The difference between LR DH50 and LR DH69 steel plate

LR DH50 is an extra-high-strength marine steel plate certified by Lloyd's Register (LR) . The "DH" designation signifies a higher-strength grade with impact toughness tested at -20°C . It has a minimum yield strength of 500 MPa and tensile strength ranging from 610 to 770 MPa, with a minimum elongation of 18% for thicknesses up to 100mm . Impact energy requirements are minimum 50J (longitudinal) or 33J (transverse) at -20°C . The chemical composition is strictly controlled with carbon ≤0.20% and manganese ≤1.70%, featuring microalloying elements including Nb, V, and Ti . This grade is typically supplied in normalized or controlled rolled conditions and is widely used for demanding structural components in shipbuilding and offshore platforms .

LR DH69 is an ultra-high-strength marine steel plate also certified by Lloyd's Register (LR) with impact toughness tested at -20°C . The "69" denotes a minimum yield strength of 690 MPa . It has a tensile strength ranging from 770 to 940 MPa and minimum elongation of 16% for thicknesses up to 100mm . Impact energy requirements are minimum 69J (longitudinal) or 46J (transverse) at -20°C . The chemical composition is similar to DH50 with carbon ≤0.20% and manganese ≤1.70%, along with microalloying elements . This grade is designed for the most demanding load-bearing applications in shipbuilding, ultra-large container vessels, and offshore structures requiring maximum strength-to-weight ratio .

Both LR DH50 and LR DH69 are LR-certified extra-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: DH50 offers a minimum yield strength of 500 MPa with tensile strength of 610-770 MPa, suitable for high-strength offshore structures, while DH69 provides a substantially higher minimum yield strength of 690 MPa with tensile strength reaching 770-940 MPa, offering approximately 38% greater strength for the most demanding applications requiring maximum weight reduction . Both grades feature similar controlled chemical composition with carbon ≤0.20% and manganese ≤1.70%, and require advanced processing like TMCP or quenching and tempering to achieve their superior mechanical properties while maintaining good weldability for critical marine service .

Chemical Composition

Mechanical Property