ASTM F1624-00
(Test Method)Standard Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique
Standard Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique
SCOPE
1.1 This test method establishes a procedure to measure the susceptibility of steel to a time-delayed failure such as that caused by hydrogen. It does so by measuring the threshold for the onset of subcritical crack growth using standard fracture mechanics specimens, irregular-shaped specimens such as notched round bars, or actual product such as fasteners (2) (threaded or unthreaded) springs or components as identified in SAE J78, J81, and J1237.
1.2 This test method is used to evaluate quantitatively:
1.2.1 The relative susceptibility of steels of different composition or a steel with different heat treatments;
1.2.2 The effect of residual hydrogen in the steel as a result of processing, such as melting, thermal mechanical working, surface treatments, coatings, and electroplating;
1.2.3 The effect of hydrogen introduced into the steel caused by external environmental sources of hydrogen, such as fluids and cleaners maintenance chemicals, petrochemical products, and galvanic coupling in an aqueous environment.
1.3 The test is performed either in air, to measure the effect if residual hydrogen is in the steel because of the processing (IHE), or in a controlled environment, to measure the effect of hydrogen introduced into the steel as a result of the external sources of hydrogen (EHE) as detailed in ASTM STP 453.
1.4 The values stated in acceptable U.S. units shall be regarded as the standard. The values stated in metric units may not be exact equivalents. Conversion of the U.S. units by appropriate conversion factors is required to obtain exact equivalence.
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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Designation: F 1624 – 00
Standard Test Method for
Measurement of Hydrogen Embrittlement Threshold in Steel
by the Incremental Step Loading Technique
This standard is issued under the fixed designation F1624; 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 (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Hydrogen embrittlement is caused by the introduction of hydrogen into steel that can initiate
fracture as a result of residual stress or in service when external stress is applied (1). The hydrogen
can be generated during cleaning or plating processes or the exposure of cathodically protected steel
parts to a service environment including fluids, cleaning treatments, or maintenance chemicals that
may contact the surface of steel componets.
The combined residual and applied stress above which time-delayed fracture will occur (finite life)
or below which fracture will never occur (infinite life) is called the threshold stress. Historically,
time-to-failure sustained load tests have been conducted to determine the threshold stress. This
technique may require 12 to 14 specimens and several high-load capacity machines to measure the
threshold stress in high-strength steel (>175 ksi), taking as long as 3 to 4 months. The run-out time
can be as long as four to five years per U.S. Navy requirements for low-strength steels (<175 ksi) at
33 to 35 HRC. In Test Method E1681, more than 10000 h (>one year) are specified for run out for
precracked specimens.
This standard provides an accelerated method to measure the threshold stress or threshold stress
intensity for the onset of hydrogen stress cracking in steel within one week on only one machine.
This method can be used to determine rapidly the effects of residual hydrogen in a part caused by
processing or quantify the relative susceptibility of a material under a fixed set of hydrogen-charging
conditions. For precracked specimens, the threshold stress intensity as defined inTest Method E1681
can be measured, only in a much shorter time.
1. Scope 1.2.3 Theeffectofhydrogenintroducedintothesteelcaused
by external environmental sources of hydrogen, such as fluids
1.1 This test method establishes a procedure to measure the
and cleaners maintenance chemicals, petrochemical products,
susceptibility of steel to a time-delayed failure such as that
and galvanic coupling in an aqueous environment.
caused by hydrogen. It does so by measuring the threshold for
1.3 The test is performed either in air, to measure the effect
the onset of subcritical crack growth using standard fracture
if residual hydrogen is in the steel because of the processing
mechanics specimens, irregular-shaped specimens such as
(IHE), or in a controlled environment, to measure the effect of
notched round bars, or actual product such as fasteners (2)
hydrogen introduced into the steel as a result of the external
(threadedorunthreaded)springsorcomponentsasidentifiedin
sources of hydrogen (EHE) as detailed in ASTM STP 543.
SAE J78, J81, and J1237.
1.4 The values stated in acceptable U.S. units shall be
1.2 This test method is used to evaluate quantitatively:
regardedasthestandard.Thevaluesstatedinmetricunitsmay
1.2.1 The relative susceptibility of steels of different
not be exact equivalents. Conversion of the U.S. units by
composition or a steel with different heat treatments;
appropriate conversion factors is required to obtain exact
1.2.2 The effect of residual hydrogen in the steel as a result
equivalence.
of processing, such as melting, thermal mechanical working,
1.5 This standard does not purport to address all of the
surface treatments, coatings, and electroplating;
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
This test method is under the jurisdiction of ASTM Committee F-7 on
priate safety and health practices and determine the applica-
Aerospace andAircraft and is the direct responsibility of Subcommittee F07.04 on
bility of regulatory limitations prior to use.
Hydrogen Embrittlement.
Current edition approved Sept. 10, 2000. Published November 2000.
Originally published as F 1624–95. Last previous edition F 1624–99.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 1624
2. Referenced Documents 3.1.4 P —threshold load where P is invariant with respect
th i
to loading rate. P is the basis for calculating the threshold
th
2.1 ASTM Standards:
stress or the threshold stress intensity.
B602 Test Method for Attribute Sampling of Metallic and
3.1.5 IHE—Internal Hydrogen Embrittlement—test con-
Inorganic Coatings
3 ducted in air.
E4 Practices for Force Verification of Testing Machines
3.1.6 EHE—Environmental Hydrogen Embrittlement—test
E6 Terminology Relating to Methods of Mechanical Test-
conducted in a specified environment.
ing
3.1.7 th—threshold—the lowest load at which subcritical
E8 TestMethodsforTensionTestingofMetallicMaterials
cracking can be detected.
E29 Practice for Using Significant Digits in Test Data to
3.2 Irregular Geometry-Type Specimens—test sample other
Determine Conformance with Specifications
than a fracture mechanics-type specimen such as a notched
E399 Test Method for Plane-Strain Fracture Toughness of
round bar or fastener.
Metallic Materials
3.2.1 s=applied stress.
E1681 Test Method for Determining Threshold Stress In-
3.2.2 s =netstressbasedonareaatminimumdiameterof
net
tensity Factor for Environment-Assisted Cracking of Me-
notched round bar.
tallic Materials
3.2.3 s =stress at crack initiation.
F519 Test Method for Mechanical Hydrogen Embrittle- i
3.2.4 s =threshold stress.
ment Testing of Plating Processes and Aircraft Mainte- th
3.2.5 s =threshold stress—test conducted in air—
nance Chemicals
th-IHE
geometry dependent.
G5 Reference Test Method for Making Potentiostatic and
3.2.6 s =threshold stress—test conducted in a speci-
Potentiodynamic Anodic Polarization Measurements
th-EHE
fied environment—geometry dependent.
2.2 SAE Standards:
J78 Self-Drilling Tapping Screws
7 4. Summary of Test Method
J81 Thread Rolling Screws
4.1 The test method is based on determining the onset of
J1237 Metric Thread Rolling Screws
subcritical crack growth with a modified, incrementally in-
2.3 ANSI/ASME:
creasing, slow strain rate step-load test under displacement
B18.18.2M Inspection and Quality Assurance for High-
control (3), (4), (5).
Volume Machine Assembly Fasteners, 1987
4.2 This test method measures the load necessary to initiate
B18.18.3M Inspection and Quality Assurance for Special
8 a subcritical crack in the steel at various, incremental loading
Purpose Fasteners, 1987
rates, for specimens of different geometry and different envi-
B18.18.4M Inspection and QualityAssurance for Fasteners
ronmental conditions.
for Highly Specialized Engineering Applications, 1987
4.2.1 By varying the incremental loading rate, the threshold
2.4 Related Publications:
stress can be determined.
ASTM STP 543, Hydrogen Embrittlement Testing, 1974
4.3 Four-point bending is used to maintain a constant
ASTM STP 962, Hydrogen Embrittlement: Prevention and
momentalongthespecimen.Thisconditionisusedtosimplify
Control, 1985
thecalculationofstressorstressintensityforanirregularcross
section.
3. Terminology
4.4 The minimum or invariant value of the stress with
3.1 Symbols—Terms not defined in this section can be
regardtotheloadingrateisthethresholdstressfortheonsetof
foundinTerminologyE6andshallbeconsideredasapplicable
crack growth as a result of hydrogen embrittlement for a given
to the terms used in this test method.
geometry.
3.1.1 P—applied load.
4.5 In tension and bending, the onset of subcritical crack
3.1.2 P —critical load required to rupture a specimen using
c growthasaresultofhydrogeninsteelisidentifiedbydecrease
a continuous loading rate.
in load while holding the displacement constant.
3.1.3 P—crack initiation load for a given loading and
i 4.6 The displacement is incrementally increased in tension
environmental condition using an incrementally increasing
or four-point bending and the resulting load is monitored.
load under displacement control.
While the displacement is held constant, the onset of subcriti-
cal crack growth is detected when the load decreases by a
predetermined amount.
4.7 The loading rate must be sufficiently slow to permit
Annual Book of ASTM Standards, Vol 02.05.
3 hydrogentodiffuseandinducecrackingthatmanifestsitselfas
Annual Book of ASTM Standards, Vol 03.01.
Annual Book of ASTM Standards, Vol 14.02. a degradation in strength.
Annual Book of ASTM Standards, Vol 15.03.
Annual Book of ASTM Standards, Vol 03.02
5. Significance and Use
Available from Society of Automotive Engineers, 400 Commonwealth Dr.,
Warrendale, PA 15096–0001.
5.1 This test method is used for research, design, service
Available from American National Standards Institute, 11 W. 42nd St., 13th
evaluation, manufacturing control, and development. This test
Floor, New York, NY 10036.
methodquantitativelymeasuresstressparametersthatareused
Available from ASTM, 100 Barr Harbor Dr., PO Box C700, West Consho-
hocken, PA 19428. inadesignorfailureanalysisthattakesintoaccounttheeffects
F 1624
of environmental exposure including that which occurs during 7.2 Test Specimens—The test specimen should be classified
processing, such as plating (6) (ASTM STP 962). as either fracture mechanics-type specimens or irregular-
5.2 For plating processes, the value of s is used to shaped specimens (8).
th-IHE
specify quantitatively the maximum operating stress for a 7.2.1 Fracture mechanics-type specimens are defined in
given structure or product. standards such as Test Method E399.
5.3 For quality control purposes, an accelerated test is
NOTE 2—Themaximumstressusedduringfatigueprecrackingmustbe
devised that uses a specified loading rate, which is equal to or
less than 60% of any measured value of load for crack initiation for the
lower than the loading rate necessary to determine the thresh-
data to be valid.
old stress (see 8.1).
7.2.2 Irregular geometry-type specimens shall be either
5.4 For fasteners, the value of s is used to specify
th-IHE
specimens as defined in standards such as Test Method F519
quantitatively the maximum stress during installation and in
or specimens from product. The product shall be tested either
servicetoavoidprematurefailurecausedbyresidualhydrogen
substantially full size or as a machined specimen.
in the steel as a result of processing.
5.5 For fasteners, the value of s is used to specify
8. Procedure
th-EHE
quantitatively the maximum stress during installation and in
8.1 Determination of Threshold Load (a Suggested Test
service to avoid failure from hydrogen absorbed during expo-
Protocol):
sure to a specific environment.
8.1.1 Load one specimen to rupture at a rate consistent with
5.6 Tomeasuretherelativesusceptibilityofsteelstohydro-
Test Methods E8 to establish the maximum fracture load for a
gen pickup from various fabrication processes, a single,
given specimen geometry, P (see Fig. 1).
c
selected, discriminating rate is used to rank the resistance of
8.1.2 Another sample (No. 1) is tested by applying an
various materials to hydrogen embrittlement.
incrementalorsteploadsunderdisplacementcontrolintension
or four-point bending, programmed to attain P .
c
6. Apparatus
8.1.3 Another sample (No. 2) is tested using load incre-
6.1 Testing Machine—Testing machines shall be within the ments programmed to attain P . In no case should the loading
i1
guidelines of calibration, force range, resolution, and verifica-
rate be faster than that of the previous sample. This load
tion of Practices E4. sequence will continue until a significant drop in load is
6.2 Gripping Devices—Various types of gripping devices detected that will establish the value designated as P .
i2
shallbeusedineithertensionorfour-pointbendingtotransmit 8.1.4 Subsequent specimens are tested in load increments
the measured load applied by the testing machine to the test
programmed to attain P , and so forth. It is suggested that the
i2
specimen. duration be doubled, at least at values in excess of 0.5 P .The
ii
6.3 Test Environment—The test shall be conducted in air or procedure shall be continued until an invariant value (P )is
th
anyothersuitablecontrolledenvironmentusinganappropriate obtained.
inert container. 8.1.5 At a minimum, equal load increments for 1 h each
6.3.1 Potentiostatic Control—Thecorrosionpotentialofthe shallbeusedinsteploadingtoattain P .Foraninitial8-htest,
c
specimen can be controlled with a reference saturated calomel each load step shall be P /8. For an initial 20-h test, each load
c
electrode (SCE) or equivalent reference electrode such as step shall be P /20.The load at which subcritical crack growth
c
Ag/AgCl in accordance with Test Method G5. The imposed occurs is detected by a significant drop in load, P . Testing
i1
potential is typically cathodic, ranging from 0.0 to −1.2 V shall be continued until crack growth is detected or rupture
occurs.Forsteelswithahardnessof48HRCorgreater,an8-h
versus SCE in a 3.5 weight percent NaCl solution (7).
step-loadingprofileissuggestedinTable1.Forsteelslessthan
NOTE 1—Apparatus, grips, load adapters, and environmental chambers
48 HRC, a 20-h step-loading profile is suggested in Table 2.
that have been found to meet the standard are available from Fracture
Diagnostics, Inc., P.O. Box 6401, Denver, Co 80206.
7. Sampling and Test Specimens
7.1 Sampling—For research, design, and service evaluation
and development, the sampling size depends on the specific
requirements of the investigator. For manufacturing control,
loading rates shall be fixed, but statistically significant sam-
pling sizes are used such as ANSI/ASME B18.18.2M,
B18.18.3M, or B18.18.4M and Test Method B602 for fasten-
ers.Forotherqualityassurancetests,thesamplingsizeshallbe
in compliance with the requirements of the specification.
The apparatus is covered by a patent. Interested parties are invited to submit
information regarding the identification of an alternative(s) to this patented item to
ASTMHeadquarters.Yourcommentswillreceivecarefulconsiderationatameeting FIG. 1 Suggested Protocol for a Loading Profile to Determine
of the responsible technical committee, which you may attend. Threshold
F 1624
TABLE 1 Suggested Protocol for Eight-Step Test
Step Duration in Hours
8-h Test Load
Load Profile
A
(% P )
ii
#1 #2 #3 #4
12.5 1 1 1
...
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