1. Direct ASTM Equivalent
ASTM A588 Grade A/B/K
Most Common Match:
A588 Grade K is nearly identical in composition and performance.
Key Similarities:
Corrosion Resistance: Both form a protective rust patina.
Mechanical Properties: Similar yield strength (~345 MPa min).
Alloying Elements: Comparable Cu, Cr, Ni, and P content.
| Property | Q355NH (GB/T 4171) | ASTM A588 Grade K |
|---|---|---|
| Yield Strength | ≥ 355 MPa | ≥ 345 MPa (50 ksi) |
| Tensile Strength | 470–630 MPa | 485–655 MPa |
| Corrosion Resistance | Excellent (P, Cu, Cr) | Excellent (P, Cu, Cr) |
| Main Applications | Bridges, containers, facades | Structural, outdoor architecture |
2. Other ASTM Weathering Steel Grades (Close Alternatives)
| ASTM Grade | Comparison with Q355NH |
|---|---|
| ASTM A242 (Type 1) | Higher P (0.07–0.15%), slightly less weldable |
| ASTM A606 (Type 4) | More common in sheet/coil form, similar corrosion resistance |
| ASTM A847 | Higher strength (for tubing), similar weathering properties |
3. Key Differences Between Q355NH & ASTM Grades
| Factor | Q355NH | ASTM A588 |
|---|---|---|
| Standard | Chinese (GB/T 4171) | ASTM (USA) |
| P Content | 0.07–0.12% | 0.04–0.12% (A588) |
| Cu Content | 0.25–0.55% | 0.20–0.50% (A588K) |
| Impact Test | Required at -20°C | Often tested at -40°C |
4. European Equivalent (EN Standard)
EN 10025-5: S355J0WP / S355J2WP
"WP" = Weathering steel (similar to Corten).
J0/J2 = Impact toughness grades.
5. Which ASTM Grade Should You Use?
For structural projects in the US/Canada: ASTM A588 Grade K (best match).
For sheet metal applications: ASTM A606 Type 4.
If higher phosphorus is acceptable: ASTM A242.
