Difference between LR AH36 and LR AH55 steel plate

LR AH36 is a high-strength shipbuilding steel plate certified by Lloyd's Register (LR) . The "A" grade signifies it is impact tested at 0°C , ensuring reliable toughness for general marine environments . It has a minimum yield strength of 355 MPa and tensile strength ranging from 490 to 620 MPa , with a minimum elongation of 21% . The chemical composition features carbon ≤0.18% and manganese 0.90-1.60% . This grade is widely used for hull structures, decks, and offshore platforms where an excellent balance of strength and weldability is required .

LR AH55 is an ultra-high-strength marine steel plate also certified by Lloyd's Register (LR) , designed for the most 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 a minimum elongation of 18% . The chemical composition features carbon ≤0.21% and manganese ≤1.70%, with microalloying elements such as Cr, Ni, and Cu to achieve higher strength while maintaining good weldability . This grade is typically supplied in quenched and tempered (QT) or TMCP conditions and is used for critical components in ultra-large vessels, offshore platforms, and ice-strengthened ships .

Both LR AH36 and LR AH55 are LR-certified high-strength marine steels with impact toughness tested at 0°C , ensuring reliable performance in general marine environments . Their primary difference lies in strength level: AH36 offers a minimum yield strength of 355 MPa with tensile strength of 490-620 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 the most demanding load-bearing applications requiring superior strength-to-weight ratio . Both grades feature controlled chemical composition and maintain good weldability for critical marine service, though AH55 requires more complex alloying and advanced processing like quenching and tempering to achieve its enhanced mechanical properties.

Chemical Composition

Mechanical Property