1. Standard & Classification
| Grade | Chinese Standard | Equivalent Int'l Grades | Category |
|---|---|---|---|
| Q355NH | GB/T 4171 | Similar to ASTM A588 (Corten B) | General Weathering Steel |
| Q355GNH | GB/T 4171 | Similar to ASTM A242 (Corten A) | High-Performance Weathering Steel |
2. Chemical Composition (%)
| Element | Q355NH | Q355GNH | Difference |
|---|---|---|---|
| C | ≤0.16 | ≤0.12 | GNH has lower carbon for better weldability. |
| P | 0.07–0.15 | 0.07–0.15 | Similar phosphorus content. |
| Cu | 0.25–0.55 | 0.25–0.55 | Copper critical for patina formation. |
| Cr | 0.40–0.80 | 0.45–0.75 | GNH has tighter Cr control. |
| Ni | ≤0.65 | 0.12–0.65 | GNH mandates minimum Ni for harsher environments. |
3. Corrosion Resistance
Q355NH: Suitable for moderate atmospheric conditions (urban/rural areas).
Q355GNH: Designed for harsh environments (coastal, industrial, high humidity/salt exposure).
Ni addition significantly improves resistance to chloride-induced corrosion.
Accelerated Test Data (Typical):
| Grade | Corrosion Rate (mm/year) |
|---|---|
| Q355NH | 0.05–0.08 |
| Q355GNH | 0.02–0.05 (30–50% lower) |
