Difference between DNV D420 and DNV D550 steel plate

DNV D420 and DNV D550 are high-strength structural steel plates certified by Det Norske Veritas (DNV) for marine and offshore applications. Both grades share the "D" designation, which guarantees that their impact toughness meets specific requirements at a moderate low temperature of -20°C. The numerical suffix indicates the minimum yield strength in megapascals (MPa). Thus, DNV D420 provides a minimum yield strength of 420 MPa, while DNV D550 offers a higher minimum yield strength of 550 MPa.

Key Differences

The primary distinction is their strength level and the resulting balance between performance and fabricability. DNV D550 provides approximately 31% higher yield strength than D420. This significant increase allows for greater load capacity and potential weight reduction in structural designs, making it suitable for more demanding components such as critical hull sections or offshore platform nodes. However, achieving this higher strength in D550 typically involves stricter alloying and controlled rolling processes, which can lead to slightly reduced ductility and more stringent welding procedures compared to D420. Consequently, DNV D420 offers superior weldability, formability, and overall ease of fabrication, making it a highly versatile and cost-effective choice for a wide range of general shipbuilding and marine structures. The selection, therefore, hinges on the specific design priorities: Choose DNV D550 where higher strength is essential to meet structural or weight-saving goals; opt for DNV D420 for applications where excellent fabricability and proven performance in moderate low-temperature conditions are the key considerations.

Chemical Composition

Mechanical Property