Difference between LR AH46 and LR AH55 steel plate

LR AH46 is an extra-high-strength marine steel plate certified by Lloyd's Register (LR) for shipbuilding and offshore applications. It has a minimum yield strength of 460 MPa and tensile strength ranging from 570 to 720 MPa, with a minimum elongation of 19% . The chemical composition is strictly controlled with carbon ≤0.21% and manganese 1.00-1.70% . This grade is typically supplied in normalized (N), thermomechanical controlled rolled (TM), or quenched and tempered (QT) conditions . Impact toughness is tested at 0°C, with minimum impact energy of 31J (transverse) and 46J (longitudinal) .

LR AH55 is an ultra-high-strength marine steel plate also certified by Lloyd's Register (LR). It has a minimum yield strength of 550 MPa and tensile strength ranging from 550 to 700 MPa . The chemical composition features carbon ≤0.18% and manganese 0.90-1.60% . This grade requires advanced processing and is typically supplied in TM or QT conditions . Impact toughness is tested at 0°C, with minimum impact energy of 37J (transverse) and 55J (longitudinal) . Maximum thickness for TM/QT supply is 150mm .

Both LR AH46 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: AH46 offers a minimum yield strength of 460 MPa with tensile strength of 570-720 MPa, suitable for high-strength hull construction and offshore structures, while AH55 provides a substantially higher minimum yield strength of 550 MPa, designed for more demanding load-bearing applications requiring superior strength-to-weight ratio. Both grades feature controlled chemical composition with carbon ≤0.18-0.21% and maintain good weldability for critical marine service, though AH55 requires more complex alloying and advanced processing like TM or QT to achieve its enhanced mechanical properties. The selection between them depends on whether the project requires the balanced strength of AH46 or the superior performance of AH55 for more extreme structural demands.

Chemical Composition

Mechanical Property