Difference between ABS FQ51 and ABS FQ70 steel plate

ABS FQ51 is an ultra-high-strength marine steel plate certified by the American Bureau of Shipping (ABS) . The "FQ" designation signifies that it is a quenched and tempered steel with impact toughness tested at -60°C . It has a minimum yield strength of 500 MPa and a tensile strength ranging from 610 to 770 MPa, with a minimum elongation of 16% . Impact energy requirements are 33J (transverse) and 50J (longitudinal) at -60°C . This grade is widely used for offshore drilling platforms, ship hulls, and critical marine structures requiring high strength and excellent corrosion resistance.

ABS FQ70 is an ultra-high-strength marine steel plate also certified by ABS, manufactured through quenching and tempering processes . Like FQ51, it is impact tested at -60°C, with minimum impact energy requirements of 41J (transverse) and 62J (longitudinal) . The "70" denotes a minimum yield strength of 690 MPa and a tensile strength ranging from 770 to 940 MPa, with a minimum elongation of 14% . Its chemical composition features carbon ≤0.18% and manganese ≤1.60% . This grade is designed for the most demanding applications, including large ships, offshore platforms, and jack-up rigs requiring maximum strength-to-weight ratio .

Both ABS FQ51 and ABS FQ70 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: FQ51 offers a minimum yield strength of 500 MPa with tensile strength of 610-770 MPa, suitable for high-strength offshore platforms and ship hulls , while FQ70 provides a substantially higher minimum yield strength of 690 MPa with tensile strength reaching 770-940 MPa, designed for the most demanding load-bearing applications requiring maximum strength-to-weight ratio . Both grades feature strictly controlled chemical composition (carbon ≤0.18%) and maintain good weldability for critical marine service . The selection between them depends on whether the project requires the balanced strength of FQ51 or the superior performance of FQ70 for more extreme structural demands.

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Mechanical Property