Difference between LR AH42 and LR AH62 steel plate

LR AH42 is an extra-high-strength shipbuilding steel plate certified by Lloyd's Register (LR). It is a fine-grain, weldable structural steel intended for marine and offshore applications. It has a minimum yield strength of 420 MPa and tensile strength ranging from 530 to 680 MPa, with a minimum elongation of 20% . The chemical composition is strictly controlled, with carbon ≤0.21% and manganese ≤1.70% . This grade is typically supplied in normalized, thermo-mechanically controlled rolled (TM), or quenched and tempered (QT) conditions .

LR AH62 is an ultra-high-strength marine steel plate also certified by Lloyd's Register (LR). It has a minimum yield strength of 620 MPa (higher than AH42) and tensile strength ranging from 720 to 890 MPa, with a minimum elongation of 17% . To achieve its superior mechanical properties, its chemical composition is more complex, including a lower carbon content (≤0.18%) and the addition of microalloying elements such as nickel (0.70-1.80%), chromium (0.40-1.60%), and molybdenum (≤0.70%) . This grade is typically delivered in normalized or QT conditions .

Both LR AH42 and LR AH62 are LR-certified high-strength marine steels, designed for demanding shipbuilding and offshore applications requiring excellent weldability and guaranteed impact toughness at 0°C . Their primary difference lies in the strength level: AH42 offers a minimum yield strength of 420 MPa, suitable for extra-high-strength hull construction , while AH62 provides a substantially higher minimum yield strength of 620 MPa, making it ideal for more critical load-bearing applications where a superior strength-to-weight ratio is required . Consequently, AH62 employs a more complex alloying design and advanced processing methods compared to AH42 to achieve its enhanced properties.

Chemical Composition

Mechanical Property