Types of Welding Techniques for Straight Seam Welded Pipes

Straight seam steel pipes can be classified into two main welding techniques: Electric Resistance Welding (ERW) and Submerged Arc Welding (SAW). ERW pipes are further divided into high-frequency (HF), medium-frequency (MF), and low-frequency (LF) welded pipes. SAW pipes, also known as double-sided submerged arc welded pipes or Longitudinally Submerged Arc Welding (LSAW) pipes, use the submerged arc welding process for production.

ERW is a common method for welding straight seam pipes and includes alternating current (AC) and direct current (DC) welding types. AC welding is categorized by frequency: low-frequency, medium-frequency, and high-frequency welding. High-frequency welding, used for producing thin-walled or standard-walled pipes, includes contact welding and induction welding. DC welding is typically used for small-diameter pipes.

High-frequency ERW pipes, referred to as ERW pipes, are advanced and economical products for the oil and gas storage and transportation sectors.

SAW pipes, also known as LSAW pipes, are produced by pressing (or rolling) a single sheet of medium-thick plate into a pipe blank, which is then welded using double-sided submerged arc welding. These pipes have a wide range of specifications and are known for their weld toughness, plasticity, uniformity, and density. They are suitable for high-pressure, low-temperature, and corrosion-resistant applications.

In constructing high-strength, high-quality long-distance oil and gas pipelines, large-diameter, thick-walled LSAW pipes are often required. According to API standards, LSAW pipes are designated for use in critical areas such as arctic regions, seabeds, and densely populated urban areas.