1、Designation: F2328 05 (Reapproved 2011)Standard Test Method forDetermining Decarburization and Carburization in Hardenedand Tempered Threaded Steel Bolts, Screws and Studs1This standard is issued under the fixed designation F2328; the number immediately following the designation indicates the year o
2、foriginal adoption 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. Scope1.1 This test method covers procedures for measuring,classifyi
3、ng, and determining the presence of decarburizationand carburization in the threaded section of hardened andtempered inch series steel bolts, screws, studs, and similar partswhich have been heated to facilitate fabrication or to modify itsmechanical properties. This test method is not intended toadd
4、ress products which are intentionally carburized to achievespecific 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 ex
5、amina-tions. The microindentation method 2 shall be considered thereferee method.1.3 For the purpose of these tests, there are three 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
6、 units 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 and health
7、practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE384 Test Method for Knoop and Vickers Hardness ofMaterialsF1789 Terminology for F16 Mechanical Fasteners3. Terminology3.1
8、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 associated with heat treatment.3.1.3 gross
9、 decarburizationalso known as complete de-carburization, 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 than that of the immediately adja
10、cent 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 created during the rod rolling pro
11、cess,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 greater the tensile strength of the
12、 product, themore susceptible to failure the product becomes if these limitsare exceeded.4.2 When testing to a particular 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 via
13、ble methods available to detectthese deficiencies, either by the visual method or the microin-dentation method. Both 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 represe
14、ntative of the whole part, the referee method em-ploys the microindentation method taken as an average ofevaluations conducted on four adjacent threads. This procedure1This test method is under the jurisdiction of ASTM Committee F16 onFasteners and is the direct responsibility of Subcommittee F16.01
15、 on Test Methods.Current edition approved May 1, 2011. Published June 2011. Originallyapproved in 2004. Last previous edition approved in 2005 as F2328 05. DOI:10.1520/F2328-05R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org
16、. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.significantly reduces the random test variables when comparedto te
17、sting 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 either test method isperformed, both conditions will be apparent and shall bereported. For example, if an order is pla
18、ced 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 Decarburization5.1 Class DeterminationThese measurements by Classare predicated upon their relationship between the height
19、 (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 dimensions forN and H are listed in Table 2 for each Class. Dimension G(Table 1 and Fig. 1) represents the maximum depth of
20、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 The use of either the optical or microindentation methodrequires the finished product to be longitudinally cross-sectio
21、ned, approximately through the threaded axis, andmounted for grinding and polishing in any suitable mediumwhich will provide edge retention of the specimen. This shallbe performed in accordance with good metallographic practice.See Practice E3.7. Evaluation by the Optical Method7.1 Etch the mounted
22、specimen (Section 6)ina2to4%nital or picral solution to exhibit the microstructure. Examinethe specimen at 1003 magnification using a method capable ofmeasuring distances to at least 0.001 in. resolution. The widthof any light-etching band of martensite defines the depth ofdecarburization. Compare t
23、he 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).7.2 Interpretation of Results:7.2.1 Allowable limits for partial decarburization shall be inaccordance with 3.1.4 and Fi
24、g. 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 (G) shall bein accordance with 3.1.3 and the measured values as defined inTable 1. The optical method is the only vali
25、d 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 a darker shade than the immediately adjacent base metal.If visible evidence of surface carburization is present on th
26、esurface 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 zinc, where the coating canaffect the etching process and distort the appearance of the basematerial microstructure. Th
27、ese 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 coating removal process.7.2.5 If the results of the optical method indicate a possiblenonconformance in the measurement of p
28、artial decarburizationor carburization, or are otherwise inconclusive, the microin-dentation method (Section 8) shall be performed after thespecimens are repolished.8. Evaluation by the Microindentation Hardness Method8.1 Prepare the sample in accordance with Section 6 andperform measurements in acc
29、ordance 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 (HK) Vickers (HV)Less than 40 500 gf 300 gf40 through 48 200 gf 200 gfGreater than 48 100 gfA100 gfAALighter loads sha
30、ll 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 intersection of a plane at the thread root diameter anda perpendicular line bisecting the thread crest. Measurement atPos
31、ition 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 the product classification or productspecification. See Figs. 2 and 3.8.2.2 For Class 1 and 2 products, Position 3 hardness shallbe measured at a depth of
32、0.005 in. from the thread flank at anapproximate distance of H/2 as measured from the plane of thethread root diameter (Fig. 2).8.2.3 For Class 3 products, Position 3 hardness shall bemeasured at an approximate depth of 0.003 in. from the threadFIG. 1 Decarburization ZonesF2328 05 (2011)2flank at an
33、 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 as the readings atPositions 1 and 2 using the same hardness scale. The long axisof the Knoop indenter shall be alig
34、ned 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 to Position 2 indicates excessivedecarburization and that the part does not conform to thespecification. If a noncon
35、formance 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 be regardedas excessive carburization and the part does not conform to thespecification. If a nonconformance is indi
36、cated, proceed toReferee Test Method in 8.5 for verification.8.4 Decarburization Referee Test Method 2Measurement:8.4.1 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
37、adjacent threads. Determine the condition of thespecimen by subtracting the average reading 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 either
38、HK or HV from Position 1 to Position 2, the part does notconform to the specification limit.8.5 Carburization Referee Test Method 2Measurement:FIG. 2 Position for Microindentation MeasurementsFIG. 3 Microindentation Measurements for Class 3 ProductsTABLE 1 Classes of Decarburization: GuideClass N G.
39、 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, or both.223 H 0.0006 in. For products with a minimum tensile strengthof 150 000 psi o
40、r a hardness range of 33 to39 HRC, or both.334 H none permitted For products with a minimum tensile strengthof 170 000 psi or a minimum specifiedhardness of 37 HRC, or both.F2328 05 (2011)38.5.1 Determine the base metal hardness as in 8.2.1, 8.2.2 or8.2.3, as appropriate, by taking the average of al
41、l Position 1 andPosition 3 readings, as first measured during the routine test,and then on three additional adjacent threads. Determine 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 se
42、ction will give evidenceof carburization if the average of the four readings indicates apositive value.8.5.2 Interpretation of ResultsIf 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 carbu
43、rization specification limit.9. Precision and Bias9.1 Precision and bias evaluations have not been conductedfor this test method. When such data is available, a precisionand bias section will be added.10. Keywords10.1 carburization; complete decarburization; decarburiza-tion; gross decarburization;
44、HK; HV; Knoop; microindenta-tion; partial decarburization; tempered martensite; VickersASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of
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46、our 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 commen
47、ts have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or mu
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49、tm.org/COPYRIGHT/).TABLE 2 Decarburization Limits per ClassificationNOTEAll values shown are in inches.Threadsper InchThreadHeightH (in.)N 0.1 HAClass 1minClass 2minClass 3minRootin.48 0.013 X X 0.010 0.00144 0.014 X X 0.011 0.00140 0.015 X X 0.011 0.00236 0.017 X X 0.013 0.00232 0.019 X X 0.014 0.00228 0.022 0.011 0.015 0.017 0.00224 0.026 0.013 0.017 0.020 0.00320 0.031 0.016 0.021 0.023 0.00318 0.034 0.017 0.023 0.026 0.00316 0.038 0.019 0.025 0.029 0.00414 0.044 0.022 0.029 0.033 0.00413 0.047 0.024 0.031 0.035 0.00512 0.051 0.026 0.034 0.038 0.00511 0.056 0.
