Difference between DNV A and DNV D steel plate

DNV A and DNV D are standardized structural steel plates certified by Det Norske Veritas (DNV) for shipbuilding and marine applications, representing different levels of notch toughness for varying service conditions. Both grades typically share a minimum yield strength of 235 MPa. Their core distinction lies in the guaranteed level of impact toughness at low temperatures, which dictates their structural usage.

Key Differences

The fundamental difference is the impact test requirement and applicable service temperature. DNV Grade A steel has no specified Charpy V-notch impact test requirement. It is intended for secondary, non-critical structures in ambient temperature environments where the risk of brittle fracture is negligible. In contrast, DNV Grade D steel is required to meet defined impact energy absorption criteria when tested at -20°C (-4°F). This certified low-temperature toughness makes it suitable for primary hull structures, such as shell plating and decks, on vessels operating in cold climates like the North Atlantic. The D grade's enhanced performance is achieved through controlled steelmaking practices, often involving fine-grain treatment. Therefore, the selection is based on structural importance and operating environment: Grade A is used where toughness is not a design parameter; Grade D is specified for critical load-bearing members exposed to cold temperatures to ensure structural integrity and safety.

Chemical Composition

Mechanical Property