Q345qE Bridge Steel Plate
High-performance structural steel specifically designed for bridge construction in extremely cold regions, meeting national and international standards for durability and reliability in sub-zero temperature conditions.
About Q345qE Steel
Q345qE is a Chinese standard (GB/T 714-2015) low alloy high strength structural steel specifically developed for bridge construction in extremely cold climate zones.
The "q" in the designation stands for bridge (qiaoliang in Chinese), while "E" indicates the steel's impact test temperature of -40°C, making it suitable for severe cold climate conditions in northern China and other frigid regions.
It offers exceptional low-temperature toughness, excellent weldability, and superior formability, making it the premium choice for critical bridge infrastructure in extreme cold environments.
Technical Specifications
Basic Information
Mechanical Properties
| Thickness (mm) | Yield Strength (MPa) ≥ | Tensile Strength (MPa) | Elongation (%) ≥ | Impact Energy (J) ≥ |
|---|---|---|---|---|
| ≤16 | 345 | 470-630 | 21 | 34 |
| >16-35 | 325 | 470-630 | 21 | 34 |
| >35-50 | 315 | 470-630 | 21 | 34 |
| >50-100 | 295 | 450-600 | 21 | 34 |
Chemical Composition (wt%)
| Element | C ≤ | Si ≤ | Mn | P ≤ | S ≤ | Nb ≤ | V ≤ | Ti ≤ | Ni ≤ | Cu ≤ |
|---|---|---|---|---|---|---|---|---|---|---|
| Content | 0.16 | 0.55 | 1.00-1.60 | 0.020 | 0.015 | 0.06 | 0.15 | 0.02 | 0.50 | 0.30 |
Note: Carbon equivalent (Ceq) ≤ 0.45%, Weldability carbon equivalent (Pcm) ≤ 0.24%. Ni content can be increased to improve low-temperature toughness as required.
International Standards Comparison
Mechanical Properties Comparison (≤16mm thickness)
| Property | Q345qE (GB/T 714-2015) | S355J4 (EN 10025) | A709 Gr50 (ASTM A709) |
|---|---|---|---|
| Yield Strength (MPa) min | 345 | 355 | 345 (50 ksi) |
| Tensile Strength (MPa) | 470-630 | 470-630 | 485-655 (70-95 ksi) |
| Elongation (%) min | 21 | 21 | 21 |
| Impact Test Temperature (°C) | -40 | -40 | -18 (0°F) |
| Impact Energy (J) min | 34 | 27 | 27 (20 ft-lb) |
| Carbon Equivalent (Ceq) max | 0.45% | 0.45% | 0.45% |
Chemical Composition Comparison (wt%)
| Element | Q345qE (max/ range) | S355J4 (EN 10025) (max/ range) | A709 Gr50 (ASTM A709) (max/ range) |
|---|---|---|---|
| Carbon (C) | ≤0.16% | ≤0.20% | ≤0.23% |
| Silicon (Si) | ≤0.55% | ≤0.55% | 0.15-0.40% |
| Manganese (Mn) | 1.00-1.60% | 1.00-1.60% | 1.00-1.50% |
| Phosphorus (P) | ≤0.020% | ≤0.025% | ≤0.035% |
| Sulfur (S) | ≤0.015% | ≤0.020% | ≤0.040% |
| Niobium (Nb) | ≤0.06% | ≤0.06% | ≤0.05% |
| Vanadium (V) | ≤0.15% | ≤0.15% | ≤0.06% |
| Titanium (Ti) | ≤0.02% | ≤0.05% | ≤0.03% |
Key Differences Summary:
- Q345qE has the strictest P/S limits (0.020/0.015%) among all grades, significantly improving low-temperature toughness and weldability
- Lower carbon content (≤0.16%) compared to Q345qD and international standards for enhanced low-temperature performance
- Higher nickel content allowance (≤0.50%) to further improve toughness at -40°C
- S355J4 (EN standard) has slightly higher minimum yield strength (355MPa vs 345MPa) at same -40°C impact test temperature
- Q345qE requires higher impact energy (34J vs 27J) at -40°C, making it ideal for extremely cold regions
- All grades maintain excellent weldability with carbon equivalent ≤0.45%
Application Cases
Northeast China Highway Bridge
Used in the main structure of a 2.4km long highway bridge in Heilongjiang Province, withstanding extreme winter temperatures down to -40°C and heavy snow loads.
- Plate thickness: 30mm-50mm
- Total usage: 8,200 metric tons
- Service life: Designed for 100 years
Inner Mongolia High-Speed Railway Bridge
Applied in a high-speed railway bridge project in Inner Mongolia, providing exceptional fatigue resistance in extreme cold climate conditions.
- Plate thickness: 20mm-55mm
- Total usage: 9,500 metric tons
- Operates at temperatures down to -38°C
China-Russia Border Bridge
Utilized in an international border bridge connecting China and Russia, designed to withstand the severe cold climate of the Siberian border region.
- Plate thickness: 25mm-60mm
- Total usage: 6,800 metric tons
- Meets both Chinese and Russian standards
Other Typical Applications
Frequently Asked Questions (FAQ)
What is the difference between Q345qE and Q345qD steel?
The main differences between Q345qE and Q345qD bridge steel plates are:
- Impact test temperature: Q345qE (-40°C) vs Q345qD (-20°C)
- Impurity limits: Q345qE (P≤0.020%, S≤0.015%) vs Q345qD (P≤0.025%, S≤0.020%)
- Carbon content: Q345qE (≤0.16%) vs Q345qD (≤0.18%)
- Nickel content allowance: Q345qE (≤0.50%) vs Q345qD (≤0.30%)
- Application scope: Q345qE for extremely cold regions, Q345qD for cold regions
- Cost: Q345qE is premium grade with higher production standards
What welding precautions are needed for Q345qE in cold weather?
Q345qE has excellent weldability (Ceq ≤0.45%), but special precautions apply for welding in cold weather:
- Preheat base metal to ≥5°C when ambient temperature < 0°C
- Preheat to 50-100°C for plates >30mm thick or when temperature < -10°C
- Use low-hydrogen welding electrodes to prevent cold cracking
- Maintain interpass temperature ≥50°C during multi-pass welding
- Post-weld heat treatment recommended for critical structural components
Follow WPS specifically qualified for low-temperature welding applications.
What is the service temperature range for Q345qE steel?
Q345qE is engineered for extreme cold environments with the following temperature range:
- Minimum operating temperature: -40°C (meets impact energy requirements at this temperature)
- Recommended continuous service: -40°C to 200°C
- Maximum short-term service temperature: 300°C
- Optimal welding temperature: ≥5°C (preheating required below this)
Q345qE is the coldest-rated grade in the Q345q series, suitable for the most severe cold climate conditions in China and worldwide.
What special treatments enhance Q345qE performance in cold regions?
Several specialized treatments optimize Q345qE for extreme cold environments:
- Nickel alloying (up to 0.50%) to improve low-temperature toughness
- Strict impurity control (P≤0.020%, S≤0.015%) to prevent brittle fracture
- Normalized heat treatment for uniform microstructure
- Special anti-corrosion coatings for cold, humid environments
- Thermal stress relief after welding for critical components
- Zinc-rich epoxy coatings with frost-resistant properties
These treatments ensure reliable performance even after decades of exposure to extreme cold cycles.
What quality certifications are provided for Q345qE steel plates?
We provide comprehensive certification for Q345qE steel plates, including:
- Mill Test Certificate (MTC) EN 10204 3.1 / 3.2 with -40°C impact test results
- GB/T 714-2015 standard compliance certificate
- Low-temperature toughness test reports (-40°C Charpy V-notch)
- Third-party inspection (SGS, BV, TUV) for critical projects
- Welding procedure qualification for low-temperature applications
- ISO 9001 and CE certification (when required)
All Q345qE plates undergo 100% ultrasonic testing to ensure internal quality for cold-region applications.
Key Advantages of Q345qE
Exceptional Ultra-Low Temperature Performance
Maintains superior toughness at -40°C, ideal for the most extreme cold climate regions in northern China and worldwide.
Highest Structural Integrity
Strictest impurity controls and chemical composition ensure maximum reliability in critical cold-region infrastructure.
Superior Weldability
Optimized chemical composition ensures excellent welding performance with minimal preheating even in cold environments.
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