1、Designation: A668/A668M 17 American Association StateHighway and Transportation Officials StandardAASHTO No.: M 102Standard Specification forSteel Forgings, Carbon and Alloy, for General IndustrialUse1This standard is issued under the fixed designation A668/A668M; the number immediately following th
2、e designation indicates the yearof 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 () indicates an editorial change since the last revision or reapproval.This standard has been approved for
3、use by agencies of the U.S. Department of Defense.1. Scope*1.1 This specification covers untreated and heat-treatedcarbon and alloy steel forgings for general industrial use. OtherASTM specifications for forgings are available for specificapplications such as pressure vessels, railroad use, turbineg
4、enerators, gearing, and others involving special temperaturerequirements.1.2 Hot-rolled or cold finished bars are not within the scopeof this specification.1.3 Six classes of carbon steel and seven classes of alloysteel forgings are listed (see Section 7), which indicates theirrequired heat treatmen
5、ts, as well as mechanical properties.1.4 Provision, with the suffix H for certification andmarking, for the supply of forgings after hardness testing only.1.5 Supplementary requirements, including those in Speci-fication A788/A788M, of an optional nature are provided.These shall apply only when spec
6、ified by the purchaser.1.6 Appendix X1 lists the current classes corresponding tothe various classes of Specifications A235, A237, and A243,which have been superseded by this specification.1.7 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard; within t
7、he text andtables, the SI units are shown in brackets. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in nonconformancewith the standard.1.8 Unless the order specifies the a
8、pplicable “M“specification, the forgings shall be furnished to the inch-poundunits.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guid
9、es and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2A275/A275M Practice for Magnetic Particle Examination ofSteel ForgingsA370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA388/A38
10、8M Practice for Ultrasonic Examination of SteelForgingsA788/A788M Specification for Steel Forgings, General Re-quirementsE290 Test Methods for Bend Testing of Material for Ductil-ityE340 Practice for Macroetching Metals and Alloys3. Terminology3.1 The terminology section of Specification A788/A788Mi
11、s applicable to this specification.3.2 Definitions of Terms Specific to This Standard:3.2.1 classa description of steel forgings based on heattreatment, mechanical properties and composition.3.2.2 controlling cross section thickness (TC)the diameterof the largest theoretical sphere which can be insc
12、ribed withinthe volume of the forging.3.2.3 TPdesignates prolongations which have a size otherthan the controlling cross section thickness (TC).1This specification is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of Subcommi
13、tteeA01.06 on Steel Forgings and Billets.Current edition approved May 1, 2017. Published May 2017. Originallyapproved in 1972. Last previous edition approved in 2016 as A668/A668M-16.DOI: 10.1520/A0668_A0668M-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cus
14、tomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
15、 PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organizatio
16、n Technical Barriers to Trade (TBT) Committee.14. Ordering Information and General Requirements4.1 Material supplied to this specification shall conform tothe requirements of Specification A788/A788M which outlinesadditional ordering information, manufacturing requirements,testing and retesting meth
17、ods and procedures, marking,certification, product analysis variations and additional supple-mentary requirements.4.1.1 If the requirements of this specification are in conflictwith the requirements of Specification A788/A788M, therequirements of this specification shall prevail.4.2 When this specif
18、ication is to be applied to an inquiry,contract, or order, the purchaser should furnish the followinginformation:4.2.1 The ordering information required by SpecificationA788/A788M,4.2.2 The class of forging desired as listed in Table 1,4.2.3 Location(s) of areas of significant loading if testspecime
19、ns are to be located in accordance with 7.1.4.5,4.2.4 The options which may be selected as found in 5.3.2,6.1, and 7.3, and4.2.5 Any applicable supplementary requirements.5. Materials and Manufacture5.1 DiscardSufficient discard shall be made from eachingot to secure freedom from piping and undue se
20、gregation.5.2 Forging Process:5.2.1 The forging shall be brought as close as practical tofinished shape and size by hot mechanical work.5.2.2 Supplementary Requirements S2, S14, and S15 maybe specified by the purchaser to satisfy concerns about theutility of the proposed forging.5.3 Heat Treatment:5
21、.3.1 All forgings, other than Class A, shall be heat treated.See Section 7.5.3.2 Where options exist within a class, the choice of heattreatment shall be left to the discretion of the manufacturer,unless the purchaser specifies one of the available options.6. Chemical Composition6.1 The steel shall
22、conform to the requirements prescribedin Table 1.6.2 The choice of chemical composition is left to thediscretion of the manufacturer, unless otherwise specified bythe purchaser. See Appendix X2.6.3 Heat Analysis:6.3.1 An analysis of each heat shall be made by themanufacturer.6.4 Product AnalysisAn a
23、nalysis may be made by thepurchaser according to the requirements of Specification A788/A788M. If a standard grade has been used to manufacture theforging the permissible variations in composition of Specifi-cation A788/A788M shall apply. If a non-standard grade ofsteel has been used, and compositio
24、n limits have not beensupplied, the product analysis can be used only to confirm thetype of steel supplied.7. Mechanical Properties7.1 Tensile Requirements:7.1.1 The material shall conform to the tensile and hardnessproperties prescribed in Table 2. See Test Methods andDefinitions A370.7.1.2 All For
25、gingsThe dimensions of the controlling crosssection thickness (TC) of the forging at time of heat treatmentdetermine the mechanical properties to be met within eachclass (see Table 2) except as noted in 7.1.4.2.7.1.3 Number of TestsUnless the purchaser specifies thatforgings shall be furnished in ac
26、cordance with the requirementsof 7.3, the number of tension tests performed shall be asfollows:7.1.3.1 For all classes of heat-treated forgings with as-heattreated weights (excluding test prolongations) less than 5000 lb2250 kg each, one test shall be made from each sizeclassification represented in
27、 each heat in each annealing ornormalizing charge, or from each size classification in eachheat in each normalizing or quenching charge represented ineach tempering charge. For untreated forgings (Class A)weighing less than 5000 lb 2250 kg each, one test from eachheat shall be made.7.1.3.2 On all cl
28、asses, for forgings with as-heat treatedweights (excluding test prolongations) of 5000 lb 2250 kg ormore, at least one test from each forging shall be made.7.1.3.3 On all classes, for forgings with as-heat treatedweights (excluding test prolongations) of 7000 lb 3200 kg ormore, two tests will be tak
29、en: on ring and disk forgings 180apart; on shafts and long hollow cylinders (over 80 in. 2.0 min length excluding test material), one from each end and offset180. Shafts and cylinder forgings 80 in. 2.0 m or less inlength (excluding test material) may have both tests located atone end 180 apart.7.1.
30、3.4 When forgings are made in multiple as a singleforging, that is, forged as one piece and divided after heattreatment, the multiple forging shall be considered as oneforging, and the number of tests required shall be as designatedin 7.1.3.1, 7.1.3.2, and 7.1.3.3.7.1.4 Prolongations:7.1.4.1 A suffi
31、cient number of the forgings shall haveprolongations for extracting specimens for testing. Examplesof test locations for various forging configurations are shown inFigs. 1 and 2.NOTE 1Figures provided demonstrate the concept of controlling crosssection thickness (TC) but do not encompass all possibl
32、e test prolongationconfigurations which meet the requirements of Section 7.7.1.4.2 For all forgings of non-uniform cross section inclasses A, B, C, D, E, G and H: The prolongation(s) may beextensions of sections other than the controlling cross sectionthickness (TC), that is TP TC. In this case, the
33、 dimension ofTPshall determine the mechanical properties to be met withineach class. When TP TC,TPshall not have more reductionthan the smallest cross section to be qualified.(1) For annealed, normalized, or normalized and temperedforgings in classes A, B, C, D, E, G and H the center of thegage leng
34、th axis of tension test specimens shall be14 thecontrolling cross section thickness (TC) from one surfaceexcept as noted in 7.1.4.2 (2).A668/A668M 172(2) If the prolongation thickness (TP) is less than thecontrolling cross section thickness (TC) the center of the gagelength axis of the tension test
35、shall be of the prolongationthickness (TP) from one surface.7.1.4.3 For quenched forgings in Classes F, J, K, L, M, andN, the center of the gage length axis of the tension testspecimen shall be at a minimum14 (TC) from one quenchedsurface and 312 in. 90 mm from the nearest second surface.7.1.4.4 In
36、place of prolongations, the manufacturer may: (1)elect to submit a representative forging(s) to represent each testlot; in this event, the representative forging must be made fromthe same heat of steel, must not receive more reduction than theforging it represents, must receive the same type of hotw
37、orking it represents, be of the same controlling cross sectionthickness (TC), and have been heat treated in the same furnacecharge as the forging(s) it represents; or (2) obtain the testspecimen from the trepanned material of transverse or radialholes, provided the required depth is met.7.1.4.5 With
38、 prior purchaser approval, test specimens maybe taken at a depth (t) corresponding to the distance from thearea of significant stress to the nearest heat treated surface andat least twice this distance (2t) from any second surface.However, the test depth shall not be nearer to one heat-treatedsurfac
39、e than34 in. 19 mm and to the second heat treatedsurface than 112 in. 38 mm. Sketches showing the exact testlocations shall be approved by the purchaser when this methodis used.7.1.5 Tests for acceptance shall be made after final heattreatment of the forgings. Thermal cycling after mechanicaltesting
40、 is complete shall not exceed 50 F 30 C less than thetemperature used to establish mechanical properties.7.1.6 Test specimen orientation relative to the axis of majormetal flow is to be at the discretion of the manufacturerprovided the requirements of Table 2 are met. Test specimenorientation shall
41、be reported.7.1.7 Yield point shall be determined on carbon steel GradesAthrough F, and yield strength on alloy steel Grades G throughN. For carbon steel grades not showing a yield point, the yieldstrength at 0.2 % offset shall be reported.7.2 Hardness TestsBrinell hardness tests shall be per-formed
42、 and reported per Test Methods and Definitions A370.Hardness testing shall be performed after heat treatment(except on Class A forgings) and rough machining on eachforging weighing under 7000 lb 3200 kg at the time of heattreatment and each multiple forging made in accordance with7.1.3.3 weighing un
43、der 7000 lb 3200 kg at the time of heattreatment.7.2.1 Hardness testing on forgings in excess of 7000 lb3200 kg at the time of heat treatment may be omittedprovided they meet the tensile requirements of Table 2. Foradditional exceptions see 7.1.3.4 and 7.3.7.2.2 When ordered without rough machining,
44、 hardnessmeasurements shall be conducted on the forgings after heattreatment. Due consideration should be provided for theremoval of oxidation and decarburization to ensure accuracy ofhardness results when forgings which have not been roughmachined are evaluated.7.2.3 The average value of the hardne
45、ss readings on eachforging shall fall within the hardness ranges specified in Table2. The permissible variation in hardness in any forging over250 lb 110 kg shall not exceed 30 Brinell Hardness forClassesAthrough E, 40 Brinell Hardness for Classes F throughJ, 50 Brinell Hardness for Classes K throug
46、h N.7.2.4 At least two hardness tests shall be taken on each flatface of disks, rings, and hollow forgings over 250 lb 110 kgapproximately at mid-radius for disk forgings and mid-wall forring and hollow forgings. When it is impractical to checkhardness on the face of hollow forgings these checks sha
47、ll bemade at each end on the OD or the ID at a distance equivalentto12 the wall thickness from each end of the forging. Hardnesschecks shall be 180 apart, for example, at the 3:00 and 9:00positions on one face, and 6:00 and 12:00 positions on theopposite face. On solid forgings over 250 lb 110 kg, a
48、t leastfour tests shall be taken on the periphery of the forging, two ateach end 180 apart.7.2.5 For forgings 250 lb 110 kg and less, Brinell testingshall be performed on one of the following: the test materialprior to machining the test specimen, the broken test specimensor the forgings themselves.
49、 Hardness tests shall be conductedon material representing the heat or heats included in each heattreating charge, or in the case of untreated forgings (Class A),on material representing each heat. The results shall meet therequirements of Table 2. If the purchaser desires Brinell testingof each forging, Supplementary Requirement S11 may be used.7.3 If so specified by the purchaser, forgings may besupplied on the basis of hardness tests alone. If this option isexercised, the class shall be identified in certification andmarki
