ERW Pipe vs. SAW Pipe

Differences between ERW and SAW pipes:

ERW (Electric Resistance Welding) is one of the main processes for producing straight seam steel pipes. It utilizes the skin effect and proximity effect of high-frequency current to rapidly heat the edges of the steel strip to a molten state, achieving solid-state pressure welding under the pressure of extrusion rollers. This process does not use welding wire or flux, and the weld composition is very similar to the base material.

SAW (Submerged Arc Welding) is a welding process applicable to various weld types, including straight seam pipes (LSAW), spiral seam pipes (SSAW/SAWH), and circumferential seams. In the welded pipe industry, when compared with ERW, "SAW pipe" usually refers to spiral seam submerged arc welded pipes (SAWH/SSAW), while straight seam submerged arc welded pipes (LSAW) are commonly referred to simply as "straight seam submerged arc welded pipes."

In the fields of long-distance pipelines, urban pipe networks, and structural pipes, ERW and SAW are the two most commonly used types of welded steel pipes. This article will comprehensively compare their differences in production processes, costs, dimensional accuracy, and application scenarios.

1. Differences in Manufacturing Processes
ERW Tube Process: The raw material is hot-rolled coil. It is continuously cold-bent into a cylindrical shape using a roll forming machine. Then, utilizing the skin effect and proximity effect of high-frequency current, the edges of the steel plate are instantly heated to a molten state, and solid-state pressure welding is achieved under the action of extrusion rollers. The entire process requires no filler wire.

Advantages: This process has a small heat-affected zone, fast welding speed, and extremely high production efficiency. Through online weld heat treatment (normalizing), the microstructure of the weld can be made consistent with the base material.

SAW Spiral Tube Process: The raw material is also hot-rolled coil. The steel strip is continuously fed into the forming machine at a certain angle (spiral angle), causing it to spirally coil into a tubular shape. Submerged arc welding is used for welding on both the inner and outer sides. This process uses welding wire and flux as filler and protective materials.

Features: Submerged arc welding (SAW) produces deep weld penetration and high weld strength. However, due to its fusion welding nature, the weld zone has a cast structure with a clear fusion line between it and the rolled structure of the base material.

2. Raw Materials and Quality Control
Whether ERW or SAW, steel pipes used in high-pressure applications such as oil and gas pipelines must use hot-rolled coils conforming to API 5L standards, with strict control over chemical composition and mechanical properties.

Some manufacturers use low-grade steel strips to produce non-standard spiral pipes solely for structural support; this does not represent a limitation of the SAW process itself. In standard long-distance pipeline projects, the raw material quality requirements for SAW pipes are exactly the same as those for ERW pipes.

3. Geometric Dimensions, Weld Seam, and Residual Stress Analysis

Performance Indicators	ERW (High-Frequency Resistance Welded Pipe)	SAW (Spiral Submerged Arc Welded Pipe)
Size Range	Outer Diameter: 1/2″ – 24″ (21.3mm – 610mm)	Outer Diameter: 16″ – 120″+ (406mm – 3000mm+)
Weld Seam Morphology	One longitudinal straight seam, internal burrs can be removed, weld reinforcement is close to the base material.	One continuous spiral seam, inner and outer weld beads have standard allowable reinforcement, can be ground to flush before 3PE coating.
Dimensional Accuracy	Extremely high, small tolerances for outer diameter and wall thickness, good straightness.	Diameter accuracy meets standards, and macroscopic roundness control is also excellent.
Residual Stress	Cold bending + online heat treatment results in low and controllable residual stress.	Forming and welding stresses are more complex, but after stress relief processes such as mechanical diameter expansion, they fully meet application standards.
Weld Coefficient	1.0 (equivalent to the base material after 100% non-destructive testing).	1.0 (equivalent to the base material on both sides after 100% non-destructive testing).

4. Procurement Costs and Selection Recommendations

Small to Medium Diameter (≤ 24 inches): ERW is the most cost-effective choice.
Reason: ERW production lines are fast, low-cost, and highly precise. SAW spiral pipe production of small diameters is uneconomical and not a mainstream product, making procurement more difficult.

Large Diameter (≥ 24 inches): SAW spiral pipe is an irreplaceable choice.
Reason: For pipes larger than 24 inches, the ERW process is no longer suitable. The SAW process can produce ultra-large diameter steel pipes using narrow strip steel, with lower equipment investment compared to straight seam submerged arc welding (LSAW), giving it an absolute advantage in water conservancy and long-distance oil and gas pipelines.

ERW vs. SAW Pipes: How to Choose?

The choice of steel pipe depends primarily on project requirements:

Reasons for choosing ERW pipes:
If your project requires pipes up to 24 inches in diameter;
You prioritize high precision, excellent straightness, and smooth inner surface;
You desire optimal procurement economy.

(Applicable scenarios: City gas, building structures, automotive piping, water pipelines)

Reasons for choosing SAW spiral pipes:
If your project requires large-diameter pipes larger than 24 inches;
You need large-diameter pipes with high steel grades (X70 and above);
You have significant needs for water conservancy and long-distance oil and gas pipelines.

(Applicable scenarios: Oil and gas trunk lines, water diversion projects, large pipe piles)

Differences between SAW, LSAW, SSAW, and DSAW:

Abbreviation	Full Name	Brief Description
SAW	Submerged Arc Welding	A welding process where the electric arc burns under a layer of flux. It has advantages such as stable welding quality, high productivity, no arc light, and less smoke. It is the common process basis for the following pipe types.
LSAW	Longitudinal Submerged Arc Welding	A type of steel pipe with a longitudinally straight weld seam, formed by welding steel plates after UOE or JCOE forming.
SSAW	Spiral Submerged Arc Welding	A type of steel pipe with a spiral weld seam, formed by continuously spirally coiling steel strips, also known as HSAW or SAWH.
DSAW	Double Submerged Arc Welding	Refers to a welding method where submerged arc welding is performed once on each side of the steel pipe. In the field of straight seam pipes, DSAW and LSAW are often used interchangeably.

Frequently Asked Questions (FAQ):

Q1: What is the essential difference between ERW and SAW?
A: 

ERW (Electric Resistance Welding) utilizes the skin effect of high-frequency current to instantly melt the edges of the steel plate, achieving solid-state pressure welding under the action of extrusion rollers. It does not use filler wire, and the weld composition closely resembles the base material. SAW (Submerged Arc Welding) ignites an electric arc under a layer of granular flux, using welding wire and flux as filler and protective materials. The weld has a cast structure, deep penetration, and high strength.

Q2: Is SAW pipe always spiral welded pipe?
A: 

Not necessarily. SAW only represents the "submerged arc welding" process, which in the welded pipe industry can be divided into:

LSAW Pipe (Straight Seam Submerged Arc Welded Pipe): Single-sheet steel plate forming, longitudinal weld, suitable for large-diameter, thick-walled, high-pressure pipelines;
SAWH/SSAW Pipe (Spiral Seam Submerged Arc Welded Pipe): Steel strip spirally rolled, spiral weld, capable of producing ultra-large diameter (over 3000mm) pipes.

Q3: Which has better weld quality, ERW or SAW pipe?
A: 

SAW pipe typically uses double-sided submerged arc welding, with the weld fused from both the inside and outside, achieving a penetration depth of over 20mm. It has more filler metal and a higher weld height, forming a reinforcing rib effect. ERW pipes are single-extrusion welded, and wall thickness is limited by weld penetration. For pipes with wall thicknesses exceeding 20mm, SAW is the only feasible welding process.

Modern ERW pipe welds have properties approaching those of the base material; LSAW's double-sided welded structure offers superior reliability in thick-walled, high-pressure applications. The Heat-Affected Zone (HAZ) of the weld area is a key area for inspection.

Q4: What is the price difference between ERW and SAW pipes?
A: Price ranking (same specifications, same steel grade): ERW < Spiral SAW < LSAW.

Read more: ERW Pipe vs. LSAW Pipe