Welded steel pipes can be classified into different types and categories according to different classification methods. Different types of welded steel pipes have different characteristics and properties in use, exhibiting different values. Welded steel pipes can be classified according to their uses as follows: general welded steel pipes, galvanized welded steel pipes, oxygen-blowing welded steel pipes, electrical conduit, metric welded steel pipes, idler roller pipes, deep well pump pipes, automotive pipes, transformer pipes, electric welded thin-walled steel pipes, electric welded special-shaped steel pipes, and spiral welded steel pipes. Different welded steel pipes exhibit different uses and functions, and their manufacturing processes and applicable national production standards also differ. Below is a brief introduction to the characteristics and advantages of different types and properties of welded steel pipes:

General Welded Steel Pipes: General welded steel pipes are used to transport low-pressure fluids. They are made from Q195A, Q215A, and Q235A steel. Other easily weldable mild steels can also be used. Steel pipes undergo water pressure, bending, and flattening tests, and have specific surface quality requirements. Delivery lengths are typically 4-10 meters, and fixed-length (or multiple-length) deliveries are often required. Welded steel pipe specifications are expressed in nominal diameter (millimeters or inches), which differs from the actual diameter. Welded steel pipes are classified into ordinary and thickened steel pipes based on wall thickness, and into threaded and unthreaded types based on pipe end form.

Transformer pipes: Used for manufacturing transformer cooling tubes and other heat exchangers, made of ordinary carbon steel, requiring flattening, flaring, bending, and hydraulic testing. Steel pipes are delivered in fixed-length or multiple-length orders, with specific requirements for bending tolerances.

Special-shaped steel pipes: Square, rectangular, cap-shaped, and hollow-core steel pipes for doors and windows, welded from ordinary carbon structural steel and 16Mn steel strips, mainly used as agricultural machinery components, steel windows and doors, etc.

Galvanized Steel Pipe: To improve the corrosion resistance of steel pipes, ordinary steel pipes (black pipes) are galvanized. Galvanized steel pipes are divided into hot-dip galvanized and electro-galvanized types. Hot-dip galvanizing has a thicker zinc coating, while electro-galvanizing is cheaper.

Idler Roller Steel Pipe: Used for welded steel pipes on belt conveyor idlers, generally made of Q215, Q235A, B steel, and 20 steel, with diameters ranging from 63.5-219.0 mm. There are specific requirements for pipe curvature, perpendicularity of the end face to the centerline, and ovality. Water pressure and flattening tests are generally performed.

Oxygen Blowing Welded Steel Pipe: Used for oxygen blowing in steelmaking, generally small-diameter welded steel pipes, with specifications ranging from 3/8 inch to 2 inches (eight types). Made of 08, 10, 15, 20, or Q195-Q235 steel strips. Some undergo aluminizing treatment for corrosion prevention.

Electric Welded Thin-Walled Steel Pipe: Mainly used for making furniture, toys, lamps, etc. In recent years, thin-walled steel pipes made of stainless steel strip have been widely used in high-end furniture, decoration, and railings.

Electric Wire Sheathing Steel Pipes: These are also ordinary carbon steel welded steel pipes used in concrete and various structural electrical distribution projects. Common nominal diameters range from 13 to 76mm. These pipes have thinner walls and are mostly coated or galvanized before use, requiring cold bending tests.

Metric Welded Steel Pipes: These are welded steel pipes with specifications in the form of seamless steel pipes, expressed as outer diameter * wall thickness in millimeters. They are made from ordinary carbon steel, high-quality carbon steel, or ordinary low-alloy steel hot or cold strips, or from hot strip welded and then cold-drawn. Metric welded steel pipes are divided into ordinary and thin-walled types. Ordinary types are used for structural components, such as drive shafts, or for fluid transportation. Thin-walled types are used in the production of furniture, lighting fixtures, etc., requiring guaranteed steel pipe strength and bending test results.

Spiral welded steel pipe: This type of pipe is made by rolling low-carbon structural steel or low-alloy structural steel strip into a pipe blank at a specific spiral angle (called the forming angle), and then welding the seam together. It allows for the production of large-diameter steel pipes from narrower steel strips. Spiral welded steel pipes are mainly used for oil and natural gas pipelines, and their specifications are expressed as outer diameter * wall thickness. Spiral welded steel pipes are available in single-sided and double-sided welded versions. The welded steel pipe must meet the specified requirements for hydrostatic testing, weld tensile strength, and cold bending performance.

Different types and properties of welded steel pipes have different applications and environments, and their production and processing methods also differ. Therefore, welded steel pipes should be used according to different situations to ensure their value in use.