1、Designation: F2328 17Standard Test Method forDetermining Decarburization and Carburization in Hardenedand Tempered Threaded Steel Bolts, Screws, Studs, andNuts1This standard is issued under the fixed designation F2328; the number immediately following the designation indicates the year oforiginal ad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers procedures for measuring,classifying, and det
3、ermining the presence of decarburizationand carburization in the threaded section of hardened andtempered inch series steel bolts, screws, studs, nuts, and similarparts which have been heated to facilitate fabrication or tomodify their mechanical properties. This test method is notintended to addres
4、s products which are intentionally carburizedto achieve specific results.1.2 Two routine methods are described for measuring thelimits of and determining the presence of decarburization orcarburizationthe optical method and the microindentationmethod 1. Either method is appropriate for routine exami
5、na-tions. The microindentation method 2 shall be considered thereferee method.1.3 For the purpose of these tests, there are four classes ofhardened and tempered steel products for which specificmeasurements must be made with respect to their physicalproperties.1.4 The values stated in inch-pound uni
6、ts are to be regardedas standard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and en
7、vironmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 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 Stan
8、dards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE384 Test Method for Microindentation Hardness of Mate-rialsF1789 Terminology for F16 Me
9、chanical Fasteners3. Terminology3.1 Definitions:3.1.1 carburizationprocess or result of increasing thecarbon content of the surface layers of the steel fastenerproduct.3.1.2 decarburizationin accordance with TerminologyF1789, is a loss of carbon from the surface layer of the fastener,normally associ
10、ated with heat treatment.3.1.3 gross decarburizationalso known as completedecarburization, is characterized by a sufficient carbon loss toshow only clearly defined ferrite grains.3.1.4 partial decarburizationcharacterized as a loss ofcarbon sufficient to cause a lighter shade of tempered marten-site
11、 than that of the immediately adjacent base metal, but asbeing of insufficient carbon loss to show clearly defined ferritegrains.4. Significance and Use4.1 Decarburization and carburization are two surface con-ditions created, either intentionally or unintentionally, as witha pre-existing condition
12、created during the rod rolling process,the rod/wire annealing process, or while heat treating threadedsteel products. Too much of either will adversely affect thesafety and performance of the threaded product. Therefore,limits have been established for three different product groups:the harder and g
13、reater the tensile strength of the product, themore susceptible to failure the product becomes if these limitsare exceeded.1This test method is under the jurisdiction of ASTM Committee F16 onFasteners and is the direct responsibility of Subcommittee F16.01 on Test Methods.Current edition approved Se
14、pt. 1, 2017. Published September 2017. Originallyapproved in 2004. Last previous edition approved in 2014 as F2328 14. DOI:10.1520/F2328-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volum
15、e 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, PA 19428-2959. United StatesThis international standard was developed i
16、n 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 Organization Technical Barriers to Trade (TBT) Committee.14.2 When testing to a par
17、ticular product specification thatlists the dimensions and microindentation data to be used, thatdata shall take precedence over the tables in this test method.4.3 There are only two viable methods available to detectthese deficiencies, either by the visual method or the microin-dentation method. Bo
18、th methods are used for routine inspec-tions when evaluations are conducted at a single location on theproduct sample.4.3.1 Because an evaluation at a specific location may notbe representative of the whole part, the referee method em-ploys the microindentation method taken as an average ofevaluatio
19、ns conducted on four adjacent threads. This proceduresignificantly reduces the random test variables when comparedto testing on a single thread.4.4 Specifying this test method does not specify or implythat testing shall be for either decarburization or carburizationalone or for both conditions. When
20、 either test method isperformed, both conditions will be apparent and shall bereported. For example, if an order is placed to test fordecarburization and none is found, but the presence of carbur-ization is detected, it shall be reported on the test report thatcarburization was found.5. Class of Dec
21、arburization5.1 Class DeterminationThese measurements by Classare predicated upon their relationship between the height (H) ofthe external thread at its maximum boundary, disregarding anysurface coating, and N, which is the minimum thread height inthe non-decarburized zone (see Figs. 1-3). The dimen
22、sions forN and H are listed in Table 2 for each Class. Dimension G(Table 1 and Fig. 1) represents the maximum depth of gross orcomplete decarburization.NOTE 1Refer to the product standard for specific requirements. Whenlimits are not specified, use Table 1 as a suggested reference.6. Preparation6.1
23、The use of either the optical or microindentation methodrequires the finished product to be longitudinally cross-sectioned, approximately through the threaded axis, andmounted for grinding and polishing in any suitable mediumwhich will provide edge retention of the specimen. This shallbe performed i
24、n accordance with good metallographic practice.See Practice E3.7. Evaluation by the Optical Method7.1 Etch the mounted specimen (Section 6)ina2to4%nital or picral solution to exhibit the microstructure. Examinethe specimen at 100 magnification using a method capable ofmeasuring distances to at least
25、 0.001 in. resolution. The widthof any light-etching band of martensite defines the depth ofdecarburization. Compare the image with Fig. 1 for themaximum limits for G by taking a measurement on a lineperpendicular to the flank of the thread midway between thethread crest and root (pitch diameter).7.
26、2 Interpretation of Results:7.2.1 Allowable limits for partial decarburization shall be inaccordance with 3.1.4 and Fig. 1, and the measured values shallbe in accordance with Table 2, when measured in accordancewith the illustrations in Figs. 2 and 3.7.2.2 Allowable limits for gross decarburization
27、(G) shall bein accordance with 3.1.3 and the measured values as defined inTable 1. The optical method is the only valid method forevaluating the depth of gross decarburization. Gross decarbur-ization is prohibited in Class 3 products.7.2.3 Carburization is identified when the tempered marten-site is
28、 a darker shade than the immediately adjacent base metal.If visible evidence of surface carburization is present on thesurface zone, the microindentation method, in accordance withSection 8, shall be used.7.2.4 The optical method may not be appropriate for speci-mens with certain coatings, such as z
29、inc, where the coating canaffect the etching process and distort the appearance of the basematerial microstructure. These coatings shall be removed priorto mounting if the coating prevents proper etching. Care mustalso be exercised to not alter the surface condition of thesubstrate during the coatin
30、g removal process.7.2.5 If the results of the optical method indicate a possiblenonconformance in the measurement of partial decarburizationor carburization, or are otherwise inconclusive, the microin-dentation method (Section 8) shall be performed after thespecimens are repolished.8. Evaluation by
31、the Microindentation Hardness Method8.1 Prepare the sample in accordance with Section 6 andperform measurements in accordance with Test Method E384on polished and unetched specimens. Use either a Vickers(136) indenter or a Knoop indenter with the following loadrequirements:Threads per InchLoadKnoop
32、(HK) Vickers (HV)Less than 40 500 gf 300 gf40 through 48 200 gf 200 gfGreater than 48 100 gfA100 gfAALighter loads shall be used if the size of the part warrants.8.2 Routine Decarburization/Carburization Test Method1Measurement:8.2.1 Determine the base metal hardness (Position 1) that isnear the int
33、ersection of a plane at the thread root diameter andFIG. 1 Decarburization ZonesF2328 172a perpendicular line bisecting the thread crest. Measurement atPosition 2 is taken on the same thread crest bisector line fromPosition 1 to an approximate distance N as determined in Table2, and as specified by
34、the product classification or productspecification. See Figs. 2 and 3.8.2.2 For Class 1, 2, and 4 products, Position 3 hardnessshall be measured at a depth of 0.005 in. from the thread flankat an approximate distance of H/2 as measured from the planeof the thread root diameter (Fig. 2).8.2.3 For Cla
35、ss 3 products, Position 3 hardness shall bemeasured at an approximate depth of 0.003 in. from the threadflank at an approximate distance of H/2, as measured from theplane of the thread root diameter (Fig. 3).8.2.4 Position 3 readings shall be taken on the same oradjacent thread and at the same time
36、as the readings atPositions 1 and 2 using the same hardness scale. The long axisof the Knoop indenter shall be aligned approximately parallelwith the thread pitch angle at Position 3.8.3 Interpretation of Results:8.3.1 A decrease of more than 30 hardness points of eitherHK or HV between Position 1 t
37、o Position 2 indicates excessivedecarburization and that the part does not conform to thespecification. If a nonconformance is indicated, proceed toReferee Test Method in 8.4 for verification.8.3.2 An increase of more than 30 hardness points of eitherHK or HV between Position 1 to Position 3 shall b
38、e regardedas excessive carburization and the part does not conform to thespecification. If a nonconformance is indicated, proceed toReferee Test Method in 8.5 for verification.8.4 Decarburization Referee Test Method 2Measurement:FIG. 2 Position for Microindentation MeasurementsFIG. 3 Microindentatio
39、n Measurements for Class 3 ProductsTABLE 1 Classes of Decarburization: GuideClass N G. max Typical Applications112 H 0.0006 in. For heat treated products which have tensilestrengths up to 120 000 psi and those with aspecified minimum tensile strength of120 000 psi or a hardness range of 24 to 34HRC,
40、 or both223 H 0.0006 in. For products with a minimum tensile strengthof 150 000 psi or a hardness range of 33 to39 HRC, or both334 H none permitted For products with a minimum tensile strengthof 170 000 psi or a minimum specifiedhardness of 37 HRC, or both412 H 0.0006 in. For heat treated nuts with
41、hardness2438HRCF2328 1738.4.1 Determine the base metal hardness as in 8.2.1 bytaking the average of all Position 1 and Position 2 readings, asfirst measured during the routine test, and then on threeadditional adjacent threads. Determine the condition of thespecimen by subtracting the average readin
42、g noted at Position2 from the average reading noted at Position 1, in accordancewith 8.3.1.8.4.2 Interpretation of ResultsIf the average of the fourreadings indicates a decrease of more than 30 points of eitherHK or HV from Position 1 to Position 2, the part does notconform to the specification limi
43、t.8.5 Carburization Referee Test Method 2Measurement:8.5.1 Determine the base metal hardness as in 8.2.1, 8.2.2 or8.2.3, as appropriate, by taking the average of all Position 1 andPosition 3 readings, as first measured during the routine test,and then on three additional adjacent threads. Determine
44、thecondition of the specimen by subtracting the average readingnoted at Position 1 from the average reading noted at Position3, as defined in 8.3.2. The threaded section will give evidenceof carburization if the average of the four readings indicates apositive value.8.5.2 Interpretation of ResultsIf
45、 the average of the fourreadings indicates an increase of more than 30 points of eitherHV or HK from Position 1 to Position 3, the part does notconform to the carburization specification limit.9. Precision and Bias9.1 Precision and bias evaluations have not been conductedfor this test method. When s
46、uch data is available, a precisionand bias section will be added.10. Keywords10.1 carburization; complete decarburization; decarburiza-tion; gross decarburization; HK; HV; Knoop; microindenta-tion; partial decarburization; tempered martensite; VickersSUMMARY OF CHANGESCommittee F16 has identified th
47、e location of selected changes to this standard since the last issue (F232814)that may impact the use of this standard. (Approved September 1, 2017.)(1) Position 3 hardness location defined for Class 4 in 8.2.2.ASTM International takes no position respecting the validity of any patent rights asserte
48、d in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by th
49、e responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown bel
