Q420qE Bridge Steel Plate
High-strength structural steel specifically designed for heavy-load and long-span bridge construction in extreme cold environments, meeting GB/T 714-2015 standards for durability and reliability in low temperature conditions down to -40°C.
About Q420qE Steel
Q420qE is a Chinese standard (GB/T 714-2015) high-strength low alloy structural steel specifically developed for heavy-load and long-span bridge construction in extreme 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 extreme cold climate conditions in northeastern China and high-altitude alpine regions.
It offers exceptional high strength (420MPa yield strength), excellent weldability, and superior ultra-low-temperature toughness, making it the premium choice for long-span, heavy-load and high-rise bridge infrastructure in extremely cold environments.
Technical Specifications
Basic Information
Mechanical Properties
| Thickness (mm) | Yield Strength (MPa) ≥ | Tensile Strength (MPa) | Elongation (%) ≥ | Impact Energy (J) ≥ |
|---|---|---|---|---|
| ≤16 | 420 | 520-680 | 19 | 34 |
| >16-35 | 400 | 520-680 | 19 | 34 |
| >35-50 | 390 | 520-680 | 19 | 34 |
| >50-100 | 380 | 500-660 | 19 | 34 |
Chemical Composition (wt%)
| Element | C ≤ | Si ≤ | Mn | P ≤ | S ≤ | Nb ≤ | V ≤ | Ti ≤ | Ni ≤ | Cu ≤ |
|---|---|---|---|---|---|---|---|---|---|---|
| Content | 0.16 | 0.55 | 1.30-1.80 | 0.020 | 0.015 | 0.08 | 0.15 | 0.02 | 0.50 | 0.30 |
Note: Carbon equivalent (Ceq) ≤ 0.45%, Weldability carbon equivalent (Pcm) ≤ 0.24%. The optimized chemical composition balances high strength (420MPa yield) with excellent ultra-low-temperature toughness at -40°C for heavy-load bridge applications in extreme cold environments.
International Standards Comparison
Mechanical Properties Comparison (≤16mm thickness)
| Property | Q420qE (GB/T 714-2015) | S420NL (EN 10025) | A709 Gr50W (ASTM A709) |
|---|---|---|---|
| Yield Strength (MPa) min | 420 | 420 | 345 (50 ksi) |
| Tensile Strength (MPa) | 520-680 | 500-630 | 485-655 (70-95 ksi) |
| Elongation (%) min | 19 | 20 | 21 |
| Impact Test Temperature (°C) | -40 | -50 | -29 (-20°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 | Q420qE (max/ range) | S420NL (EN 10025) (max/ range) | A709 Gr50W (ASTM A709) (max/ range) |
|---|---|---|---|
| Carbon (C) | ≤0.16% | ≤0.20% | ≤0.23% |
| Silicon (Si) | ≤0.55% | ≤0.55% | 0.15-0.40% |
| Manganese (Mn) | 1.30-1.80% | 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) | ≤0.08% | ≤0.06% | ≤0.05% |
| Vanadium (V) | ≤0.15% | ≤0.15% | ≤0.06% |
| Titanium (Ti) | ≤0.02% | ≤0.05% | ≤0.03% |
Key Differences Summary:
- Q420qE offers higher yield strength (420MPa) with ultra-low temperature toughness (-40°C), ideal for long-span and heavy-load bridge applications in extreme cold environments
- Lower carbon content (≤0.16%) and stricter P/S control (0.020/0.015%) ensure excellent ultra-low temperature toughness at -40°C
- Higher nickel allowance (0.50%) significantly enhances low-temperature performance for extreme cold regions without compromising weldability
- Impact test temperature of -40°C makes it suitable for extreme cold regions in northeastern China and high-altitude alpine areas
- Lower carbon equivalent (0.45%) maintains excellent weldability while achieving high strength for extreme cold applications
- Higher manganese content (1.30-1.80%) optimizes strength-toughness balance for heavy-load applications in extreme cold conditions
Application Cases
Heilongjiang Grand Bridge Project
Used in the main girders of a 4.2km long long-span highway bridge in Heilongjiang, supporting high traffic loads in extreme winter conditions down to -40°C.
- Plate thickness: 40mm-80mm
- Total usage: 32,500 metric tons
- Service life: Designed for 100 years in extreme cold climate
Inner Mongolia High-Speed Railway Bridge
Applied in a high-speed railway bridge project in Inner Mongolia, providing exceptional fatigue resistance and ultra-low temperature performance at -40°C.
- Plate thickness: 30mm-70mm
- Total usage: 35,800 metric tons
- Operates at altitudes over 2000m, -40°C
Xinjiang Expressway Bridge
Utilized in a heavy-duty expressway bridge in Xinjiang province, designed to withstand heavy truck loads and extreme cold climate conditions down to -38°C.
- Plate thickness: 35mm-85mm
- Total usage: 28,900 metric tons
- Special anti-corrosion coating for extreme cold, dry environment
Other Typical Applications
Frequently Asked Questions (FAQ)
What is the difference between Q420qE and Q420qD steel?
The main differences between Q420qE and Q420qD bridge steel plates are:
- Impact test temperature: Q420qE (-40°C) vs Q420qD (-20°C)
- Carbon content: Q420qE (≤0.16%) vs Q420qD (≤0.18%)
- Phosphorus/Sulfur limits: Q420qE (0.020/0.015%) vs Q420qD (0.025/0.020%)
- Nickel allowance: Q420qE (0.50%) vs Q420qD (0.30%)
- Carbon equivalent: Q420qE (0.45%) vs Q420qD (0.48%)
- Applications: Q420qE for extreme cold (-40°C), Q420qD for cold regions (-20°C)
What welding precautions are needed for Q420qE in extreme cold weather?
Q420qE has excellent weldability (Ceq ≤ 0.45%), but special precautions apply for welding in extreme cold weather:
- Preheat base metal to ≥15°C when ambient temperature < -10°C (higher than Q420qD)
- Preheat to 100-150°C for plates >40mm thick or when temperature < -20°C
- Use low hydrogen welding electrodes (E5515-G/E5516-G) to prevent cold cracking
- Maintain interpass temperature ≥100°C during multi-pass welding in extreme cold conditions
- Post-weld heat treatment recommended for thickness >50mm or critical components
- Welding should be performed in heated sheltered areas when ambient temperature < -20°C
Follow WPS specifically qualified for high-strength steels in extreme cold environments.
What is the service temperature range for Q420qE steel?
Q420qE 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: ≥15°C (higher preheating required below this)
- Storage/transport temperature: No lower limit with proper handling and insulation
Q420qE is the extreme cold temperature grade in the Q420q series, suitable for extreme cold climate heavy-load applications in northeastern China and high-altitude alpine regions.
What special treatments enhance Q420qE performance in extreme cold regions?
Several specialized treatments optimize Q420qE for extreme cold environment heavy-load applications:
- TMCP (Thermo-Mechanical Control Process) with accelerated cooling for ultra-fine grain structure
- Strict impurity control (P≤0.020%, S≤0.015%) to prevent brittle fracture at -40°C
- Normalized heat treatment with precise temperature control for uniform microstructure
- Niobium microalloying (up to 0.08%) for strength enhancement and grain refinement
- Stress relief annealing after welding for heavy-load components in extreme cold conditions
- Special anti-corrosion coatings with ultra-low-temperature flexibility for -40°C environments
- Shot peening for critical components to improve fatigue resistance in extreme cold conditions
These treatments ensure reliable heavy-load performance in extreme cold climate conditions down to -40°C.
What quality certifications are provided for Q420qE steel plates?
We provide comprehensive certification for Q420qE 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 for extreme temperature grades
- Ultra-low-temperature toughness test reports (-40°C Charpy V-notch)
- Third-party inspection (SGS, BV, TUV) for extreme cold region projects
- Welding procedure qualification for high-strength steel applications in extreme cold
- ISO 9001 and CE certification (when required for export to arctic climate countries)
- Special certification for high-altitude/extreme cold region applications (when required)
All Q420qE plates undergo 100% ultrasonic testing and additional -40°C impact testing to ensure internal quality for extreme cold-region heavy-load applications.
Key Advantages of Q420qE
Superior High-Strength Performance
420MPa yield strength provides exceptional load-bearing capacity for long-span and heavy-load bridge applications in extreme cold regions.
Excellent Ultra-Low Temperature Toughness
Maintains superior toughness at -40°C, ideal for extreme cold climate regions in northeastern China and high-altitude alpine areas.
Enhanced Weldability
Optimized carbon equivalent (0.45%) ensures excellent welding performance while maintaining high strength in extreme cold construction conditions.
Inventory Check
Check real-time inventory availability for Q420qE steel plates by entering your requirements