A302 Gr.B vs A204 Gr.B
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.
A302 Gr.B
Structural & HSLA Steel
ASTM A302 Grade B is a manganese-molybdenum-nickel vessel plate: the Mn-Mo base of A204 with a nickel addition for toughness and hardenability in thicker sections. It has a long history in boiler drums and nuclear-adjacent pressure equipment.
Standards: AISI A302 Gr.B
A204 Gr.B
Structural & HSLA Steel
ASTM A204 Grade B is a molybdenum-alloy (0.5Mo) pressure-vessel plate whose Mo addition lifts elevated-temperature strength above the plain-carbon A516 family. The carbon limit rises in steps with plate thickness in the standard; the value shown is for plate up to 25 mm.
Standards: AISI A204 Gr.B
Chemical composition compared (%)
| Element | A302 Gr.B | A204 Gr.B |
|---|---|---|
| C | ≤0.20 (≤25 mm) | ≤0.20 (≤25 mm) |
| Si | 0.15–0.40 | 0.15–0.40 |
| Mn | 1.15–1.50 | ≤0.90 |
| P | ≤0.025 | ≤0.025 |
| S | ≤0.025 | ≤0.025 |
| Mo | 0.45–0.60 | 0.45–0.60 |
| Ni | 0.40–0.70 | — |
Properties compared
| Property | A302 Gr.B | A204 Gr.B |
|---|---|---|
| Yield strength | ≥345 MPa | ≥275 MPa |
| Tensile strength | 550–690 MPa | 485–620 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: A302 Gr.B · A204 Gr.B. Substitution decisions for certified parts stay with the design authority.