A709 Gr.50 vs A572 Gr.50
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
A709 Gr.50
Structural & HSLA Steel
ASTM A709 Grade 50 is the bridge version of A572 Gr.50: the same 50 ksi HSLA chemistry, but purchased to the bridge specification with Charpy toughness requirements tied to service-temperature zones, and fracture-critical options for tension members.
Standards: DIN S355J2 (near) · AISI A709 Gr.50 · JIS SM520B (near) · GB Q355B (near)
A572 Gr.50
Structural & HSLA Steel
ASTM A572 Grade 50 is the standard American HSLA structural steel — the 50 ksi yield grade that replaced A36 in most US bridge and heavy construction work. Strength comes from Nb/V microalloying and grain refinement rather than carbon, so weldability remains good.
Standards: DIN S355J2 (near) · AISI A572 Gr.50 · JIS SM520B (near) · GB Q355B (near)
Chemical composition compared (%)
| Element | A709 Gr.50 | A572 Gr.50 |
|---|---|---|
| C | ≤0.23 | ≤0.23 |
| Si | ≤0.40 | ≤0.40 |
| Mn | ≤1.35 | ≤1.35 |
| P | ≤0.035 | ≤0.035 |
| S | ≤0.045 | ≤0.045 |
| Note | CVN toughness mandatory for bridge (T/F) zones per A709 | — |
| V | — | 0.01–0.15 (Type 2) |
Properties compared
| Property | A709 Gr.50 | A572 Gr.50 |
|---|---|---|
| Yield strength | ≥345 MPa (50 ksi) | ≥345 MPa |
| Tensile strength | ≥450 MPa (65 ksi) | ≥450 MPa |
| Impact | CVN per temperature zone (bridge requirement) | — |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: A709 Gr.50 · A572 Gr.50. Substitution decisions for certified parts stay with the design authority.