ASTM A668/A668M-96(2001)
(Specification)Standard Specification for Steel Forgings, Carbon and Alloy, for General Industrial Use
Standard Specification for Steel Forgings, Carbon and Alloy, for General Industrial Use
SCOPE
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.
1.2 Hot-rolled or cold finished bars are not within the scope of this specification.
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.
1.4 Supplementary requirements of an optional nature are provided. These shall apply only when specified by the purchaser.
1.5 Appendix X1 lists the grades corresponding to the various grades of Specifications A235, A237, and A243 which have been superseded by this specification.
1.6 The values stated in either inch-pound units or SI units are to be regarded separately as the standard; within the text and tables, the SI units are shown in brackets. The values stated in each system are not exactly equivalent; therefore; each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
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An American National Standard
Designation: A 668/A 668M – 96 (Reapproved 2001) American Association State
Highway and Transportation Officials Standard
AASHTO No.: M 102
Standard Specification for
Steel Forgings, Carbon and Alloy, for General Industrial
Use
This standard is issued under the fixed designationA 668/A 668M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (ε) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope A 654 Specification for Special Requirements for Steel
Forgings and Bars for Nuclear and Other Special Appli-
1.1 This specification covers untreated and heat-treated
cations
carbon and alloy steel forgings for general industrial use. Other
A 788 Specification for Steel Forgings, General Require-
ASTM specifications for forgings are available for specific
ments
applications such as pressure vessels, railroad use, turbine
E 381 Method of Macroetch Testing Steel Bars, Billets,
generators, gearing, and others involving special temperature
Blooms, and Forgings
requirements.
1.2 Hot-rolled or cold finished bars are not within the scope
3. Terminology
of this specification.
3.1 Definitions of Terms Specific to This Standard:
1.3 Six classes of carbon steel and seven classes of alloy
3.1.1 hollow cylindrical forging—a forging whose length,
steel forgings are listed (see Section 7) , which indicates their
as measured on its longitudinal axis is more than its diameter,
required heat treatments, as well as mechanical properties.
shall be considered as a hollow cylinder within the scope of
1.4 Supplementary requirements of an optional nature are
this specification if it has been lengthened by extrusion or
provided. These shall apply only when specified by the
forged in a manner similar to that of a ring, namely, expanded
purchaser.
in diameter on a mandrel.
1.5 Appendix X1 lists the grades corresponding to the
3.1.2 ring-shaped or disk-shaped forging—a forging whose
various grades of Specifications A 235, A 237, and A 243,
length, as measured on its longitudinal axis, is less than its
which have been superseded by this specification.
diameter or main transverse dimension is considered a ring or
1.6 The values stated in either inch-pound units or SI units
disk within the meaning of this specification.
are to be regarded separately as the standard; within the text
andtables,theSIunitsareshowninbrackets.Thevaluesstated
4. Ordering Information
in each system are not exactly equivalent; therefore; each
4.1 When this specification is to be applied to an inquiry,
system must be used independently of the other. Combining
contract, or order, the purchaser should furnish the following
values from the two systems may result in nonconformance
information:
with the specification.
4.1.1 The ordering information required by Specification A
788.
2. Referenced Documents
4.1.2 The class of forging desired as listed in Section 7,
2.1 ASTM Standards:
4.1.3 The options which may be selected as found in 5.4.2,
A 275/A 275M Test Method for Magnetic Particle Exami-
2 7.1.2, 7.3, and 14.1, and
nation of Steel Forgings
4.1.4 Applicable supplementary requirements.
A 370 Test Methods and Definitions for MechanicalTesting
of Steel Products
5. Materials and Manufacture
A 388/A 388M Practice for Ultrasonic Examination of
2 5.1 Melting Process—The steel shall be made by the
Heavy Steel Forgings
open-hearth, basic-oxygen, or electric-furnace process.
5.2 Discard—Sufficient discard shall be made from each
ingot to secure freedom from piping and undue segregation.
This specification is under the jurisdiction of ASTM Committee A01 on Steel,
5.3 Forging Process—The forging shall be brought as close
Stainless Steel, and RelatedAlloys, and is the direct responsibility of Subcommittee
as practical to finished shape and size by hot mechanical work.
A01.06 on Steel Forgings and Billets.
Current edition approved May 10, 1996. Published July 1996. Originally
published as A 668 – 72. Last previous edition A 668 – 95a.
2 4
Annual Book of ASTM Standards, Vol 01.05. Discontinued. See 1983 Annual Book of ASTM Standards, Vol 01.05.
3 5
Annual Book of ASTM Standards, Vol 01.03. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A 668/A 668M
5.3.1 After forging and before reheating for heat treatment, 7.1.3.1 Solid Forgings—Either the as forged or rough ma-
the forgings shall be allowed to cool in a manner to prevent chined diameter or thickness of solid forgings, disregarding
injury and to accomplish transformation. large ends, collars, flanges, and journals, at time of heat
5.4 Heat Treatment: treatment shall determine the size classification.
5.4.1 All forgings, other than ClassA, shall be heat treated.
7.1.3.2 Ring or Hollow Cylinder Forging— The size clas-
See Section 7.
sification shall be determined by its wall thickness or width,
5.4.2 Where options exist within a class, the choice of heat
whichever is the smaller dimension of either the as forged or
treatment shall be left to the discretion of the manufacturer, rough machined forging at time of heat treatment.
unless the purchaser specifies one of the available options.
7.1.4 Number of Tests—Unless the purchaser specifies that
forgingsshallbefurnishedinaccordancewiththerequirements
6. Chemical Composition
of 7.3, the number of tension tests performed shall be as
6.1 Thesteelshallconformtotherequirementsforchemical
follows:
composition prescribed in Table 1.
7.1.4.1 For all classes of heat-treated forgings with rough
6.2 The choice of chemical composition is left to the
machined weights less than 5000 lb [2270 kg] each, one test
discretion of the manufacturer, unless otherwise specified by
shall be made from each size classification represented in each
the purchaser. See Appendix X2.
heatineachannealingornormalizingcharge,orfromeachsize
6.3 Heat Analysis:
classification in each heat in each normalizing or quenching
6.3.1 An analysis of each heat shall be made by the
charge represented in each tempering charge. For untreated
manufacturer. When possible, the test sample shall be taken
forgings (Class A) weighing less than 5000 lb each, one test
during the pouring of the heat. If the test sample is lost or
from each heat shall be made.
declared inadequate for chemical determinations, the manufac-
7.1.4.2 On all classes, for forgings with rough machined
turer may take alternative samples from locations near the
weights of 5000 lb or more, at least one test from each forging
surface of an ingot or bloom, as necessary to establish the
shall be made.
analysis.
7.1.4.3 On all classes, for forgings with rough machined
6.3.2 In the case of large ingots poured from two or more
weights of 7000 lb [3180 kg] or more, two tests will be taken:
heats, the weighted average of the chemical determinations of
on ring and disk forgings 180 ° apart; on shafts and long
the several heats shall conform to the requirements specified in
hollow cylinders (over 80 in. [2.0 m] in length excluding test
Table 1 or by agreement (see 6.2).
material), one from each end and offset 180 °. Shafts and
6.4 Product Analysis—An analysis may be made by the
cylinder forgings 80 in. [2.0 m] or less in length (excluding test
purchaser from a forging representing each heat, or multiple
material) may have both tests located at one end 180 ° apart.
heat if made in accordance with 6.3.2. Samples for analysis
7.1.4.4 When forgings are made in multiple as a single
may be taken from the forging, or from a full-size prolongation
forging, that is, forged as one piece and divided after heat
at any point from the midradius to the outside diameter in the
treatment, the multiple forging shall be considered as one
caseofdiskorsolidforgings,ormidwaybetweentheinnerand
forging, and the number of tests required shall be as designated
outer surfaces of hollow forgings or rings, or from a test
in 7.1.4.1, 7.1.4.2, and 7.1.4.3.
specimen.The chemical composition thus determined shall not
7.1.5 Prolongations:
vary from the requirements specified inTable 1 or agreed upon
7.1.5.1 A sufficient number of the forgings shall have
(see 6.2) by more than the amounts prescribed in Table 2.
prolongations for extracting specimens for testing. Locations
of test specimens for various types of forgings shall be as
7. Mechanical Properties
shown in Fig. 1.
7.1 Tensile Requirements:
7.1.5.2 The nominal or principal outside rough machine
7.1.1 The material shall conform to the tensile properties
diameter or thickness of the forgings, disregarding large ends,
prescribed in Table 3.
collars, flanges, and journals shall determine the size of the
7.1.2 Tensile specimens shall be machined to the form and
prolongations for test specimens; however, the prolongations
dimensions illustrated in Test Methods and Definitions A 370
on annealed, normalized, or normalized and tempered shafts
and shall be tested in accordance with the latest issue of Test
may be extensions of the small diameter end of the shaft, as
Methods and Definitions A 370.
shown in Fig. 1.
7.1.3 Size Classification—The dimensions of the forging at
7.1.5.3 For quenched forgings in Classes F, J, K, L, M, and
time of heat treatment determine the size classification (see
N, the prolongations shall be sufficiently long so that the center
Table 3):
of the gage length (for longitudinal specimens) or axis (for
tangential specimens) of the tension test specimen shall be at
TABLE 1 Chemical Requirements
the following locations:
Elements Composition, max, %
(1) On solid round forgings, bars, or billets (see Fig. 1 (a)),
1 1
Classes A to F Classes G to N at midradius and from the end, 3 ⁄2 in. [89 mm] or ⁄2 the
and AH to FH and GH to NH
diameter, whichever is less.
Manganese 1.35 .
(2) On solid rectangular forgings, bars, or billets, at ⁄4 the
Phosphorus 0.050 0.040
1 1
thicknessandwidthandfromtheend,3 ⁄2 in.[89mm]or ⁄2the
Sulfur 0.050 0.040
thickness, whichever is less.
A 668/A 668M
TABLE 2 Permissible Variations in Product Analysis
NOTE 1—Product cross-sectional area is defined as either (Area taken at right angles to the axis of the original ingot or billet):
(a) maximum cross-sectional area of rough machined forging (excluding boring), or
(b) maximum cross-sectional area of the unmachined forging, or
(c) maximum cross-sectional area of the billet.
Permissible Variation over the Maximum Limit or Under the Minimum Limit, %
2 2 2
Up to and incl. Over 200 in. Over 400 in. Over 800 in.
Unit or Maximum Specified
Element 2 2 2 2 2
200 in. incl to 400 in. incl to 800 in. incl to 1600 in. incl Over 1600 in.
Range, %
[645 to [1290 to 2580 [2580 to 5160 [5160 to 10320 [over 10320 cm ]
2 2 2 2
1290 cm ] cm ] cm ] cm ]
Carbon Up to and incl 0.25 0.03 0.03 0.04 0.05 0.05
0.26 to 0.55 0.04 0.04 0.05 0.06 0.06
0.56 and over 0.05 0.05 0.06 0.07 0.07
Manganese Up to and incl 0.90 0.04 0.05 0.06 0.07 0.08
0.91 and over 0.06 0.07 0.08 0.08 0.09
Phosphorus Up to and incl 0.05 0.008 0.010 0.010 0.015 0.015
Sulfur Up to and incl 0.030 0.005 0.005 0.005 0.006 0.006
0.030 and over 0.010 0.010 0.010 0.015 0.015
Silicon Up to and incl 0.35 0.03 0.04 0.04 0.05 0.06
0.35 and over 0.06 0.06 0.07 0.07 0.09
Nickel Up to and incl 1.00 0.03 0.03 0.03 0.03 0.03
1.01 to 2.00 incl 0.05 0.05 0.05 0.05 0.05
2.01 to 5.30 incl 0.07 0.07 0.07 0.07 0.07
Chromium Up to and incl 0.90 0.04 0.04 0.05 0.05 0.06
0.91 to 2.10 incl 0.06 0.06 0.07 0.07 0.03
2.11 to 10.00 incl 0.10 0.12 0.14 0.15 0.16
Molybdenum Up to and incl 0.20 0.02 0.02 0.02 0.03 0.03
0.21 to 0.40 incl 0.03 0.03 0.03 0.04 0.04
0.41 to 1.15 incl 0.04 0.05 0.06 0.07 0.08
1.16 to 5.50 incl 0.06 0.08 0.10 0.12 0.12
Vanadium Up to and incl 0.10 0.01 0.01 0.01 0.01 0.01
0.11 to 0.25 incl 0.02 0.02 0.02 0.02 0.02
0.26 to 0.50 incl 0.03 0.03 0.03 0.03 0.03
0.51 to 1.25 incl 0.04 0.04 0.04 0.04 0.04
(3) On disk forgings (see Fig. 1(c)) (with prolongation on 7.1.7 Test specimens shall be parallel to the axis of the
1 1
OD), at midthickness and from the OD 3 ⁄2 in. [89 mm] or ⁄2 forging in the direction in which the metal is most drawn out
the thickness, whichever is less. except that rings, hollow forgings which are expanded, and
(4) On disk forgings (see Fig. 1(c)) (with prolongation on disks shall be tested in the tangential direction.
1 1
the width or thickness) 3 ⁄2 in. [89 mm] or ⁄2 the thickness, 7.1.8 YieldpointshallbedeterminedoncarbonsteelGrades
whichever is less, from any heat treated surface. AthroughF,andyieldstrengthonalloysteelGradesGthrough
(5) On ring forgings (see Fig. 1(d)) (with prolongation on N. For carbon steel grades not showing a yield point, the yield
width), at midwall and from the ring face 3 ⁄2 in. [89 mm] or strength at 0.2 % offset shall be reported.
⁄2 the wall thickness, whichever is less. 7.2 Hardness Tests—Brinell hardness tests shall be per-
(6) On ring forgings (see Fig. 1(d)) (with prolongation on formed after heat treatment (except on Class A forgings) and
1 1
the OD), at midwidth and from the OD 3 ⁄2 in. [89 mm] or ⁄2 rough machining on each forging weighing under 7000 lb
the width, whichever is less. [3180 kg] and each multiple forging made in accordance with
7.1.5.4 Inplaceofprolongs,themanufacturermay:(1)elect 7.1.4.3 weighing under 7000 lb. For exceptions see 7.1.4.4 and
to submit an extra forging(s) to represent each test lot; in this 7.2.3.
event, the representative forging must be made from the same 7.2.1 The average value of the hardness readings on each
heat of steel, have received the same reduction and type of hot forging shall fall within the hardness ranges specified in Table
working, be of the same nominal thickness, and have been heat 3. The permissible variation in hardness in any forging over
treated in the same furnace charge as the forging(s) it repre- 250 lb [113 kg] shall not exceed 30 HB for Classes A through
sents; or (2) obtain the test specimen from the trepanned E, 40 HB for Classes F through J, 50 HB for Classes K through
material of transverse or radial holes, provided depth is equal N.
to or greater than the minimum depth required by 7.1.5.3. 7.2.2 At least two hardness tests shall be taken on each flat
7.1.6 Tests for acceptance shall be made after final heat face of disks, rings, and hollow forgings over 250 lb [113 kg]
treatment of the forgings. approximately at midradius and 180° apart, for example, at the
A 668/A 668M
TABLE 3 Tensile Requiremen
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