Difference between ABS FQ47 and ABS FQ56 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 -60°C . It has a minimum yield strength of 460 MPa and tensile strength ranging from 570 to 720 MPa , with a minimum elongation of 17% . Impact energy requirements are 31J (transverse) and 46J (longitudinal) at -60°C . This grade is widely used for offshore drilling platforms, hull structures, and critical marine components requiring excellent low-temperature toughness.

ABS FQ56 is an ultra-high-strength marine steel plate also certified by ABS , manufactured through quenching and tempering processes . Like FQ47, it is impact tested at -60°C, with impact energy requirements of 37J (transverse) and 55J (longitudinal) . The "56" denotes a minimum yield strength of 550 MPa and tensile strength ranging from 670 to 835 MPa , with a minimum elongation of 16% . Its chemical composition features carbon ≤0.18% and manganese ≤1.60% . This grade is designed for the most demanding applications, including jack-up rig legs, ultra-large container vessels, and critical offshore structures requiring maximum strength-to-weight ratio.

Both ABS FQ47 and ABS FQ56 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 FQ56 provides a substantially higher minimum yield strength of 550 MPa with tensile strength reaching 670-835 MPa, designed for more demanding load-bearing applications requiring superior strength-to-weight ratio . Both grades feature strictly controlled chemical composition (carbon ≤0.18%) and maintain good weldability for critical marine service. 

Chemical Composition

Mechanical Property