1.1 This specification covers vacuum treated, alloy steel forgings, differentially heat treated for turbine rotors.

1.2 Differential heat treatment of a rotor forging involves subjecting two portions of the forging concurrently to two different austenitizing temperatures followed by two different cooling rates for normalizing and quenching, and then tempering, to achieve creep resistance in the high pressure (HP) portion and high toughness in the low pressure (LP) portion.

1.3 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.