This specification covers vacuum-treated basic electric steel forgings for use in generator rotors. Steel materials shall be manufactured by vacuum degassing, heat treatment, rough machining, and boring. Heat and product analyses shall be carried out to examine conformation of the specimens with chemical compositions of carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, vanadium, and antimony. Forgings shall also go through tension, impact, and Charpy V-notch tests, and shall conform with the following tensile and notch toughness requirements: tensile strength, yield strength, elongation, reduction of area, FATT₅₀, and Charpy absorbed energy. Nondestructive test methods such as ultrasonic and internal inspection shall be performed.

1.1 This specification covers vacuum-treated basic electric steel forgings for generator rotors.

1.2 Supplementary requirements are provided, both in this standard and in Specification A788/A788M, for use when additional testing, inspection or processing is required by the purchaser.

1.3 The values stated in either inch-pound 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 must be used independent of the other. Combining values from the two systems may result in nonconformance with the specification.

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