Analysis Of The Differences Between SAW Steel Pipes And ERW Steel Pipes

--A Systematic Comparison from Manufacturing Processes to Performance Characteristics

In the carbon steel pipe product system, welded steel pipes are widely used in energy transmission, municipal engineering, industrial manufacturing, and other fields due to their high production efficiency and wide specification coverage. According to differences in welding methods and forming processes, welded steel pipes can be further divided into various types, among which Electric Resistance Welded (ERW) steel pipes and Submerged Arc Welded (SAW) steel pipes are the most common. SAW steel pipes can be further classified into Longitudinal Submerged Arc Welded (LSAW) steel pipes and Spiral Submerged Arc Welded (SSAW) steel pipes based on weld forms.

In practical engineering applications, SAW steel pipes and ERW steel pipes exhibit significant differences in manufacturing processes, weld characteristics, performance, and applicable working conditions. This article conducts a systematic comparative analysis of these two types of steel pipes from multiple key dimensions.

ERW steel pipes use hot-rolled steel coils as raw materials. The steel strip is gradually bent into a circular pipe shape through a continuous forming unit, and high-frequency current is used to generate resistance heat at the pipe edge, bringing the metal to a plastic state before forming a weld through extrusion. No filler metal is used during the entire welding process, and the weld is completed through metallurgical bonding of the base metal itself.

This process features strong continuity and high automation, making it particularly suitable for large-scale production of small and medium-diameter steel pipes.

SAW steel pipes are welded using the submerged arc welding process. During welding, the electric arc burns under the flux layer, and the welding wire is continuously fed into the molten pool to form weld metal. Welding usually consists of two steps: internal welding and external welding, resulting in a thick weld metal with a deep penetration depth.

Based on weld morphology, SAW steel pipes can be divided into longitudinal and spiral types. Their common characteristics include stable welding processes and suitability for manufacturing large-diameter and thick-walled steel pipes.

After welding, the weld of ERW steel pipes undergoes extrusion and shaping processes, resulting in a low weld height, relatively flat internal and external surfaces, and a natural transition with the base metal. This gives ERW steel pipes excellent overall appearance quality and high surface finish, making them particularly suitable for engineering scenarios requiring strict appearance and inner wall flatness.

The weld metal of SAW steel pipes is formed by filler wire, so the weld is usually higher than the base metal surface, with a certain weld reinforcement on both internal and external welds. Although the weld size is controllable and meets relevant standards, its appearance flatness is slightly inferior to that of ERW steel pipes.

The weld zone of ERW steel pipes is concentrated, and the welding heat input is relatively small. Common defects are mainly concentrated near the weld centerline. These defects have relatively simple morphologies and can be easily detected and controlled using non-destructive testing (NDT) methods such as ultrasonic testing.

The SAW process uses flux and welding wire, resulting in a large volume of weld metal and a relatively wide range of potential defect types. In addition to inspecting the weld itself, strict inspection of the base metal steel plate is also required. Especially for large-diameter and thick-walled steel pipes, the inspection process is more complex.

During the production of ERW steel pipes, the pipe undergoes multiple forming and sizing processes, with repeated plastic adjustments to the pipe body. This process helps release welding residual stress to a certain extent, resulting in a relatively uniform stress distribution in the finished steel pipe.

SAW steel pipes have high welding heat input and a large volume of weld metal, leading to relatively concentrated residual stress after welding. Although improvements can be made through heat treatment or process control, the uniformity of stress distribution is generally not as good as that of ERW steel pipes.

From the perspective of overall mechanical properties, both qualified ERW and SAW steel pipes can meet engineering requirements when complying with the same standards. However, ERW steel pipes have certain advantages in post-processing and maintenance.

If local weld defects are found during the manufacturing of ERW steel pipes, they can be corrected through repair or local treatment; in contrast, if severe defects occur in the weld or welding zone of SAW steel pipes, repair is difficult and may even affect the service safety of the entire pipe.

ERW steel pipes are more suitable for small and medium-diameter engineering projects requiring high appearance quality and dimensional accuracy, such as urban pipe networks, general industrial pipelines, and structural pipes.

With their deep weld penetration and strong load-bearing capacity, SAW steel pipes are more suitable for large-diameter, thick-walled, and high-strength engineering projects, such as long-distance oil and gas transmission pipelines, large-scale water conservancy projects, and certain key structural projects.

SAW steel pipes and ERW steel pipes have their own focuses in terms of manufacturing processes, weld seam profile, inspection characteristics, and engineering adaptability, and there is no absolute superiority or inferiority. The key to engineering material selection lies in comprehensive judgment based on specific operating conditions, diameter range, pressure level, and quality requirements.

In-depth understanding of the technical characteristics of these two types of steel pipes helps make more reasonable, economical, and safe material choices in practical projects, thereby ensuring the long-term stable operation of the project.