Seamless steel tube/pipe detailed introduction

A seamless steel tube is a long strip of steel with a hollow cross-section and no seams along its periphery. Steel tubes, characterized by their hollow cross-section, are extensively used as pipelines for transporting fluids, such as petroleum, natural gas, coal gas, water, and certain solid materials. Compared to solid steel sections like round bars, steel tubes are lighter in weight while offering the same bending and torsional strength, making them an economical cross-sectional steel. They are widely used in manufacturing structural components and mechanical parts, such as petroleum drill pipes, automobile transmission shafts, bicycle frames, and steel scaffolding used in construction. Using steel tubes to manufacture annular parts can improve material utilization, simplify manufacturing processes, and save materials and machining time. Examples include rolling bearing rings and jack sleeves, which are now commonly made from steel tubes. Steel tubes are also indispensable materials for various conventional weapons; gun barrels and artillery tubes must be made from steel tubes.

Steel tubes can be classified into round tubes and special-shaped tubes based on their cross-sectional shape. Under equal circumference conditions, a circle has the largest area, allowing round tubes to transport more fluid. Additionally, the circular ring section bears internal or external radial pressure more evenly, which is why the vast majority of steel tubes are round. However, round tubes have certain limitations. For instance, under planar bending conditions, round tubes do not have as high bending strength as square or rectangular tubes. Therefore, square and rectangular tubes are often used for agricultural machinery frames and steel-wood furniture. Depending on the application, special-shaped steel tubes with other cross-sectional shapes are also required.

1.Seamless steel tubes for structural purposes (GB/T8162-1999):Used for general structures and mechanical structures.

2.Seamless steel tubes for fluid transportation (GB/T8163-1999):Used for conveying fluids such as water, oil, and gas.

3.Seamless steel tubes for low and medium pressure boilers (GB3087-1999):Used for manufacturing superheater tubes, boiling water tubes for various low and medium pressure boiler structures, and superheater tubes, large smoke tubes, small smoke tubes, and arch brick tubes for locomotive boilers. Made from high-quality carbon structural steel by hot-rolling or cold-drawing (rolling).

4.Seamless steel tubes for high-pressure boilers (GB5310-1995):Used for manufacturing heating surfaces of water tube boilers with high pressure and above. Made from high-quality carbon steel, alloy steel, and stainless heat-resistant steel.

5.High-pressure seamless steel tubes for fertilizer equipment (GB6479-86):Suitable for chemical equipment and pipelines operating at temperatures of -40~400°C and pressures of 10~30 MPa. Made from high-quality carbon structural steel and alloy steel.

6.Seamless steel tubes for petroleum cracking (GB9948-88):Suitable for furnace tubes, heat exchangers, and pipelines in petroleum refineries.

7.Steel tubes for geological drilling (YB235-70):Used by geological departments for core drilling. Classified by use into drill rods, drill collars, core barrels, casings, and sediment tubes.

8.Seamless steel tubes for diamond core drilling (GB3423-82):Used for drill rods, core barrels, and casings in diamond core drilling.

9.Steel tubes for petroleum drilling (YB528-65):Seamless steel tubes with internal or external upset ends for petroleum drilling. Divided into threaded and non-threaded types. Threaded tubes use couplings for connection, while non-threaded tubes are connected to tool joints by butt welding.

10.Carbon steel seamless tubes for ships (GB5213-85):Carbon steel seamless tubes used for manufacturing ship Class I pressure piping systems, Class II pressure piping systems, boilers, and superheaters. The wall working temperature for carbon steel seamless tubes does not exceed 450°C; for alloy steel seamless tubes, it exceeds 450°C.

11.Seamless steel tubes for automobile axle housings (GB3088-82):Hot-rolled seamless tubes made from high-quality carbon structural steel and alloy structural steel for manufacturing automobile axle housings and drive axle housing tubes.
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12.High-pressure fuel injection pipes for diesel engines (GB3093-86):Cold-drawn seamless tubes for manufacturing high-pressure pipes in diesel engine injection systems.

13.Seamless steel tubes with precise inner diameters for hydraulic and pneumatic cylinders (GB8713-88):Cold-drawn or cold-rolled precision seamless tubes with precise inner diameter dimensions for manufacturing hydraulic and pneumatic cylinders.

14.Cold-drawn or cold-rolled precision seamless steel tubes (GB3639-83):Cold-drawn or cold-rolled precision seamless tubes with high dimensional accuracy and good surface finish for mechanical structures and hydraulic equipment. Using them can significantly save machining time, improve material utilization, and enhance product quality.

15.Stainless steel seamless tubes for structures (GB/T14975-1994):Hot-rolled (extruded, expanded) and cold-drawn (rolled) seamless tubes made from stainless steel, widely used for corrosion-resistant pipelines, structural components, and parts in industries such as chemical, petroleum, light textile, medical, food, and machinery.

16.Stainless steel seamless tubes for fluid transportation (GB/T14976-1994):Hot-rolled (extruded, expanded) and cold-drawn (rolled) seamless tubes made from stainless steel for transporting fluids.

17.Special-shaped seamless steel tubes:The general term for seamless steel tubes with cross-sectional shapes other than round. They can be further classified into constant-wall-thickness special-shaped seamless steel tubes (Code D), variable-wall-thickness special-shaped seamless steel tubes (Code BD), and variable-diameter special-shaped seamless steel tubes (Code BJ). Special-shaped seamless tubes are widely used in various structural components, tools, and mechanical parts. Compared to round tubes, special-shaped tubes generally have larger moments of inertia and section moduli, providing greater bending and torsional resistance, which can significantly reduce structural weight and save steel.