1、Designation: F2328 14F2328 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 ofori
2、ginal 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. Scope*1.1 This test method covers procedures for measuring, classifying
3、, and determining the presence of decarburization andcarburization in the threaded section of hardened and tempered inch series steel bolts, screws, studs, nuts, and similar parts whichhave been heated to facilitate fabrication or to modify their mechanical properties. This test method is not intend
4、ed to addressproducts which are intentionally carburized to achieve specific results.1.2 Two routine methods are described for measuring the limits of and determining the presence of decarburization orcarburizationthe optical method and the microindentation method 1. Either method is appropriate for
5、 routine examinations. Themicroindentation method 2 shall be considered the referee method.1.3 For the purpose of these tests, there are four classes of hardened and tempered steel products for which specificmeasurements must be made with respect to their physical properties.1.4 The values stated in
6、 inch-pound units are to be regarded as standard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety
7、 safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Developm
8、ent of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE384 Test Method for Microindentation Hardness of MaterialsF1789
9、 Terminology for F16 Mechanical Fasteners3. Terminology3.1 Definitions:3.1.1 carburizationprocess or result of increasing the carbon content of the surface layers of the steel fastener product.3.1.2 decarburizationin accordance with Terminology F1789, is a loss of carbon from the surface layer of th
10、e fastener,normally associated with heat treatment.3.1.3 gross decarburizationalso known as complete decarburization, is characterized by a sufficient carbon loss to show onlyclearly defined ferrite grains.3.1.4 partial decarburizationcharacterized as a loss of carbon sufficient to cause a lighter s
11、hade of tempered martensite thanthat of the immediately adjacent base metal, but as being of insufficient carbon loss to show clearly defined ferrite grains.1 This test method is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.01 on Test
12、 Methods.Current edition approved Aug. 1, 2014Sept. 1, 2017. Published September 2014September 2017. Originally approved in 2004. Last previous edition approved in 20112014as F2328 05F2328 14.(2011). DOI: 10.1520/F2328-14.10.1520/F2328-17.2 For referencedASTM standards, visit theASTM website, www.as
13、tm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what c
14、hanges have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the of
15、ficial document.*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 States14. Significance and Use4.1 Decarburization and carburization are two surface conditions created, either i
16、ntentionally or unintentionally, as with apre-existing condition created during the rod rolling process, the rod/wire annealing process, or while heat treating threaded steelproducts. Too much of either will adversely affect the safety and performance of the threaded product. Therefore, limits have
17、beenestablished for three different product groups: the harder and greater the tensile strength of the product, the more susceptible tofailure the product becomes if these limits are exceeded.4.2 When testing to a particular product specification that lists the dimensions and microindentation data t
18、o be used, that datashall take precedence over the tables in this test method.4.3 There are only two viable methods available to detect these deficiencies, either by the visual method or the microindentationmethod. Both methods are used for routine inspections when evaluations are conducted at a sin
19、gle location on the product sample.4.3.1 Because an evaluation at a specific location may not be representative of the whole part, the referee method employs themicroindentation method taken as an average of evaluations conducted on four adjacent threads. This procedure significantlyreduces the rand
20、om test variables when compared to testing on a single thread.4.4 Specifying this test method does not specify or imply that testing shall be for either decarburization or carburization aloneor for both conditions. When either test method is performed, both conditions will be apparent and shall be r
21、eported. For example,if an order is placed to test for decarburization and none is found, but the presence of carburization is detected, it shall be reportedon the test report that carburization was found.5. Class of Decarburization5.1 Class DeterminationThese measurements by Class are predicated up
22、on their relationship between the height (H) of theexternal thread at its maximum boundary, disregarding any surface coating, and N, which is the minimum thread height in thenon-decarburized zone (see Figs. 1-3). The dimensions for N and H are listed in Table 2 for each Class. Dimension G (Table 1an
23、d Fig. 1) represents the maximum depth of gross or complete decarburization.NOTE 1Refer to the product standard for specific requirements. When limits are not specified, use Table 1 as a suggested reference.6. Preparation6.1 The use of either the optical or microindentation method requires the finis
24、hed product to be longitudinally cross-sectioned,approximately through the threaded axis, and mounted for grinding and polishing in any suitable medium which will provide edgeretention of the specimen. This shall be performed in accordance with good metallographic practice. See Practice E3.7. Evalua
25、tion by the Optical Method7.1 Etch the mounted specimen (Section 6) in a 2 to 4 % nital or picral solution to exhibit the microstructure. Examine thespecimen at 100 magnification using a method capable of measuring distances to at least 0.001 in. resolution. The width of anylight-etching band of mar
26、tensite defines the depth of decarburization. Compare the image with Fig. 1 for the maximum limits forG by taking a measurement on a line perpendicular to the flank of the thread midway between the thread crest and root (pitchdiameter).7.2 Interpretation of Results:7.2.1 Allowable limits for partial
27、 decarburization shall be in accordance with 3.1.4 and Fig. 1, and the measured values shallbe in accordance with Table 2, when measured in accordance with the illustrations in Figs. 2 and 3.7.2.2 Allowable limits for gross decarburization (G) shall be in accordance with 3.1.3 and the measured value
28、s as defined inTable 1. The optical method is the only valid method for evaluating the depth of gross decarburization. Gross decarburization isprohibited in Class 3 products.7.2.3 Carburization is identified when the tempered martensite is a darker shade than the immediately adjacent base metal. Ifv
29、isible evidence of surface carburization is present on the surface zone, the microindentation method, in accordance with Section8, shall be used.7.2.4 The optical method may not be appropriate for specimens with certain coatings, such as zinc, where the coating can affectthe etching process and dist
30、ort the appearance of the base material microstructure. These coatings shall be removed prior tomounting if the coating prevents proper etching. Care must also be exercised to not alter the surface condition of the substrateduring the coating removal process.FIG. 1 Decarburization ZonesF2328 1727.2.
31、5 If the results of the optical method indicate a possible nonconformance in the measurement of partial decarburization orcarburization, or are otherwise inconclusive, the microindentation method (Section 8) shall be performed after the specimens arerepolished.8. Evaluation by the Microindentation H
32、ardness Method8.1 Prepare the sample in accordance with Section 6 and perform measurements in accordance with Test Method E384 onpolished and unetched specimens. Use either a Vickers (136) indenter or a Knoop indenter with the following load requirements:FIG. 2 Position for Microindentation Measurem
33、entsFIG. 3 Microindentation Measurements for Class 3 ProductsTABLE 1 Classes of Decarburization: GuideClass N G. max Typical Applications1 12 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 har
34、dness range of 24 to 34HRC, or both2 23 H 0.0006 in. For products with a minimum tensile strengthof 150 000 psi or a hardness range of 33 to39 HRC, or both3 34 H none permitted For products with a minimum tensile strengthof 170 000 psi or a minimum specifiedhardness of 37 HRC, or both4 12 H 0.0006 i
35、n. For heat treated nuts with hardness2438HRCF2328 173Threads per Inch LoadKnoop (HK) Vickers (HV)Less than 40 500 gf 300 gf40 through 48 200 gf 200 gfGreater than 48 100 gfA 100 gfAA Lighter loads shall be used if the size of the part warrants.8.2 Routine Decarburization/Carburization Test Method 1
36、Measurement:8.2.1 Determine the base metal hardness (Position 1) that is near the intersection of a plane at the thread root diameter and aperpendicular line bisecting the thread crest. Measurement at Position 2 is taken on the same thread crest bisector line from Position1 to an approximate distanc
37、e N as determined in Table 2, and as specified by the product classification or product specification.See Figs. 2 and 3.8.2.2 For Class 1 1, 2, and 24 products, Position 3 hardness shall be measured at a depth of 0.005 in. from the thread flank atan approximate distance of H/2 as measured from the p
38、lane of the thread root diameter (Fig. 2).8.2.3 For Class 3 products, Position 3 hardness shall be measured at an approximate depth of 0.003 in. from the thread flankat an approximate distance of H/2, as measured from the plane of the thread root diameter (Fig. 3).8.2.4 Position 3 readings shall be
39、taken on the same or adjacent thread and at the same time as the readings at Positions 1 and2 using the same hardness scale. The long axis of the Knoop indenter shall be aligned approximately parallel with the thread pitchangle at Position 3.8.3 Interpretation of Results:8.3.1 A decrease of more tha
40、n 30 hardness points of either HK or HV between Position 1 to Position 2 indicates excessivedecarburization and that the part does not conform to the specification. If a nonconformance is indicated, proceed to Referee TestMethod in 8.4 for verification.8.3.2 An increase of more than 30 hardness poin
41、ts of either HK or HV between Position 1 to Position 3 shall be regarded asexcessive carburization and the part does not conform to the specification. If a nonconformance is indicated, proceed to RefereeTest Method in 8.5 for verification.8.4 Decarburization Referee Test Method 2Measurement:8.4.1 De
42、termine the base metal hardness as in 8.2.1 by taking the average of all Position 1 and Position 2 readings, as firstmeasured during the routine test, and then on three additional adjacent threads. Determine the condition of the specimen bysubtracting the average reading noted at Position 2 from the
43、 average reading noted at Position 1, in accordance with 8.3.1.8.4.2 Interpretation of ResultsIf the average of the four readings indicates a decrease of more than 30 points of either HK orHV from Position 1 to Position 2, the part does not conform to the specification limit.8.5 Carburization Refere
44、e Test Method 2Measurement:TABLE 2 Decarburization Limits per ClassificationNOTE 1All 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
45、 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 0.028 0.037 0.042 0.006
46、10 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 0.015A For Class 3 product only, in reference to Fig.
47、3.F2328 1748.5.1 Determine the base metal hardness as in 8.2.1, 8.2.2 or 8.2.3, 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 the conditionof the specimen by subtract
48、ing the average reading noted at Position 1 from the average reading noted at Position 3, as definedin 8.3.2. The threaded section will give evidence of carburization if the average of the four readings indicates a positive value.8.5.2 Interpretation of ResultsIf the average of the four readings ind
49、icates an increase of more than 30 points of either HVor HK from Position 1 to Position 3, the part does not conform to the carburization specification limit.9. Precision and Bias9.1 Precision and bias evaluations have not been conducted for this test method. When such data is available, a precision andbias section will be added.10. Keywords10.1 carburization; complete decarburization; decarburization; gross decarburization; HK; HV; Knoop; microindentation;partial decarburization; tempered martensite; VickersSUMMARY OF CHANGESCommittee F16 has identified
