Difference between LR AH36 and LR AH69 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 is strictly controlled with 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 AH69 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 690 MPa and tensile strength ranging from 770 to 940 MPa, with a minimum elongation of 16-18% . The chemical composition features carbon ≤0.21%, manganese ≤1.70%, and microalloying elements such as Ni, Cr, and Mo to achieve superior mechanical properties while maintaining good weldability . This grade is typically supplied in normalized, quenched and tempered (QT), or TMCP conditions and is used for critical components in large vessels and offshore platforms requiring maximum strength-to-weight ratio .

Both LR AH36 and LR AH69 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 AH69 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 superior strength-to-weight ratio . Both grades feature controlled chemical composition and maintain good weldability for critical marine service, though AH69 requires more complex alloying and advanced processing like quenching and tempering to achieve its enhanced mechanical properties . 

Chemical Composition

Mechanical Property