ASTM A 940/A 940M - 06 Standard Specification for Vacuum Treated Steel Forgings, Alloy, Differentially Heat Treated, for Turbine Rotors

American Society for Testing and Materials (ASTM). Current edition approved March 1, 2006. Published March 2006. Originally approved in 1995. Last previous edition approved in 2001 as A 940 – 96 (2001). 4 p. This specification covers vacuum treated, alloy steel forgings, differentially heat treated for turbine rotors.
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.