Difference between BV D620 and BV D690 steel plate

Both BV D620 and BV D690 are high-strength steel plates certified by Bureau Veritas (BV), a leading international classification society. These grades are primarily designed for demanding marine and offshore applications, such as ship hulls, offshore structures, and pressure vessels. They offer an excellent combination of high strength, good toughness, and weldability, enabling the construction of lighter and more resilient structures.

Key Differences:

The primary distinction lies in their minimum yield strength. BV D620 has a minimum yield strength of 620 MPa, while BV D690 offers a higher minimum yield strength of 690 MPa. This makes D690 the stronger of the two, allowing for designs with reduced plate thickness under equivalent loading conditions, which is critical for weight-sensitive applications.

To achieve this higher strength, D690 typically has a more stringent alloy composition and controlled rolling or quenching and tempering (Q&T) heat treatment process. Consequently, D690 may have slightly lower inherent toughness and require more precise welding procedures to maintain its mechanical properties in the heat-affected zone compared to D620. The choice between the two grades is an engineering decision balancing the need for higher strength (D690) against factors like fabrication complexity, toughness requirements, and overall cost.

Chemical Composition

Mechanical Property