Mechanical Properties of Q550NH Weathering Steel (GB/T 4171 Standard)
Yield Strength (ReH)
Minimum requirement: ≥550 MPa
Typical range: 550-650 MPa
This high yield strength makes it suitable for heavy-load structural applications where both strength and corrosion resistance are required
Tensile Strength (Rm)
Standard range: 630-800 MPa
Typical values: 650-750 MPa
The balance between tensile and yield strength ensures good structural performance
Elongation
Minimum: ≥17% (for thickness ≤16mm)
Decreases slightly with increasing thickness (≥15% for >16-40mm, ≥14% for >40mm)
Impact Toughness
Charpy V-notch impact energy: ≥27J at 0°C
Can maintain good toughness down to -20°C with proper processing
Comparison with Other Grades
About 55% stronger in yield strength than Q355NH (355 MPa)
Approximately 30% stronger than ASTM A588 Grade K
Maintains similar corrosion resistance to other weathering steels
Material Characteristics
The strength is achieved through microalloying and controlled rolling (TMCP)
Maintains good weldability despite high strength (CEV typically 0.40-0.45)
Strength properties remain stable after weathering layer formation
Application Considerations
Higher strength allows for lighter structures compared to conventional weathering steels
Requires proper design to utilize full strength potential
Material certificates should be verified for actual test values
