1、Designation: F 2328 05Standard Test Method forDetermining Decarburization and Carburization in Hardenedand Tempered Threaded Steel Bolts, Screws and Studs1This standard is issued under the fixed designation F 2328; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for measuring,classifying, and determi
3、ning 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 toaddress products w
4、hich 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 examina-tions. Th
5、e 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 This standard does not purport to address all
6、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 practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E3 Practice for Prepar
7、ation of Metallographic SpecimensE 384 Test Method for Microindentation Hardness of Ma-terialsF 1789 Terminology for F16 Mechanical 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 dec
8、arburizationin accordance with TerminologyF 1789, is a loss of carbon from the surface layer of thefastener, normally associated with heat treatment.3.1.3 gross decarburizationalso known as complete de-carburization, is characterized by a sufficient carbon loss toshow only clearly defined ferrite gr
9、ains.3.1.4 partial decarburizationcharacterized as a loss ofcarbon sufficient to cause a lighter shade of tempered marten-site 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 an
10、d carburization are two surface con-ditions created, either intentionally or unintentionally, as witha pre-existing condition 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 p
11、erformance of the threaded product. Therefore,limits have been established for three different product groups:the harder and greater the tensile strength of the product, themore susceptible to failure the product becomes if these limitsare exceeded.4.2 When testing to a particular product specificat
12、ion 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. Both methods are used for ro
13、utine 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 ofevaluations conducted on four adjac
14、ent threads. This proceduresignificantly reduces the random test variables when comparedto testing on a single thread.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 May 1,
15、2005. Published May 2005. Originallyapproved in 2004. Last previous edition approved in 2004 as F 2328 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standa
16、rds Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.4 Specifying this test method does not specify or implythat testing shall be for either decarburization or carburizationalone or for both
17、conditions. When 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
18、.5. Class of Decarburization5.1 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.
19、 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 gross orcomplete decarburization.NOTE 1Refer to the product standard for specific requirements. Whenlimits are not specified, use Table 1 as a suggested reference.6.
20、 Preparation6.1 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 sha
21、llbe performed in 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 1003 magnification using a method capable ofmeasuring dist
22、ances to at least 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 (p
23、itch diameter).7.2 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
24、 decarburization (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 temper
25、ed marten-site is 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 co
26、atings, such as zinc, 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
27、during the coating 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.
28、8. Evaluation by the Microindentation Hardness Method8.1 Prepare the sample in accordance with Section 6 andperform measurements in accordance with Test Method E 384on polished and unetched specimens. Use either a Vickers(136) indenter or a Knoop indenter with the following loadrequirements:Threads
29、per InchLoadKnoop (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) t
30、hat isnear the intersection of a plane at the thread root diameter anda 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 the product classif
31、ication 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 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
32、 3 hardness shall bemeasured at an approximate depth of 0.003 in. from the threadFIG. 1 Decarburization ZonesF2328052flank 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 t
33、he same time 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
34、 Position 1 to 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 Posit
35、ion 3 shall be 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:8.4.1 Determine the base metal hardness as in 8.2.1 bytaki
36、ng 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 reading noted at Position2 from the average reading noted at Position 1, in accordancewi
37、th 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 limit.8.5 Carburization Referee Test Method 2Measurement:FIG. 2 Position for Microinde
38、ntation MeasurementsFIG. 3 Microindentation 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 0
39、00 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 or 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
40、.F23280538.5.1 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 thecondition of the specimen by subtracting
41、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 the average of the fourreadings indicates a
42、n 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 such data is available, a precisionand bias s
43、ection will be added.10. Keywords10.1 carburization; complete decarburization; decarburiza-tion; gross decarburization; HK; HV; Knoop; microindenta-tion; partial decarburization; tempered martensite; VickersASTM International takes no position respecting the validity of any patent rights asserted in
44、 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 the re
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46、ful 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 below.This standard is copyrighted by ASTM Internationa
47、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the A
48、STM website(www.astm.org).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.
49、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 0.028 0.037 0.042 0.00610 0.061 0.031 0.041 0.046 0.0069 0.068 0.034 0.045 0.051 0.0078 0.077 0.039 0.051 0.058 0.0087 0.088 0.044 0.059 0.066 0.0096 0.102 0.051 0.068 0.077 0.0105 0.123 0.062 0.082 0.092 0.0124.5 0.136 0.068 0.091 0.102 0.0144 0.153 0.077 0.102 0.115 0.015AFor Class 3 product onl
