EN 10217 P355NH Electric Resistance Welded (ERW) Pipe
Basic Overview
A European standard specification for high-strength, fine-grain carbon steel welded tubes designed for pressure equipment applications. P355NH is a normalized fine-grain steel specifically engineered for elevated temperature service in boilers, pressure vessels, and industrial piping systems .
Name Explanation
| Part | Meaning |
|---|---|
| EN | European Norm (standard) |
| 10217 | Standard for welded steel tubes for pressure purposes |
| P | Pressure purpose steel |
| 355 | Minimum yield strength: 355 MPa (~51,500 psi) |
| NH | Normalized for elevated temperature applications |
| Electric Resistance Welded | Manufacturing process – pipe formed from strip and welded longitudinally without filler metal |
Key Features of EN 10217 P355NH ERW Pipe
| Feature | Description |
|---|---|
| Material Type | Fine-grain, fully-killed carbon-manganese steel with micro-alloying elements (Nb, V, Ti) |
| Manufacturing | Electric Resistance Welded (ERW) or High Frequency Welded (HFW) – longitudinal weld seam fully removed (OD and ID) |
| Material Number | 1.0565 (DIN designation) |
| Former Designation | WStE 355 |
| Yield Strength | 355 MPa minimum (for thickness ≤16mm) |
| Tensile Strength | 490-650 MPa (71,000-94,000 psi) |
| Elongation | 22% minimum (longitudinal) |
| Impact Properties | 40J at -20°C (longitudinal) / 27J at -20°C (transverse) |
| Temperature Range | -20°C to +400°C for pressure applications |
| Key Advantages | High strength-to-weight ratio, excellent low-temperature toughness, fine-grain structure, suitable substitute for seamless tubes |
| Certification | Supplied with EN 10204 3.1 inspection certificate (standard) |
Chemical Composition
| Element | Content (%) | Notes |
|---|---|---|
| Carbon (C) | 0.16 max | Low carbon for weldability |
| Silicon (Si) | 0.40 max | |
| Manganese (Mn) | 0.50 - 1.50 | Provides strength |
| Phosphorus (P) | 0.025 max | Tight control |
| Sulfur (S) | 0.015-0.020 max | Critical for toughness |
| Aluminum (Al) | 0.02 min | Grain refinement |
| Niobium (Nb) | 0.05 max | Micro-alloying |
| Vanadium (V) | 0.10 max | Micro-alloying |
| Titanium (Ti) | 0.03 max | Micro-alloying |
| Chromium (Cr) | 0.30 max | Residual |
| Nickel (Ni) | 0.50 max | Residual |
| Molybdenum (Mo) | 0.08 max | Residual |
| Copper (Cu) | 0.30 max | Residual |
| Nitrogen (N) | 0.02 max |
Note: For each reduction of 0.01% below the specified maximum carbon content, an increase of 0.05% above the specified maximum manganese content is permissible.
Mechanical Properties
Room Temperature Properties
| Property | Value | Test Direction |
|---|---|---|
| Yield Strength (ReH) | 355 MPa min | Longitudinal |
| Tensile Strength (Rm) | 490-650 MPa | Longitudinal |
| Elongation (A) | 22% min | Longitudinal |
| Elongation (A) | 20% min | Transverse |
Impact Properties (Charpy V-notch)
| Test Temperature | Min. Average Impact Energy (Longitudinal) | Min. Average Impact Energy (Transverse) |
|---|---|---|
| -20°C | 40 J | 27 J |
| -10°C | 43 J | 31 J |
| 0°C | 47 J | 35 J |
| +20°C | 55 J | 39 J |
Elevated Temperature Yield Strength (Rp0.2)
| Temperature (°C) | Min. Yield Strength (MPa) |
|---|---|
| 100 | ~335 |
| 150 | ~315 |
| 200 | ~295 |
| 250 | ~275 |
| 300 | ~255 |
| 350 | ~235 |
| 400 | ~215 |
| 450 | ~200 |
Delivery Conditions & Size Availability
| Parameter | Hot-Finished | Weld Line Annealed (WLA) |
|---|---|---|
| Outside Diameter | 17.2 mm to 193.7 mm | 219.1 mm to 508 mm |
| Wall Thickness | 1.8 mm to 16 mm | Up to 25 mm |
| Delivery Condition | Normalized throughout | Weld seam normalized |
| Weld Bead | Fully removed (OD & ID) | Fully removed |
| Length | 3-18 m (customizable) | 3-18 m (customizable) |
Dimensional Tolerances (Class B)
| Parameter | Tolerance | Test Method |
|---|---|---|
| Outer Diameter (D) | ±0.75% D or ±1.0mm (whichever larger) | EN ISO 8502 |
| Wall Thickness (t ≤15mm) | +10% / -5% t | Ultrasonic thickness measurement (EN 10246-2) |
| Length | +100/-0 mm (fixed length) | Laser ranging |
Heat Treatment Specifications
| Process | Parameters | Purpose |
|---|---|---|
| Normalizing (N) | 910±10°C × 1.5min/mm, air cooling | Refine grains to ASTM 6-8 grade |
| Weld Line Annealing (WLA) | Induction heating to 550-600°C, slow cooling | Normalize weld zone structure |
| Stress Relief Annealing (SR) | 580-620°C × 2min/mm, furnace cooling (≤200°C/h) | Eliminate welding residual stress |
Test Categories: TC1 vs. TC2
| Category | Description | Availability |
|---|---|---|
| TC1 | Standard quality, supplied as standard | All sizes |
| TC2 | Enhanced quality with mandatory ultrasonic testing of weld seam | Sizes ≥ OD219.1mm (option) |
Non-Destructive Testing Requirements
| Test Type | Requirements |
|---|---|
| Ultrasonic Testing (UT) | Sensitivity: Φ3.2mm flat bottom hole (EN ISO 10893-3) |
| UT Coverage | 100% weld + 10mm parent material on both sides |
| Hydrostatic Test | Test pressure = 2 × allowable working pressure (min 20MPa, hold ≥15s) |
Multi-Certification Examples (Tata Steel Inflow™ Plus 355)
| Standard | Grade | Notes |
|---|---|---|
| Primary Standard | EN 10217-3 Grade P355NH | Pressure purposes |
| Structural Engineering | EN 10219 Grade S355J2H | For sizes ≥ OD219.1mm |
| German Standards | DIN1626 St52.0N/G, DIN1628 St52.4, DIN17178 WSt E 355 | Historical equivalents |
| Seamless Equivalents | DIN1629 St52.0N, DIN1630 St52.4, DIN17179 WSt E355 | Suitable seamless substitutes |
Common Applications
| Industry | Applications |
|---|---|
| Power Generation | Steam boilers, superheaters, heat exchangers, power plant piping |
| Oil & Gas | Onshore gas pipelines (≤100 bar), process plant piping |
| Petrochemical | Industrial conveyance, pressure vessels, process equipment |
| Industrial | General purpose pressure and industrial conveyance, HVAC, steam services |
| Fire Protection | Fire sprinkler systems and protection applications |
| District Heating | High-temperature district heating networks |
| Wear Applications | Increased wear resistance for abrasive services |
Pressure Equipment Directive (PED) Compliance
| Aspect | Compliance |
|---|---|
| PED 2014/68/EU | Fully compliant – suitable for equipment in PED categories I, II, III, or IV |
| AD2000 | Aligned with AD2000 Merkblatt W4 |
| Temperature Range | Standard: -20°C to +400°C |
| Low Temperature Option | May be possible upon request with full application details |
Advantages Summary
| Advantage | Description |
|---|---|
| Multi-Certified | Satisfies multiple industry standards (EN 10217, EN 10219, DIN equivalents) |
| Seamless Alternative | Suitable substitute for equivalent hot-finished fine grain seamless tube grades |
| Weight Savings | Higher strength allows thinner walls – reduces supporting structures, hangers, brackets |
| Wear Resistance | Increased wear resistance provides improved service life |
| PED Compliance | Fully compliant with Pressure Equipment Directive |
| Fully Weldable | Excellent weldability with standard methods |
| Weld Removal | OD and ID weld beads fully removed for smooth internal surface |
| Technical Support | Backed by technical experts for application advice |
| Responsible Sourcing | Certified to BES 6001 Responsible Sourcing standard (Tata Steel) |
International Equivalents (Approximate)
| Standard | Equivalent Grade | Notes |
|---|---|---|
| EN 10028-3 | P355NH | Flat products for pressure purposes |
| EN 10222-4 | P355NH | Forgings for pressure purposes |
| EN 10216-3 | P355NH | Seamless tubes for pressure purposes |
| EN 10253-2 | P355NH | Butt-welding pipe fittings |
| DIN 1629 | St52.0N | Seamless equivalent |
| DIN 1630 | St52.4 | Seamless equivalent |
| DIN 17179 | WSt E355 | Historical designation |
| ASTM A662 | Gr.C | Approximate US equivalent |
| ISO 3183 | L360 | Similar strength level |
| API 5L | X52 | Similar strength level (360 MPa) |
Important Selection Notes
1. Grade Designation Meaning
P = Pressure purpose steel
355 = Minimum yield strength (355 MPa)
NH = Normalized for elevated temperature applications
2. Quality Level Selection
TC1: Standard quality, supplied as standard – sufficient for most applications
TC2: Enhanced quality with ultrasonic weld examination – recommended for critical service, available for sizes ≥219.1mm OD
3. Temperature Considerations
Standard range: -20°C to +400°C for pressure applications
For temperatures below -20°C, specify low-temperature options (P355NL1 for -40°C, P355NL2 for -50°C)
For temperatures above 400°C, consider higher alloy grades
4. Supplementary Requirements
Low temperature (-50°C): Impact energy ≥60J average, single specimen ≥45J; use Al+Ti composite deoxidation process
High temperature endurance (300°C): 10⁵ hours creep rupture strength ≥150 MPa; Rp0.2@300°C ≥300 MPa
5. Certification Requirements
Standard: EN 10204 3.1 (manufacturer's independent testing)
For critical applications: EN 10204 3.2 (third-party witnessed)
Must include: chemical composition, mechanical properties, NDT results, heat treatment curve
6. Advantages over Lower Grades
Higher strength (355 MPa vs. 235/265 MPa) allows thinner walls for same pressure rating
Weight savings reduce supporting structure requirements
Fine-grain structure provides better toughness and weldability
Cost-effective alternative to seamless tubes
Final Takeaway: EN 10217 P355NH ERW Pipe is a high-strength, fine-grain normalized steel welded tube specifically designed for pressure equipment applications requiring guaranteed properties at both elevated and low temperatures. With minimum yield strength of 355 MPa and impact properties of 40J at -20°C, it offers an excellent balance of strength, toughness, and weldability for demanding applications in power generation, petrochemical, oil & gas, and industrial pressure systems. The material is fully compliant with the Pressure Equipment Directive (PED) and is supplied with EN 10204 3.1 certification as standard. Major manufacturers offer multi-certified tubes that also meet EN 10219 S355J2H structural requirements, providing flexibility for projects requiring both pressure and structural certifications. For critical service, specify EN 10217-3 P355NH with TC2 test category (ultrasonic weld examination) for sizes ≥219.1mm OD.
