Q345q steel is a high-strength low-alloy structural steel specifically designed for bridge construction, offering a balance of mechanical performance, weldability, and cost-effectiveness. Here's a comprehensive overview tailored to bridge engineering requirements:

Material Classification and Standards

Q345q falls under GB/T 714-2015 (Chinese standard for bridge structural steel), with "Q" indicating yield strength, "345" specifying a minimum yield strength of 345 MPa (for thickness ≤16 mm), and "q" denoting its bridge-specific application. It is equivalent to ASTM A709 Grade 50 in international standards, making it suitable for global bridge projects .

 

Mechanical Properties

Q345q's performance is optimized for dynamic loading and harsh environments:

 

Property	Typical Values	Test Standard
Yield Strength (Rp0.2)	≥345 MPa (≤16 mm thickness)	GB/T 228.1-2010
Tensile Strength (Rm)	490–630 MPa	GB/T 228.1-2010
Elongation (A50)	≥21%	GB/T 228.1-2010
Impact Toughness (KV2)	≥20 J at 0°C (Grade C)	GB/T 229-2020
Fatigue Strength	≥180 MPa (at 2×10⁶ cycles)	ASTM E466 (equivalent)

 

 

 

 

 

 

 

Key Features for Bridge Applications

High Strength & Stiffness: Supports heavy traffic loads and long spans while minimizing material usage.

Fatigue Resistance: Engineered to withstand cyclic loading from vehicles and wind, critical for bridge longevity.

Weldability: Low carbon equivalent (CEV ≤0.43%) allows reliable welding with low-hydrogen electrodes (e.g., E5015-G) after preheating to 100–150°C for thick sections .

Cold-Weather Performance: Grade Q345qE achieves ≥27 J impact energy at -40°C, suitable for frigid regions .

Corrosion Resistance: While standard Q345q lacks weathering elements, it can be coated or paired with corrosion inhibitors for marine or industrial environments. Weathering variants like Q345qNH (with Cu/Cr/Ni additions) offer 2–8× better atmospheric corrosion resistance for maintenance-free designs .

 

 

 

 

 

 

Why Choose Us?
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