Difference between CCS FQ47 and CCS FQ70 steel plate

CCS FQ47 is an extra-high-strength marine steel plate certified by the China Classification Society (CCS) for demanding offshore and shipbuilding applications . The "FQ" designation signifies that it is a quenched and tempered steel with impact toughness tested at the extremely low temperature of -60°C . It has a minimum yield strength of 460 MPa and a tensile strength range of 570-720 MPa . This grade is designed for critical structural components in offshore drilling rigs, ice-class vessels, and Arctic marine environments requiring exceptional low-temperature toughness.

CCS FQ70 is an ultra-high-strength marine steel plate also certified by CCS, manufactured through quenching and tempering (QT) or thermomechanical control processing (TMCP) . The "70" denotes a minimum yield strength of 690 MPa and a tensile strength range of 770-940 MPa. Like FQ47, it is impact tested at -60°C, with minimum impact energy requirements of 46J (transverse) and 69J (longitudinal) . It is widely used in self-elevating drilling platforms, ultra-large container ships, and the most demanding marine structures where maximum strength-to-weight ratio is essential.

Both CCS FQ47 and CCS FQ70 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 FQ70 provides a substantially higher minimum yield strength of 690 MPa with tensile strength reaching 770-940 MPa, designed for the most critical load-bearing applications requiring maximum weight reduction . Both grades feature strictly controlled chemical composition with carbon ≤0.21% and manganese ≤1.70%, and maintain good weldability for critical marine service.

Chemical Composition

Mechanical Property