Difference between ABS DQ56 and CCS DQ56

ABS DQ56 and CCS DQ56 are both extra-high-strength quenched and tempered steel plates specifically designed for the most demanding marine and offshore engineering applications. They are certified by two major classification societies-ABS (American Bureau of Shipping) and CCS (China Classification Society)-and represent a higher strength tier within the DQ series, offering enhanced low-temperature toughness suitable for critical structural components.

ABS Grade DQ56 is certified by the American Bureau of Shipping. The designation "DQ56" indicates it is an extra-high-strength steel with a minimum yield strength of 550 MPa and a tensile strength range of 670-835 MPa . The "D" signifies the impact test temperature, with some suppliers indicating testing at -20°C requiring minimum Charpy V-Notch impact energy of 37J (transverse) or 55J (longitudinal) , while others indicate testing at -40°C requiring ≥47J . These plates are manufactured using advanced heat treatment processes such as quenched and tempered (QT) , controlled rolling, or normalizing to achieve their exceptional combination of strength and toughness . Typical applications include offshore drilling platforms, floating production and storage vessels (FPSOs), ships transporting liquefied gas, and critical marine structures operating in harsh environments.

CCS Grade DQ56 is certified by the China Classification Society and serves as the direct equivalent to ABS DQ56 in the Chinese classification system . According to classification society standards, CCS DQ56 shares identical mechanical property requirements with its ABS counterpart: minimum yield strength of 550 MPa. It belongs to the same product family as AQ56, DQ56, EQ56, and FQ56 series for shipbuilding and offshore applications, with each letter representing a different impact test temperature.

Key Differences:
The primary distinction between these two grades lies in their certifying authority and the corresponding quality control system . ABS DQ56 complies with American Bureau of Shipping rules and is recognized internationally, particularly in projects requiring ABS certification for offshore platforms and vessels destined for ABS-classed fleets. CCS DQ56 complies with China Classification Society rules and is typically specified for offshore structures built in Chinese shipyards or for projects under Chinese classification . From a technical perspective, these steels are considered interchangeable, and major manufacturers can produce plates certified by both societies simultaneously. The choice between them is typically determined by the flag state of the vessel, shipyard preferences, or specific project requirements. Both grades must be supplied with mill test certificates (MTC) bearing classification society surveyor signatures.

Chemical Composition

CCS DQ56 Extra high Strength Chemical Composition in Tempering and Quenching

Mechanical Property

CCS DQ56 Extra high strength property in tempering and quenching