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Q345q Series | Structural Steel for Bridge

Q345q Series | Structural Steel for Bridge

SteelPRO Group provides Q345q series structural steel plates for bridges in stock.

Standards: ISO, ASTM/ASME/AISI, EN, GB/T, DIN, JIS, BS, etc.
Grades: Q345qD/E/F,  Q345qDNH/ENH/FNH
Material: High-Strength Low-Alloy Steel (HSLA)
Thickness: 6-100 mm, or customized
Width: 900-4800 mm, or customized
Length: 3000-25000 mm, or customized
Shape: Plate, Profile (I-beam, H-beam, Angle, Channel, Square bar, Flat bar), Pipe, Coil, Bar, or as request
Condition of Delivery: N/HR/A/T/Q+T/TMCP, or as request
Stock: In stock
Origin: Hebei/Henan/Jiangsu, China
Port: Qingdao

Description

What Is Q345q?

Q345q series steel is low-alloy, high-strength structural steel primarily composed of carbon, manganese, and silicon. It offers excellent toughness, weldability, and high tensile strength while also performing well in low temperatures and resisting atmospheric corrosion.

Naming Rules: 

  • Q: Yield strength.
  • 345: Minimum yield strength of 345 MPa.
  • q: Suitable for bridge structure.
  • C/D/E/F: Quality grades. Toughness at 0℃/-20℃/-40℃/-60℃. (e.g. Q345qD)
  • NH: Weather-resistant, designed to withstand atmospheric corrosion. (e.g. Q345qDNH)
  • Z-: Z-direction performance grade, such as Z15, Z25. (e.g. Q345qDNHZ15)

It is commonly used in bridge construction, large infrastructure, and structural supports, where its durability and load-bearing capacity are essential for stability in challenging environments.

Characteristics of Q345q Series Steel

  • High strength, making it suitable for heavy structures.
  • Reliable performance under stress, reducing the risk of failure.
  • Good weldability, allowing easy fabrication and assembly.
  • Excellent toughness, ensuring durability in low temperatures.
  • Corrosion resistance, extending the lifespan of structures.

Chemical Compositions

ElementQ345qDQ345qE
Carbon, C≤0.18≤0.18
Silicon, Si≤0.55≤0.55
Manganese, Mn0.9 – 1.60.9 – 1.6
Phosphorus, P≤0.025≤0.02
Sulfur, S≤0.02≤0.01
Chromium, Cr≤0.3≤0.3
Nickel, Ni≤0.3≤0.3
Copper, Cu≤0.3≤0.3
Nitrogen, N≤0.008≤0.008
Titanium, Ti0.006 – 0.030.006 – 0.03
Vanadium, V0.01 – 0.080.01 – 0.08
Niobium, Nb0.005 – 0.060.005 – 0.06
Boron, B≤0.0005≤0.0005
Aluminum, Al0.01 – 0.0450.01 – 0.045
Hydrogen, H≤0.0002≤0.0002

Note:

  • According to standard GB/T 714-2015.
  • Al, Nb, V, and Ti can be added individually or in combination. When added individually, they must meet the specified limits in the table. If combined, at least one element must meet the table’s minimum limit, and the total of Nb + V + Ti ≤ 0.22%.
  • Total aluminum content must be 0.015% – 0.050%.
  • Analysis of B and H is not required if the supplier guarantees their presence.

Physical Properties

PropertyMetricImperial
Density7.85 g/cm³0.284 lb/in³
Melting Point1450–1530 °C2640–2800 °F
Thermal Conductivity43 W/m·K25 BTU/ft·h·°F
Electrical Conductivity6.99 MS/m6.99 MS/m
Specific Heat Capacity480 J/kg·K0.115 BTU/lb·°F
Thermal Expansion Coefficient12.1 × 10⁻⁶ /K6.72 × 10⁻⁶ /°F
Electrical Resistivity0.145 μΩ·m0.145 μΩ·m

Mechanical Properties

GradesYield Strength(MPa) min for Thickness in mmTensile Strength min.ElongationV-Type Impact Test
Q345qD≤16mm16–40mm40–63mm63–80mm80–100mmMPa% minTest temperature ℃Impact Absorption Energy KV₂/J
≥345 MPa≥335 MPa≥325 MPa≥315 MPa≥305 MPa450–630 MPa≥21%-20≥34 J

*+HR/N (hot rolled or normalized)

Industries & Applications

IndustryApplication
Bridge ConstructionBridge girders, Piers, Trusses, Beams
Railway InfrastructureRailway bridges, Rail tracks, Sleepers, Structural supports
Heavy ConstructionHigh-rise buildings, Structural supports, Beams, Frames
Hydropower EngineeringDams, Hydraulic gates, Water pipelines, Structural supports

Machining

Heat Treatment

  • Normalization: Heat to 900–950°C, then air cool to refine the grain structure and improve toughness.
  • Quenching: Heat to 880–920°C, hold at temperature, then rapidly cool in water or oil to increase hardness.
  • Tempering: After quenching, heat to 500–650°C, hold at temperature, then air cool to reduce brittleness and improve ductility.
  • Stress Relieving: Heat to 540–600°C, hold for 1–2 hours, then air cool to relieve residual stresses without significantly altering mechanical properties.

Surface Finish

  • Galvanizing: Coating the steel with zinc for corrosion resistance.
  • Powder Coating: Applying a dry powder that forms a protective layer when heated.
  • Painting: Adding a protective and decorative layer with paint.
  • Pickling: Removing impurities like rust and scale using acid.
  • Anodizing: Electrochemical process to enhance corrosion resistance.

*Customization is available upon request.

Our Service

SteelPRO Group – manufacturer and solution provider for special steel, offering multi-industry application solutions and customised services, 100% quality free, accompanying customers in their growth!

Our Quality Control

  • Roundness
  • Tolerance
  • Microstructure
  • Non-Destructive Testing
  • Destructive Testing
  • Process Control

Service Integration Processing

  • Welding
  • Metal Fabrication
  • CNC Machining
  • Lathe
  • Forming

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