Difference between ABS EQ51 and CCS EQ51 steel plate

ABS EQ51 and CCS EQ51 are both extra-high-strength quenched and tempered steel plates specifically engineered for the most demanding marine and offshore applications, particularly those requiring excellent toughness at low temperatures. They are certified by two major classification societies-ABS (American Bureau of Shipping) and CCS (China Classification Society)-and represent the "E" toughness tier within the 51 kgf/mm² strength class.

ABS Grade EQ51 is certified by the American Bureau of Shipping. The designation "EQ51" indicates a minimum yield strength of 500 MPa and a tensile strength range of 610-770 MPa . The "E" signifies the Charpy V-notch impact test temperature of -40°C (-40°F) , requiring minimum average energy of 41J (transverse) or 62J (longitudinal) . These plates are manufactured using quenched and tempered (QT) processes, available in thicknesses from 8mm to 300mm, with widths of 1200-3950mm and lengths of 3000-20000mm . Typical applications include offshore drilling platforms, ship hulls, jack-up rig legs, and critical marine structures.

CCS Grade EQ51 is certified by the China Classification Society and serves as the direct equivalent to ABS EQ51 in the Chinese classification system. According to classification society standards, CCS EQ51 shares identical mechanical property requirements with its ABS counterpart: minimum yield strength of 500 MPa . It belongs to the same product family as AQ51, DQ51, EQ51, and FQ51 series for shipbuilding and offshore applications, with each letter representing a different impact test temperature. Like ABS EQ51, CCS EQ51 requires Charpy impact testing at -40°C with similar energy requirements.

Key Differences:
The primary distinction between these two grades lies in their certifying authority and the corresponding quality control system. ABS EQ51 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 EQ51 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 and can be produced with various delivery conditions including quenched and tempered, normalized, or as-rolled depending on thickness requirements.

Chemical Composition

CCS EQ51 Extra high Strength Chemical Composition in Tempering and Quenching

Mechanical Property

CCS EQ51 Extra high strength property in tempering and quenching