ASTM A668 / A668M

This specification covers untreated and heat-treated carbon and alloy steel forgings for general industrial use. Other ASTM specifications for forgings are available for specific applications such as pressure vessels, railroad use, turbine generators, gearing, and others involving special temperature requirements.Hot-rolled or cold finished bars are not within the scope of this specification.Six classes of carbon steel and seven classes of alloy steel forgings are listed (see Section 7), which indicates their required heat treatments, as well as mechanical properties.Provision, with the suffix H for certification and marking, for the supply of forgings after hardness testing only.Supplementary requirements, including those in Specification A788/A788M, of an optional nature are provided.These shall apply only when specified by the purchaser.Appendix X1 lists the current classes corresponding to the various classes of Specifications A235, A237, and A243, which have been superseded by this specification.

Chemical Properties

Grade	Manganese	Phosphorus	Sulphur
Classes A to F and AH to FH	1.35	0.050	0.025
Classes G to N and GH to NH	...	0.040	0.025

Mechanical Properties

Tensile strength, psi (MPa)	Yield strength (0.2 % offset), min,psi [MPa]	Elongation in 2 in. [50 mm],min, %	Reduction of area, min, %