ABS FQ56 Steel Plate – Properties, Chemistry & Equivalents

ABS FQ56 (also written AB/FQ56, ABS Grade FQ56, FQ56 steel plate) is an extra-high-strength steel plate to ABS Rules Part 2, Chapter 1, Section 8 (2018). The number 56 is the yield category (550 MPa minimum, tensile 670-835 MPa) and the prefix FQ sets the Charpy test temperature of -60°C. Grades of this family are supplied quenched and tempered (QT) or thermo-mechanically rolled (TM). It corresponds to grade F550 in IACS UR W16; ASTM A131 does not cover this strength level.

Related grades: ABS AQ56 steel plate ABS DQ56 steel plate ABS EQ56 steel plate ABS FQ51 steel plate.

Gangsteel is specialized in supplying ABS Extra high strength steel plate in ABS Grade FQ56. For more information of Grade FQ56 steel plate, please check them in following:

AB/FQ56  Extra high Strength Chemical Composition in Tempering and Quenching

AB/FQ56

ABS 2022: limits shown are for the quenched and tempered (QT) condition; N/NR/CR and TM supply have different limits in Table 4A. Al/N ≥ 2:1 (not required when other N-binding elements are used); higher C or N may be agreed with ABS; Ni content agreed at qualification; final chemistry must also meet the mill's ABS-approved specification. Product analysis = heat limit ± ASTM A6/A6M Table A permitted variation (band chosen by the specified maximum/upper limit); applies only when product (check) analysis is required; for a range, results may not vary both above and below it. Per ABS Rules for Materials and Welding Part 2 (2022); product analysis tolerances per ABS 2-1-2/5.3 (“chemical tolerances of ASTM A6”) and ASTM A6/A6M 7.2, Table A (also invoked by ASTM A131). Heat limits: ABS 2-1-8/4 Table 4A (2022), QT column.

Crack Sensitivity:  Pcm = (C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B)%
Carbon Equivalent:  Ceq = 【C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15】%

AB/FQ56 Extra high strength property in tempering and quenching

AB/FQ56

Source: ABS Rules Pt 2, 2-1-8, Table 5A. Either longitudinal or transverse specimens per the order.

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 Related steel grades: AB/FQ47, AB/FQ51 ,AB/FQ63, AB/FQ70

ABS FQ56 thickness and impact requirements

For ABS FQ56 the Charpy V-notch test is run at -60°C with a minimum average of 55 J longitudinal or 37 J transverse. The requirement does not change with thickness the way it does for hull grades; the maximum thickness depends on the supply condition and the mill approval (ABS 2-1-8, Table 3). Confirm the thickness limit with the mill approval before ordering.

Grades are equivalent in chemistry and properties because the IACS societies use the same unified requirements. A plate still needs a certificate from the vessel's own classification society, so one plate can carry dual or multiple class certification only when each society's surveyor tests it.