Difference between CCS FQ47 and CCS FQ56 steel plate

CCS FQ47 is an extra-high-strength marine steel plate certified by the China Classification Society (CCS) . 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 460 MPa (67 ksi) and tensile strength ranging from 570 to 720 MPa (83-104 ksi) . Minimum elongation is typically 17% . The chemical composition is strictly controlled with carbon ≤0.21% and manganese ≤1.70% . This grade is designed for critical structural components in offshore drilling rigs, ice-class vessels, and Arctic marine environments.

CCS FQ56 is an ultra-high-strength marine steel plate also certified by CCS, manufactured through quenching and tempering (QT) . The "56" denotes a minimum yield strength of 550 MPa and tensile strength ranging from 670 to 835 MPa, with minimum elongation of 16% . Like FQ47, it is impact tested at -60°C, with minimum impact energy requirements of 46J (transverse) and 69J (longitudinal) . The chemical composition features a lower maximum carbon content of 0.16% to enhance weldability . This grade is designed for the most demanding applications such as self-elevating drilling platforms, ultra-large container ships, and critical marine structures requiring maximum strength-to-weight ratio.

Both CCS FQ47 and CCS FQ56 are CCS-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 ice-class vessels , 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 . Additionally, FQ56 has a lower maximum carbon content (0.16% vs. 0.21%), which can offer enhanced weldability for critical fabrication . Both grades feature strictly controlled chemical composition and maintain good weldability for critical marine service.

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Mechanical Property