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1.1 This specification covers steel plates in three grades of carbon steel, designated Grades A, B, and C. At the option of the supplier, Grade C may be produced with a boron addition up to the maximum content specified in Section 6. The plates are quenched-and-tempered and are primarily intended for welded-layered pressure vessels.
1.2 Material under this specification is available in three grades as follows:Yield Strength, Tensile Strength, Grade min, ksi [MPa] ksi [MPa] A 70  90-110 [620-760] B 75  95-115 [655-795] C 70  90-110 [620-760]
1.3 The maximum thickness of plates supplied under this specification is limited only by the capability of the chemical composition to meet the specified mechanical requirements. However, current practice normally limits the maximum thickness to 7/8 in. [22 mm] for Grades A and B, and to 2 in. [50 mm] for Grade C.
1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
A20/A20M Specification for General Requirements for Steel Plates for Pressure Vessels
ICS Number Code 77.140.30 (Steels for pressure purposes)