1、Designation: F2328 05 (Reapproved 2011)F2328 14Standard Test Method forDetermining Decarburization and Carburization in Hardenedand Tempered Threaded Steel Bolts, Screws Screws, Studs,and StudsNuts1This standard is issued under the fixed designation F2328; the number immediately following the design
2、ation indicates the year oforiginal 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 Scope*1.1 This test method covers p
3、rocedures for measuring, classifying, 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 itstheir mechanical pro
4、perties. This test method is not intended 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 met
5、hod 1. Either method is appropriate for routine examinations. Themicroindentation method 2 shall be considered the referee method.1.3 For the purpose of these tests, there are threefour classes of hardened and tempered steel products for which specificmeasurements must be made with respect to their
6、physical properties.1.4 The values stated in 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 t
7、his standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE384 Test Method for Knoop and Vickers Hardness of MaterialsF1789 Ter
8、minology 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 the fa
9、stener,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 shade
10、 of tempered martensite thanthat of the immediately adjacent base metal, but as being of insufficient carbon loss to show clearly defined ferrite grains.4. Significance and Use4.1 Decarburization and carburization are two surface conditions created, either intentionally or unintentionally, as with a
11、pre-existing condition created during the rod rolling process, the rod/wire annealing process, or while heat treating threaded steel1 This test method is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.01 on Test Methods.Current edition
12、approved May 1, 2011Aug. 1, 2014. Published June 2011September 2014. Originally approved in 2004. Last previous edition approved in 20052011 asF2328 05.F2328 05(2011). DOI: 10.1520/F2328-05R11.10.1520/F2328-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Custom
13、er 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 changes have been made to the
14、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 official document.*A Summary of
15、 Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1products. Too much of either will adversely affect the safety and performance of the threaded product. Therefore, limits have beenesta
16、blished 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 to be use
17、d, 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 single loca
18、tion 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 random test
19、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 reported.
20、 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 upon their
21、 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 1and Fig. 1
22、) 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 finished prod
23、uct 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. Evaluation by
24、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 martensite
25、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 decarbu
26、rization 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 values as def
27、ined 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. Ifvisible e
28、vidence 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 distort the
29、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.7.2.5 If the results of the optical method indica
30、te 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.FIG. 1 Decarburization ZonesF2328 1428. Evaluation by the Microindentation Hardness
31、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:Threads per Inch LoadKnoop (HK) Vickers (HV)Less than
32、 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 1Measurement:8.2.1 Determine the base metal hardness (Position 1) that is near the intersection of a plane a
33、t 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 distance N as determined in Table 2, and as specified by the product classification or product specification.See F
34、igs. 2 and 3.8.2.2 For Class 1 and 2 products, Position 3 hardness shall be measured at a depth of 0.005 in. from the thread flank at anapproximate distance of H/2 as measured from the plane of the thread root diameter (Fig. 2).8.2.3 For Class 3 products, Position 3 hardness shall be measured at an
35、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 taken on the same or adjacent thread and at the same time as the readings at Positions 1 and2 using the same hardn
36、ess 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:FIG. 2 Position for Microindentation MeasurementsFIG. 3 Microindentation Measurements for Class 3 ProductsF2328 1438.3.1 A decrease of more th
37、an 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 poi
38、nts 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:TABLE 1
39、 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 hardness range of 24 to 34HRC, or both.2 23 H 0.0006 in. For products w
40、ith a minimum tensile strengthof 150 000 psi or a hardness range of 33 to39 HRC, or both.3 34 H none permitted For products with a minimum tensile strengthof 170 000 psi or a minimum specifiedhardness of 37 HRC, or both.TABLE 1 Classes of Decarburization: GuideClass N G. max Typical Applications1 12
41、 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 both2 23 H 0.0006 in. For products with a minimum tensile strengthof 150 000 psi or a hardness range of 33 to3
42、9 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 in. For heat treated nuts with hardness2438HRCTABLE 2 Decarburization Limits per ClassificationNOTE 1All values shown are in inches.Threadsper
43、 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
44、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 0.0
45、096 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. 3.F2328 1448.4.1 Determine the base metal hardness as in 8.2.1 by taking the average of all Position 1 and Position 2 readi
46、ngs, 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 average reading noted at Position 1, in accordance with 8.3.1.8.4.2 Interpretation of ResultsIf the ave
47、rage 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 Referee Test Method 2Measurement:8.5.1 Determine the base metal hardness as in 8.2.1, 8.2.2 or 8.2.3, as appro
48、priate, 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 subtracting the average reading noted at Position 1 from the average reading noted at Position 3
49、, 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 indicates 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.
