Difference between RINA D620 and RINA D690 steel plate

RINA D620 is an ultra-high-strength marine steel plate certified by the Italian classification society RINA (Registro Italiano Navale) for shipbuilding and offshore applications. The "D" grade signifies it is impact tested at -20°C, with a minimum impact energy of 41J (longitudinal) for thicknesses under 150mm . It has a minimum yield strength of 620 MPa and tensile strength ranging from 720 to 890 MPa, with a minimum elongation of 15% . The chemical composition is strictly controlled with carbon ≤0.20% and manganese ≤1.70%, featuring microalloying elements such as Nb, V, Ti, Cr, Ni, 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 the most demanding structural components in shipbuilding, ultra-deepwater offshore platforms, Arctic-class vessels, and FPSO units requiring maximum strength-to-weight ratio .

RINA D690 is an ultra-high-strength marine steel plate also certified by RINA, with impact toughness tested at -20°C (and also available at -60°C) . The "690" denotes a minimum yield strength of 690 MPa and tensile strength ranging from 770 to 940 MPa, with a minimum elongation of 14% . Impact energy requirements are a minimum of 46J (transverse) and 69J (longitudinal) at -20°C . The chemical composition features carbon ≤0.21%, manganese ≤1.70%, and microalloying elements such as Nb, V, Ti, Cr, Ni, 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 the most demanding structural components in shipbuilding, ultra-deepwater offshore platforms, Arctic-class vessels, and jack-up rig legs requiring maximum strength-to-weight ratio .

Both RINA D620 and RINA D690 are RINA-certified ultra-high-strength marine steels with excellent low-temperature toughness tested at -20°C, ensuring reliable performance in harsh marine environments . Their primary difference lies in strength level: D620 offers a minimum yield strength of 620 MPa with tensile strength of 720-890 MPa, suitable for critically stressed structural components requiring high strength-to-weight ratio, while D690 provides a substantially higher minimum yield strength of 690 MPa with tensile strength reaching 770-940 MPa, offering approximately 11% greater strength for the most demanding load-bearing applications requiring maximum weight reduction . Both grades feature strictly controlled chemical composition with carbon ≤0.20-0.21% and maintain good weldability for critical marine service, though D690 typically requires more complex alloying and advanced processing like QT or TMCP to achieve its superior mechanical properties . The selection between them depends on whether the project requires the high strength of D620 or the enhanced performance of D690 for more extreme structural demands.

RINA D620 extra high Strength Chemical Composition in Tempering and Quenching

RINA D690 extra high Strength Chemical Composition in Tempering and Quenching

RINA D620 extra high strength property in Tempering and Quenching

RINA D690 extra high strength property in Tempering and Quenching

Note: the impact energy under less 150mm thickness; longitudinal min impact energy