ASTM F1940-07a(2014)
(Test Method)Standard Test Method for Process Control Verification to Prevent Hydrogen Embrittlement in Plated or Coated Fasteners
Standard Test Method for Process Control Verification to Prevent Hydrogen Embrittlement in Plated or Coated Fasteners
SIGNIFICANCE AND USE
5.1 This test method establishes a means to verify the prevention, to the extent possible, of IHE in steel fasteners during manufacture by maintaining strict controls during production operations such as surface preparation, pretreatments, and plating or coating. It is intended to be used as a qualification test for new or revised plating or coating processes and as a periodic inspection audit for the control of a plating or coating process.
5.2 Passing this test allows fasteners to be stressed in tension to the minimum specified tensile load in air with almost no possibility of time delayed fracture in air as a result of IHE from processing. If the amount of residual hydrogen is not sufficient to induce cracking or fracture in the specimen under worst case conditions, then it can be concluded that all of the lots of fasteners processed during that period will not have sufficient residual hydrogen from processing to induce hydrogen embrittlement of the fasteners under stress in air if the process remains in control, unchanged and stable.
5.3 If certified specimens with demonstrated sensitivity to IHE, processed with the fasteners, have a threshold ≥75 % of the incremental step load notched bend fracture stress, NFS(B)F1624, it is assumed that all fasteners processed the same way during the period will also pass any sustained load IHE test.
SCOPE
1.1 This test method covers a procedure to prevent, to the extent possible, internal hydrogen embrittlement (IHE) of fasteners by monitoring the plating or coating process, such as those described in Specifications F1137 and F1941. The process is quantitatively monitored on a periodic basis with a minimum number of specimens as compared to qualifying each lot of fasteners being plated or coated. Trend analysis is used to ensure quality as compared to statistical sampling analysis of each lot of fasteners. This test method consists of a mechanical test for the evaluation and control of the potential for IHE that may arise from various sources of hydrogen in a plating or coating process.
1.2 This test method consists of a mechanical test, conducted on a standard specimen used as a witness, for the evaluation and control of the potential for IHE that may arise from various sources of hydrogen in a plating or coating process.
1.3 This test method is limited to evaluating hydrogen induced embrittlement due only to processing (IHE) and not due to environmental exposure (EHE, see Test Method F1624).
1.4 This test method is not intended to measure the relative susceptibility of steels to either IHE or EHE.
1.5 This test method is limited to evaluating processes used for plating or coating ferrous fasteners.
1.6 This test method uses a notched square bar specimen that conforms to Test Method F519, Type 1e, except that the radius is increased to accommodate the deposition of a larger range of platings and coatings. For the background on Test Method F519 testing, see publications ASTM STP 5432 and ASTM STP 962.3 The stress concentration factor is at a Kt = 3.1 ± 0.2. The sensitivity is demonstrated with a constant imposed cathodic potential to control the amount of hydrogen. Both the sensitivity and the baseline for residual hydrogen will be established with tests on bare metal specimens in air.
1.7 The sensitivity of each lot of specimens to IHE shall be demonstrated. A specimen made of AISI E4340 steel heat treated to a hardness range of 50 to 52 HRC is used to produce a “worst case” condition and maximize sensitivity to IHE.
1.8 The test is an accelerated (≤24 h) test method to measure the threshold for hydrogen stress cracking, and is used to quantify the amount of residual hydrogen in the specimen. The specimen undergoes sustained load and slow strain rate testing by using incremental loads and hold times under displacement control to measure a threshold stress in an accelerated manner in accordance with Test Method F1624.
1.9...
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Designation:F1940 −07a (Reapproved 2014)
Standard Test Method for
Process Control Verification to Prevent Hydrogen
Embrittlement in Plated or Coated Fasteners
This standard is issued under the fixed designation F1940; 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 3.1 6 0.2. The sensitivity is demonstrated with a constant
imposed cathodic potential to control the amount of hydrogen.
1.1 This test method covers a procedure to prevent, to the
Boththesensitivityandthebaselineforresidualhydrogenwill
extent possible, internal hydrogen embrittlement (IHE) of
be established with tests on bare metal specimens in air.
fasteners by monitoring the plating or coating process, such as
those described in Specifications F1137 and F1941. The 1.7 The sensitivity of each lot of specimens to IHE shall be
process is quantitatively monitored on a periodic basis with a demonstrated. A specimen made of AISI E4340 steel heat
minimumnumberofspecimensascomparedtoqualifyingeach treatedtoahardnessrangeof50to52HRCisusedtoproduce
lotoffastenersbeingplatedorcoated.Trendanalysisisusedto a “worst case” condition and maximize sensitivity to IHE.
ensure quality as compared to statistical sampling analysis of
1.8 The test is an accelerated (≤24 h) test method to
eachlotoffasteners.Thistestmethodconsistsofamechanical
measurethethresholdforhydrogenstresscracking,andisused
test for the evaluation and control of the potential for IHE that
to quantify the amount of residual hydrogen in the specimen.
may arise from various sources of hydrogen in a plating or
The specimen undergoes sustained load and slow strain rate
coating process.
testing by using incremental loads and hold times under
1.2 This test method consists of a mechanical test, con- displacement control to measure a threshold stress in an
ducted on a standard specimen used as a witness, for the accelerated manner in accordance with Test Method F1624.
evaluation and control of the potential for IHE that may arise
1.9 In this test method, bending is used instead of tension
from various sources of hydrogen in a plating or coating
becauseitproducesthemaximumlocallimitloadtensilestress
process.
in a notched bar of up to 2.3 times the yield strength as
1.3 This test method is limited to evaluating hydrogen measured in accordance withTest Method E8/E8M.Afastener
induced embrittlement due only to processing (IHE) and not that is unintentionally exposed to bending on installation may
duetoenvironmentalexposure(EHE,seeTestMethodF1624). attain this maximum local tensile stress.
1.4 This test method is not intended to measure the relative 1.10 The values stated in inch-pound units are to be re-
susceptibility of steels to either IHE or EHE. garded as standard. The values given in parentheses are
mathematical conversions to SI units that are provided for
1.5 This test method is limited to evaluating processes used
information only and are not considered standard.
for plating or coating ferrous fasteners.
1.11 This standard does not purport to address all of the
1.6 This test method uses a notched square bar specimen
safety concerns, if any, associated with its use. It is the
that conforms to Test Method F519, Type 1e, except that the
responsibility of the user of this standard to establish appro-
radius is increased to accommodate the deposition of a larger
priate safety and health practices and determine the applica-
range of platings and coatings. For the background on Test
2 bility of regulatory limitations prior to use.
Method F519 testing, see publications ASTM STP 543 and
ASTM STP 962. The stress concentration factor is at a K =
t 2. Referenced Documents
2.1 ASTM Standards:
D1193Specification for Reagent Water
This test method is under the jurisdiction of ASTM Committee F16 on
E4Practices for Force Verification of Testing Machines
Fasteners and is the direct responsibility of Subcommittee F16.93 on Quality
Assurance Provisions for Fasteners.
E8/E8MTest Methods for Tension Testing of Metallic Ma-
Current edition approved Aug. 1, 2014. Published November 2014. Originally
terials
published as approved in 1998. Last previous edition approved in 2007 as
F1940–07a. DOI: 10.1520/F1940-07AR14.
2 4
Hydrogen Embrittlement Testing, ASTM STP 543, American Society for For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Testing and Materials, 1974. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Hydrogen Embrittlement; Prevention and Control, ASTM STP 962, American Standards volume information, refer to the standard’s Document Summary page on
Society for Testing and Materials, 1985. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1940−07a (2014)
E18Test Methods for Rockwell Hardness of Metallic Ma- 4. Summary of Test Method
terials
4.1 Specimensoffixedgeometry,certifiedtohavebeenheat
E29Practice for Using Significant Digits in Test Data to
treated to a hardness range of 50 to 52 HRC, and which have
Determine Conformance with Specifications
beencertifiedtoexhibitsensitivitytoembrittlementfromtrace
E177Practice for Use of the Terms Precision and Bias in
amounts of residual hydrogen in steel, are processed with
ASTM Test Methods
actual parts.
E399Test Method for Linear-Elastic Plane-Strain Fracture
4.2 An unstressed test specimen is processed in accordance
Toughness K of Metallic Materials
Ic
with the plating or coating process being qualified. The
E691Practice for Conducting an Interlaboratory Study to
specimenisthentestedunderincrementalsteploadtomeasure
Determine the Precision of a Test Method
the threshold stress. The loading rate must be slow enough to
E1823TerminologyRelatingtoFatigueandFractureTesting
ensure that the threshold stress will be detected if deleterious
F519Test Method for Mechanical Hydrogen Embrittlement
amounts of hydrogen are present in “worst case” sensitized
Evaluation of Plating/Coating Processes and Service En-
specimens. Loading rate protocols are defined in 9.2 and Test
vironments
Method F1624.
F1137Specification for Phosphate/Oil Corrosion Protective
Coatings for Fasteners
4.3 If the threshold in air of the specimen is ≥75%
F1624Test Method for Measurement of Hydrogen Em- NFS(B) , then the process is considered as to not produce
F1624
brittlement Threshold in Steel by the Incremental Step
sufficient hydrogen to induce time delayed IHE failures in the
Loading Technique plated or coated fasteners. See 9.3 for optional limits.
F1941 Specification for Electrodeposited Coatings on
4.4 If the threshold in air of the specimen is <75%
Threaded Fasteners (Unified Inch Screw Threads (UN/
NFS(B) ,thentheprocessisconsideredpotentiallyembrit-
F1624
UNR))
tling.Actualfastenersmadewithsteelhavingahardnesslower
G5Reference Test Method for Making Potentiodynamic
than that of the square bar specimen have more tolerance for
Anodic Polarization Measurements
residual hydrogen because of the process.Therefore, threshold
2.2 SAE Standards:
requirements must be adjusted based upon the correlation
AMS 2759Hot Drawn, Normalized and Tempered Steel
between the specimen fracture strength NBS(B) and
F1624
Bars. UNS G43406 (AISI E4340)
actual fastener hardness. An example of this adjustment is
AMS 3078 Corrosion Preventive Compound, Solvent
presented in Appendix X1.
Cutback, Cold-Application
5. Significance and Use
AMS 6415
5.1 This test method establishes a means to verify the
3. Terminology
prevention, to the extent possible, of IHE in steel fasteners
during manufacture by maintaining strict controls during
3.1 Terms and Symbols Specific to This Standard:
production operations such as surface preparation,
3.1.1 environmental hydrogen embrittlement (EHE)—test
pretreatments, and plating or coating. It is intended to be used
conducted in a specified environment—embrittlement caused
as a qualification test for new or revised plating or coating
by hydrogen introduced into steel from external sources.
processes and as a periodic inspection audit for the control of
3.1.2 internal hydrogen embrittlement (IHE)—test con-
a plating or coating process.
ducted in air—embrittlement caused by residual hydrogen
5.2 Passing this test allows fasteners to be stressed in
from processing
tensiontotheminimumspecifiedtensileloadinairwithalmost
3.1.3 ISL —thresholdfromanincrementalsteploadteston
th
no possibility of time delayed fracture in air as a result of IHE
a plated or processed specimen.
from processing. If the amount of residual hydrogen is not
3.1.4 NFS(B)—notched fracture strength in air of a bare
sufficient to induce cracking or fracture in the specimen under
specimeninbendingatloadingratesof50to250ksi/min(350
worst case conditions, then it can be concluded that all of the
to 1700 MPa/min).
lots of fasteners processed during that period will not have
3.1.5 NFS(B) —notched fracture strength in air of a
sufficient residual hydrogen from processing to induce hydro-
F1624
bare specimen in bending at Test Method F1624 step loading
gen embrittlement of the fasteners under stress in air if the
rates.
process remains in control, unchanged and stable.
3.1.6 process—a defined event or sequence of events that
5.3 If certified specimens with demonstrated sensitivity to
may include pretreatments, plating, or coating and posttreat-
IHE, processed with the fasteners, have a threshold ≥75% of
ments that are being evaluated or qualified.
the incremental step load notched bend fracture stress,
3.1.7 threshold—themaximumloadattheonsetofcracking NFS(B) , it is assumed that all fasteners processed the
F1624
same way during the period will also pass any sustained load
that is identified by a 5% drop in load of NSF(B) under
F1624
displacement control. IHE test.
6. Apparatus
6.1 Testing Machine—A computerized, four-point bend,
Available from Society of Automotive Engineers (SAE), 400 Commonwealth
Dr., Warrendale, PA 15096-0001, http://www.sae.org. digitaldisplacementcontrolledloadingframethatiscapableof
F1940−07a (2014)
FIG. 1Dimensional Requirements for a 0.4W-Notched Square Bar Bend Specimen
holding 0.5% of the NFS(B) and is programmed to increase 8. Test Specimen
incrementally in steps of load and time to vary the effective
8.1 The test specimen shall be a 0.4W-notched square bar
−5 −8 −1
strainrateattherootofthenotchbetween10 and10 s is
bend specimen: 0.4W-SqB(B), as shown in Fig. 1.
required to conduct these tests. Testing machines shall be
8.2 The notch shall be in the LS orientation in accordance
within the guidelines of calibration, force range, resolution,
with Terminology E1823.
and verification of Practice E4.
8.3 The stress concentration factor for the specimen is K =
t
6.2 Gripping Devices—Pin-loading devices consistent with
3.1 6 0.2.
Test Method E399 four-point bend fixtures shall be used to
transmit the measured load applied by the testing machine to
NOTE 2—For the relationship between geometry and K see Stress
t,
the test specimen. Concentration Factors.
8.4 Manufacture:
6.3 Potentiostatic Control—For verification testing of the
8.4.1 The test specimen blanks shall be heat treated in
sensitivity of the specimens to residual hydrogen from
accordance withAMS 2759 to meet the hardness requirement
processing, an inert container and potentiostat shall be used to
of 50 to 52 HRC in accordance with Test Methods E18.
impose a cathodic potential on the specimen. The cathodic
RoundinginaccordancewithPracticeE29permitsanabsolute
charging potential of the specimen can be controlled with a
hardness range of 49.6 to 52.5 HRC. The hardness shall be
reference saturated calomel electrode (SCE) or equivalent
determined by the average of three measurements made
reference electrode such as with A/AgCl in accordance with
approximately midway between the notch and the end of the
Practice G5.
specimen.
NOTE1—Aloadingdevicethatmeetsthedisplacementcontrolstepload
8.4.2 The surface finish of all notches shall be finished with
test requirements and the potentiostatic control requirements of Test
a tool capable of attaining a surface roughness of 16 RMS or
Method F1624 and Test Method F519 is available.
better. The other surfaces shall have a finish of 32 RMS or
7. Materials and Reagents
better.
8.4.3 Alldimensionsexceptforthelengthshallbeproduced
7.1 Materials—UNS G43406 (AISI E4340) in accordance
after quenching and tempering to final hardness. The 0.40-in.
with AMS 6415.
(10-mm) dimension shall be produced by low stress grinding.
7.2 Reagents:
The notch shall be rough machined by wire EDM to within
7.2.1 Corrosion preventive compound, meeting require-
ments of AMS 3078.
7.2.2 Solution of reagent water in accordance with Specifi-
Peterson,R.E., Stress Concentration Factors,JohnWileyandSons,NewYork,
cation D1193 Type IV, and 3.5% reagent grade NaCl. 1974.
F1940−07a (2014)
TABLE 2 Minimum Step-Loading Profile Requirements for
0.020 in. (0.5 mm) of the final notch depth and low stress
Accelerated (< 24h) Incremental Step Load Sensitivity Tests
ground to the final depth. No chemical or mechanical cleaning
%NFS(B) # h ^h %NFS(B) # h ^h %NFS(B) # h ^h
shall be allowed after final machining.
10 1 1 65 1 8 88 1 15
8.4.4 Straighteningafterfinalheattreatmentbeforemachin-
20 1 2 70 1 9 90 1 16
ing is prohibited.
30 1 3 75 1 10 92 1 17
40 1 4 80 1 11 94 1 18
8.5 Storage—Before plating or coating, all specimens shall
50 1 5 82 1 12 96 1 19
be protected during storage to prevent corrosion. A suitable
55 1 6 84 1 13 98 1 20
60 1 7 86 1 14 100 1 21
means of protection is to coat the specimen with a corrosion
preventive compound meeting the requirements ofASM 3078.
8.6 Inspection:
8.6.1 A lot shall consist of only those specimens cut from
the same heat of steel in the same orientation, heat treated
h at an imposed potential of −1.2 V versus SCE in a 3.5%
together in the same furnace, quenched and tempered together,
NaCl solution and no delayed fracture occurs in less than 14 h
and subjected to the same manufacturing processes.
or≥85%NFS(B)onbarespecimenstestedinair(seeTable3).
8.6.2 One transverse section shall be microstructurally ex-
8.7.4 The average of the results of the three bare specimens
amined to ensure that if any orientation effects exist, the notch
tested in air shall be used as the baseline notched fracture
will be in the LS orientation in accordance with Terminology
strength, NFS(B) .
F1624
E1823.
8.8 Certification:
8.6.3 All notched square bar bend spe
...
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 previous version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: F1940 − 07a F1940 − 07a (Reapproved 2014)
Standard Test Method for
Process Control Verification to Prevent Hydrogen
Embrittlement in Plated or Coated Fasteners
This standard is issued under the fixed designation F1940; 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
1.1 This test method covers a procedure to prevent, to the extent possible, internal hydrogen embrittlement (IHE) of fasteners
by monitoring the plating or coating process, such as those described in Specifications F1137 and F1941. The process is
quantitatively monitored on a periodic basis with a minimum number of specimens as compared to qualifying each lot of fasteners
being plated or coated. Trend analysis is used to ensure quality as compared to statistical sampling analysis of each lot of fasteners.
This test method consists of a mechanical test for the evaluation and control of the potential for IHE that may arise from various
sources of hydrogen in a plating or coating process.
1.2 This test method consists of a mechanical test, conducted on a standard specimen used as a witness, for the evaluation and
control of the potential for IHE that may arise from various sources of hydrogen in a plating or coating process.
1.3 This test method is limited to evaluating hydrogen induced embrittlement due only to processing (IHE) and not due to
environmental exposure (EHE, see Test Method F1624).
1.4 This test method is not intended to measure the relative susceptibility of steels to either IHE or EHE.
1.5 This test method is limited to evaluating processes used for plating or coating ferrous fasteners.
1.6 This test method uses a notched square bar specimen that conforms to Test Method F519, Type 1e, except that the radius
is increased to accommodate the deposition of a larger range of platings and coatings. For the background on Test Method F519
2 3
testing, see publications ASTM STP 543 and ASTM STP 962. The stress concentration factor is at a K = 3.1 6 0.2. The
t
sensitivity is demonstrated with a constant imposed cathodic potential to control the amount of hydrogen. Both the sensitivity and
the baseline for residual hydrogen will be established with tests on bare metal specimens in air.
1.7 The sensitivity of each lot of specimens to IHE shall be demonstrated. A specimen made of AISI E4340 steel heat treated
to a hardness range of 50 to 52 HRC is used to produce a “worst case” condition and maximize sensitivity to IHE.
1.8 The test is an accelerated (≤24 h) test method to measure the threshold for hydrogen stress cracking, and is used to quantify
the amount of residual hydrogen in the specimen. The specimen undergoes sustained load and slow strain rate testing by using
incremental loads and hold times under displacement control to measure a threshold stress in an accelerated manner in accordance
with Test Method F1624.
1.9 In this test method, bending is used instead of tension because it produces the maximum local limit load tensile stress in
a notched bar of up to 2.3 times the yield strength as measured in accordance with Test Method E8E8/E8M. A fastener that is
unintentionally exposed to bending on installation may attain this maximum local tensile stress.
1.10 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.11 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.
This test method is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.93 on Quality Assurance Provisions
for Fasteners.
Current edition approved Sept. 1, 2007Aug. 1, 2014. Published September 2007November 2014. Originally published as approved in 1998. Last previous edition approved
in 2007 as F1940 – 07.F1940 – 07a. DOI: 10.1520/F1940-07A.10.1520/F1940-07AR14.
Hydrogen Embrittlement Testing, ASTM STP 543, American Society for Testing and Materials, 1974.
Hydrogen Embrittlement; Prevention and Control, ASTM STP 962, American Society for Testing and Materials, 1985.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1940 − 07a (2014)
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
E4 Practices for Force Verification of Testing Machines
E8E8/E8M Test Methods for Tension Testing of Metallic Materials
E18 Test Methods for Rockwell Hardness of Metallic Materials
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness K of Metallic Materials
Ic
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1823 Terminology Relating to Fatigue and Fracture Testing
F519 Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
F1137 Specification for Phosphate/Oil Corrosion Protective Coatings for Fasteners
F1624 Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique
F1941 Specification for Electrodeposited Coatings on Threaded Fasteners (Unified Inch Screw Threads (UN/UNR))
G5 Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
2.2 SAE Standards:
AMS 2759 Hot Drawn, Normalized and Tempered Steel Bars. UNS G43406 (AISI E4340)
AMS 3078 Corrosion Preventive Compound, Solvent Cutback, Cold-Application
AMS 6415
3. Terminology
3.1 Terms and Symbols Specific to This Standard:
3.1.1 environmental hydrogen embrittlement (EHE)—test conducted in a specified environment—embrittlement caused by
hydrogen introduced into steel from external sources.
3.1.2 internal hydrogen embrittlement (IHE)—test conducted in air—embrittlement caused by residual hydrogen from
processing
3.1.3 ISL —threshold from an incremental step load test on a plated or processed specimen.
th
3.1.4 NFS(B)—notched fracture strength in air of a bare specimen in bending at loading rates of 50 to 250 ksi/min (350 to 1700
MPa/min).
3.1.5 NFS(B) —notched fracture strength in air of a bare specimen in bending at Test Method F1624 step loading rates.
F1624
3.1.6 process—a defined event or sequence of events that may include pretreatments, plating, or coating and posttreatments that
are being evaluated or qualified.
3.1.7 threshold—the maximum load at the onset of cracking that is identified by a 5 % drop in load of NSF(B) under
F1624
displacement control.
4. Summary of Test Method
4.1 Specimens of fixed geometry, certified to have been heat treated to a hardness range of 50 to 52 HRC, and which have been
certified to exhibit sensitivity to embrittlement from trace amounts of residual hydrogen in steel, are processed with actual parts.
4.2 An unstressed test specimen is processed in accordance with the plating or coating process being qualified. The specimen
is then tested under incremental step load to measure the threshold stress. The loading rate must be slow enough to ensure that
the threshold stress will be detected if deleterious amounts of hydrogen are present in “worst case” sensitized specimens. Loading
rate protocols are defined in 9.2 and Test Method F1624.
4.3 If the threshold in air of the specimen is ≥75 % NFS(B) , then the process is considered as to not produce sufficient
F1624
hydrogen to induce time delayed IHE failures in the plated or coated fasteners. See 9.3 for optional limits.
4.4 If the threshold in air of the specimen is <75 % NFS(B) , then the process is considered potentially embrittling. Actual
F1624
fasteners made with steel having a hardness lower than that of the square bar specimen have more tolerance for residual hydrogen
because of the process. Therefore, threshold requirements must be adjusted based upon the correlation between the specimen
fracture strength NBS(B) and actual fastener hardness. An example of this adjustment is presented in Appendix X1.
F1624
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
F1940 − 07a (2014)
5. Significance and Use
5.1 This test method establishes a means to verify the prevention, to the extent possible, of IHE in steel fasteners during
manufacture by maintaining strict controls during production operations such as surface preparation, pretreatments, and plating or
coating. It is intended to be used as a qualification test for new or revised plating or coating processes and as a periodic inspection
audit for the control of a plating or coating process.
5.2 Passing this test allows fasteners to be stressed in tension to the minimum specified tensile load in air with almost no
possibility of time delayed fracture in air as a result of IHE from processing. If the amount of residual hydrogen is not sufficient
to induce cracking or fracture in the specimen under worst case conditions, then it can be concluded that all of the lots of fasteners
processed during that period will not have sufficient residual hydrogen from processing to induce hydrogen embrittlement of the
fasteners under stress in air if the process remains in control, unchanged and stable.
5.3 If certified specimens with demonstrated sensitivity to IHE, processed with the fasteners, have a threshold ≥75 % of the
incremental step load notched bend fracture stress, NFS(B) , it is assumed that all fasteners processed the same way during
F1624
the period will also pass any sustained load IHE test.
6. Apparatus
6.1 Testing Machine—A computerized, four-point bend, digital displacement controlled loading frame that is capable of holding
0.5 % of the NFS(B) and is programmed to increase incrementally in steps of load and time to vary the effective strain rate at the
−5 −8 −1
root of the notch between 10 and 10 s is required to conduct these tests. Testing machines shall be within the guidelines of
calibration, force range, resolution, and verification of Practice E4.
6.2 Gripping Devices—Pin-loading devices consistent with Test Method E399 four-point bend fixtures shall be used to transmit
the measured load applied by the testing machine to the test specimen.
6.3 Potentiostatic Control—For verification testing of the sensitivity of the specimens to residual hydrogen from processing, an
inert container and potentiostat shall be used to impose a cathodic potential on the specimen. The cathodic charging potential of
the specimen can be controlled with a reference saturated calomel electrode (SCE) or equivalent reference electrode such as with
A/AgCl in accordance with Practice G5.
NOTE 1—A loading device that meets the displacement control step load test requirements and the potentiostatic control requirements of Test Method
F1624 and Test Method F519 is available.
FIG. 1 Dimensional Requirements for a 0.4W-Notched Square Bar Bend Specimen
F1940 − 07a (2014)
7. Materials and Reagents
7.1 Materials—UNS G43406 (AISI E4340) in accordance with AMS 6415.
7.2 Reagents:
7.2.1 Corrosion preventive compound, meeting requirements of AMS 3078.
7.2.2 Solution of reagent water in accordance with Specification D1193 Type IV, and 3.5 % reagent grade NaCl.
8. Test Specimen
8.1 The test specimen shall be a 0.4W-notched square bar bend specimen: 0.4W-SqB(B), as shown in Fig. 1.
8.2 The notch shall be in the LS orientation in accordance with Terminology E1823.
8.3 The stress concentration factor for the specimen is K = 3.1 6 0.2.
t
NOTE 2—For the relationship between geometry and K see Stress Concentration Factors.
t,
8.4 Manufacture:
8.4.1 The test specimen blanks shall be heat treated in accordance with AMS 2759 to meet the hardness requirement of 50 to
52 HRC in accordance with Test Methods E18. Rounding in accordance with Practice E29 permits an absolute hardness range of
49.6 to 52.5 HRC. The hardness shall be determined by the average of three measurements made approximately midway between
the notch and the end of the specimen.
8.4.2 The surface finish of all notches shall be finished with a tool capable of attaining a surface roughness of 16 RMS or better.
The other surfaces shall have a finish of 32 RMS or better.
8.4.3 All dimensions except for the length shall be produced after quenching and tempering to final hardness. The 0.40-in.
(10-mm) dimension shall be produced by low stress grinding. The notch shall be rough machined by wire EDM to within 0.020
in. (0.5 mm) of the final notch depth and low stress ground to the final depth. No chemical or mechanical cleaning shall be allowed
after final machining.
8.4.4 Straightening after final heat treatment before machining is prohibited.
8.5 Storage—Before plating or coating, all specimens shall be protected during storage to prevent corrosion. A suitable means
of protection is to coat the specimen with a corrosion preventive compound meeting the requirements of ASM 3078.
8.6 Inspection:
8.6.1 A lot shall consist of only those specimens cut from the same heat of steel in the same orientation, heat treated together
in the same furnace, quenched and tempered together, and subjected to the same manufacturing processes.
8.6.2 One transverse section shall be microstructurally examined to ensure that if any orientation effects exist, the notch will
be in the LS orientation in accordance with Terminology E1823.
8.6.3 All notched square bar bend specimens shall be considered suitable for test purposes if the sampling and inspection results
conform to the requirements of Table 1.
Peterson, R. E., Stress Concen
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