Carbon Steel Bridge Plate – ASTM A709 Factory Direct Supplier | Huaxia-Steel
Carbon steel bridge plate is the structural plate specified for highway, railway and pedestrian bridges, including main girders, deck plates, cross frames and stiffeners. Huaxia-Steel supplies factory-direct bridge plate per ASTM A709 (US standard) and equivalent EN 10025 S275JR / S355JR, JIS G3106 SM400 / SM490, and GB/T 1591 Q345B / Q345C. Grades A709 Gr.36, Gr.50, Gr.50W (weathering) and Gr.70W (high-strength weathering) cover the full strength range from 250 MPa yield to 485 MPa yield, in thicknesses 4.7 to 100 mm. Charpy impact testing is mandatory at zone-appropriate temperatures, and weathering grades carry tightly controlled copper, chromium and nickel additions. Every shipment carries EN 10204 3.1 mill test certificate, optional 3.2 with third-party witnessed Charpy.
1. Standard Scope and Grades
| ASTM A709 Grade | Yield min (MPa) | Tensile min (MPa) | Charpy requirement | Atmosphere |
|---|---|---|---|---|
| 36 | 250 | 400 | optional (zone dependent) | regular carbon steel |
| 50 | 345 | 450 | optional (zone dependent) | regular carbon steel |
| 50W | 345 | 450 | 34 J avg at 21 deg C (zone 2) | weathering |
| 70W | 485 | 620 | 34 J avg at -12 deg C (zone 3) | weathering |
| HPS 50W | 345 | 450 | 48 J avg at -23 deg C | high-performance weathering |
| HPS 70W | 485 | 620 | 48 J avg at -23 deg C | high-performance weathering |
| HPS 100W | 690 | 760 | 48 J avg at -34 deg C | high-performance weathering |
For most highway bridges in temperate climate zones, ASTM A709 Gr.50 is the default specification. Gr.50W (weathering) eliminates the need for painting if the environment supports stable rust patina. HPS 70W and HPS 100W are used in long-span bridges and high-stress zones.
2. Chemical Composition
| Element (percent) | 36 / 50 | 50W | 70W | HPS 50W | HPS 70W |
|---|---|---|---|---|---|
| Carbon (C, max) | 0.26 | 0.19 | 0.21 | 0.11 | 0.11 |
| Manganese (Mn) | 0.80 to 1.20 | 0.80 to 1.25 | 1.10 to 1.50 | 1.10 to 1.35 | 1.10 to 1.35 |
| Phosphorus (P, max) | 0.04 | 0.04 | 0.04 | 0.020 | 0.020 |
| Sulfur (S, max) | 0.05 | 0.05 | 0.05 | 0.015 | 0.015 |
| Silicon (Si) | 0.40 max | 0.30 to 0.50 | 0.30 to 0.50 | 0.30 to 0.50 | 0.30 to 0.50 |
| Copper (Cu) | 0.20 min (50W) | 0.25 to 0.40 | 0.25 to 0.40 | 0.25 to 0.40 | 0.25 to 0.40 |
| Chromium (Cr) | – | 0.45 to 0.70 | 0.45 to 0.70 | 0.45 to 0.70 | 0.45 to 0.70 |
| Nickel (Ni) | – | 0.25 to 0.40 | 0.25 to 0.40 | 0.25 to 0.40 | 0.25 to 0.40 |
| Vanadium (V) | – | 0.02 to 0.10 | 0.02 to 0.10 | 0.04 to 0.08 | 0.04 to 0.08 |
| CEV max | 0.45 | 0.48 | 0.55 | 0.38 | 0.46 |
The weathering grades require the “weathering package” – copper, chromium, nickel and vanadium. The copper content 0.25 to 0.40 percent is the key marker of a true weathering steel. Generic carbon-manganese steel will not develop the protective rust patina.
3. Mechanical Properties
| Property | 36 | 50 | 50W | 70W | HPS 70W |
|---|---|---|---|---|---|
| Yield strength, min (MPa) | 250 | 345 | 345 | 485 | 485 |
| Tensile strength (MPa) | 400 to 550 | 450 min | 485 min | 620 min | 620 to 760 |
| Elongation 200 mm, min (percent) | 20 | 18 | 18 | 17 | 17 |
| Reduction of area, min (percent) | – | – | – | – | 40 |
| Charpy zone 2 (21 deg C, J avg / J min) | optional | optional | 34 / 24 | 34 / 24 | 48 / 34 |
| Charpy zone 3 (-12 deg C, J avg / J min) | optional | optional | by agreement | 34 / 24 | 48 / 34 |
4. Charpy Impact Zone Map (A709)
| Zone | Climate | Test temp (deg C) | Required for |
|---|---|---|---|
| 1 | warmest / no fracture critical | none required | Gr.36 / Gr.50 only if non-FCM |
| 2 | temperate (annual mean above 0 deg C) | 21 | FCM components in Gr.50W / 70W / HPS grades |
| 3 | cold (annual mean below 0 deg C) | -12 | FCM in weathering or HPS grades |
| 4 | very cold | -34 | rare, mostly HPS 100W |
FCM = Fracture Critical Member. A fracture-critical member is a tension component whose failure would cause collapse of part of the bridge. The Charpy zone, testing temperature and acceptance energy must be specified on the RFQ when FCM is in the contract.
5. Thickness Range and Weight
| Thickness (mm) | Weight per m2 (kg) | Typical role |
|---|---|---|
| 4.7 to 6 | 36.9 to 47.1 | thin deck plate for orthotropic steel deck |
| 8 to 12 | 62.8 to 94.2 | diaphragm, web stiffener |
| 14 to 22 | 109.9 to 172.7 | main girder web, typical bridge plate |
| 25 to 32 | 196.3 to 251.2 | flange plates for main girders |
| 40 to 50 | 314.0 to 392.5 | thick flange and cross-girder joint |
| 60 to 100 | 471.0 to 785.0 | special heavy sections |
Bridge plates are usually supplied as cut-to-shape pieces already, especially for the main girders, deck plates and box-girder flange. The mill CNC-cuts the plate to shape per the buyer’s drawings and welds with coping and edge preparation for shop welding in the bridge fabricator’s yard.
6. Cross References
| ASTM A709 | EN 10025-2 / -4 | JIS G3106 | GB/T 1591 | AASHTO |
|---|---|---|---|---|
| 36 | S235JR (1.0038) | SS400 | Q235B | M270 Gr.36 |
| 50 | S355JR (1.0045) | SM490A | Q345B | M270 Gr.50 |
| 50W | S355J0WP (1.8945) | SM490A weathering | Q345NH | M270 Gr.50W |
| 70W | S460ML (1.8838) / QStE 460 TM | SM570 | Q460NH | M270 Gr.70W |
| HPS 50W | S355J2W (1.8965) | SM490C weathering | Q345GNH | M270 HPS Gr.50W |
| HPS 70W | S460J2W (1.8967) – approximate | SM570 weathering | Q460NH | M270 HPS Gr.70W |
| HPS 100W | S690Q (1.8931) | SHY685 | Q690E | M270 HPS Gr.100W |
For European bridge orders, EN 10025-4 thermomechanical-rolled weathering grades (S355ML, S420ML) are the closest equivalents. For Chinese state-owned bridge projects, GB/T 1591 Q345qD / Q420qD are the specified grades with Charpy at -40 deg C.
7. Welding Considerations
Bridge plate welding is governed by AASHTO / AWS D1.5 (Bridge Welding Code). The welding procedure must address:
- Preheat 50 to 150 deg C for thicker plates or higher CEV
- Interpass temperature limit 230 to 260 deg C
- Heat input limit 1.5 to 2.5 kJ/mm for fracture-critical welds
- Post-weld ultrasonic or radiographic inspection
- Post-weld condition (as-welded or stress relieved)
HPS 50W / 70W / 100W plate requires the HPS consumable family because the higher nickel content needs matching weld metal chemistry. Plain carbon-manganese wire will not deliver the weathering performance of the parent metal.
8. Common Bridge Applications
- Steel girder highway bridges – A709 Gr.50 / Gr.50W deck and girders
- Steel truss pedestrian bridges – A709 Gr.36 lattice + Gr.50 chords
- Steel box girder long-span bridges – A709 Gr.50W or HPS 70W
- Railway bridges – A709 Gr.50 with fatigue Charpy at -20 to -40 deg C
- Movable bridges – A709 Gr.50 with enhanced weld repair procedures
- Cable-stayed bridge pylon – HPS 100W for critical sections
- Bridge deck plates – A709 Gr.36 thin gauge
- Bridge bearings – A709 Gr.50 plate, machined for bearings
- Retrofit steel plate – HPS 70W for FRP strengthening
9. Quality Assurance and Certification
Every bridge plate shipment includes:
- EN 10204 Type 3.1 mill test certificate (Type 3.2 with third-party stamp typically required for FCM)
- Heat-traceable stamp on each plate
- Charpy test report at the zone-appropriate temperature
- Heat treatment condition code (TMCP, normalized, QT as applicable)
- Visual and dimensional per ASTM A6 / A20
- Ultrasonic test per ASTM A435 or A578 (supplementary requirement)
- Plate identification by light-colored paint pen (low chloride, weldable)
Third-party witnessed Charpy at zone temperature is mandatory for FCM orders. Inspection typically takes 1 to 3 working days at the mill.
10. Marking, Storage and Shipping
Bridge plates are delicate compared to standard structural plate because the cut-to-shape geometry is rarely symmetrical and the mark must travel with each piece to the bridge yard. Standard practice:
- Stencil: “PIECE NO. / HEAT NO. / GRADE / THICKNESS / DIMENSION”
- Stack on timber bearers in the yard
- Strap to skid for export lifting
- Transport in 20 ft open-top or 40 ft high-cube containers
- Sketch / piece list on bundle tag
Rough stock plate is supplied uncut when the buyer has its own workshop CNC line. Cut-to-shape plate is supplied per shop drawing with finished edges ground and weld preparation bevelled per AWS D1.5.
11. Specification Checklist for RFQ
- Plate standard – ASTM A709 grade
- Yield class – 250 / 345 / 485 / 690 MPa (and weathering if required)
- Charpy zone – 1 / 2 / 3 / 4 (with test temperature and energy)
- Plate thickness range
- Rough stock or cut-to-shape (with drawing set)
- Heat treatment condition – TMCP, normalized, QT
- Surface – hot rolled mill scale, shot blasted, prepainted
- MTC – EN 10204 3.1 or 3.2
- FCM flag on the order
- Third-party inspection – SGS / BV / Intertek / TUV
- Inspection witness of Charpy
- Delivery – FOB / CIF / CFR / DDP
Request a Quotation
Huaxia-Steel is a factory-direct Chinese supplier of ASTM A709 bridge plate in grades 36, 50, 50W, HPS 50W, 70W and HPS 70W in thicknesses up to 100 mm. Full EN 10204 3.1 / 3.2 certification, Charpy impact reporting at the zone temperature, optional cut-to-shape and bevelling per your drawing, third-party witnessed inspection on request. Send your grade, Charpy zone, plate thickness list and target port to [email protected] for a complete offer.
