Difference between DNV D420 and DNV D620 steel plate

DNV D420 is an extra-high-strength structural steel plate certified by DNV (Det Norske Veritas) for marine and offshore applications . The "D" designation signifies that the material's impact toughness is tested and guaranteed at -20°C . It has a minimum yield strength of 420 MPa and tensile strength ranging from 530 to 680 MPa . Minimum elongation is 18% for thicknesses up to 150mm . Impact energy requirements are minimum 42J (longitudinal) or 28J (transverse) at -20°C . The chemical composition is strictly controlled with carbon ≤0.20% and manganese ≤1.70% . This grade can be delivered in as-rolled, normalized, or quenched and tempered conditions . It is widely used for shipbuilding hulls, offshore platforms, and marine structures.

DNV D620 is an ultra-high-strength structural steel plate also certified by DNV with impact toughness tested at -20°C . The "620" denotes a minimum yield strength of 620 MPa . It has a tensile strength ranging from 720 to 890 MPa and minimum elongation of 15% (longitudinal) . Impact energy requirements are minimum 62J (longitudinal) or 41J (transverse) at -20°C . The chemical composition features carbon ≤0.20%, manganese ≤1.70%, with microalloying elements including Nb, V, Ti, Ni, Cr, and Mo for enhanced properties . This grade requires advanced processing and is typically supplied in quenched and tempered (QT) or TMCP conditions . It is designed for demanding structural components in shipbuilding, ultra-deepwater offshore platforms, and marine structures requiring maximum strength-to-weight ratio.

Both DNV D420 and DNV D620 are DNV-certified high-strength marine steels with impact toughness tested at -20°C, ensuring reliable performance in cold marine environments. Their primary difference lies in strength level: D420 offers a minimum yield strength of 420 MPa with tensile strength of 530-680 MPa, suitable for general high-strength hull construction and offshore platforms where excellent weldability and formability are prioritized, while D620 provides a substantially higher minimum yield strength of 620 MPa with tensile strength reaching 720-890 MPa, designed for the most demanding load-bearing applications requiring maximum strength-to-weight ratio. Both grades feature controlled chemical composition with carbon ≤0.20% and manganese ≤1.70% , and require advanced processing like TMCP or QT to achieve their mechanical properties while maintaining good weldability for critical marine service.

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Mechanical Property