This Weathering Steel Billet Q345B combines the high strength of Q345B with enhanced corrosion resistance, thanks to its optimized alloying elements (Cr, Cu, P). The natural patina layer that forms over time protects the steel from further corrosion, making it a cost-effective choice for long-term outdoor applications where maintenance access is limited.
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Product details
Weathering Steel Billet Q345B is a high-performance low-alloy steel engineered to excel in outdoor and harsh environments, combining the strength of Q345B with enhanced atmospheric corrosion resistance. Compliant with GB/T 1591-2008 and GB/T 4171-2008 standards, this billet forms a protective, self-healing patina over time, eliminating the need for frequent painting or coatings—making it a cost-effective and sustainable choice for long-term outdoor applications.
| Parameter | Value | Remarks |
|---|---|---|
| Standard | GB/T 1591-2008, GB/T 4171-2008 | Compliant with low alloy high-strength steel and weathering steel standards |
| Grade | Q345B (Weathering Type) | Impact tested at 20℃ with enhanced atmospheric corrosion resistance |
| Chemical Composition (wt%) | ||
| – Carbon (C) | ≤0.20 | Controlled for weldability and corrosion resistance |
| – Silicon (Si) | ≤0.55 | Aids in forming protective oxide layer |
| – Manganese (Mn) | ≤1.70 | Enhances strength and toughness |
| – Phosphorus (P) | 0.015 – 0.040 | Promotes patina formation for weather resistance |
| – Sulfur (S) | ≤0.040 | Minimized to reduce brittleness and corrosion risks |
| – Chromium (Cr) | 0.30 – 0.70 | Key element for improving atmospheric corrosion resistance |
| – Nickel (Ni) | ≤0.50 | Enhances corrosion resistance in harsh environments |
| – Copper (Cu) | 0.20 – 0.50 | Critical for forming protective patina layer |
| – Niobium (Nb) | ≤0.07 | Microalloying for grain refinement |
| – Vanadium (V) | ≤0.15 | Improves strength and toughness |
| – Titanium (Ti) | ≤0.20 | Enhances structural stability |
| Mechanical Properties | ||
| – Yield Strength (ReL) | ≥345 MPa | For thickness ≤16mm |
| – Tensile Strength (Rm) | 470 – 630 MPa | Ensures structural integrity under load |
| – Elongation (A) | ≥21% | Provides ductility for fabrication |
| – Impact Energy (Akv) | ≥34 J | At 20℃ (longitudinal specimen), resists brittle fracture |
| – Bending Test | 180° | Bend diameter: 2a (≤16mm) / 3a (>16mm) |
| Corrosion Resistance | 2 – 5 times better than ordinary carbon steel | Forms dense, adherent patina (protective oxide layer) in atmospheric conditions |
| Delivery Condition | Hot rolled, normalized, TMCP | Surface may develop initial rust layer during storage |
| Typical Applications | Bridges, building facades, outdoor structures, transportation infrastructure, and industrial equipment exposed to weather | Ideal for reducing maintenance and extending service life in outdoor environments |
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