1.1 This specification covers ferritic steel forgings for boilers, pressure vessels, high-temperature parts, and associated equipment.

1.2 Forgings made of steel grades listed in Specification A 335/A 335M, may also be ordered under this specification. The chemical, tensile, heat treatment, and marking requirements of Specification A 335/A 335M shall apply, except the forging shall conform to the chemical requirements of Tables 1 and 2 of Specification A 335/A 335M only with respect to heat analysis. On check analysis they may deviate from these limits to the extent permitted in Table 1 of this specification.

Current	Formerly
Grade F1	Class F1
Grade F11, Class 2	Class F11
Grade F11, Class 3	Class F11A
Grade F11, Class 1	Class F11B
Grade F12	Class F12
Grade F5	Class F5
Grade F5A	Class F5A
Grade F9	Class F9
Grade F6	Class F6
Grade F21 Class 1	Class F21A
Grade F21, Class 3	Class F21
Grade F22, Class 1	Class F22A
Grade F22, Class 3	Class F22
Grade F91	Class F91
Grade F3V	Class F3V
Grade F22V	Class F22V

1.3 Supplementary Requirements S1 to S9 are provided for use when additional testing or inspection is desired. These shall apply only when specified individually by the purchaser in the order.

1.4 Unless the order specifies the applicable “M” specification designation, the material shall be furnished to the inch-pound units.

1.5 Specification A 336/A 336M formerly included austenitic steel forgings, which are now found in Specification A 965/A 965M.

1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.