Difference between LR DH32 and LR DH55 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), with minimum elongation of 22% . The chemical composition features carbon ≤0.18% and manganese 0.90-1.60% . This grade is typically supplied in normalized or controlled rolled conditions and is widely used for hull structures and general shipbuilding components.

LR DH55 is an extra-high-strength marine steel plate also certified by Lloyd's Register (LR) with impact toughness tested at -20°C . The "55" denotes a minimum yield strength of 550 MPa and tensile strength ranging from 670 to 830 MPa, with minimum elongation of 18% for thicknesses up to 100mm . Impact energy requirements are minimum 55J (longitudinal) or 37J (transverse) at -20°C . The chemical composition features carbon ≤0.20%, manganese ≤1.70%, and microalloying elements such as Nb and V . This grade is designed for critical, highly stressed structural members in shipbuilding and offshore applications.

Both LR DH32 and LR DH55 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 DH55 provides a substantially higher minimum yield strength of 550 MPa with tensile strength reaching 670-830 MPa, designed for more demanding load-bearing applications requiring superior strength. Both grades feature controlled chemical composition, with DH55 requiring more advanced processing and alloying to achieve its enhanced mechanical properties while maintaining good weldability for critical marine service.

Chemical Composition

Mechanical Property