1、Designation: A668/A668M 15 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X1 lists the current classes corresponding tothe various classes of Specifications A235, A237, and A243,which have been superseded by this specification.1.7 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard; within t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.2. Referenced Documents2.1 ASTM Standards:2A275/A275M Practice for Magnetic Particle Examination ofSteel ForgingsA370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA388/A388M Practice for Ultraso
9、nic Examination of SteelForgingsA788/A788M Specification for Steel Forgings, General Re-quirementsE290 Test Methods for Bend Testing of Material for Ductil-ityE340 Test Method for Macroetching Metals and Alloys3. Terminology3.1 The terminology section of Specification A788/A788Mis applicable to this
10、 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 inscribed withinthe volu
11、me of the forging.3.2.3 TPdesignates prolongations which have a size otherthan the controlling cross section thickness (TC).4. Ordering Information and General Requirements4.1 Material supplied to this specification shall conform tothe requirements of Specification A788/A788M which outlinesadditiona
12、l ordering information, manufacturing requirements,testing and retesting methods and procedures, marking,certification, product analysis variations and additional supple-mentary requirements.1This specification is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Allo
13、ys and is the direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current edition approved March 1, 2015. Published March 2015. Originallyapproved in 1972. Last previous edition approved in 2014 as A668/A668M 14.DOI: 10.1520/A0668_A0668M-15.2For referenced ASTM standards, visit
14、 the ASTM website, www.astm.org, orcontact ASTM Customer 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
15、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.1.1 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 specification is to be applied to an in
16、quiry,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 testspecimens are to be located in accordanc
17、e 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 segregation.5.2 Forging Process:5.2
18、.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 may bespecified by the purchaser to satisfy concerns about the utilityof the proposed forging.5.3 Heat Treatment:5.3.1 All forgings, other than Cla
19、ss 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 conform to the requirements presc
20、ribedin 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 analysis may be made by thepurchas
21、er 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 composition limits have not beensupplied, t
22、he 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 propertiesprescribed in Table 2. See Test Methods and Definitions A370.7.1.2 All ForgingsThe dimensions of the controlling crosss
23、ection 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 accordance with the requirementsof 7.3, the num
24、ber 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 each heat in each annealing ornormalizing ch
25、arge, 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 classes, for forgings with as-heat treatedweigh
26、ts (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 taken: on ring and disk forgings 180apart; on sh
27、afts 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.7.1.3.4 When forgings are made in multiple as a s
28、ingleforging, 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 sufficient number of the forgings shall haveprolon
29、gations 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 possible test prolongationconfigurations which meet
30、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 dimension ofTPshall determine the mechanical
31、 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 length axis of tension test specimens shall be14
32、thecontrolling cross section thickness (TC) from one surfaceexcept as noted in 7.1.4.2 (2).(2) If the prolongation thickness (TP) is less than thecontrolling cross section thickness (TC) the center of the gagelength axis of the tension test shall be of the prolongationthickness (TP) from one surface
33、.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.A668/A668M 1527.1.4.4 In place of prolongations, the manufacturer may:
34、 (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 hotworking it represents, be of the same controll
35、ing 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 prior purchaser approval, test specimens may
36、be 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-treatedsurface than34 in. 19 mm and to the second heat tre
37、atedsurface 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 is complete shall not exceed 50F 30C less th
38、an 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 be reported.7.1.7 Yield point shall be determin
39、ed 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 after heat treatment (except on Class A forgin
40、gs) andrough machining on each forging weighing under 7000 lb3200 kg at the time of heat treatment and each multipleforging made in accordance with 7.1.3.3 weighing under 7000lb 3200 kg at the time of heat treatment.7.2.1 Hardness testing on forgings in excess of 7000 lb3200 kg at the time of heat t
41、reatment 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, hardnessmeasurements shall be conducted on the forgings after heattreatment. Due consideration should be provided for theremoval of
42、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 hardness readings on eachforging shall fall within the hardness ranges specified in Table2. The permissible variation in hardness in any fo
43、rging over250 lb 110 kg shall not exceed 30 HBWfor ClassesAthroughE, 40 HB for Classes F through J, 50 HB for Classes K throughN.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 and 180 apart, for exa
44、mple, at the3:00 and 9:00 positions on one face, and 6:00 and 12:00positions on the opposite face. On solid forgings over 250 lb110 kg, at least four tests shall be taken on the periphery ofthe forging, two at each end 180 apart.7.2.5 For forgings 250 lb 110 kg and less, Brinell testingshall be perf
45、ormed on one of the following: the test materialprior to machining the test specimen, the broken test specimensor the forgings themselves. 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),
46、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
47、 isexercised, the class shall be identified in certification andmarking with the suffix “H,” that is, “AH,” “BH,” “CH,” etc.8. Retreatment8.1 When heat-treated forgings are specified, and the me-chanical test results of any test lot do not conform to therequirements specified, the manufacturer may r
48、e-austenitizethe lot not more than three additional times, and retests shall bemade according to Section 7. Multiple retempering is notprecluded by this requirement.8.2 When untreated forgings (ClassA) are specified, and themechanical test results of any test lot do not conform to therequirements sp
49、ecified, the manufacturer may anneal,normalize, or normalize and temper, one or more times, but notmore than three times; and retests shall be made in accordancewith Section 7. The tensile properties shall conform to therequirements for the class of forgings ordered (Class A).9. Inspection, Rejection, and Certification9.1 Facilities for inspection at the place of manufacture,rejection of forgings and certification shall comply with Speci-fication A788/A788M.10. Product Marking10.1 The marking requirements of Specification A78
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