ASTM F2328-17(2022)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2328 − 17 (Reapproved 2022)
Standard Test Method for
Determining Decarburization and Carburization in Hardened
and Tempered Threaded Steel Bolts, Screws, Studs, and
Nuts
This standard is issued under the fixed designation F2328; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers procedures for measuring,
E3Guide for Preparation of Metallographic Specimens
classifying, and determining the presence of decarburization
E384Test Method for Microindentation Hardness of Mate-
and carburization in the threaded section of hardened and
rials
temperedinchseriessteelbolts,screws,studs,nuts,andsimilar
F1789Terminology for F16 Mechanical Fasteners
parts which have been heated to facilitate fabrication or to
modify their mechanical properties. This test method is not
3. Terminology
intendedtoaddressproductswhichareintentionallycarburized
to achieve specific results.
3.1 Definitions:
3.1.1 carburization—process or result of increasing the
1.2 Two routine methods are described for measuring the
carbon content of the surface layers of the steel fastener
limits of and determining the presence of decarburization or
product.
carburization—the optical method and the microindentation
method 1. Either method is appropriate for routine examina- 3.1.2 decarburization—in accordance with Terminology
F1789,isalossofcarbonfromthesurfacelayerofthefastener,
tions. The microindentation method 2 shall be considered the
normally associated with heat treatment.
referee method.
3.1.3 gross decarburization—also known as complete
1.3 For the purpose of these tests, there are four classes of
decarburization, is characterized by a sufficient carbon loss to
hardened and tempered steel products for which specific
show only clearly defined ferrite grains.
measurements must be made with respect to their physical
properties. 3.1.4 partial decarburization—characterized as a loss of
carbon sufficient to cause a lighter shade of tempered marten-
1.4 Thevaluesstatedininch-poundunitsaretoberegarded
site than that of the immediately adjacent base metal, but as
asstandard.Nootherunitsofmeasurementareincludedinthis
being of insufficient carbon loss to show clearly defined ferrite
standard.
grains.
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 Decarburization and carburization are two surface con-
priate safety, health, and environmental practices and deter-
ditions created, either intentionally or unintentionally, as with
mine the applicability of regulatory limitations prior to use.
a pre-existing condition created during the rod rolling process,
1.6 This international standard was developed in accor-
the rod/wire annealing process, or while heat treating threaded
dance with internationally recognized principles on standard-
steel products. Too much of either will adversely affect the
ization established in the Decision on Principles for the
safety and performance of the threaded product. Therefore,
Development of International Standards, Guides and Recom-
limits have been established for three different product groups:
mendations issued by the World Trade Organization Technical
the harder and greater the tensile strength of the product, the
Barriers to Trade (TBT) Committee.
more susceptible to failure the product becomes if these limits
are exceeded.
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2022. Published December 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2004. Last previous edition approved in 2017 as F2328–17. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F2328-17R22. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2328 − 17 (2022)
4.2 When testing to a particular product specification that of any light-etching band of martensite defines the depth of
lists the dimensions and microindentation data to be used, that decarburization. Compare the image with Fig. 1 for the
data shall take precedence over the tables in this test method. maximum limits for G by taking a measurement on a line
perpendicular to the flank of the thread midway between the
4.3 There are only two viable methods available to detect
thread crest and root (pitch diameter).
these deficiencies, either by the visual method or the microin-
dentation method. Both methods are used for routine inspec- 7.2 Interpretation of Results:
tionswhenevaluationsareconductedatasinglelocationonthe 7.2.1 Allowablelimitsforpartialdecarburizationshallbein
product sample. accordancewith3.1.4andFig.1,andthemeasuredvaluesshall
4.3.1 Because an evaluation at a specific location may not be in accordance with Table 2, when measured in accordance
be representative of the whole part, the referee method em- with the illustrations in Figs. 2 and 3.
ploys the microindentation method taken as an average of 7.2.2 Allowablelimitsforgrossdecarburization(G)shallbe
evaluationsconductedonfouradjacentthreads.Thisprocedure inaccordancewith3.1.3andthemeasuredvaluesasdefinedin
significantlyreducestherandomtestvariableswhencompared Table 1. The optical method is the only valid method for
to testing on a single thread. evaluating the depth of gross decarburization. Gross decarbur-
ization is prohibited in Class 3 products.
4.4 Specifying this test method does not specify or imply
7.2.3 Carburization is identified when the tempered marten-
that testing shall be for either decarburization or carburization
siteisadarkershadethantheimmediatelyadjacentbasemetal.
alone or for both conditions. When either test method is
If visible evidence of surface carburization is present on the
performed, both conditions will be apparent and shall be
surfacezone,themicroindentationmethod,inaccordancewith
reported. For example, if an order is placed to test for
Section 8, shall be used.
decarburization and none is found, but the presence of carbur-
7.2.4 The optical method may not be appropriate for speci-
ization is detected, it shall be reported on the test report that
menswithcertaincoatings,suchaszinc,wherethecoatingcan
carburization was found.
affecttheetchingprocessanddistorttheappearanceofthebase
material microstructure.These coatings shall be removed prior
5. Class of Decarburization
to mounting if the coating prevents proper etching. Care must
5.1 Class Determination—These measurements by Class
also be exercised to not alter the surface condition of the
arepredicatedupontheirrelationshipbetweentheheight(H)of
substrate during the coating removal process.
the external thread at its maximum boundary, disregarding any
7.2.5 If the results of the optical method indicate a possible
surface coating, and N, which is the minimum thread height in
nonconformanceinthemeasurementofpartialdecarburization
the non-decarburized zone (see Figs. 1-3). The dimensions for
or carburization, or are otherwise inconclusive, the microin-
N and H are listed in Table 2 for each Class. Dimension G
dentation method (Section 8) shall be performed after the
(Table 1 and Fig. 1) represents the maximum depth of gross or
specimens are repolished.
complete decarburization.
NOTE1—Refertotheproductstandardforspecificrequirements.When
8. Evaluation by the Microi
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