Here is a more detailed breakdown of the standard mechanical properties of Q460NH weathering steel based on EN 10025-5:2019 and related industrial specifications, including additional technical insights:
1. Mechanical Properties (EN 10025-5:2019)
| Property | Standard Value | Notes |
|---|---|---|
| Yield Strength (ReH) | ≥ 460 MPa | - Measured at 0.2% offset. |
| Tensile Strength (Rm) | 550–720 MPa | - Must fall within this range; typical average ~620 MPa. |
| Elongation (A₅) | ≥ 17% (thickness ≤16mm) | - Decreases with thickness: ≥16–40mm: ≥16%, ≥40–63mm: ≥15%. |
| Impact Toughness (KV) | ≥ 27 J at -20°C | - Charpy V-notch test; some specs require ≥40 J for critical applications. |
2. Thickness-Dependent Variations
Yield & Tensile Strength:
Thicker sections (e.g., >63mm) may exhibit marginally lower yield/tensile values due to slower cooling rates during rolling.
Elongation:
Reduced ductility in thicker plates (see table above).
3. Additional Requirements for Weathering Steel
Corrosion Resistance:
Patina Formation: Q460NH develops a stable rust layer (loss rate ≤0.1 mm/year in mild climates).
Alloy Content: Cu, Cr, Ni, and P enhance atmospheric corrosion resistance (per ISO 14788).
Hardness: Typically 150–200 HBW; avoid excessive hardening during welding/cold working.
4. Comparison with Non-Weathering Q460
| Property | Q460NH | Ordinary Q460 |
|---|---|---|
| Corrosion Resistance | Self-protecting patina | Requires coatings |
| Impact Toughness | Higher (due to alloying elements) | Standard |
| Cost | 10–20% higher | Lower |
5. Testing & Certification
Mandatory Tests: Tensile, impact (Charpy), and bend tests per EN 10025-5.
Mill Test Certificate (MTC): Must include:
Chemical composition (Cu, Cr, Ni, P levels).
Mechanical properties (actual values, not just minima).
Corrosion performance data (if specified).
6. Practical Implications for Design
Structural Use: Ensure weld procedures account for alloy content (preheat/PWHT if needed).
Aesthetic Applications: Allow 6–18 months for uniform patina formation; initial runoff may stain surfaces.
For project-specific tolerances (e.g., offshore or seismic designs), consult EN 1993-1-1 (Eurocode 3) or AISC 303. Always validate with actual material test reports (MTRs).
