1. Key Mechanical Properties Affecting Cold Bending
| Property | S355J0WP Typical Value | Relevance to Bending |
|---|---|---|
| Yield Strength (Re) | ≥355 MPa | Higher strength requires more bending force. |
| Tensile Strength (Rm) | 470–630 MPa | Limits maximum deformation before fracture. |
| Elongation (A₅) | ≥20% (thickness-dependent) | Higher elongation improves bendability. |
| Impact Toughness | ≥27 J at –20°C (EN 10025-5) | Critical for low-temperature bending. |
2. Cold Bending Guidelines
(A) Bendability
Minimum Bend Radius:
For S355J0WP, the recommended minimum bend radius is typically 2× to 3× the material thickness (e.g., 20 mm radius for 10 mm plate).
Tighter bends (e.g., 1.5× thickness) may be possible but require testing due to risk of surface cracking.
(B) Process Recommendations
Material State:
Best bent in normalized or hot-rolled condition (avoids brittleness from cold work).
Avoid bending pre-weathered steel (patina may flake at sharp bends).
Temperature:
Room temperature bending is standard, but below 0°C, pre-heating (100–150°C) may reduce cracking risk.
Tooling:
Use smooth, rounded dies to prevent surface damage.
Lubrication can reduce friction-induced defects.
(C) Post-Bending Considerations
Stress Relief: Not usually required for S355J0WP, but critical for highly constrained bends.
Patina Formation: Bent areas may rust faster initially; the patina will stabilize over time.
3. Potential Risks & Mitigation
| Risk | Cause | Solution |
|---|---|---|
| Edge Cracking | Excessive deformation or sharp bends. | Use larger bend radii; anneal if needed. |
| Surface Defects | Tool marks or oxide scale. | Polish contact surfaces; use protective films. |
| Reduced Corrosion Resistance | Micro-cracks from bending. | Avoid bends in highly corrosive zones (e.g., coastal splash areas). |
