Q355NH High Strength Weathering Steel For Bridges
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Q355NH High Strength Weathering Steel is a premium low-alloy structural steel designed for critical bridge infrastructure, adhering strictly to GB/T 4171-2008 standards. Its unique alloy composition and mechanical properties deliver exceptional strength, ductility, and corrosion resistance, making it ideal for long-term exposure to harsh outdoor environments.
Chemical Composition (GB/T 4171-2008, Mass Fraction, %)
| C | P | S | ||||||
|---|---|---|---|---|---|---|---|---|
| <=0.16 | <=0.50 | 0.50-1.50 | <=0.030 | <=0.030 | 0.25-0.55 | 0.30-1.25 |
<=0.65 |
Key alloying elements--promote the formation of a dense, adherent -FeO(OH)– -FeO(OH) oxide layer, which acts as a natural barrier against moisture and corrosive gases. This self-protective rust layer reduces corrosion rates to 1/5–1/3 of ordinary carbon steel, extending service life by 3–5 times with minimal maintenance.
Mechanical Properties (Thickness <=16mm, GB/T 4171-2008)
| >=355 MPa | |
| 490–630 MPa | |
| >=20% | |
| Charpy Impact Energy (20℃, V-Notch) | >=47 J |
Supplied in hot-rolled or normalized conditions, Q355NH ensures reliable performance under dynamic loading and temperature fluctuations (-20℃ to 60℃), critical for bridges subjected to heavy traffic and cyclic stress .
In moderate-humidity environments (urban, rural, or mild industrial), Q355NH forms a stable rust layer that self-heals over time. Unlike ordinary steel, which suffers from continuous pitting, Q355NH exhibits , minimizing thickness loss. However, it is not recommended for high-salt (coastal) or strongly acidic (pH <4) environments .
Q355NH supports standard cold/hot forming processes (bending, punching, shearing) with performance comparable to low-alloy carbon steels. For welding, use E5015-NH or E5515-NH electrodes to maintain corrosion consistency between the base metal and welds. Post-weld treatments (e.g., slag removal) are essential to prevent localized corrosion at joints .
High Strength-to-Weight Ratio: Reduces structural weight while meeting load-bearing requirements, optimizing material usage and construction costs.
Low Life-Cycle Cost: Eliminates frequent repainting through natural rust-layer protection, cutting maintenance expenses by up to 60% .
Hong Kong-Zhuhai-Macao Bridge and Lanzhou Xigu Bridge, demonstrating resistance to complex climates and heavy loads .
GB/T 4171-2008: Ensures chemical and mechanical consistency for atmospheric corrosion resistance.
ASTM A588 Grade A Equivalence: Exhibits comparable corrosion resistance to international standards, making it suitable for global bridge projects .
By integrating advanced alloy design and rigorous quality control, Q355NH High Strength Weathering Steel sets a benchmark for durability and cost-efficiency in bridge construction.
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