ASTM F2328M-07(2014)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F2328M − 07(Reapproved 2014)
Standard Test Method for
Determining Decarburization and Carburization in Hardened
and Tempered Threaded Steel Bolts, Screws and Studs
(Metric)
This standard is issued under the fixed designation F2328M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope A574M Specification for Alloy Steel Socket-Head Cap
Screws (Metric)
1.1 This test method covers procedures for measuring,
E3 Guide for Preparation of Metallographic Specimens
classifying, and determining the presence of decarburization
E384 Test Method for Knoop and Vickers Hardness of
and carburization in the threaded section of hardened and
Materials
tempered metric steel bolts, screws, studs, and similar parts
F835M Specification forAlloy Steel Socket Button and Flat
whichhavebeenheatedtofacilitatefabricationortomodifyits
Countersunk Head Cap Screws (Metric)
mechanical properties. This test method is not intended to
F912M Specification for Alloy Steel Socket Set Screws
address products which are intentionally carburized to achieve
(Metric)
specific results.
F1789 Terminology for F16 Mechanical Fasteners
1.2 Two routine methods are described for measuring the
limits of and determining the presence of decarburization or
3. Terminology
carburization; the Optical Method and the Microindentation
3.1 Definitions:
Method 1. Either method is appropriate for routine examina-
tions. The Microindentation Method 2 shall be considered the 3.1.1 carburization—process or result of increasing the
carbon content of the surface layers of the steel fastener
referee method.
product.
1.3 For the purpose of these tests, there are four classes of
hardened and tempered steel products for which specific 3.1.2 decarburization—in accordance with Terminology
measurements must be made with respect to their physical
F1789,isalossofcarbonfromthesurfacelayerofthefastener,
properties.
normally associated with heat treatment.
1.4 The values stated in SI units are to be regarded as
3.1.3 gross decarburization—also known as complete
standard. No other units of measurement are included in this
decarburization, is characterized by a sufficient carbon loss to
standard.
show only clearly defined ferrite grains.
1.5 This standard does not purport to address all of the
3.1.4 partial decarburization—characterized as a loss of
safety concerns, if any, associated with its use. It is the
carbon sufficient to cause a lighter shade of tempered marten-
responsibility of the user of this standard to establish appro-
site than that of the immediately adjacent base metal, but as
priate safety and health practices and determine the applica-
being of insufficient carbon loss to show clearly defined ferrite
bility of regulatory limitations prior to use.
grains.
2. Referenced Documents
4. Significance and Use
2.1 ASTM Standards:
4.1 Decarburization and carburization are two surface con-
ditions created, either intentionally or unintentionally, as with
a pre-existing condition created during the rod rolling process,
This test method is under the jurisdiction of ASTM Committee F16 on
the rod/wire annealing process, or while heat treating threaded
Fasteners and is the direct responsibility of Subcommittee F16.01 on Test Methods.
steel products. Too much of either will adversely affect the
Current edition approved Feb. 1, 2014. Published March 2014. Originally
safety and performance of the threaded product. Therefore,
approved in 2004. Last previous edition approved in 2013 as F2328M – 07(2013).
DOI: 10.1520/F2328M-07R14.
limits have been established for four different product groups:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the harder and greater the tensile strength of the product, the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
more susceptible to failure the product becomes if these limits
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. are exceeded.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2328M − 07 (2014)
4.2 When testing to a particular product specification that maximum limits for G by taking a measurement on a line
lists the dimensions and microindentation data to be used, that perpendicular to the flank of the thread midway between the
data shall take precedence over the tables in this test method. thread crest and root (pitch diameter).
4.3 There are only two viable methods available to detect 7.2 Interpretation of Results:
these deficiencies: either by the visual method or the microin- 7.2.1 Allowable limits for partial decarburization shall be in
dentation method. Both methods are used for routine inspec- accordancewith3.1.4andFig.1,andthemeasuredvaluesshall
tionswhenevaluationsareconductedatasinglelocationonthe be in accordance with Table 2, when measured in accordance
product sample. Because an evaluation at a specific location with the illustrations in Figs. 2 and 3.
maynotberepresentativeofthewholepart,therefereemethod 7.2.2 Allowablelimitsforgrossdecarburization(G)shallbe
employs the microindentation method taken as an average of in accordance with 3.1.3 and the measured values as defined in
evaluationsconductedonfouradjacentthreads.Thisprocedure Table 1. The optical method is the only valid method for
significantly reduces random test variables when compared to evaluating the depth of gross decarburization. Gross decarbur-
testing on a single thread. ization is prohibited in Class 3 and Class 4 products.
7.2.3 Carburization is identified when the tempered marten-
4.4 Specifying this test method does not specify or imply
siteisadarkershadethantheimmediatelyadjacentbasemetal.
that testing shall be for either decarburization or carburization
If visible evidence of surface carburization is present on the
alone or for both conditions. When either test method is
surface zone, the microindentation hardness method, in accor-
performed, both conditions will be apparent and shall be
dance with Section 8, shall be used.
reported. For example, if an order is placed to test for
7.2.4 The optical method may not be appropriate for speci-
decarburization and none is found but the presence of decar-
mens with certain coatings, such as zinc, where the coating can
burization is detected, it shall be reported on the test report that
affecttheetchingprocessanddistorttheappearanceofthebase
carburization was found.
material microstructure. These coatings shall be removed prior
to mounting if the coating prevents proper etching. Care must
5. Class of Decarburization
also be exercised to not alter the surface condition of the
5.1 Class Determination—These measurements by Class
substrate during the coating removal process.
arepredicatedupontheirrelationshipbetweentheheight(H)of
7.2.5 If the results of the optical method indicate a possible
the external thread at its maximum boundary, disregarding any
nonconformance in the measurement of partial decarburization
surface coating, and N, which is the minimum thread height in
or carburization, or are otherwise inconclusive, the microin-
the non-decarburized zone (see Figs. 1-3). The dimensions for
dentation hardness method (Section 8) shall be performed after
N and H are listed in Table 2 for each Class. Dimension G
the specimens are repolished.
(Table 1 and Fig. 1) represents the maximum depth of gross or
complete decarburization.
8. Evaluation by the Microindentation Hardness Method
NOTE 1—Refer to the product standard for specific requirements.When
limits are not specified, use Table 1 as a suggested reference.
8.1 Prepare the sample in accordance with Section 6 and
perform measurements in accordance with Test Method E384
6. Preparation
on polished and unetched specimens. Use either a Vickers
6.1 The use of either the optical or microindentation hard- (136°) indenter or a Knoop indenter w
...