overview
ERW and EFW pipe are not competing products - they are engineered for different jobs. ERW pipe is the economical, high-efficiency choice for small-to-medium diameter, low-to-medium pressure transmission and structural applications. EFW pipe is the high-integrity choice for large diameters, heavy walls, and high-pressure, high-temperature, or corrosive service - a proven cost-effective alternative to seamless pipe. Specifying the right one comes down to pressure, size, media, and budget.
Choosing between EFW pipe (Electric Fusion Welded) and ERW pipe (Electric Resistance Welded) is one of the most common decisions in welded steel pipe procurement. Although both belong to the welded pipe family and both use electricity to form the seam, they are built on completely different welding principles - one is a forge weld, the other a fusion weld. That single metallurgical difference drives everything else: weld strength, pressure rating, achievable wall thickness, cost, and the applications each pipe can safely serve.
What Is ERW Pipe?
ERW (Electric Resistance Welded) pipe is produced by cold-forming a hot-rolled steel coil into a cylindrical shape through a series of rollers, then joining the two edges with high-frequency electric current. The current - typically 200–800 kHz in modern HFW (High Frequency Welding) lines - exploits the skin effect and proximity effect to heat only the facing edges to a forgeable temperature (approx. 1,200–1,400°C) within seconds. Squeeze rollers then press the edges together with high force, forging them into a solid seam.
Key characteristics of the ERW process:
No filler metal or flux - the seam is pure parent metal, forged together
Narrow, smooth longitudinal weld seam, often nearly invisible after trim and heat treatment
High dimensional accuracy and uniform wall thickness, thanks to continuous coil forming
High production speed and low cost - a fully automated continuous process
Quality ERW pipe is normally post-weld normalized to refine the grain structure of the heat-affected zone (HAZ) and restore ductility and toughness at the seam.
What Is EFW Pipe?
EFW (Electric Fusion Welded) pipe is produced by forming a steel plate (not coil) into a pipe - typically via the JCOE (progressive bending) or UOE (press forming) process - and then joining the edges with an electric arc. The arc melts the parent metal edges together with a filler metal (welding wire) into a molten pool, which cools and solidifies into a full-penetration fusion weld. In practice, most large-diameter EFW pipe is welded by SAW (Submerged Arc Welding), in which the arc is shielded under a blanket of granular flux for maximum weld purity.
Key characteristics of the EFW process:
Fusion welding with filler metal - the weld chemistry can be engineered to match or exceed the parent metal
Wide, full-penetration weld bead on both inner and outer surfaces
Capable of large diameters and heavy wall thickness that ERW equipment cannot reach
Higher weld integrity for high-pressure, high-temperature, and corrosive service - a cost-effective alternative to seamless pipe
Manufacturing Process Comparison
| Aspect | ERW Pipe | EFW Pipe |
|---|---|---|
| Welding principle | Resistance heating + pressure forging (a forge weld) | Electric arc heating, parent metal + filler metal fully melted (a fusion weld) |
| Filler material | None - no filler metal or flux | Filler wire (and flux in SAW variant) required |
| Raw material | Hot-rolled steel coil (continuous strip) | Steel plate (discrete, typically medium-to-heavy plate) |
| Forming method | Continuous cold roll forming | JCOE progressive bending or UOE press forming |
| Welding speed | Very fast - continuous automated line | Slower - welding performed after forming |
| Weld seam | Narrow, smooth longitudinal seam; can be trimmed flush | Wide, full-penetration seam, welded inside and outside |
Performance Comparison
| Property | ERW Pipe | EFW Pipe |
|---|---|---|
| Weld strength | Seam strength close to parent metal (no filler); seam quality highly dependent on process control | Higher - filler metal is fused with parent metal; weld chemistry can be engineered to match or exceed the pipe body |
| Pressure capability | Suitable for low-to-medium pressure service | Suitable for high and ultra-high pressure service (typically ≥ 6 MPa applications) |
| Corrosion resistance | Moderate - seam may be susceptible to selective corrosion if the HAZ is not properly heat treated | Excellent - fully penetrated, homogeneous weld with strong resistance to corrosive media |
| Fatigue resistance | Moderate | Superior - uniform weld structure and HAZ deliver better fatigue performance |
| Dimensional accuracy | High - uniform wall thickness from coil forming | Good - plate-formed, with weld cap dressed internally and externally |
| Cost | Lower - high production efficiency, simpler equipment | Higher - more complex process, filler metal, longer cycle time |
Size Ranges & Specifications
ERW Pipe Specifications
- Outer diameter: NPS 1/2″ – 48″ (OD 21.3 – 660 mm)
- Wall thickness: 1.0 – 22 mm (thin to medium wall; Sch 5 – Sch 160, XS, XXS)
- Length: 0.5 – 22 m (fixed length, SRL, DRL)
- Standards: API 5L (PSL1/PSL2), ASTM A53 Type E, ASTM A135, ASTM A178, EN 10217
- Grades: API 5L Gr. A, Gr. B, X42, X46, X52, X56, X60, X65, X70; ASTM A53 Gr. A/B
- Ends: plain, beveled, threaded
EFW Pipe Specifications
- Outer diameter: NPS 1/8″ – 100″ (4″ – 24″ is the most common working range; large diameters per plate width)
- Wall thickness: medium to heavy wall - including heavy-wall specifications beyond ERW capability
- Standards:
- ASTM A672 - EFW steel pipe for high-pressure service at moderate temperatures (−29°C to 343°C)
- ASTM A691 - carbon & alloy steel EFW pipe for high-pressure service at high temperatures (up to 593°C)
ASTM A671, A358, A409, A928; API 5L for large-diameter line pipe
- Grades: ASTM A672 CL 12/22/32/…, A691 GR. 1¼ Cr – 9 Cr alloy grades; API 5L up to X80 in large diameters
- Surface finishes: HF pickled, sandblasted, matte polish; ends plain, beveled, or threaded
Applications: ERW vs EFW Pipe
| Industry | ERW Pipe | EFW Pipe |
|---|---|---|
| Oil & gas | Low/medium-pressure gathering lines, flow lines | High-pressure transmission pipelines (≥ 6 MPa), wellhead piping |
| Petrochemical / chemical | General process piping, utility lines | High-temperature, high-pressure, and corrosive-media piping |
| Power generation | - | Boiler and power plant piping systems |
| Construction / structural | Structural hollow sections, scaffolding, piling | - |
| Municipal engineering | Water supply, general transmission, fire protection | - |
| Marine & offshore | - | Subsea pipelines, offshore platform piping |
| Mechanical & automotive | Machinery parts, automotive components, HVAC | - |
selection
ERW pipe :
Your project involves low-to-medium pressure fluid transmission or structural use
You need small-to-medium diameters (up to 24″ is the ERW sweet spot) with thin-to-medium wall
Budget is a primary concern and standard-compliant mass production is required
Delivery volume is large and lead time is critical
EFW pipe :
Service conditions involve high temperature, high pressure (≥ 6 MPa), or corrosive media
You need large diameters or heavy wall thickness beyond ERW capability
The project is a long-distance, high-pressure oil & gas transmission pipeline
The environment is demanding - chemical plants, power stations, offshore and subsea engineering
You want a cost-effective alternative to seamless pipe in critical service
FAQ:
What is the difference between ERW and EFW pipe?
The core difference is the welding mechanism. ERW is a forge weld: high-frequency current heats the strip edges, which are pressed together without filler metal. EFW is a fusion weld: an electric arc melts the plate edges together with filler metal into a full-penetration seam. ERW is faster and cheaper for small-to-medium pipe; EFW delivers higher weld integrity for large-diameter, heavy-wall, high-pressure pipe.
Which is stronger, ERW or EFW pipe?
A properly made ERW seam can approach the strength of the parent metal, but its properties are limited to the parent metal chemistry. EFW welds use engineered filler metal and full fusion, giving higher and more controllable weld strength - which is why EFW is preferred for high-pressure (≥ 6 MPa) and critical service applications.
What are the size ranges for ERW and EFW pipes?
ERW pipe commonly covers NPS 1/2″ – 48″ (OD 21.3 – 660 mm) with wall thickness of 1.0 – 22 mm. EFW pipe covers NPS 1/8″ – 100″ and is the practical choice above 24″ diameter or for heavy wall thickness that ERW mills cannot form or weld reliably.
What standards apply to ERW and EFW pipes?
ERW pipe: API 5L PSL1/PSL2, ASTM A53 Type E, ASTM A135, ASTM A178, EN 10217. EFW pipe: ASTM A672 (high-pressure, moderate temperature), ASTM A691 (high-pressure, high temperature, alloy steel), ASTM A671, A358, A409, A928, and API 5L for large-diameter line pipe. Dimensional requirements follow ASME B36.10M.
Is EFW pipe more expensive than ERW pipe?
Generally yes. EFW production is slower, uses plate instead of coil, and consumes filler metal and flux, so the unit cost is higher. However, EFW is usually more economical than seamless pipe of equivalent pressure rating, and its longer service life in severe service often lowers total lifecycle cost.
Can ERW pipe be used for high-pressure applications?
ERW pipe is suitable for low-to-medium pressure service. For high or ultra-high pressure (≥ 6 MPa), heavy wall, critical low-temperature toughness, or corrosive media, EFW pipe is the recommended and typically specified option. Always confirm pressure class against the applicable standard and mill test reports.
What is the difference between API 5L ERW and EFW pipe?
Both fall under API 5L for line pipe. API 5L ERW pipe is made by high-frequency resistance welding without filler, typically for smaller diameters up to X70. API 5L EFW pipe (in practice usually SAW/LSAW) uses fusion welding with filler metal, suitable for large diameters, heavy walls, and higher grades - and is the standard choice for critical transmission pipelines.
What is the manufacturing process of EFW pipe?
Plate inspection → edge milling → JCOE or UOE forming → internal and external submerged arc welding (with filler wire under flux) → online ultrasonic inspection → expanding and sizing → hydrostatic test - producing a wide, full-penetration, double-sided weld seam.
Which pipe should I choose for my project - ERW or EFW?
Decide by four factors: operating pressure and temperature, diameter and wall thickness, media corrosivity, and budget. Low/medium pressure + small/medium diameter + cost-sensitive → ERW. High pressure/high temperature + large diameter/heavy wall + corrosive or critical service → EFW. If in doubt, send your working conditions to the manufacturer for a standards-based recommendation.
