Weathering Steel Billet Q345B

Weathering Steel Billet Q345B

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