Difference between RINA D420 and RINA D690 steel plate

RINA D420 is an extra-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. It has a minimum yield strength of 420 MPa and tensile strength ranging from 530 to 680 MPa, with a minimum elongation of 18%. The chemical composition is strictly controlled with carbon ≤0.20% and manganese ≤1.70%, and it may include microalloying elements such as Nb and V. This grade is typically supplied in normalized or quenched and tempered (QT) conditions and is available in thicknesses up to 260mm. It is widely used for hull structures, offshore platforms, and critical marine engineering components.

RINA D690 is an ultra-high-strength marine steel plate also certified by RINA, with impact toughness tested at -20°C (with some suppliers also offering -60°C testing). The "690" denotes a minimum yield strength of 690 MPa and tensile strength ranging from 770 to 940 MPa, with a minimum elongation of 14-16%. Impact energy requirements are minimum 46J (transverse) and 69J (longitudinal) at -20°C. The chemical composition features carbon ≤0.21% and manganese ≤1.70%, with 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.

Both RINA D420 and RINA D690 are RINA-certified 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: D420 offers a minimum yield strength of 420 MPa with tensile strength of 530-680 MPa, suitable for high-strength offshore platforms and general shipbuilding, while D690 provides a substantially higher minimum yield strength of 690 MPa with tensile strength reaching 770-940 MPa, designed for the most demanding load-bearing applications requiring maximum strength-to-weight ratio. Both grades feature controlled chemical composition with carbon ≤0.20-0.21% and maintain good weldability for critical marine service, though D690 requires more advanced processing like QT or TMCP to achieve its superior mechanical properties. 

RINA D420 extra high Strength Chemical Composition in Tempering and Quenching

RINA D690 extra high Strength Chemical Composition in Tempering and Quenching

RINA D420 extra high strength property in Tempering and Quenching

RINA D690 extra high strength property in Tempering and Quenching