AH40 vs DH40
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.
AH40
Structural & HSLA Steel
AH40 is the 390 MPa higher-tensile hull steel of the classification-society system (ASTM A131 / GB/T 712 family). It steps above AH36 where scantlings get thin — large container ships and VLCCs use AH40/DH40/EH40 to cut hull weight while keeping 0 °C-class toughness for the A grade.
Standards: AISI A131 AH40 · JIS KA40 (near) · GB AH40 (GB/T 712)
DH40
Structural & HSLA Steel
DH40 pairs the 390 MPa strength of the 40-series hull steels with impact toughness certified at −20 °C. It is specified for hull zones and vessel types that see cold water or winter service, where AH40’s 0 °C guarantee is not enough.
Standards: AISI A131 DH40 · JIS KD40 (near) · GB DH40 (GB/T 712)
Chemical composition compared (%)
| Element | AH40 | DH40 |
|---|---|---|
| C | ≤0.18 | ≤0.18 |
| Si | ≤0.50 | ≤0.50 |
| Mn | 0.90–1.60 | 0.90–1.60 |
| P | ≤0.035 | ≤0.035 |
| S | ≤0.035 | ≤0.035 |
| Note | Nb/V/Ti grain-refining per class rules | Nb/V/Ti grain-refining per class rules |
Properties compared
| Property | AH40 | DH40 |
|---|---|---|
| Yield strength | ≥390 MPa | ≥390 MPa |
| Tensile strength | 510–660 MPa | 510–660 MPa |
| Impact | 0 °C, ≥41 J longitudinal (≤50 mm) | −20 °C, ≥41 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: AH40 · DH40. Substitution decisions for certified parts stay with the design authority.