Difference between LR AH32 and LR AH55 steel plate

LR AH32 is a higher-strength shipbuilding steel plate certified by Lloyd's Register (LR) . The "A" grade signifies it is impact tested at 0°C (32°F), ensuring adequate toughness for general marine environments . 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 is strictly controlled with carbon ≤0.18% and manganese 0.90-1.60% . This grade is widely used for hull structures and general shipbuilding components .

LR AH55 is an ultra-high-strength marine steel plate also certified by Lloyd's Register (LR) , designed for demanding structural applications. It is impact tested at 0°C and has a minimum yield strength of 550 MPa and tensile strength ranging from 670 to 830 MPa, with minimum elongation of 18% . The chemical composition features carbon ≤0.21%, manganese ≤1.70%, and microalloying elements such as Cr, Ni, and Cu to achieve higher strength while maintaining good weldability .

Both LR AH32 and LR AH55 are LR-certified shipbuilding steels with impact toughness tested at 0°C, ensuring reliable performance in general marine environments . Their primary difference lies in strength level: AH32 offers a minimum yield strength of 315 MPa with tensile strength of 440-590 MPa, suitable for general high-strength hull construction , while AH55 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-to-weight ratio . Both grades feature controlled chemical composition and maintain good weldability for critical marine service.

Chemical Composition

Mechanical Property