Difference between LR DH32 and LR DH69 steel plate

LR DH32 is a higher-strength structural steel plate certified by Lloyd's Register (LR) for shipbuilding and marine applications . The "D" grade signifies it is impact tested at -20°C . It has a minimum yield strength of 315 MPa (46 ksi) and tensile strength ranging from 440 to 590 MPa (64-83 ksi) . Minimum elongation is 22% . The chemical composition is strictly controlled with carbon ≤0.18% and manganese 0.90-1.60% . It is typically supplied in normalized or controlled rolled conditions and is widely used for hull structures and general shipbuilding components.

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 and tensile strength ranging from 770 to 940 MPa . Minimum elongation is 16% for thicknesses up to 100mm . Impact energy requirements are minimum 69J (longitudinal) or 46J (transverse) at -20°C . The chemical composition features carbon ≤0.20% and manganese ≤1.70%, with microalloying elements including Nb, V, Ti, Cu, Cr, Ni, and Mo . This grade requires advanced processing such as TMCP or quenching and tempering and is designed for the most critically stressed structural components in modern shipbuilding and offshore engineering.

Both LR DH32 and LR DH69 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: DH32 offers a minimum yield strength of 315 MPa with tensile strength of 440-590 MPa, suitable for general high-strength hull construction and secondary structures, while DH69 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 weight reduction. Both grades feature controlled chemical composition, but DH69 requires more advanced processing like TMCP or QT to achieve its superior mechanical properties while maintaining good weldability for critical marine service.

Chemical Composition

Mechanical Property