Grade A (ship) vs Grade D (ship)
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.
Grade A (ship)
Structural & HSLA Steel
Grade A is the baseline ordinary-strength hull steel of the classification-society system (IACS UR W11, mirrored by ASTM A131 and GB/T 712). At 235 MPa yield with no impact-test requirement, it covers the least demanding hull zones — internal structure and sheltered areas on classed vessels.
Standards: AISI A131 A · JIS KA (near) · GB A (GB/T 712)
Grade D (ship)
Structural & HSLA Steel
Grade D extends ordinary-strength hull steel to −20 °C impact service. It is the 235 MPa grade chosen for hulls that trade in cold waters, and a common stepping stone before moving a design up to the DH36/DH40 higher-tensile grades.
Standards: AISI A131 D · JIS KD (near) · GB D (GB/T 712)
Chemical composition compared (%)
| Element | Grade A (ship) | Grade D (ship) |
|---|---|---|
| C | ≤0.21 | ≤0.21 |
| Si | ≤0.50 | 0.10–0.35 |
| Mn | ≥2.5×C | 0.70–1.20 |
| P | ≤0.035 | ≤0.035 |
| S | ≤0.035 | ≤0.035 |
| Note | Chemistry per classification-society rules (IACS UR W11) | Al-treated fine-grain practice; chemistry per class rules (IACS UR W11) |
Properties compared
| Property | Grade A (ship) | Grade D (ship) |
|---|---|---|
| Yield strength | ≥235 MPa | ≥235 MPa |
| Tensile strength | 400–520 MPa | 400–520 MPa |
| Impact | No impact test required | −20 °C, ≥27 J longitudinal (≤50 mm) |
| 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: Grade A (ship) · Grade D (ship). Substitution decisions for certified parts stay with the design authority.