Longitudinal Seam Welded Steel Pipe (LSAW/ERW)

• ​Introduction

Longitudinal Seam Welded Steel Pipe is a type of steel pipe manufactured by rolling a steel plate or strip into a tubular shape and then welding a continuous seam along the axial direction (length direction). Its weld runs parallel to the pipe’s length, making it a widely used basic component in pipeline systems. Compared with seamless steel pipes, it features high production efficiency and lower cost, suitable for various low to medium pressure fluid transportation, structural support, and other scenarios.

• ​Main Functions

Fluid transportation: Used to convey liquids or gases such as water, natural gas, oil, and steam, commonly seen in municipal water supply, gas pipeline networks, etc.

Structural support: Serves as structural components in construction, bridges, and machinery manufacturing to provide support or framing, such as scaffolding and steel structure columns.

Industrial processing: Used as raw materials for manufacturing pressure vessels, etc., to meet the size and performance requirements of specific industrial production.

• ​Tubing Standards

ASTM A53，ASTM A500，API 5L； EN 10217-1，EN 10219-1； GB/T 13793，GB/T 3091，GB/T 9711.

• ​Material & Performance

ASTM A53: Grade A、B，ASTM A500: Grade B、C、D，API 5L: L245(B),L290(X42),L320(X46),L360(X52),L390(X56),L415(X60)；

EN 10217-1: P235GH、P355GH、P355NH，EN 10219-1: S235JRH、S355NH、S355J2H；

GB/T 13793: Q195、Q215A/B、Q235A/B、Q355B、Q390B, GB/T 3091: Q215A/B、Q235A/B、Q355B, GB/T 9711: L245(B),L290(X42),L320(X46),L360(X52),L390(X56),L415(X60)；

Mechanical properties: The yield strength is generally above 235MPa, tensile strength ≥375MPa, and elongation ≥20% (varying with material grades), ensuring it is not easy to break under stress.

Welding performance: The weld strength is not less than 85% of the base metal strength, and the welded joint has good toughness to avoid cracking under low temperature or impact load.

Corrosion resistance: Untreated steel pipes are susceptible to environmental corrosion, and anti-corrosion treatment can significantly improve their service life in humid, acid-base environments.

• ​Manufacturing Process

Raw material preparation: Select steel plates or strips that meet the standards, and perform surface cleaning (removing rust, oil stains) and size cutting.

Forming: Roll the steel plate/strip into a circular tube using a roll forming machine, ensuring the pipe diameter and roundness meet requirements, and the edge of the steel plate forms a straight seam to be welded.

Welding: Use processes such as high-frequency resistance welding (ERW) and submerged arc welding (SAW) to weld the longitudinal joints. High-frequency resistance welding is suitable for small and medium pipe diameters with high efficiency; submerged arc welding is suitable for large pipe diameters with more stable weld quality.

Weld treatment: Remove weld beads and burrs, and perform non-destructive testing on the weld (such as ultrasonic testing, X-ray testing) to ensure no cracks, pores, or other defects.

Sizing and straightening: Adjust the outer diameter of the steel pipe to the standard size through a sizing machine, and the straightening machine corrects the straightness of the steel pipe.

Heat treatment (optional): Perform heat treatment such as annealing on pipes with higher requirements to eliminate welding stress and improve mechanical properties.

Anti-corrosion treatment (optional): Carry out galvanizing, painting, or anti-corrosion coating construction as needed to enhance corrosion resistance.

Finished product inspection and packaging: After inspecting the size, performance, and appearance, label and package for delivery.

• Specifications