A572 Gr.55 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.
A572 Gr.55
Structural & HSLA Steel
ASTM A572 Grade 55 is a columbium-vanadium HSLA structural steel one step above the ubiquitous Gr.50: yield rises to ≥380 MPa (55 ksi) and tensile to ≥485 MPa (70 ksi) while chemistry stays lean and weldable. It is used where Gr.50 sections become too heavy but Gr.65 hardenability is not wanted.
Standards: DIN S355J2 (near) · AISI A572 Gr.55 · JIS SM490B (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 | A572 Gr.55 | A572 Gr.50 |
|---|---|---|
| C | ≤0.25 | ≤0.23 |
| Si | ≤0.40 | ≤0.40 |
| Mn | ≤1.35 | ≤1.35 |
| P | ≤0.04 | ≤0.035 |
| S | ≤0.05 | ≤0.045 |
| Note | Strength comes from a Nb, V or Nb-V addition — Type 1, 2, 3 or 5 must be specified on the order | — |
| V | — | 0.01–0.15 (Type 2) |
Properties compared
| Property | A572 Gr.55 | A572 Gr.50 |
|---|---|---|
| Yield strength | ≥380 MPa | ≥345 MPa |
| Tensile strength | ≥485 MPa | ≥450 MPa |
| 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: A572 Gr.55 · A572 Gr.50. Substitution decisions for certified parts stay with the design authority.