Difference between LR AH50 and LR AH62 steel plate

LR AH50 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 500 MPa and tensile strength ranging from 610 to 770 MPa, with a minimum elongation of 18% . The chemical composition is strictly controlled with carbon ≤0.21% and manganese ≤1.70%, along with microalloying elements such as Nb and V . Impact toughness is tested at 0°C, requiring minimum 33J (transverse) and 50J (longitudinal) . This grade is typically supplied in normalized or TMCP conditions and is used for critical components in large vessels and offshore platforms.

LR AH62 is an ultra-high-strength marine steel plate also certified by Lloyd's Register (LR), designed for the most demanding structural applications. It has a minimum yield strength of 620 MPa and tensile strength ranging from 720 to 890 MPa, with a minimum elongation of 17% . The chemical composition is more complex than AH50, with carbon ≤0.21%, manganese ≤1.70%, and additional alloying elements including nickel (0.70-1.80%), chromium (0.40-1.60%), and molybdenum (≤0.70%) to achieve superior mechanical properties . This grade is delivered in normalized or quenched and tempered (QT) conditions. Impact toughness is tested at 0°C, requiring minimum 41J (transverse) and 62J (longitudinal) .

Both LR AH50 and LR AH62 are LR-certified high-strength marine steels designed for shipbuilding and offshore applications. Their primary difference lies in strength level: AH50 offers a minimum yield strength of 500 MPa, suitable for extra-high-strength hull construction, while AH62 provides a substantially higher minimum yield strength of 620 MPa, designed for the most demanding load-bearing applications requiring maximum strength-to-weight ratio . Consequently, AH62 employs a more complex alloying design (with Ni, Cr, Mo additions) and advanced processing methods such as QT compared to AH50 to achieve its enhanced properties, while both grades maintain good weldability for critical marine service .

Chemical Composition

Mechanical Property