Difference between ABS FQ47 and ABS FQ51 steel plate

ABS FQ47 is an extra-high-strength marine steel plate certified by the American Bureau of Shipping (ABS) . The "FQ" designation signifies it is a quenched and tempered steel with impact toughness tested at the extremely low temperature of -60°C, ensuring exceptional performance in polar and Arctic environments . It has a minimum yield strength of 460 MPa and a tensile strength ranging from 570 to 720 MPa , with a minimum elongation of 17% . This grade is widely used for offshore drilling platforms, ship hulls, and critical marine structures requiring high strength and excellent corrosion resistance .

ABS FQ51 is an ultra-high-strength marine steel plate also certified by ABS, manufactured through quenching and tempering or thermomechanical control processes (TMCP) . Like FQ47, it is impact tested at -60°C, with minimum impact energy requirements of 33J (transverse) and 50J (longitudinal) . The "51" denotes a minimum yield strength of 500 MPa and a tensile strength ranging from 610 to 770 MPa , with a minimum elongation of 16% . This grade is designed for the most demanding load-bearing applications, including jack-up rig legs, ultra-large container vessels, and critical marine structures requiring maximum strength-to-weight ratio .

Both ABS FQ47 and ABS FQ51 are ABS-certified quenched and tempered marine steels with exceptional low-temperature toughness tested at -60°C, ensuring reliable performance in the most extreme Arctic and harsh marine environments . Their primary difference lies in strength level: FQ47 offers a minimum yield strength of 460 MPa with tensile strength of 570-720 MPa, suitable for high-strength offshore platforms and ship hulls , while FQ51 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 strictly controlled chemical composition (carbon ≤0.18%, manganese ≤1.60%) and maintain good weldability for critical marine service.

Chemical Composition

Mechanical Property