Difference between CCS FQ63 and CCS FQ70 steel plate

CCS FQ63 is an ultra-high-strength marine steel plate certified by the China Classification Society (CCS) for demanding offshore and shipbuilding applications. The "FQ" designation signifies quenched and tempered steel with impact toughness tested at the extremely low temperature of -60°C, ensuring exceptional performance in Arctic and polar environments. It has a minimum yield strength of 620 MPa and a tensile strength range of 720-890 MPa, with typical minimum elongation of 15-17%. Its chemical composition is strictly controlled with low carbon content to ensure good weldability. This grade is designed for critical structural components in ultra-large container ships, jack-up rig legs, and Arctic-class vessels requiring maximum strength-to-weight ratio.

CCS FQ70 is an ultra-high-strength marine steel plate also certified by CCS, manufactured through quenching and tempering . The "70" denotes a minimum yield strength of 690 MPa and a tensile strength range of 770-940 MPa . Like FQ63, it is impact tested at -60°C, with minimum impact energy requirements of 46J (transverse) . Its chemical composition includes carbon 0.125-0.165%, nickel 0.8-1.5%, chromium 0.6-1.0%, and boron 0.0008-0.0030% to achieve superior strength and toughness . 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 FQ63 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: FQ63 offers a minimum yield strength of 620 MPa with tensile strength of 720-890 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 more demanding load-bearing applications requiring maximum weight reduction. Both grades feature strictly controlled chemical composition and maintain good weldability for critical marine service. The selection between them depends on whether the project requires the balanced strength of FQ63 or the superior performance of FQ70 for more extreme structural demands.

Chemical Composition

Mechanical Property