Difference between LR AH40 and LR AH50 steel plate

LR AH40 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 390 MPa and tensile strength ranging from 510 to 650 MPa, with a minimum elongation of 20% . The chemical composition is strictly controlled with carbon ≤0.18% and manganese 0.90-1.60% . This grade is typically supplied in normalized or controlled rolling condition and is widely used for hull structures and offshore platforms .

LR AH50 is an extra-high-strength marine steel plate also certified by Lloyd's Register (LR) , designed for more demanding structural applications . It is impact tested at 0°C and has a minimum yield strength of 500 MPa and tensile strength ranging from 610 to 770 MPa, with a minimum elongation of 18% . The chemical composition features carbon ≤0.21% and manganese ≤1.70%, with microalloying elements such as Nb and V to enhance strength while maintaining weldability . This grade is used for critical components in large vessels and offshore platforms requiring superior strength-to-weight ratio .

Both LR AH40 and LR AH50 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: AH40 offers a minimum yield strength of 390 MPa with tensile strength of 510-650 MPa, suitable for general high-strength hull construction , while AH50 provides a higher minimum yield strength of 500 MPa with tensile strength reaching 610-770 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