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ERW Welded Steel Pipe

OD Range :

1/2″ ~ 24″（21.3 mm ~ 609.6 mm）

WT Range :

SCH10 ~ SCH160

Length :

6m、12m

Tolerance :

Outer diameter ±1%, wall thickness ±12.5% ​​(according to ASTM/EN standards)

Material :

Carbon steel, low alloy steel (such as ASTM A53, ASTM A500 Grade B)

Standard :

ASTM A53 / ASTM A500 / EN 10219 / EN 10210

Surface :

Hot-dip galvanizing, cold galvanizing, paint rust prevention, pickling, black pipe

Application :

Conveying water, gas, and low-pressure fluids; structural pipes; machinery manufacturing; supporting beams and frames.

I. Overview of ERW Welded Steel Pipes

ERW welded steel pipes are straight seam steel pipes manufactured using resistance welding, where hot-rolled or cold-rolled steel strips are heated and welded together by high-frequency current after forming. This process does not use welding wire or flux, resulting in a dense weld structure and stable quality, suitable for mass production.

ERW welded steel pipes are characterized by high outer diameter accuracy, uniform wall thickness, and good weld consistency, and are widely used in industrial pipelines, building structures, machinery manufacturing, municipal engineering, and general fluid transportation.

Depending on the operating conditions, different steel grades, wall thicknesses, and surface treatments (such as black pipe, hot-dip galvanized, anti-corrosion coating, etc.) are available to meet pressure resistance, corrosion resistance, and structural strength requirements.

II. Types of ERW Welded Steel Pipes

i. Classification by Application

  1. Industrial ERW Welded Steel Pipes
  • Mainly used for general fluid transportation, equipment connection, and industrial structural applications, requiring high dimensional accuracy and weld stability.
  • Common Applications: Factory pipelines, machinery, low and medium pressure transmission systems
  • Common Standards: ASTM A53, ASTM A500, EN 10255
  1. Structural ERW Welded Steel Pipes
  • Primarily focused on load-bearing capacity and structural strength, emphasizing yield strength and dimensional stability.
  • Common Applications: Steel structure buildings, factory frames, scaffolding, bridge structures
  • Common Standards: ASTM A500, EN 10219, GB/T 6728
  1. Transportation ERW Welded Steel Pipes
  • Used for transporting water, oil, gas, etc., requiring high weld quality and pipe body consistency.
  • Common Applications: Water supply and drainage pipelines, oil and gas gathering and transportation pipelines, municipal engineering
  • Common Standards: API 5L, GB/T 9711

ii. Classification by Manufacturing Standards and Steel Grades

  1. Ordinary Carbon Steel ERW Welded Steel Pipes
  • Suitable for conventional working conditions, cost control is a priority.
  • Common steel grades: Q195, Q235, ASTM A53 Grade A Applicable scenarios: Low-pressure fluids, general structures.
  1. Medium-High Strength ERW Welded Steel Pipes
  • Suitable for engineering projects with higher requirements for pressure resistance and strength.
  • Common steel grades: Q345, ASTM A500 Grade B/C, API 5L X42–X52 Applicable scenarios: Industrial pipelines, structural load-bearing systems.

iii. Classification by Surface Condition and Corrosion Protection Method

  1. Black-skinned ERW Welded Steel Pipe
  • No surface anti-corrosion treatment; suitable for dry environments or subsequent processing.
  • Features: Low cost, flexible processing.
  1. Galvanized ERW Welded Steel Pipe
  • Corrosion resistance is improved through hot-dip galvanizing or pre-galvanizing.
  • Features: Long service life, low maintenance cost.
  • Applications: Water supply pipelines, building structures, outdoor projects.
  1. Anti-corrosion Coated ERW Welded Steel Pipe
  • Anti-corrosion coatings such as paint, epoxy, and 3PE can be added as needed.
  • Applications: Underground pipelines, humid or corrosive environments.

III. Real-world Selection Recommendations for ERW Welded Steel Pipe Applications

i. Factory/Steel Structure/Workshop

Working Conditions:

  • The pipeline primarily bears weight, does not transport media.
  • Long-term static load + wind load. Priority is given to strength, straightness, and dimensional consistency.

Selection Recommendations:

  • Type: Structural ERW welded steel pipe
  • Standard: ASTM A500 / EN 10219 / GB/T 6728
  • Steel Grade: Q345 or ASTM A500 Grade B

Surface Finish:

  • Indoor → Black pipe is sufficient
  • Outdoor → Hot-dip galvanized

ii. Internal Fluid Transportation within the Factory

Operating Conditions:

  • Transporting water, compressed air, and low-corrosive liquids
  • Ambient or slightly elevated temperature
  • Low pressure, but requiring long-term stable operation

Selection Recommendations:

  • Type: ERW welded steel pipe for low-pressure fluids
  • Standard: ASTM A53 / GB/T 3091
  • Steel Grade: ASTM A53 Grade B
  • Wall Thickness: Select based on working pressure; avoid unnecessary thickening
  • Surface Treatment: Internal and external anti-rust paint or light corrosion protection

iii. Municipal Water Supply and Drainage / Underground Pipeline Network

Operating Conditions:

  • Pipes are buried underground for extended periods.
  • Humid and corrosive environment.
  • High maintenance costs; problems are difficult to resolve once they occur.

Selection Recommendations:

  • Type: Corrosion-resistant ERW welded steel pipe
  • Standard: GB/T 3091 / EN 10255
  • Steel Grade: Q235 is sufficient

iv. Oil and Gas Gathering and Transportation / Energy Pipelines

Operating Conditions:

  • Medium pressure
  • Extremely high requirements for weld reliability
  • Must pass inspection and comply with specifications

Selection Recommendations:

  • Type: Pipeline-grade ERW welded steel pipe
  • Standards: API 5L / GB/T 9711
  • Steel Grade: X42 / X52

Requirements:

  • Specify PSL1 or PSL2
  • Non-destructive testing (UT / RT) is mandatory

v. Equipment Manufacturing / Frames / Mechanical Structures

Operating Conditions:

  • High requirements for outer diameter and wall thickness consistency
  • Subsequent cutting, welding, and machining required
  • The pipe itself is not a pressure vessel

Selection Recommendations:

  • Type: High-dimensional accuracy ERW welded steel pipe
  • Standards: ASTM A500 / EN 10219

Key Considerations:

  • Outer diameter tolerance
  • Weld formation quality
  • Surface flatness

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ERW Welded Steel Pipe Specifications and Dimensions Table

NPS (inch) Outside Diameter OD (mm) Wall Thickness WT (mm) (Full Range) Theoretical Weight (kg/m) Tolerance
1/2″ 21.34 2.11 / 2.77 / 3.73 / 4.78 0.99 / 1.27 / 1.62 / 2.08 OD ±1%, WT −12.5%
3/4″ 26.67 2.11 / 2.87 / 3.91 / 5.16 1.25 / 1.63 / 2.12 / 2.78 Same as above
1″ 33.40 2.77 / 3.38 / 4.55 / 6.02 2.09 / 2.54 / 3.24 / 4.27 Same as above
1-1/4″ 42.16 2.77 / 3.56 / 4.85 / 6.35 2.73 / 3.39 / 4.12 / 5.38 Same as above
1-1/2″ 48.26 2.77 / 3.68 / 5.08 / 6.35 3.12 / 4.05 / 5.41 / 6.76 Same as above
2″ 60.33 2.77 / 3.91 / 5.54 / 7.11 4.08 / 5.44 / 7.48 / 9.55 Same as above
2-1/2″ 73.03 3.05 / 4.78 / 6.35 / 7.92 5.41 / 8.63 / 11.6 / 14.6 Same as above
3″ 88.90 3.05 / 5.49 / 7.62 / 9.27 6.29 / 11.3 / 15.3 / 18.4 Same as above
4″ 114.30 3.05 / 6.02 / 8.56 / 10.97 8.56 / 16.1 / 22.3 / 28.6 Same as above
5″ 141.30 3.40 / 6.55 / 9.53 / 12.70 11.6 / 21.8 / 30.9 / 41.2 Same as above
6″ 168.28 3.40 / 7.11 / 10.97 / 12.70 14.6 / 28.3 / 42.6 / 49.4 Same as above
8″ 219.08 4.78 / 6.35 / 10.31 / 12.70 25.0 / 32.7 / 52.0 / 63.3 Same as above
10″ 273.05 4.78 / 6.35 / 9.27 / 12.70 34.0 / 45.2 / 64.6 / 88.5 Same as above
12″ 323.85 5.56 / 6.35 / 10.31 / 12.70 42.5 / 48.9 / 78.6 / 96.8 Same as above
14″ 355.60 6.35 / 9.53 / 12.70 54.6 / 81.3 / 106.9 Same as above
16″ 406.40 6.35 / 9.53 / 12.70 62.8 / 93.8 / 123.8 Same as above
18″ 457.20 6.35 / 9.53 / 12.70 71.0 / 106.3 / 140.7 Same as above
20″ 508.00 6.35 / 9.53 / 12.70 79.2 / 118.8 / 157.6 Same as above
24″ 609.60 6.35 / 9.53 / 12.70 95.6 / 143.8 / 191.9 Same as above

Table Explanation
OD: Pipe outer diameter (mm), fixed size
Wall Thickness WT: Corresponding to common SCH (Schedule) grades, in mm
Theoretical Weight: Calculated based on carbon steel density of 7.85 g/cm³, in kg/m
Tolerance: OD ±1%, wall thickness -12.5%, conforming to ASTM A53 / API 5L standards
For large diameter (>12″) or thick-walled pipes, ERW process capabilities are limited; LSAW/SSAW can be used instead.

Comparison Table of Standards for ERW Welded Steel Pipes

Standard System Standard No. Applicable Pipe Type Main Applications Remarks
ASTM (USA) ASTM A53 Welded steel pipe for general service Low-pressure fluid transmission, industrial piping, structural use Common grades: Grade A / Grade B
ASTM (USA) ASTM A500 Structural welded steel pipe Building structures, steel structure projects Emphasis on yield strength and dimensional accuracy
ASTM (USA) ASTM A252 Welded steel pipe for piling Foundation engineering, pile driving works Suitable for load-bearing and impact conditions
API API 5L Line pipe (welded) Oil, gas, and water transmission Commonly supplied as PSL1 / PSL2
EN (Europe) EN 10219 Cold formed welded hollow structural sections Building structures, bridge engineering Cold-formed welded pipes
EN (Europe) EN 10255 Non-alloy welded steel tubes Water, gas, and general fluid conveyance Can replace EN 10217 in some applications
GB / GB-T (China) GB/T 3091 Welded steel pipe for low-pressure fluid transmission Water supply & drainage, municipal pipelines Widely used in domestic projects
GB / GB-T (China) GB/T 9711 Line pipe (welded) Oil, gas, and water pipeline projects Technical requirements similar to API 5L
GB / GB-T (China) GB/T 6728 Structural welded steel pipe Building structures, steel construction works Cold-formed welded pipe

 

ERW Welded Steel Pipe Production Process Flowchart

Steel Coil → Annealing (Optional) → Longitudinal Forming → High-Frequency Resistance Welding → Weld Seam Shaping → Straightening → Heat Treatment (Optional) → Inspection → Surface Treatment → Cutting and Packaging → Finished Product Shipment

1. Raw Material Preparation
Material: Hot-rolled or cold-rolled steel coils
Requirements: Chemical composition meets standards (e.g., ASTM A53, GB/T 3091)
Inspection: No cracks or rust on the surface, uniform steel coil thickness

2. Annealing / Tempering (Optional)
Purpose: Improve steel strip structure, reduce internal stress, and improve formability
Method: Continuous annealing or normalizing
Applicable to: High-precision pipes or large-diameter thick-walled pipes

3. Longitudinal Forming
Equipment: Plate rolling machine or forming machine
Process: Rolling the steel strip into a circular pipe blank, aligning the edges
Note: Ensure uniform pipe diameter and accurate weld seam position

4. Welding
Method: High-frequency resistance welding (HF-ERW)
Principle: Using high-frequency current to heat the pipe blank edges to melting point, then applying pressure to weld them into a pipe
Features: Continuous, dense, and high-strength weld seam

5. Weld Seam Shaping
Purpose: Eliminate weld seam protrusions and ensure outer diameter roundness
Method: Pressing with polishing and shaping rollers
Result: Weld seam is flush with the pipe body, resulting in a smooth appearance

6. Dimensional Correction
Content: Straightening the pipe, correcting length and straightness
Tools: Straightening machine
Effect: Ensures installation accuracy and ease of construction

7. Heat Treatment (Optional)
Purpose: Improve mechanical properties
Method: Annealing or normalizing
Applicable to: Medium and high-pressure pipelines or high-strength pipes for structural use

8. Inspection
Dimensional inspection: Outer diameter, wall thickness, length
Weld seam inspection: Ultrasonic or X-ray non-destructive testing (UT/RT)
Mechanical properties: Tensile, impact, and bending tests
Standards: ASTM A53 / API 5L / GB/T 3091

9. Surface Treatment
Types: Black pipe, hot-dip galvanizing, painting, or epoxy anti-corrosion
Purpose: Rust prevention, corrosion protection, and adaptation to different working conditions

10. Cutting and Packaging
Cutting: Cut to customer’s required length
Packaging: Bundling, packing with wooden pallets or skids
Transportation: Suitable for sea, land, or rail transport

ERW Welded Steel Pipe Inspection Standards Table

Inspection Item Inspection Details Standard / Requirement Value to the End User
Visual Inspection Surface condition of the pipe body: smoothness, cracks, zinc lumps, scratches Visual inspection in accordance with GB/T 3091 / ASTM A53 / EN 10219 Ensures good surface quality and helps prevent corrosion or installation issues
Dimensional Inspection Outside diameter, wall thickness, length, straightness GB/T 3091 ±1–2% / ASTM A53 / EN 10219 Ensures accurate fit during installation and avoids joint mismatch
Weld Seam Quality Weld strength, weld appearance, absence of porosity and slag inclusions Ultrasonic Testing (UT) or Radiographic Testing (RT) Ensures weld integrity, pressure resistance, and operational safety
Mechanical Properties Yield strength, tensile strength, elongation, impact toughness As per GB/T 3091 / ASTM A53 / EN 10219 requirements Ensures the pipe resists fracture or deformation during service
Bending Test Single-side bending, double-side bending According to ASTM / GB/T standards Verifies ductility and fabrication suitability
Coating / Galvanizing Thickness Thickness of zinc coating or anti-corrosion coating Hot-dip galvanizing ≥ 50 μm / Epoxy coating ≥ 250 μm Ensures corrosion resistance and long service life
Theoretical Weight Comparison of calculated weight (kg/m) with actual weight ±5% Confirms material compliance with design and construction specifications

 

ERW Welded Steel Pipe Selection – Frequently Asked Questions

Q1: Should I choose ERW welded steel pipe or seamless steel pipe?

A1:
For low-pressure, structural, or municipal pipelines → ERW pipes are sufficient, offering lower cost and higher dimensional accuracy.
For high-pressure, critical fluid pipelines → Seamless pipes are more reliable, with fewer welds and higher strength.
Pipe selection principle: First determine the operating pressure and safety level, then decide on the material type.

Q2: How do I select the pipe diameter and wall thickness based on pressure and operating conditions?

A2:
Calculate the maximum pressure the pipe can withstand based on the conveyed medium and pressure.
Select the wall thickness according to the corresponding standard SCH/WT:
Low pressure/structural → SCH10~40
Medium pressure → SCH40~80
High pressure → Choose seamless or thick-walled ERW
Ensure uniform wall thickness and that the outer diameter meets the standard to avoid mismatched connections.

Q3: When should I choose corrosion-resistant ERW pipes?

A3:
Underground buried pipes or humid environments
Chemical or corrosive media transportation
Treatment methods for long-term outdoor use: hot-dip galvanizing, epoxy coating, 3PE.
For dry indoor environments, black pipes or painted pipes can be used to save costs.

Q4: Is the reliability of ERW welds sufficient? Will they leak?

A4:
High-frequency resistance welds typically achieve or exceed the strength of the base material.
Non-destructive testing (UT/RT) is mandatory for critical pipelines or high-pressure applications to ensure weld integrity.
Passing the inspection is a prerequisite for safe use.

Q5: Can ERW pipes of different standards be interchanged? For example, ASTM, GB, EN?

A5:
Interchangeability is not recommended. Different standards may vary in outer diameter, wall thickness, mechanical properties, and tolerances.
The standard must be confirmed before purchasing to ensure matching interfaces and pressure bearing capacity, avoiding construction and safety hazards.

Q6: Are ERW pipes suitable for machining or structural applications?

A6:
Yes, but pipes with high dimensional accuracy and uniform wall thickness should be selected.
Structural engineering → ASTM A500 / EN 10219
Machining or secondary welding → Outer diameter and wall thickness tolerances must be strict, and the weld location should be convenient for processing.