Welded Steel Pipe: Manufacturing Guide and Advantages (ERW, HFW/HFI, LSAW, SSAW)

Welded Steel Pipes: Essential Components Across Industries

Welded steel pipes are a vital component in countless industries—from construction and infrastructure to the transportation of oil, gas, and water. Their versatility comes from the various manufacturing and welding methods that give them unique characteristics in terms of strength, dimensions, and application.This evergreen article explores in detail the main manufacturing and welding processes for steel pipes, helping you understand the key differences between ERW, LSAW, and SSAW, including the associated HFW and HFI technologies, and enabling you to choose the optimal solution for your projects.

General Manufacturing Method of Welded Pipes

Welded pipes are produced from steel strips or plates that are rolled and joined through various welding processes. The core stages include:

Raw material preparation:Steel coils (strips) or plates of specific widths and thicknesses are selected.

Forming:The material is continuously or progressively bent into an open tubular (cylindrical) shape.

Welding:The open edges are joined using a specific welding method, creating a continuous and reliable seam.

Finishing:The welded pipe may undergo additional steps such as heat treatment, non-destructive testing (ultrasound, X-ray), sizing, and final inspection.

Welding Types and Specific Processes: Methods & Advantages

The main welding methods used for steel pipes are categorized according to the joining technique and the orientation of the weld (longitudinal or spiral).

1. Longitudinal Welded Pipes (Straight-Seam Pipes)

These pipes have a single straight weld running along their length. The main technologies are ERW (including HFW/HFI) and LSAW.

A. ERW (Electric Resistance Welding), including HFW and HFI

Manufacturing Method:ERW is an umbrella term that includes the modern technologies HFW (High-Frequency Welding) and HFI (High-Frequency Induction).A continuous cold-formed steel strip is used. A high-frequency electric current (via contact—HFW, or via induction—HFI) rapidly heats the edges. These heated edges are then pressed together by mechanical rolls, forming a solid-state forged weld without filler material. Surface oxides (burr) are removed immediately.

Key Advantages:

• High production speed: Continuous, efficient process.

• Excellent weld integrity: Forged weld, with metallurgical properties (after heat treatment) similar to the base metal.

• Cost-efficient: Ideal for large-scale production of small and medium diameters.

• Clean surface: No filler material or residual flux.

B. LSAW (Longitudinal Submerged Arc Welding)

Manufacturing Method:The LSAW process begins with a thick steel plate formed into a cylindrical shape using pressing methods (UOE, JCOE). The edges are welded using submerged arc welding (SAW), with a consumable electrode and granular flux that fully covers the arc. Welding is performed both inside and outside, producing a deep-penetration, robust weld.

Key Advantages:

• Suitable for large diameters and thick walls: The only viable method for extreme dimensions.

• Superior mechanical strength: Submerged arc welds provide exceptional toughness and durability.

• High reliability: Meets the strict quality requirements for high-pressure oil and gas transportation.

2. Spiral Welded Pipes (Helical-Seam Pipes)

These pipes have a continuous weld that wraps helically around the pipe body.

C. SSAW (Spiral Submerged Arc Welding)

Manufacturing Method:SSAW (also called HSAW) uses a steel strip (coil) that is unwound and angled at a specific pitch. As the strip is continuously rolled, the edges form a spiral seam that is welded using the same submerged arc welding process (inside and outside) as LSAW.

Key Advantages:

• Dimensional flexibility: The same strip width can produce a wide range of diameters simply by adjusting the spiral angle.

• Efficient raw material use: Excellent utilization of steel coils.

• Structural integrity: The helical weld distributes stresses evenly, increasing resistance to cracking and impact—ideal for structural uses (e.g., piling).

• Lower production costs: Often more economical than LSAW for large diameters, though applications may differ.

Choosing the Right Welded Pipe

Selecting the proper welded steel pipe depends on the specific requirements of your project, including:

• required diameter

• wall thickness

• operating pressure

• service environment

Understanding the unique advantages of each manufacturing method (ERW, HFW/HFI, LSAW, SSAW) ensures optimal performance and reliability for industrial applications.