Difference between DNV A and DNV B steel plate

DNV A and DNV B are standard strength shipbuilding steel plates certified by Det Norske Veritas (DNV). As the foundational grades in the DNV classification system, they are widely used for general structural components in ship hulls and marine applications where extreme low-temperature toughness is not a primary requirement. Both grades possess a minimum yield strength of 235 MPa, with their core distinction defined by their differing impact toughness specifications.

Key Differences

The key difference lies in the mandatory Charpy V-notch impact test requirement and thus their suitability for different structural areas. DNV Grade A steel has no specified impact test requirement. It is intended for use in non-critical, secondary structures where the risk of brittle fracture is considered low under normal service conditions. In contrast, DNV Grade B steel is required to meet a defined impact energy value when tested at room temperature (typically +20°C). This guaranteed notch toughness makes Grade B significantly more reliable for primary hull structures and other critical components that may be subjected to dynamic loads or incidental stresses.

Chemical Composition

Mechanical Property