ASTM F1940-07a(2019)
(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.
FIG. 1 Dimensional Requirements for a 0.4W-Notched Square Bar Bend Specimen
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 threshol...
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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:F1940 −07a (Reapproved 2019)
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 Method F519 testing, see publications ASTM STP 543 and
ASTM STP 962. The stress concentration factor is at a K =
t
1.1 This test method covers a procedure to prevent, to the
3.1 6 0.2. The sensitivity is demonstrated with a constant
extent possible, internal hydrogen embrittlement (IHE) of
imposed cathodic potential to control the amount of hydrogen.
fasteners by monitoring the plating or coating process, such as
Boththesensitivityandthebaselineforresidualhydrogenwill
those described in Specifications F1137 and F1941. The
be established with tests on bare metal specimens in air.
process is quantitatively monitored on a periodic basis with a
minimumnumberofspecimensascomparedtoqualifyingeach 1.7 The sensitivity of each lot of specimens to IHE shall be
lotoffastenersbeingplatedorcoated.Trendanalysisisusedto demonstrated. A specimen made of AISI E4340 steel heat
ensure quality as compared to statistical sampling analysis of treatedtoahardnessrangeof50to52HRCisusedtoproduce
eachlotoffasteners.Thistestmethodconsistsofamechanical a “worst case” condition and maximize sensitivity to IHE.
test for the evaluation and control of the potential for IHE that
1.8 The test is an accelerated (≤24 h) test method to
may arise from various sources of hydrogen in a plating or
measurethethresholdforhydrogenstresscracking,andisused
coating process.
to quantify the amount of residual hydrogen in the specimen.
1.2 This test method consists of a mechanical test, con- The specimen undergoes sustained load and slow strain rate
ducted on a standard specimen used as a witness, for the testing by using incremental loads and hold times under
evaluation and control of the potential for IHE that may arise displacement control to measure a threshold stress in an
from various sources of hydrogen in a plating or coating accelerated manner in accordance with Test Method F1624.
process.
1.9 In this test method, bending is used instead of tension
1.3 This test method is limited to evaluating hydrogen becauseitproducesthemaximumlocallimitloadtensilestress
induced embrittlement due only to processing (IHE) and not in a notched bar of up to 2.3 times the yield strength as
duetoenvironmentalexposure(EHE,seeTestMethodF1624). measured in accordance withTest Method E8/E8M.Afastener
that is unintentionally exposed to bending on installation may
1.4 This test method is not intended to measure the relative
attain this maximum local tensile stress.
susceptibility of steels to either IHE or EHE.
1.10 The values stated in inch-pound units are to be re-
1.5 This test method is limited to evaluating processes used
garded as standard. The values given in parentheses are
for plating or coating ferrous fasteners.
mathematical conversions to SI units that are provided for
1.6 This test method uses a notched square bar specimen
information only and are not considered standard.
that conforms to Test Method F519, Type 1e, except that the
1.11 This standard does not purport to address all of the
radius is increased to accommodate the deposition of a larger
safety concerns, if any, associated with its use. It is the
range of platings and coatings. For the background on Test
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
This test method is under the jurisdiction of ASTM Committee F16 on mine the applicability of regulatory limitations prior to use.
Fasteners and is the direct responsibility of Subcommittee F16.93 on Quality
Assurance Provisions for Fasteners.
Current edition approved Aug. 1, 2019. Published September 2019. Originally L. Raymond, ed., Hydrogen Embrittlement Testing.ASTM International, 1974.
published as approved in 1998. Last previous edition approved in 2014 as L. Raymond, ed., Hydrogen Embrittlement: Prevention and Control. ASTM
F1940–07a(2014). DOI: 10.1520/F1940-07AR19. International, 1988.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1940−07a (2019)
1.12 This international standard was developed in accor- 3.1.3 ISL —thresholdfromanincrementalsteploadteston
th
dance with internationally recognized principles on standard- a plated or processed specimen.
ization established in the Decision on Principles for the
3.1.4 NFS(B)—notched fracture strength in air of a bare
Development of International Standards, Guides and Recom-
specimeninbendingatloadingratesof50to250ksi/min(350
mendations issued by the World Trade Organization Technical
to 1700 MPa/min).
Barriers to Trade (TBT) Committee.
3.1.5 NFS(B) —notched fracture strength in air of a
F1624
bare specimen in bending at Test Method F1624 step loading
2. Referenced Documents
rates.
2.1 ASTM Standards:
3.1.6 process—a defined event or sequence of events that
D1193Specification for Reagent Water
may include pretreatments, plating, or coating and posttreat-
E4Practices for Force Verification of Testing Machines
ments that are being evaluated or qualified.
E8/E8MTest Methods for Tension Testing of Metallic Ma-
3.1.7 threshold—themaximumloadattheonsetofcracking
terials
that is identified by a 5% drop in load of NSF(B) under
E18Test Methods for Rockwell Hardness of Metallic Ma- F1624
displacement control.
terials
E29Practice for Using Significant Digits in Test Data to
4. Summary of Test Method
Determine Conformance with Specifications
E177Practice for Use of the Terms Precision and Bias in 4.1 Specimensoffixedgeometry,certifiedtohavebeenheat
ASTM Test Methods treated to a hardness range of 50 to 52 HRC, and which have
E399Test Method for Linear-Elastic Plane-Strain Fracture beencertifiedtoexhibitsensitivitytoembrittlementfromtrace
Toughness K of Metallic Materials amounts of residual hydrogen in steel, are processed with
Ic
E691Practice for Conducting an Interlaboratory Study to actual parts.
Determine the Precision of a Test Method
4.2 An unstressed test specimen is processed in accordance
E1823TerminologyRelatingtoFatigueandFractureTesting
with the plating or coating process being qualified. The
F519Test Method for Mechanical Hydrogen Embrittlement
specimenisthentestedunderincrementalsteploadtomeasure
Evaluation of Plating/Coating Processes and Service En-
the threshold stress. The loading rate must be slow enough to
vironments
ensure that the threshold stress will be detected if deleterious
F1137Specification for Phosphate/Oil Corrosion Protective
amounts of hydrogen are present in “worst case” sensitized
Coatings for Fasteners
specimens. Loading rate protocols are defined in 9.2 and Test
F1624Test Method for Measurement of Hydrogen Em-
Method F1624.
brittlement Threshold in Steel by the Incremental Step
4.3 If the threshold in air of the specimen is ≥75%
Loading Technique
NFS(B) , then the process is considered as to not produce
F1624
F1941 Specification for Electrodeposited Coatings on
sufficient hydrogen to induce time delayed IHE failures in the
Threaded Fasteners (Metric) F1941_F1941M
plated or coated fasteners. See 9.3 for optional limits.
G5Reference Test Method for Making Potentiodynamic
Anodic Polarization Measurements 4.4 If the threshold in air of the specimen is <75%
NFS(B) ,thentheprocessisconsideredpotentiallyembrit-
2.2 SAE Standards: F1624
tling.Actualfastenersmadewithsteelhavingahardnesslower
AMS 2759Hot Drawn, Normalized and Tempered Steel
than that of the square bar specimen have more tolerance for
Bars. UNS G43406 (AISI E4340)
residual hydrogen because of the process.Therefore, threshold
AMS 3078 Corrosion Preventive Compound, Solvent
requirements must be adjusted based upon the correlation
Cutback, Cold-Application
between the specimen fracture strength NBS(B) and
AMS 6415 F1624
actual fastener hardness. An example of this adjustment is
presented in Appendix X1.
3. Terminology
3.1 Terms and Symbols Specific to This Standard:
5. Significance and Use
3.1.1 environmental hydrogen embrittlement (EHE)—test
5.1 This test method establishes a means to verify the
conducted in a specified environment—embrittlement caused
prevention, to the extent possible, of IHE in steel fasteners
by hydrogen introduced into steel from external sources.
during manufacture by maintaining strict controls during
3.1.2 internal hydrogen embrittlement (IHE)—test con-
production operations such as surface preparation,
ducted in air—embrittlement caused by residual hydrogen
pretreatments, and plating or coating. It is intended to be used
from processing
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.
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
5.2 Passing this test allows fasteners to be stressed in
Standards volume information, refer to the standard’s Document Summary page on
tensiontotheminimumspecifiedtensileloadinairwithalmost
the ASTM website.
no possibility of time delayed fracture in air as a result of IHE
Available from Society of Automotive Engineers (SAE), 400 Commonwealth
Dr., Warrendale, PA 15096-0001, http://www.sae.org. from processing. If the amount of residual hydrogen is not
F1940−07a (2019)
sufficient to induce cracking or fracture in the specimen under charging potential of the specimen can be controlled with a
worst case conditions, then it can be concluded that all of the reference saturated calomel electrode (SCE) or equivalent
lots of fasteners processed during that period will not have reference electrode such as with A/AgCl in accordance with
sufficient residual hydrogen from processing to induce hydro- Practice G5.
gen embrittlement of the fasteners under stress in air if the
NOTE1—Aloadingdevicethatmeetsthedisplacementcontrolstepload
process remains in control, unchanged and stable.
test requirements and the potentiostatic control requirements of Test
Method F1624 and Test Method F519 is available.
5.3 If certified specimens with demonstrated sensitivity to
IHE, processed with the fasteners, have a threshold ≥75% of
7. Materials and Reagents
the incremental step load notched bend fracture stress,
7.1 Materials—UNS G43406 (AISI E4340) in accordance
NFS(B) , it is assumed that all fasteners processed the
F1624
with AMS 6415.
same way during the period will also pass any sustained load
IHE test.
7.2 Reagents:
7.2.1 Corrosion preventive compound, meeting require-
6. Apparatus
ments of AMS 3078.
6.1 Testing Machine—A computerized, four-point bend, 7.2.2 Solution of reagent water in accordance with Specifi-
digitaldisplacementcontrolledloadingframethatiscapableof cation D1193 Type IV, and 3.5% reagent grade NaCl.
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
−5 −8 −1
strainrateattherootofthenotchbetween10 and10 s is
8.1 The test specimen shall be a 0.4W-notched square bar
required to conduct these tests. Testing machines shall be
bend specimen: 0.4W-SqB(B), as shown in Fig. 1.
within the guidelines of calibration, force range, resolution,
8.2 The notch shall be in the LS orientation in accordance
and verification of Practice E4.
with Terminology E1823.
6.2 Gripping Devices—Pin-loading devices consistent with
8.3 The stress concentration factor for the specimen is K =
t
Test Method E399 four-point bend fixtures shall be used to
3.1 6 0.2.
transmit the measured load applied by the testing machine to
the test specimen. NOTE 2—For the relationship between geometry and K see Stress
t,
Concentration Factors.
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 6
Peterson,R.E., Stress Concentration Factors,JohnWileyandSons,NewYork,
impose a cathodic potential on the specimen. The cathodic 1974.
FIG. 1Dimensional Requirements for a 0.4W-Notched Square Bar Bend Specimen
F1940−07a (2019)
8.4 Manufacture: 8.6.4 The notched bend fracture strength, NFS(B), of bare
8.4.1 The test specimen blanks shall be heat treated in specimens is measured in air in four-point bending under
accordance withAMS 2759 to meet the hardness requirement displacementcontrolatloadingratesof50to250ksi/min(350
of 50 to 52 HRC in accordance with Test Methods E18. to 1700 MPa/min). The rupture load is used as a measure of
RoundinginaccordancewithPracticeE29permitsanabsolute strength.
hardness range of 49.6 to 52.5 HRC. The hardness shall be
8.7 Sensitivity Test:
determined by the average of three measurements made
8.7.1 The sensitivity to IHE must be demonstrated for each
approximately midway between the notch and the end of the
lot of specimens by exposing three trial specimens in air and
specimen.
three trial specimens in an embrittling environmental after
8.4.2 The surface finish of all notches shall be finished with
manufacture and inspection in accordance with 8.4 through
a tool capable of attaining a surface roughness of 16 RMS or
8.6. The specimens tested shall be representative of the lot.
better. The other surfaces shall have a finish of 32 RMS or
8.7.2 Sensitivity Specimen Preparation:
better.
8.7.2.1 Ultrasonically clean in acetone for 5 to 10 min to
8.4.3 Alldimensionsexceptforthelengthshallbeproduced
remove the corrosion preventive compound and oils/dirt.
after quenching and tempering to final hardness. The 0.40-in.
8.7.2.2 Do not acid clean.
(10-mm) dimension shall be produced by low stress grinding.
8.7.3 Based on the loading profile schedule in Table 2, the
The notch shall be rough machined by wire EDM to within
requirementsforsensitivityoftheheat-treatedlotofspecimens
0.020 in. (0.5 mm) of the final notch depth and low stress
shall be demonstrated if bare specimens fracture in less than 5
ground to the final depth. No chemical or mechanical cleaning
h at an imposed potential of −1.2 V versus SCE in a 3.5%
shall be allowed after final machining.
NaCl solution
...
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