Electric Resistance Welded (ERW) steel pipe is manufactured by cold-forming flat steel coil into a cylindrical shape and passing high-frequency alternating electric current (HFW) through the abutting edges to create a solid-state longitudinal seam weld without filler metal.
Production relies on continuous automated roll-forming, high-frequency induction welding (200–500 kHz), inline seam deburring (internal and external ID/OD bead removal), and full-length seam heat treatment (post-weld induction annealing) to eliminate residual stress and homogenize the metallurgical structure across the weld zone.
Outer Diameter (OD): 21.3 mm – 610 mm (1/2" – 24" NPS)
Wall Thickness (WT): 1.5 mm – 22.2 mm (SCH 10 through SCH 160 / STD / XS / XXS)
Length: Single Random Length (5–7m), Double Random Length (10–12m), or custom cut-to-length up to 18m.
Manufacturing Process: Cold forming from hot-rolled coil (HRC) + High-Frequency Electric Resistance Welding (HFW/ERW).
Key Product Characteristics
Concentricity & Dimensional Tolerances: Uniform wall thickness throughout the pipe body derived from precision-rolled steel coils, minimizing wall thinning issues compared to seamless alternatives.
Inline Weld Seam Heat Treatment: Automatic induction seam annealing at 850°C–950°C eliminates brittle martensitic microstructures in the heat-affected zone (HAZ), restoring grain refinement and toughness matching the base metal.
Internal/External Flash Removal: OD bead trimming is standard; ID weld flash is scraped flush (<= 0.3 mm remaining height) to reduce flow resistance and turbulent pressure losses during liquid/gas conveyance.
Straightness & Ovality Control: Multi-stand rotary straightening machines maintain straightness within 1.0 mm/m, ensuring accurate alignment for automated field butt-welding and mechanical joining.
Technical Specifications
|
Parameter |
Standard Range / Option |
|
Manufacturing Standard |
API 5L, ASTM A53, ASTM A135, ASTM A252, ASTM A500, EN 10217, EN 10219 |
|
Outer Diameter (OD) |
21.3 mm – 610.0 mm |
|
Wall Thickness (WT) |
1.5 mm – 22.2 mm |
|
Pipe End Options |
Plain End (PE), Beveled End (BE 30° / 37.5° per ANSI B16.25), Threaded & Coupled (T&C) |
|
Length Tolerance |
+/- 10 mm for fixed lengths |
|
Straightness |
<= 1.0 mm / meter |
|
Ovality (Out-of-Roundness) |
Within 85%–100% of nominal diameter tolerance per relevant standard |
Grades & Standards
|
Standard |
Grade / Steel Material |
Typical Application Target |
|
API 5L (PSL1 / PSL2) |
Grade B, X42, X46, X52, X56, X60, X65, X70 |
Onshore oil, gas, and hydrocarbon transportation pipelines |
|
ASTM A53 / A135 |
Grade A, Grade B |
Low-pressure water, steam, air, and structural fluid lines |
|
ASTM A500 |
Grade A, B, C, D |
Structural framing, equipment chassis, support columns |
|
ASTM A252 |
Grade 1, Grade 2, Grade 3 |
Structural piling, foundation casing, deep-foundation pipes |
|
EN 10217-1 / EN 10219 |
P195TR1, P235TR1, S235JRH, S275J2H, S355J2H |
Pressure vessel lines, mechanical engineering, structural hollow sections |
Surface & Processing Options
Bare / Black Uncoated: Oiled or dry surface for immediate downstream processing or indoor structural framing.
Varnish / Black Paint Coating: Anti-corrosion asphalt base or synthetic varnish coating for temporary protection during ocean transit and storage.
Hot-Dip Galvanizing (HDG): Zinc coating thickness exceeding 55 μm (400 g/m²) or up to 85 μm (610 g/m²) according to ASTM A53 / ISO 1461 for outdoor corrosion protection.
3-Layer Polyethylene (3LPE) / 3LPP: Epoxy primer + adhesive layer + PE/PP topcoat (2.5 mm - 3.7 mm thick) applied according to DIN 30670 / ISO 21809 for direct-burial oil and gas pipelines.
Fusion Bonded Epoxy (FBE): Single or dual-layer FBE (300 - 500 μm) for high-operating-temperature gas lines and water mains.
End Fabrication: Beveling with plastic end protectors, grooved ends (Victaulic system), expanded or swaged ends, threaded according to NPT / ISO 7-1.
Applications
Energy & Hydrocarbon Transport: Onshore natural gas gathering lines, crude oil transmission, refined product supply pipelines meeting API 5L PSL2 sour-service requirements.
Municipal Infrastructure: Low and medium-pressure municipal water supply systems, industrial fluid handling, fire sprinkler pipe systems (UL/FM compliant).
Structural & Civil Engineering: Deep foundation pipe piles, micro-piling, bridge pier casings, heavy equipment booms, airport terminal roof trusses using ASTM A500/A252 hollow sections.
District Heating & Cooling: Steam lines and insulated jacket pipe carriers for chilled or heated water loops.
Quality Control & Inspection
Every production lot undergoes non-destructive and destructive testing in accordance with ISO 9001, API 5L, and EN standards:
Hydrostatic Testing: 100% full-length hydrostatic testing up to 100% SMYS (Specified Minimum Yield Strength), holding pressure for a minimum of 5 seconds.
Non-Destructive Testing (NDT): Continuous online Ultrasonic Testing (UT) along the weld seam for longitudinal flaws, combined with Eddy Current (ET) surface defect detection.
Destructive Testing: Flattening test (welds positioned at 90° and 0°), reverse bend test, Charpy V-Notch impact testing (down to -40°C for low-temperature applications), guided bend tests, and Tensile / Yield strength verifications.
Traceability: Full heat-number stenciling and Mill Test Certificates (MTC) issued according to EN 10204 3.1 or 3.2 (with independent third-party inspection like SGS, BV, or TUV).
Supply & Customization Options
Sourcing Flexibility: Direct mill-run manufacturing for project-based orders with custom wall thickness tolerances and chemical restrictions (e.g., restricted CEQ for field weldability).
Packaging Solutions: Bare bundles tied with heavy-duty steel bands for small diameters (<= 8"), plastic end caps, woven bag wrapping for coated surfaces, wooden crates for machined or threaded ends.
Logistics Handling: Bulk vessel chartering for large-tonnage infrastructure projects; 20ft / 40ft container loading with internal lashing and damp-proof silicas for export sea freight.
What Buyers Should Provide for a Quote
To receive an accurate commercial and technical quotation, include the following details in your inquiry:
Dimensions: Outer Diameter (NPS or mm) and Wall Thickness (Schedule or mm)
Quantity: Total tonnage or total linear meters/feet
Pipe Length: Fixed length (e.g., 6.0m, 11.8m, 12.0m) or random length range
End Condition: Plain End Square Cut, Beveled Ends, Threaded & Coupled
Surface Finish & Coating: Bare, Black Varnish, Galvanized (g/m²), 3LPE, FBE
Testing Requirements: Specific Charpy impact test temperatures, additional NDT, or third-party inspection (SGS/BV/TUV)
Destination Port & Incoterm: FOB, CFR, or CIF (specify port of discharge)
FAQ
Q: What is the main difference between ERW and Seamless (SMLS) steel pipes?
A: ERW pipes are made from cold-formed hot-rolled steel coils with a longitudinal weld seam, resulting in highly uniform wall thickness, tight dimensional tolerances, and lower cost. Seamless pipes are produced by piercing a solid steel billet, providing a continuous structure without a weld seam, typically selected for extreme ultra-high-pressure conditions where seamless design codes are mandatory.
Q: How is the weld seam reliability ensured in ERW pipes?
A: Weld seam integrity is secured through full-length inline induction heat treatment (normalization) that eliminates stress and refines the microstructure. Afterwards, 100% online Ultrasonic Testing (UT) scans the weld zone for longitudinal flaws, followed by 100% full-length hydrostatic pressure testing.
Q: What is the difference between API 5L PSL1 and PSL2?
A: PSL2 enforces stricter requirements than PSL1. PSL2 specifies mandatory limits on Carbon Equivalent (CEQ), notch toughness (Charpy impact testing), yield and tensile strength upper bounds, and full-length non-destructive testing for all steel grades.
Q: Can ERW steel pipes be used for bending and field fabrication?
A: Yes. ERW pipes made from ductile steel grades (such as ASTM A53 Grade B or API 5L Grade B/X42 through X70) undergo flattening and bend tests during production. They can be cold-bent and field-welded provided proper welding procedures matching the base metal carbon equivalent are followed.
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