Active Standard ASTM A668 / A668M | Developed by Subcommittee: A01.06
Book of Standards Volume: 01.05
Historical (view previous versions of standard)
This specification deals with the standard requirements for untreated and heat-treated carbon and alloy steel forgings for general industrial use. This specification covers six classes of carbon steels (Class A to F) and seven classes of alloy steels (Class G, H, and J to N). Materials shall be forged by hot mechanical work. Except for Class A, all forgings shall be heat treated, depending on class, by the following techniques: annealed, or normalized, or normalized and tempered (Classes B, C, D, and G); normalized and tempered, or double-normalized and tempered (Class E); quenched and tempered, or normalized, quenched, and tempered (Classes F); normalized and tempered (Class H); normalized and tempered, or normalized, quenched, and tempered (Class J); and normalized, quenched, and tempered (Classes K, L, M, and N). Steel specimens shall undergo heat and product analyses, and shall conform to required chemical compositions for manganese, phosphorus, and sulfur. Steel forgings shall also be tested on their conformance to the following tensile requirements: tensile strength, yield point, yield strength, elongation, reduction of area, and Brinell hardness.
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1.1 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.
1.3 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.
1.5 Supplementary requirements, including those in Specification A788/A788M, of an optional nature are provided. These shall apply only when specified by the purchaser.
1.6 Appendix X1 lists the current classes corresponding to the various classes of Specifications A235, A237, and A243, which have been superseded by this specification.
1.7 The values stated in either SI units or inch-pound units are to be regarded separately as standard; within the text and tables, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
A275/A275M Practice for Magnetic Particle Examination of Steel Forgings
A370 Test Methods and Definitions for Mechanical Testing of Steel Products
A388/A388M Practice for Ultrasonic Examination of Steel Forgings
A788/A788M Specification for Steel Forgings, General Requirements
E290 Test Methods for Bend Testing of Material for Ductility
E381 Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings
ICS Number Code 77.140.85 (Iron and steel forgings)
UNSPSC Code 31132100(Steel forgings)