ASTM F2328-05(2011)
(Test Method)Standard Test Method for Determining Decarburization and Carburization in Hardened and Tempered Threaded Steel Bolts, Screws and Studs
Standard Test Method for Determining Decarburization and Carburization in Hardened and Tempered Threaded Steel Bolts, Screws and Studs
SIGNIFICANCE AND USE
Decarburization and carburization are two surface conditions created, either intentionally or unintentionally, as with a pre-existing condition created during the rod rolling process, the rod/wire annealing process, or while heat treating threaded steel products. Too much of either will adversely affect the safety 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 product, the more susceptible to failure the product becomes if these limits are exceeded.
When testing to a particular product specification that lists the dimensions and microindentation data to be used, that data shall take precedence over the tables in this test method.
There are only two viable methods available to detect these deficiencies, either by the visual method or the microindentation method. Both methods are used for routine inspections when evaluations are conducted at a single location on the product sample.
Because an evaluation at a specific location may not be representative of the whole part, the referee method employs the microindentation method taken as an average of evaluations conducted on four adjacent threads. This procedure significantly reduces the random test variables when compared to testing on a single thread.
Specifying this test method does not specify or imply that testing shall be for either decarburization or carburization alone or for both conditions. When either test method is performed, both conditions will be apparent and shall be reported. 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 reported on the test report that carburization was found.
SCOPE
1.1 This test method covers procedures for measuring, classifying, and determining the presence of decarburization and carburization in the threaded section of hardened and tempered inch series steel bolts, screws, studs, and similar parts which have been heated to facilitate fabrication or to modify its mechanical properties. This test method is not intended to address products 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 or carburizationthe optical method and the microindentation method 1. Either method is appropriate for routine examinations. The microindentation method 2 shall be considered the referee method.
1.3 For the purpose of these tests, there are three classes of hardened and tempered steel products for which specific measurements must be made with respect to their 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 this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: F2328 − 05(Reapproved 2011)
Standard Test Method for
Determining Decarburization and Carburization in Hardened
and Tempered Threaded Steel Bolts, Screws and Studs
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 F1789Terminology for F16 Mechanical Fasteners
1.1 This test method covers procedures for measuring,
3. Terminology
classifying, and determining the presence of decarburization
3.1 Definitions:
and carburization in the threaded section of hardened and
3.1.1 carburization—process or result of increasing the
temperedinchseriessteelbolts,screws,studs,andsimilarparts
carbon content of the surface layers of the steel fastener
whichhavebeenheatedtofacilitatefabricationortomodifyits
product.
mechanical properties. This test method is not intended to
address products which are intentionally carburized to achieve
3.1.2 decarburization—in accordance with Terminology
specific results.
F1789,isalossofcarbonfromthesurfacelayerofthefastener,
normally associated with heat treatment.
1.2 Two routine methods are described for measuring the
limits of and determining the presence of decarburization or 3.1.3 gross decarburization—also known as complete
carburization—the optical method and the microindentation
decarburization, is characterized by a sufficient carbon loss to
method 1. Either method is appropriate for routine examina- show only clearly defined ferrite grains.
tions. The microindentation method 2 shall be considered the
3.1.4 partial decarburization—characterized as a loss of
referee method.
carbon sufficient to cause a lighter shade of tempered marten-
1.3 For the purpose of these tests, there are three classes of site than that of the immediately adjacent base metal, but as
being of insufficient carbon loss to show clearly defined ferrite
hardened and tempered steel products for which specific
measurements must be made with respect to their physical grains.
properties.
4. Significance and Use
1.4 Thevaluesstatedininch-poundunitsaretoberegarded
4.1 Decarburization and carburization are two surface con-
asstandard.Nootherunitsofmeasurementareincludedinthis
ditions created, either intentionally or unintentionally, as with
standard.
a pre-existing condition created during the rod rolling process,
1.5 This standard does not purport to address all of the
the rod/wire annealing process, or while heat treating threaded
safety concerns, if any, associated with its use. It is the
steel products. Too much of either will adversely affect the
responsibility of the user of this standard to establish appro-
safety and performance of the threaded product. Therefore,
priate safety and health practices and determine the applica-
limits have been established for three different product groups:
bility of regulatory limitations prior to use.
the harder and greater the tensile strength of the product, the
2. Referenced Documents more susceptible to failure the product becomes if these limits
2 are exceeded.
2.1 ASTM Standards:
E3Guide for Preparation of Metallographic Specimens 4.2 When testing to a particular product specification that
E384Test Method for Knoop and Vickers Hardness of lists the dimensions and microindentation data to be used, that
Materials data shall take precedence over the tables in this test method.
4.3 There are only two viable methods available to detect
This test method is under the jurisdiction of ASTM Committee F16 on
these deficiencies, either by the visual method or the microin-
Fasteners and is the direct responsibility of Subcommittee F16.01 on Test Methods.
dentation method. Both methods are used for routine inspec-
Current edition approved May 1, 2011. Published June 2011. Originally
tionswhenevaluationsareconductedatasinglelocationonthe
approved in 2004. Last previous edition approved in 2005 as F2328–05. DOI:
10.1520/F2328-05R11.
product sample.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.3.1 Because an evaluation at a specific location may not
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
be representative of the whole part, the referee method em-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. ploys the microindentation method taken as an average of
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2328 − 05 (2011)
evaluationsconductedonfouradjacentthreads.Thisprocedure 7.2.2 Allowablelimitsforgrossdecarburization(G)shallbe
significantlyreducestherandomtestvariableswhencompared inaccordancewith3.1.3andthemeasuredvaluesasdefinedin
to testing on a single thread. Table 1. The optical method is the only valid method for
evaluating the depth of gross decarburization. Gross decarbur-
4.4 Specifying this test method does not specify or imply
ization is prohibited in Class 3 products.
that testing shall be for either decarburization or carburization
7.2.3 Carburization is identified when the tempered marten-
alone or for both conditions. When either test method is
siteisadarkershadethantheimmediatelyadjacentbasemetal.
performed, both conditions will be apparent and shall be
If visible evidence of surface carburization is present on the
reported. For example, if an order is placed to test for
surfacezone,themicroindentationmethod,inaccordancewith
decarburization and none is found, but the presence of carbur-
Section 8, shall be used.
ization is detected, it shall be reported on the test report that
7.2.4 The optical method may not be appropriate for speci-
carburization was found.
menswithcertaincoatings,suchaszinc,wherethecoatingcan
affecttheetchingprocessanddistorttheappearanceofthebase
5. Class of Decarburization
material microstructure.These coatings shall be removed prior
5.1 Class Determination—These measurements by Class
to mounting if the coating prevents proper etching. Care must
arepredicatedupontheirrelationshipbetweentheheight(H)of
also be exercised to not alter the surface condition of the
the external thread at its maximum boundary, disregarding any
substrate during the coating removal process.
surface coating, and N, which is the minimum thread height in
7.2.5 If the results of the optical method indicate a possible
the non-decarburized zone (see Figs. 1-3). The dimensions for
nonconformanceinthemeasurementofpartialdecarburization
N and H are listed in Table 2 for each Class. Dimension G
or carburization, or are otherwise inconclusive, the microin-
(Table 1 and Fig. 1) represents the maximum depth of gross or
dentation method (Section 8) shall be performed after the
complete decarburization.
specimens are repolished.
NOTE1—Refertotheproductstandardforspecificrequirements.When
limits are not specified, use Table 1 as a suggested reference.
8. Evaluation by the Microindentation Hardness Method
6. Preparation
8.1 Prepare the sample in accordance with Section 6 and
6.1 Theuseofeithertheopticalormicroindentationmethod
perform measurements in accordance with Test Method E384
requires the finished product to be longitudinally cross-
on polished and unetched specimens. Use either a Vickers
sectioned, approximately through the threaded axis, and
(136°) indenter or a Knoop indenter with the following load
mounted for grinding and polishing in any suitable medium
requirements:
which will provide edge rete
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