Difference between DNV E620 and DNV E690

DNV E620 and DNV E690 are ultra-high-strength structural steel plates classified by DNV (Det Norske Veritas), a leading international maritime and energy classification society. These grades are engineered for the most demanding offshore and marine applications, such as heavy-lift vessel decks, topside modules for offshore platforms, and specialized Arctic structures. They are designed to offer an exceptional combination of ultimate tensile strength, good toughness at low temperatures, and weldability, enabling the construction of lighter and more efficient structures.

Key Differences:

The primary difference is their minimum specified ultimate tensile strength (UTS). DNV E620 has a UTS of 620 MPa, while DNV E690 offers a higher UTS of 690 MPa. The suffix 'E' in the grade denotes an elevated yield-to-tensile ratio, which is a critical requirement for these grades. Both are quenched and tempered steels, but achieving the higher strength of E690 requires a more precise and stringent alloy composition and heat treatment process.

Consequently, while both grades require advanced fabrication techniques, DNV E690 typically presents greater challenges. It demands even stricter control over welding procedures, including the selection of specific high-toughness filler metals, precise control of preheating and interpass temperatures, and stringent post-weld heat treatment (PWHT) to maintain the integrity of the heat-affected zone and prevent hydrogen-assisted cracking. Therefore, the selection between E620 and E690 involves balancing the need for maximum structural efficiency and weight savings (E690) against factors of increased material cost and more complex fabrication requirements.

Chemical Composition

Mechanical Property