubes. Consequently, square and rectangular tubes are commonly used in the frames of agricultural machinery and in steel-and-wood furniture. Depending on specific applications, other cross-sectional shapes of special-shaped steel tubes are also required.

  1. Seamless Steel Tubes for Structural Purposes (GB/T 8162-2008) are seamless steel tubes used for general structural and mechanical applications.

  2. Seamless Steel Tubes for Fluid Conveyance (GB/T 8163-2008) are general-purpose seamless steel tubes used for conveying fluids such as water, oil, and gas.

  3. Seamless steel tubes for low- and medium-pressure boilers (GB 3087-2008) are high-quality carbon structural steel hot-rolled and cold-drawn (rolled) seamless steel tubes used to manufacture superheated

  steam tubes, boiling water tubes, and superheated steam tubes for locomotive boilers, as well as large and small smoke tubes and arch brick tubes for various low- and medium-pressure boiler structures.

  4. Seamless steel pipes for high-pressure boilers (GB/T 5310-2017) are high-quality carbon steel, alloy steel, and stainless heat-resistant steel seamless pipes used to manufacture heat-exchanging components for water-tube boilers operating at high pressure and above.

  5. High-pressure seamless steel pipes for fertilizer equipment (GB 6479-2013) are high-quality carbon structural steel and alloy steel seamless pipes suitable for chemical equipment and pipelines operating at temperatures ranging from -40°C to 400°C and pressures from 10 to 30 MPa.

  6. Seamless Steel Pipes for Petroleum Cracking (GB9948-2013) are seamless steel pipes suitable for furnace tubes, heat exchangers, and pipelines in petroleum refineries.

  7. Steel Pipes for Geological Drilling (YB235-70) are steel pipes used by geological departments for core drilling; based on their application, they can be classified into drill pipes, drill collars, core tubes, casing, and sedimentation tubes, among others.

  8. Seamless Steel Pipes for Diamond Core Drilling (GB3423-82) are seamless steel pipes used for drill pipes, core rods, and casing in diamond core drilling.

  9. Oil Drilling Pipes (YB528-65) are seamless steel pipes with internal or external thickening at both ends, used for oil drilling. Steel pipes are classified into threaded and non-threaded types. Threaded pipes are connected using couplings, while non-threaded pipes are connected to tool joints via butt welding.

  10. Seamless carbon steel pipes for ships (GB5213-85) are seamless carbon steel pipes used to manufacture Class I and Class II pressure piping systems, as well as boilers and superheaters for ships. The operating temperature of the wall of carbon steel seamless steel pipes does not exceed 450°C, while that of alloy steel seamless steel pipes exceeds 450°C.

  11. Seamless steel pipes for automotive half-shaft sleeves (GB3088-82) are hot-rolled seamless steel pipes made of high-quality carbon structural steel and alloy structural steel, used for manufacturing automotive half-shaft sleeves and drive axle housing tubes.

  12. High-pressure fuel lines for diesel engines (GB 3093-2002) are cold-drawn seamless steel tubes used to manufacture high-pressure lines for diesel engine injection systems.

  13. Precision-bore seamless steel tubes for hydraulic and pneumatic cylinders (GB 8713-2009) are cold-drawn or cold-rolled precision seamless steel tubes with precise inner diameters, used to manufacture hydraulic and pneumatic cylinder barrels.

  14. Cold-drawn or cold-rolled precision seamless steel tubes (GB/T 3639-2009) are cold-drawn or cold-rolled precision seamless steel tubes with high dimensional accuracy and good surface finish, used in mechanical structures and hydraulic equipment.

  15. Seamless stainless steel tubes for structural use (GB/T 14975-2002) are hot-rolled (extruded, expanded) and cold-drawn (rolled) seamless stainless steel tubes widely used in the chemical, petroleum, light textile, medical, food, and machinery industries for corrosion-resistant piping, structural components, and parts.

  16. Seamless stainless steel pipes for fluid conveyance (GB/T 14976-2002) are hot-rolled (extruded, expanded) and cold-drawn (rolled) seamless pipes made of stainless steel, used for conveying fluids.

  17. Special-shaped seamless steel pipes is a general term for seamless steel pipes with cross-sectional shapes other than circular. Based on differences in cross-sectional shape and dimensions, they can be further classified into constant-wall-thickness special-shaped seamless steel pipes (designated as D), variable-wall-thickness special-shaped seamless steel pipes (designated as BD), and variable-diameter special-shaped seamless steel pipes (designated as BJ). Special-shaped seamless steel pipes are widely used in various structural components, tools, and mechanical parts. Compared to round pipes, special-shaped pipes generally have larger moments of inertia and section moduli, offering greater resistance to bending and torsion. This allows for significant reduction in structural weight and savings in steel consumption.