1、Designation: F1940 07a (Reapproved 2014)Standard Test Method forProcess Control Verification to Prevent HydrogenEmbrittlement in Plated or Coated Fasteners1This standard is issued under the fixed designation F1940; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure to prevent, to theextent possible, int
3、ernal hydrogen embrittlement (IHE) offasteners by monitoring the plating or coating process, such asthose described in Specifications F1137 and F1941. Theprocess is quantitatively monitored on a periodic basis with aminimum number of specimens as compared to qualifying eachlot of fasteners being pla
4、ted or coated. Trend analysis is used toensure quality as compared to statistical sampling analysis ofeach lot of fasteners. This test method consists of a mechanicaltest for the evaluation and control of the potential for IHE thatmay arise from various sources of hydrogen in a plating orcoating pro
5、cess.1.2 This test method consists of a mechanical test, con-ducted on a standard specimen used as a witness, for theevaluation and control of the potential for IHE that may arisefrom various sources of hydrogen in a plating or coatingprocess.1.3 This test method is limited to evaluating hydrogenind
6、uced embrittlement due only to processing (IHE) and notdue to environmental exposure (EHE, see Test Method F1624).1.4 This test method is not intended to measure the relativesusceptibility of steels to either IHE or EHE.1.5 This test method is limited to evaluating processes usedfor plating or coati
7、ng ferrous fasteners.1.6 This test method uses a notched square bar specimenthat conforms to Test Method F519, Type 1e, except that theradius is increased to accommodate the deposition of a largerrange of platings and coatings. For the background on TestMethod F519 testing, see publications ASTM STP
8、 5432andASTM STP 962.3The stress concentration factor is at a Kt=3.1 6 0.2. The sensitivity is demonstrated with a constantimposed cathodic potential to control the amount of hydrogen.Both the sensitivity and the baseline for residual hydrogen willbe established with tests on bare metal specimens in
9、 air.1.7 The sensitivity of each lot of specimens to IHE shall bedemonstrated. A specimen made of AISI E4340 steel heattreated to a hardness range of 50 to 52 HRC is used to producea “worst case” condition and maximize sensitivity to IHE.1.8 The test is an accelerated (24 h) test method tomeasure th
10、e threshold for hydrogen stress cracking, and is usedto quantify the amount of residual hydrogen in the specimen.The specimen undergoes sustained load and slow strain ratetesting by using incremental loads and hold times underdisplacement control to measure a threshold stress in anaccelerated manner
11、 in accordance with Test Method F1624.1.9 In this test method, bending is used instead of tensionbecause it produces the maximum local limit load tensile stressin a notched bar of up to 2.3 times the yield strength asmeasured in accordance with Test Method E8/E8M. A fastenerthat is unintentionally e
12、xposed to bending on installation mayattain this maximum local tensile stress.1.10 The values stated in inch-pound units are to be re-garded as standard. The values given in parentheses aremathematical conversions to SI units that are provided forinformation only and are not considered standard.1.11
13、 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 safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Docu
14、ments2.1 ASTM Standards:4D1193 Specification for Reagent WaterE4 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of Metallic Ma-terials1This test method is under the jurisdiction of ASTM Committee F16 onFasteners and is the direct responsibility of Subcomm
15、ittee F16.93 on QualityAssurance Provisions for Fasteners.Current edition approved Aug. 1, 2014. Published November 2014. Originallypublished as approved in 1998. Last previous edition approved in 2007 asF1940 07a. DOI: 10.1520/F1940-07AR14.2Hydrogen Embrittlement Testing, ASTM STP 543, American Soc
16、iety forTesting and Materials, 1974.3Hydrogen Embrittlement; Prevention and Control, ASTM STP 962, AmericanSociety for Testing and Materials, 1985.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandard
17、s volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE29 Practice for Using Significant Digi
18、ts in Test Data toDetermine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precisi
19、on of a Test MethodE1823 Terminology Relating to Fatigue and Fracture TestingF519 Test Method for Mechanical Hydrogen EmbrittlementEvaluation of Plating/Coating Processes and Service En-vironmentsF1137 Specification for Phosphate/Oil Corrosion ProtectiveCoatings for FastenersF1624 Test Method for Me
20、asurement of Hydrogen Em-brittlement Threshold in Steel by the Incremental StepLoading TechniqueF1941 Specification for Electrodeposited Coatings onThreaded Fasteners (Unified Inch Screw Threads (UN/UNR)G5 Reference Test Method for Making PotentiodynamicAnodic Polarization Measurements2.2 SAE Standa
21、rds:AMS 2759 Hot Drawn, Normalized and Tempered SteelBars. UNS G43406 (AISI E4340)5AMS 3078 Corrosion Preventive Compound, SolventCutback, Cold-Application5AMS 641553. Terminology3.1 Terms and Symbols Specific to This Standard:3.1.1 environmental hydrogen embrittlement (EHE)testconducted in a specif
22、ied environmentembrittlement causedby hydrogen introduced into steel from external sources.3.1.2 internal hydrogen embrittlement (IHE)test con-ducted in airembrittlement caused by residual hydrogenfrom processing3.1.3 ISLththreshold from an incremental step load test ona plated or processed specimen
23、.3.1.4 NFS(B)notched fracture strength in air of a barespecimen in bending at loading rates of 50 to 250 ksi/min (350to 1700 MPa/min).3.1.5 NFS(B)F1624notched fracture strength in air of abare specimen in bending at Test Method F1624 step loadingrates.3.1.6 processa defined event or sequence of even
24、ts thatmay include pretreatments, plating, or coating and posttreat-ments that are being evaluated or qualified.3.1.7 thresholdthe maximum load at the onset of crackingthat is identified by a 5 % drop in load of NSF(B)F1624underdisplacement control.4. Summary of Test Method4.1 Specimens of fixed geo
25、metry, certified to have been heattreated to a hardness range of 50 to 52 HRC, and which havebeen certified to exhibit sensitivity to embrittlement from traceamounts of residual hydrogen in steel, are processed withactual parts.4.2 An unstressed test specimen is processed in accordancewith the plati
26、ng or coating process being qualified. Thespecimen is then tested under incremental step load to measurethe threshold stress. The loading rate must be slow enough toensure that the threshold stress will be detected if deleteriousamounts of hydrogen are present in “worst case” sensitizedspecimens. Lo
27、ading rate protocols are defined in 9.2 and TestMethod F1624.4.3 If the threshold in air of the specimen is 75 %NFS(B)F1624, then the process is considered as to not producesufficient hydrogen to induce time delayed IHE failures in theplated or coated fasteners. See 9.3 for optional limits.4.4 If th
28、e threshold in air of the specimen is 75 % NFS(B)F1624threshold used to qualify theprocess is specified as a minimum value for individual data. Ifstatistical limits are to be applied, they are to be establishedthrough agreement between the manufacturer and purchaser.11. Report11.1 A test report shal
29、l be produced upon completion oftesting that bears the following minimum information:11.1.1 A specimen lot acceptance and sensitivity certifica-tion report,11.1.2 Identification of the process line,11.1.3 A description of the plating or coating process,11.1.4 The threshold load, or percent of notche
30、d fracturestrength or notch bend strength of bare specimens, asappropriate,11.1.5 The time under load, and11.1.6 Disposition of the results.TABLE 4 Minimum Requirements for a Step-Loading Profile forAccelerated (#24 h) Incremental Step Load ThresholdDetermination%NFSF1624#h h %NFSF1624#h h %NFSF1624
31、#h h10 1 1 65 1 8 85 1 1520 1 2 70 1 9 90 1 1630 1 3 72 1 10 95 1 1740 1 4 74 1 11 100 1 1850 1 5 76 1 12 105 1 1955 1 6 78 1 13 110 1 2060 1 7 80 1 14 . . .TABLE 5 Within Laboratory Notch Fracture Strength,NFS(Baseline)Summary of ResultsSQBsTestedNAvg.xStd. DevsMin. Max.95 %Repeat-abilityLimitrStud
32、y 1 37 219.5 6.52 204.4 232.1 18.26Study 2 30 218.5 4.22 210.8 225.9 11.82Average of study averages, x= 219.0Average of study standard deviations, s= 5.37TABLE 6 Precision StatisticsImposedPotentialFractureStrengthAveragexRepea-tabilityStandardDeviationSrReprod-ucibilityStandardDeviationSR95 %Repeat
33、-abilityLimitr95 %Reprod-ucibilityLimitR-1.2 V 71.22 9.88 9.88 27.66 27.66-1.0 V 85.12 9.70 9.70 27.15 27.15-0.9 V 102.97 10.02 10.02 28.06 28.06-0.8 V 179.33 9.77 12.44 27.35 34.83AIR 221.82 5.81 7.16 16.27 20.06F1940 07a (2014)512. Precision and Bias12.1 PrecisionAn interlaboratory test program7wa
34、s de-signed to estimate the precision of the ISL test as it applies tothis test method. The experimental results were entirely gen-erated using notched square bar standard test specimens. Twotesting modes were used; testing in air (that is, no imposedpotential) and testing under potential (for simul
35、ated hydrogencharging conditions).12.1.1 Within Laboratory StudyIn this part of the testprogram, a large number of specimens (minimum 30) weretested in air within 1 laboratory to estimate repeatability withina single laboratory. The time span for testing 30 specimens wasapproximately 8 weeks. This w
36、as due to the length of the testcycle, which can be as long as 24 h. Therefore, to detect anysystematic shift in the values generated by the test apparatus,this test was repeated twice in the space of 1 year. Thesummary results of the study are presented in Table 5.The term repeatability limit is us
37、ed as specified in PracticeE177.12.1.2 Interlaboratory StudyFour testing facilities8, eachusing a single ISL loading frame, participated in the study.With the exception of the number of participating laboratories,four instead of a minimum of six, the study was modeled onPractice E691.9The study cons
38、isted of testing square barspecimens at five different conditions, four at different appliedpotentials, 0.8, -0.9, -1.0, and -1.2 V and one in air. Eachlaboratory performed five replicate tests for each condition.The precision statistics are presented in Table 6.The terms repeatability limit and rep
39、roducibility limit areused as specified in Practice E177.12.2 Bias:12.2.1 To eliminate any bias of results as a result ofvariation in the conditions of specimen manufacture, all thespecimens used for this study were E4340 notched square barspecimens, obtained from a single controlled production lot,
40、manufactured with minimal variation. Therefore, note thatvariance within the specimen population, however minimal,was implicitly considered in the precision estimates.12.2.2 All of the instruments were subject to normal cali-bration procedures by the equipment manufacturer.Any resultsobtained throug
41、h obvious error in procedure or equipmentmalfunction were disqualified from the study.12.2.3 This method has no bias because comparative mea-surement of hydrogen embrittlement is defined only in terms ofthis test method.12.2.4 Random lot-to-lot bias in the properties of square barspecimens related t
42、o raw material or specimen manufacturemay exist. This test method produces a quantitative fractionalmeasure based on the baseline fracture strength of square barspecimens not exposed to hydrogen. Since there is no univer-sally accepted reference or laboratory suitable for determiningthe bias for squ
43、are bar specimens, no justifiable statement ofbias can be made in relation to the baseline fracture strength ofspecimens. However, lot-to-lot bias for square bar specimensdoes not affect the test fractional results provided a baselinefracture strength is established for every lot of square barspecim
44、ens.13. Keywords13.1 coating; delayed failure; displacement control; EHE;fasteners; hydrogen embrittlement; IHE; incremental step load;loading rate; plating; steel; thresholdAPPENDIXES(Nonmandatory Information)X1. ALTERNATE SQUARE BAR THRESHOLD DETERMINATION FOR SPECIFIC PRODUCT LOTSX1.1 ScopeX1.1.1
45、 Since embrittlement related to hydrogen content canvary with hardness, actual fasteners made of low-strength steelmight have more tolerance for residual hydrogen because ofthe process and might not need the rigorous requirement setforth in this standard for threshold. Therefore, adjustments inthres
46、hold requirements can be made for a specific lot offasteners once a correlation is established.NOTE X1.1Note that embrittlement related to hydrogen can also varywith other metallurgical and chemical characteristics of steel and that“low-strength steel” is not always a predictor of more tolerance for
47、residual hydrogen.X1.1.2 To obtain a correlation between actual productionfasteners from singular lots and specimen threshold levels inthis standard, the threshold level or hydrogen tolerance levelfor the production hardware can be measured using four-pointbending in accordance with Test Method F162
48、4 as a functionof an applied electrical potential verses a saturated calomelelectrode, (SCE) in a 3.5 % sodium chloride solution. Anexample of four-point bend fixturing used for Test MethodF1624 testing is shown in Fig. X1.1 in which the tensile stressin bending, b, at the root of the thread can be
49、computed usingthe following formula:7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:F16-1000.8Galvano Division of Ifastgroupe, Camcar-Textron, Elco-Textron, RSL Tech-nology Center.9This study was conducted in 19971998. At the time, there was a very limitednumber of facilities equipped to perform such testing. Further testing involvingmore facilities shall be conducted to make the study fully compliant with PracticeE691.F1940 07a (2014)6b5 32 M/Dt3! (X1.1)where:Dt= minimum thread dia
