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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 F1Class F1Grade F11, Class 2 Class F11Grade F11, Class 3 Class F11A Grade F11, Class 1 Class F11B Grade F12Class F12Grade F5Class F5Grade F5AClass F5AGrade F9Class F9Grade F6Class F6Grade F21 Class 1Class F21AGrade F21, Class 3Class F21Grade F22, Class 1Class F22AGrade F22, Class 3Class F22Grade F91Class F91Grade F3VClass F3VGrade F22VClass 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 inch-pound units or SI (metric) units are to be regarded separately as standards. Within the text and tables, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.