Difference between LR DH40 and LR DH50 steel plate

LR DH40 is a high-strength shipbuilding steel plate certified by Lloyd's Register (LR) . The "D" grade signifies it is impact tested at -20°C . It has a minimum yield strength of 390 MPa and tensile strength ranging from 510 to 660 MPa . The chemical composition is strictly controlled with carbon ≤0.18% and manganese 0.90-1.60% . Minimum elongation is 20% . Impact energy requirements are minimum 39J (longitudinal) or 26J (transverse) at -20°C . This grade is typically supplied in normalized, quenched and tempered, or TMCP conditions . It is widely used for hull construction, offshore platforms, and large ships such as bulk carriers and tankers .

LR DH50 is an extra-high-strength marine steel also certified by Lloyd's Register (LR) with impact toughness tested at -20°C . The "50" denotes a minimum yield strength of 500 MPa . It has a tensile strength ranging from 610 to 770 MPa and minimum elongation of 18% . Impact energy requirements are minimum 50J (longitudinal) or 33J (transverse) at -20°C . The chemical composition features carbon ≤0.20% and manganese ≤1.70%, with microalloying elements including Nb and V . This grade requires advanced processing and is typically supplied in normalized or controlled rolled conditions . It is designed for demanding structural components in shipbuilding and offshore platforms where higher strength is required .

Both LR DH40 and LR DH50 are LR-certified 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: DH40 offers a minimum yield strength of 390 MPa with tensile strength of 510-660 MPa, suitable for general high-strength hull construction , while DH50 provides a higher minimum yield strength of 500 MPa with tensile strength reaching 610-770 MPa, designed for more demanding load-bearing applications requiring superior strength. Both grades feature controlled chemical composition with carbon ≤0.18-0.20% and maintain good weldability for marine service.

Chemical Composition

Mechanical Property