Q500qD Bridge Steel Plate
High-strength low alloy structural steel specifically designed for large-span and heavy-load bridge construction, meeting national standards for high performance and durability in critical infrastructure projects.
About Q500qD Steel
Q500qD is a Chinese standard (GB/T 714-2015) high-strength low alloy structural steel specifically developed for heavy-duty bridge construction applications.
The "q" in the designation stands for bridge (qiaoliang in Chinese), "500" represents the minimum yield strength of 500MPa, while "D" indicates the steel's impact test temperature of -20°C, making it suitable for cold climate conditions and high-stress applications.
It offers exceptional strength-to-weight ratio, excellent weldability, formability, and toughness, making it the preferred material for long-span bridges, cable-stayed bridges, and other critical infrastructure projects requiring high load-bearing capacity.
Technical Specifications
Basic Information
Mechanical Properties
| Thickness (mm) | Yield Strength (MPa) ≥ | Tensile Strength (MPa) | Elongation (%) ≥ | Impact Energy (J) ≥ |
|---|---|---|---|---|
| ≤16 | 500 | 630-780 | 18 | 47 |
| >16-35 | 480 | 630-780 | 18 | 47 |
| >35-50 | 470 | 630-780 | 18 | 47 |
| >50-100 | 460 | 610-760 | 18 | 47 |
Chemical Composition (wt%)
| Element | C ≤ | Si ≤ | Mn | P ≤ | S ≤ | Nb | V | Ti ≤ | Ni ≤ | Cu ≤ |
|---|---|---|---|---|---|---|---|---|---|---|
| Content | 0.18 | 0.60 | 1.00-1.80 | 0.025 | 0.020 | 0.02-0.06 | 0.08-0.15 | 0.02 | 0.80 | 0.55 |
Note: Carbon equivalent (Ceq) ≤ 0.55%, Weldability carbon equivalent (Pcm) ≤ 0.28%. Mo ≤ 0.20%, Cr ≤ 0.30%, Als ≥ 0.015%.
International Standards Comparison
Mechanical Properties Comparison (≤16mm thickness)
| Property | Q500qD (GB/T 714-2015) | S500Q (EN 10137-2) | A709 Gr70 (ASTM A709) |
|---|---|---|---|
| Yield Strength (MPa) min | 500 | 500 | 485 (70 ksi) |
| Tensile Strength (MPa) | 630-780 | 630-780 | 620-760 (90-110 ksi) |
| Elongation (%) min | 18 | 18 | 18 |
| Impact Test Temperature (°C) | -20 | -40 | -18 (0°F) |
| Impact Energy (J) min | 47 | 40 | 34 (25 ft-lb) |
| Carbon Equivalent (Ceq) max | 0.55% | 0.55% | 0.50% |
Chemical Composition Comparison (wt%)
| Element | Q500qD (max/ range) | S500Q (EN 10137-2) (max/ range) | A709 Gr70 (ASTM A709) (max/ range) |
|---|---|---|---|
| Carbon (C) | ≤0.18% | ≤0.20% | ≤0.21% |
| Silicon (Si) | ≤0.60% | ≤0.60% | 0.15-0.50% |
| Manganese (Mn) | 1.00-1.80% | 1.00-2.00% | 1.30-1.80% |
| Phosphorus (P) | ≤0.025% | ≤0.025% | ≤0.035% |
| Sulfur (S) | ≤0.020% | ≤0.020% | ≤0.040% |
| Niobium (Nb) | 0.02-0.06% | 0.015-0.060% | ≤0.05% |
| Vanadium (V) | 0.08-0.15% | 0.06-0.15% | ≤0.10% |
| Titanium (Ti) | ≤0.02% | ≤0.05% | ≤0.03% |
Key Differences Summary:
- Q500qD offers higher minimum yield strength (500MPa) compared to A709 Grade 70 (485MPa), providing superior load-bearing capacity
- Q500qD requires higher impact energy (47J vs 40J for S500Q) at -20°C, ensuring excellent toughness in cold environments
- S500Q (EN standard) is tested at lower temperature (-40°C) but with lower impact energy requirement
- Q500qD has optimized microalloying (Nb/V) for better strength-toughness balance in bridge applications
- All three grades maintain good weldability despite higher strength levels (Ceq ≤ 0.55%)
- Q500qD has stricter impurity control (P/S) for enhanced fatigue resistance in cyclic loading conditions
Application Cases
Cable-Stayed Bridge Construction
Used in the main girders and pylons of a 2.8km long cable-stayed bridge in Eastern China, providing exceptional strength-to-weight ratio and fatigue resistance.
- Plate thickness: 30mm-80mm
- Total usage: 12,500 metric tons
- Designed for 120-year service life
Suspension Bridge Deck
Applied in the deck structure of a major suspension bridge, reducing overall weight by 18% compared to conventional Q345qD steel while maintaining structural integrity.
- Plate thickness: 20mm-50mm
- Total usage: 8,700 metric tons
- Meets seismic design category IV
High-Speed Railway Bridge
Utilized in a high-speed railway bridge project, providing superior dynamic load resistance and fatigue performance for 350km/h train operations.
- Plate thickness: 16mm-40mm
- Total usage: 6,200 metric tons
- Special TMCP process applied
Other Typical Applications
Frequently Asked Questions (FAQ)
What is the difference between Q500qD and Q345qD steel?
Q500qD is a high-strength version of bridge steel with significantly higher mechanical properties compared to Q345qD:
- Yield strength: 500MPa vs 345MPa (45% higher)
- Tensile strength: 630-780MPa vs 470-630MPa
- Impact energy requirement: 47J vs 34J at -20°C
- Allows for thinner plate thickness while maintaining same load capacity (weight reduction 20-30%)
- More sophisticated alloy design (higher Ni, Cu content) for better strength-toughness balance
- Typically produced with TMCP process for optimal properties
What welding precautions are needed for Q500qD steel?
Q500qD has good weldability but requires special attention due to its higher strength:
- Preheating recommended for plates >25mm thick (80-120°C) to prevent cold cracking
- Use low-hydrogen welding consumables (AWS E7018-G or equivalent)
- Interpass temperature control (<=200°C) to avoid overheating
- Post-weld heat treatment not required for most applications if proper procedures are followed
- Submerged Arc Welding (SAW) recommended for main structural welds with matched strength consumables
Welding procedure qualification (WPQ) is mandatory for all Q500qD welding applications.
What is the maximum service temperature for Q500qD steel?
Q500qD is designed to perform reliably in the following temperature range:
- Minimum operating temperature: -20°C (meets impact energy requirements at this temperature)
- Q500qE grade available for -40°C applications
- Maximum operating temperature: 250°C (for short-term service)
- Continuous service temperature: Up to 150°C
For elevated temperature applications (>150°C), consider specialized heat-resistant steel grades or additional thermal protection.
What are the cost benefits of using Q500qD vs Q345qD?
Although Q500qD has a higher material cost, it offers significant overall project savings:
- Material weight reduction: 20-30% less steel required for same load capacity
- Lower transportation and erection costs due to lighter components
- Reduced foundation costs for bridge piers and abutments
- Longer service life (100+ years vs 50-75 years for conventional grades)
- Lower maintenance costs due to thicker corrosion allowance relative to structural thickness
Life-cycle cost analysis typically shows 15-25% overall savings with Q500qD despite higher initial material cost (approx. 15-20% premium over Q345qD).
What quality control measures apply to Q500qD steel plates?
Q500qD requires stringent quality control beyond standard bridge steel:
- 100% ultrasonic testing (UT) per GB/T 2970 (Class I acceptance)
- Charpy V-notch impact testing at -20°C (3 specimens per heat)
- Tensile testing for yield strength, tensile strength and elongation
- Chemical composition verification (spectrometric analysis)
- Z-direction performance testing (Z15/Z25/Z35) for thick plates (>40mm)
- Fatigue testing for critical applications
- Strict dimensional tolerance control (±0.5mm for thickness)
Mill Test Certificate (MTC) to EN 10204 3.1 standard is mandatory for all Q500qD deliveries.
Key Advantages of Q500qD
Superior Strength-to-Weight Ratio
500MPa yield strength enables significant weight reduction (20-30%) compared to conventional bridge steel while maintaining structural integrity.
Excellent Low-Temperature Toughness
Maintains high toughness (47J) at -20°C, suitable for cold climate regions and critical structural applications requiring superior fracture resistance.
Enhanced Durability
Optimized chemical composition and production process provide exceptional fatigue resistance and corrosion performance for 100+ year service life.
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