Mechanical Properties
| Property | S275 | S355 | Advantage |
|---|---|---|---|
| Yield Strength (ReH) | ≥275 MPa | ≥355 MPa | S355 is ~29% stronger |
| Tensile Strength (Rm) | 410-560 MPa | 470-630 MPa | Higher load capacity |
| Elongation (A₅) | ≥22% (thickness-dependent) | ≥22% (similar) | Comparable ductility |
| Impact Toughness (Charpy V-notch) | Varies by subgrade (JR/J0/J2) | Similar subgrades (JR/J0/J2/K2) | S355K2 offers better low-temp toughness |
Chemical Composition
| Element (Max %) | S275JR | S355JR | Key Difference |
|---|---|---|---|
| Carbon (C) | 0.21 | 0.22 | S355 may have slightly higher carbon for strength |
| Manganese (Mn) | 1.50 | 1.60 | Higher Mn in S355 improves hardenability |
| Phosphorus (P) | 0.035 | 0.035 | Similar (affects brittleness) |
| Sulfur (S) | 0.035 | 0.035 | Similar (affects machinability) |
| CEV (Carbon Equivalent) | ~0.35 | ~0.40 | S275 is slightly easier to weld |
Cost & Weight Savings
Material Cost: S355 typically costs 15–20% more than S275.
Weight Savings: Using S355 can reduce structural weight by ~20% for the same load capacity.
Fabrication Cost: S355 may require more precise welding procedures (higher CEV).
Applications
| Scenario | Preferred Grade | Reason |
|---|---|---|
| Light structures (e.g., platforms, non-critical frames) | S275 | Lower cost, sufficient strength |
| Heavy construction (e.g., bridges, high-rises) | S355 | Higher strength-to-weight ratio |
| Low-temperature environments (e.g., offshore, cold regions) | S355J2/K2 or S275J2 | Better toughness at -20°C to -50°C |
| Welded assemblies (e.g., machinery) | S275 (if low CEV is critical) | Easier welding with preheat |
Key Decision Factors
Choose S275 if:
Budget is tight.
Loads are moderate (e.g., light buildings, supports).
Welding simplicity is prioritized.
Choose S355 if:
High strength-to-weight ratio is needed (e.g., bridges, cranes).
Reducing material weight saves overall costs.
Low-temperature toughness is critical (J2/K2 grades).
Conclusion
S355 is technically superior for high-stress applications, but S275 is more cost-effective for lighter loads. Always consult design codes (e.g., Eurocode 3) and perform a cost-benefit analysis before selecting.
For critical projects, consider S355J2/K2 for enhanced toughness or S275JR for basic structural needs.
