The S355J2WP weathering steel is typically delivered in the following states, depending on manufacturing standards (e.g., EN 10025-5) and application requirements:
1. Hot Rolled (HR)
Process: Rolled at high temperatures (≈900°C), then air-cooled.
Properties:
Standard delivery state for most structural applications.
Good formability and weldability.
Rust-resistant but may require natural weathering to stabilize the patina.
Typical Uses: Bridges, building facades, non-critical structural parts.
2. Normalized (N)
Process: Hot-rolled steel is reheated to ≈900°C and cooled in still air for uniform microstructure.
Properties:
Improved toughness and mechanical consistency vs. hot-rolled.
Better weldability and impact resistance at low temperatures.
Typical Uses: Heavy-load bridges, offshore structures, or harsh climates.
3. Thermomechanical Controlled Rolling (TMCR or CR)
Process: Precise rolling at controlled temperatures (below recrystallization) followed by accelerated cooling.
Properties:
Higher strength and finer grain structure than hot-rolled.
Excellent toughness and corrosion resistance.
No additional heat treatment needed.
Typical Uses: High-stress components (e.g., crane rails, seismic-resistant structures).
Key Comparison
| State | Advantages | Limitations | Common Applications |
|---|---|---|---|
| Hot Rolled | Cost-effective, readily available | Lower toughness vs. normalized | General construction, façades |
| Normalized | Better mechanical properties | Higher cost, longer lead time | Critical bridges, heavy industry |
| TMCR | Superior strength/toughness | Complex production process | High-performance infrastructure |
Selection Guidance
For most weathering applications: Hot-rolled suffices.
For extreme environments: Normalized or TMCR offers enhanced durability.
Check specifications: EN 10025-5 defines delivery conditions (e.g., +N for normalized).
