1、Designation: F 1624 06Standard Test Method forMeasurement of Hydrogen Embrittlement Threshold in Steelby the Incremental Step Loading Technique1This standard is issued under the fixed designation F 1624; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONHydrogen embrittlement is caused by the introduction of hydrogen into steel that can
3、 initiatefracture as a result of residual stress or in service when external stress is applied (1).2The hydrogencan be generated during cleaning or plating processes or the exposure of cathodically protected steelparts to a service environment including fluids, cleaning treatments, or maintenance ch
4、emicals thatmay contact the surface of steel components. This method can be used to rapidly determine the effectsof residual hydrogen in a part caused by processing or quantify the relative susceptibility of a materialunder a fixed set of hydrogen-charging conditions.The combined residual and applie
5、d stress above which time-delayed fracture will occur (finite life)or below which fracture will never occur (infinite life) is called the threshold stress or threshold stressintensity (K) for precracked specimens. Historically, sustained load time-to-failure tests have beenconducted on notched bars
6、to determine the threshold stress for the onset of hydrogen stress cracking.This technique may require 12 to 14 specimens and several high-load capacity machines. Forprecracked specimens, the run-out time can be as long as four to five years per U.S. Navy requirementsfor low-strength steels at 33 to
7、 35 HRC. In Test Method E 1681, more than 10 000 h ( one year) arespecified for low-strength steel ( 175 ksi).This standard provides an accelerated method to measure the threshold stress or threshold stressintensity as defined in Test Method E 1681 for the onset of hydrogen stress cracking in steel
8、withinone week on only one machine.1. Scope1.1 This test method establishes a procedure to measure thesusceptibility of steel to a time-delayed failure such as thatcaused by hydrogen. It does so by measuring the threshold forthe onset of subcritical crack growth using standard fracturemechanics spec
9、imens, irregular-shaped specimens such asnotched round bars, or actual product such as fasteners (2)(threaded or unthreaded) springs or components as identified inSAE J78, J81, and J1237.1.2 This test method is used to evaluate quantitatively:1.2.1 The relative susceptibility of steels of different
10、com-position or a steel with different heat treatments;1.2.2 The effect of residual hydrogen in the steel as a resultof processing, such as melting, thermal mechanical working,surface treatments, coatings, and electroplating;1.2.3 The effect of hydrogen introduced into the steel causedby external en
11、vironmental sources of hydrogen, such as fluidsand cleaners maintenance chemicals, petrochemical products,and galvanic coupling in an aqueous environment.1.3 The test is performed either in air, to measure the effectif residual hydrogen is in the steel because of the processing(IHE), or in a control
12、led environment, to measure the effect ofhydrogen introduced into the steel as a result of the externalsources of hydrogen (EHE) as detailed in ASTM STP 543.1.4 The values stated in acceptable inch-pound units shallbe regarded as the standard. The values stated in metric unitsmay not be exact equiva
13、lents. Conversion of the inch-poundunits by appropriate conversion factors is required to obtainexact equivalence.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate s
14、afety and health practices and determine the applica-bility of regulatory limitations prior to use.1This test method is under the jurisdiction of ASTM Committee F07 onAerospace and Aircraft and is the direct responsibility of Subcommittee F07.04 onHydrogen Embrittlement.Current edition approved Apri
15、l 1, 2006. Published May 2006. Originallyapproved in 1995. Last previous edition approved in 2000 as F 1624 00.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1942
16、8-2959, United States.2. Referenced Documents2.1 ASTM Standards:3B 602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE8 Test Methods for Tension Testing of Metallic M
17、aterialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE 399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE 812 Test Method for Crack Strength of Slow-Bend Pre-cracked Charpy Specimens of High-Strength Metall
18、icMaterials4E 1681 Test Method for Determining Threshold Stress In-tensity Factor for Environment-Assisted Cracking of Me-tallic MaterialsF 519 Test Method for Mechanical Hydrogen Embrittle-ment Evaluation of Plating/Coating Processes and ServiceEnvironmentsF 606 Test Methods for Determining the Mec
19、hanical Prop-erties of Externally and Internally Threaded Fasteners,Washers, and RivetsF 2078 Terminology Relating to Hydrogen EmbrittlementTestingG5 Reference Test Method for Making Potentiostatic andPotentiodynamic Anodic Polarization MeasurementsG 129 Practice for Slow Strain Rate Testing to Eval
20、uate theSusceptibility of Metallic Materials to EnvironmentallyAssisted Cracking2.2 SAE Standards:J78 Self-Drilling Tapping Screws5J81 Thread Rolling Screws5J1237 Metric Thread Rolling Screws52.3 ANSI/ASME:B18.18.2M Inspection and Quality Assurance for High-Volume Machine Assembly Fasteners, 19876B1
21、8.18.3M Inspection and Quality Assurance for SpecialPurpose Fasteners, 19876B18.18.4M Inspection and Quality Assurance for Fastenersfor Highly Specialized Engineering Applications, 198762.4 Related Publications:ASTM STP 543, Hydrogen Embrittlement Testing, 19747ASTM STP 962, Hydrogen Embrittlement:
22、Prevention andControl, 198573. Terminology3.1 SymbolsTerms not defined in this section can be foundin Terminologies F 2078 and E6and shall be considered asapplicable to the terms used in this test method.3.1.1 Papplied load.3.1.2 Pccritical load required to rupture a specimen usinga continuous loadi
23、ng rate.3.1.3 Picrack initiation load for a given loading andenvironmental condition using an incrementally increasingload under displacement control.3.1.4 Pththreshold load where Piis invariant with respectto loading rate. Pthis the basis for calculating the thresholdstress or the threshold stress
24、intensity.3.1.5 IHEInternal Hydrogen Embrittlement test con-ducted in air.3.1.6 EHEEnvironmental Hydrogen Embrittlement test conducted in a specified hydrogen-charging environment.3.1.7 ththreshold the lowest load at which subcriticalcracking can be detected.3.2 Irregular Geometry-Type Specimenstest
25、 sample otherthan a fracture mechanics-type specimen; examples include anotched round bar or fastener.3.2.1 s = applied stress.3.2.2 snet= net stress based on area at minimum diameter ofnotched round bar or per Test Method E 812 for bend speci-mens.3.2.3 si= stress at crack initiation.3.2.4 sth= thr
26、eshold stress.3.2.5 sth-IHE= IHE threshold stress test conducted in air geometry dependent.3.2.6 sth-EHE= EHE threshold stress test conducted in aspecified hydrogen charging environment geometry depen-dent.3.2.7 Kth-IHE= IHE threshold stress intensity at a specifiedloading rate test conducted in air
27、 not geometry depen-dent.3.2.8 Kth-EHE= EHE threshold stress intensity at a specifiedloading rate test conducted in a specified hydrogen chargingenvironment not geometry dependent.3.2.9 KIIHE= invariant value of the IHE threshold stressintensity test conducted in air not geometry dependent.3.2.10 KI
28、EHE= invariant value of the EHE threshold stressintensity test conducted in a specified hydrogen chargingenvironment not geometry dependent equivalent toKIEAC.3.2.11 NFS = Notched Fracture Strength.4. Summary of Test Method4.1 The test method is based on determining the onset ofsubcritical crack gro
29、wth with a step modified, incrementallyincreasing, slow strain rate test (Practice G 129) under dis-placement control (3), (4), (5).4.2 This test method measures the load necessary to initiatea subcritical crack in the steel at progressively decreasingloading rates, for specimens of different geomet
30、ry and differentenvironmental conditions.4.2.1 By progressively decreasing the loading rate, thethreshold stress can be determined.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informa
31、tion, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.5Available from Society of Automotive Engineers (SAE), 400 CommonwealthDr., Warrendale, PA 15096-0001.6Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.7Available
32、 from ASTM, 100 Barr Harbor Dr., PO Box C700, West Consho-hocken, PA 19428.F16240624.3 Four-point bending is used to maintain a constantmoment along the specimen. This condition is used to simplifythe calculation of stress or stress intensity for an irregular crosssection.4.4 The minimum or invarian
33、t value of the stress intensity(KIEHE) or stress for a given geometry with regard to theloading rate, is the threshold for the onset of crack growth dueto hydrogen embrittlement.4.5 In tension and bending, the onset of subcritical crackgrowth as a result of hydrogen in steel is identified by decreas
34、ein load while holding the displacement constant.4.6 The displacement is incrementally increased in tensionor four-point bending and the resulting load is monitored.While the displacement is held constant, the onset of subcriti-cal crack growth is detected when the load decreases.4.7 The loading rat
35、e must be sufficiently slow to permithydrogen to diffuse and induce cracking that manifests itself asa degradation in strength (see Pollock (6) and (7).5. Significance and Use5.1 This test method is used for research, design, serviceevaluation, manufacturing control, and development. This testmethod
36、 quantitatively measures stress parameters that are usedin a design or failure analysis that takes into account the effectsof environmental exposure including that which occurs duringprocessing, such as plating (8) (ASTM STP 962).5.2 For plating processes, the value of sth-IHEis used tospecify quant
37、itatively the maximum operating stress for agiven structure or product.5.3 For quality control purposes, an accelerated test isdevised that uses a specified loading rate, which is equal to orlower than the loading rate necessary to determine the thresh-old stress (see 8.1).5.4 For fasteners, the val
38、ue of sth-IHEis used to specifyquantitatively the maximum stress during installation and inservice to avoid premature failure caused by residual hydrogenin the steel as a result of processing.5.5 For fasteners, the value of sth-EHEis used to specifyquantitatively the maximum stress during installati
39、on and inservice to avoid failure from hydrogen absorbed during expo-sure to a specific environment.5.6 To measure the relative susceptibility of steels to hydro-gen pickup from various fabrication processes, a single,selected, discriminating rate is used to rank the resistance ofvarious materials t
40、o hydrogen embrittlement.6. Apparatus6.1 Testing MachineTesting machines shall be within theguidelines of calibration, force range, resolution, and verifica-tion of Practices E4.6.2 Gripping DevicesVarious types of gripping devicesshall be used in either tension or four-point bending to transmitthe
41、measured load applied by the testing machine to the testspecimen.6.3 Test EnvironmentThe test shall be conducted in air orany other suitable controlled environment using an appropriateinert container.6.3.1 Potentiostatic ControlThe corrosion potential of thespecimen can be controlled with a referenc
42、e saturated calomelelectrode (SCE) or equivalent reference electrode such asAg/AgCl in accordance with Test Method G5. The imposedpotential is typically cathodic, ranging from 0.0 to 1.2 Vversus SCE (VSCE) in a 3.5 weight percent NaCl solution (9).7. Sampling and Test Specimens7.1 SamplingFor resear
43、ch, design, and service evaluationand development, the sampling size depends on the specificrequirements of the investigator. For manufacturing control,loading rates shall be fixed, but statistically significant sam-pling sizes are used such as Test Methods F 606, ANSI/ASMEB18.18.2M, B18.18.3M, or B
44、18.18.4M andTest Method B 602for fasteners. For other quality assurance tests, the samplingsize shall be in compliance with the requirements of thespecification.7.2 Test SpecimensThe test specimen should be classifiedas either fracture mechanics-type specimens or irregular-shaped specimens (10).7.2.
45、1 Fracture mechanics-type specimens are defined instandards such as Test Method E 399.NOTE 1The maximum stress used during fatigue precracking must beless than 60 % of any measured value of load for crack initiation for thedata to be valid.7.2.2 Irregular geometry-type specimens shall be eitherspeci
46、mens as defined in standards such as Test Method F 519or specimens from product. The product shall be tested eithersubstantially full size or as a machined specimen.8. Procedure8.1 Determination of Threshold Load:8.1.1 Load one specimen to rupture at a rate consistent withTest Methods E8to establish
47、 the maximum fracture load orNFS for a given specimen geometry, (NFS = Pcin Fig. 1).8.1.2 Another sample (#1) is tested by applying an incre-mental or step loads under displacement control in tension orfour-point bending, programmed to attain Pc.FIG. 1 Schematic of Suggested Protocol for a Step Load
48、ingProfile to Determine ThresholdF16240638.1.3 Another sample (#2) is tested using load incrementsprogrammed to attain Pc, only at a slower loading rate, byusing the same load increment and doubling the time incre-ment. In no case should the loading rate be faster than that ofthe previous sample. Th
49、is load sequence will continue until asignificant drop in load is detected that will establish the valuedesignated as Pi2.8.1.4 Subsequent specimens are tested at progressivelydecreasing loading rates to attain Pc. This load sequence willcontinue until a significant drop in load is detected that willestablish the value designated as Pi3. It is suggested that thetime increment be doubled, at least at values in excess of 0.5 Piias shown for Sample #4 in Fig. 1. The procedure shall becontinued until an invariant value (Pth) is obtained.8.1
