1.1 This specification² covers three grades of carbon-manganese-silicon steel, designated Grades A, B, and C. Grade C may be produced with a boron addition. The plates are quenched and tempered and are intended for welded-layered pressure vessels.

1.2 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.

1.3 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.