1.1 This specification covers heat-treated carbon-manganese-silicon steel plates intended for use in welded pressure vessels at moderate and lower temperature service.

1.2 Material under this specification is available in three strength levels, 75 ksi [515 MPa], 85 ksi [585 MPa], and 80 ksi [550 MPa], minimum ultimate tensile strengths.

1.3 The maximum thickness of Grade A plates is limited only by the capacity of the chemical composition and heat treatment to meet the specified mechanical property requirements. The maximum thickness of Grade B plates is limited to 2.5 in. [65 mm]. The maximum thickness of Grade C is limited to 6 in.

1.4 Grade A is the material that, prior to 1984, was covered by Specification A738 without a grade designation.

1.5 The values stated in either inch-pound units or SI units are to be regarded separately as standards. 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.