ASTM F2660-2012 Standard Test Method for Qualifying Coatings for Use on A490 Structural Bolts Relative to Hydrogen Embrittlement《用于A490氢脆结构螺栓的合格涂层的标准试验方法》.pdf

《ASTM F2660-2012 Standard Test Method for Qualifying Coatings for Use on A490 Structural Bolts Relative to Hydrogen Embrittlement《用于A490氢脆结构螺栓的合格涂层的标准试验方法》.pdf》由会员分享，可在线阅读，更多相关《ASTM F2660-2012 Standard Test Method for Qualifying Coatings for Use on A490 Structural Bolts Relative to Hydrogen Embrittlement《用于A490氢脆结构螺栓的合格涂层的标准试验方法》.pdf（7页珍藏版）》请在麦多课文档分享上搜索。

1、Designation: F2660 12Standard Test Method forQualifying Coatings for Use on A490 Structural BoltsRelative to Hydrogen Embrittlement1This standard is issued under the fixed designation F2660; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re

2、vision, 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 defines the procedures and tests toevaluate the effect of a coating system on the

3、 susceptibility toenvironmental hydrogen embrittlement (EHE) of an ASTMA490 high strength structural bolt.1.2 This test method shall qualify a coating system for usewith any size of A490 bolts (that is,12 to 1-12 in.) high strengthstructural bolts, relative to EHE.1.3 The characteristic to be evalua

4、ted by this test method isthe susceptibility to EHE caused by hydrogen generated fromcorrosion protection of the steel bolt by sacrificial galvaniccorrosion of the coating. Testing shall be performed on coated,specimen ASTM A490 bolts manufactured to the maximumsusceptible tensile strength values (s

5、ee Table 1) of the bolt (seeSection 5 Specimen Bolt Requirements). The internal hydro-gen embrittlement (IHE) susceptibility will also be inherentlyevaluated when the EHE is tested through this test method.There is no need for a separate IHE susceptibility test.1.4 This standard does not purport to

6、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 Documents2.1 ASTM Standards:2A490 Speci

7、fication for Structural Bolts, Alloy Steel, HeatTreated, 150 ksi Minimum Tensile StrengthE4 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of Metallic Ma-terialsF519 Test Method for Mechanical Hydrogen EmbrittlementEvaluation of Plating/Coating Processes

8、and Service En-vironmentsF606 Test Methods for Determining the Mechanical Proper-ties of Externally and Internally Threaded Fasteners,Washers, Direct Tension Indicators, and RivetsF1624 Test Method for Measurement of Hydrogen Em-brittlement Threshold in Steel by the Incremental StepLoading Technique

9、F1789 Terminology for F16 Mechanical FastenersF2078 Terminology Relating to Hydrogen EmbrittlementTestingG3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion TestingG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)3G44 Practice for Exposure o

10、f Metals andAlloys byAlternateImmersion in Neutral 3.5 % Sodium Chloride SolutionG82 Guide for Development and Use of a Galvanic Seriesfor Predicting Galvanic Corrosion Performance2.2 Research Council on Structural Connections:Specification for Structural Joints Using High Strength Bolts(LRFD) Load

11、and Resistance Factor DesignSpecification for Structural Joints Using High Strength Bolts(ASD) Allowable Stress Design2.3 Other References:Townsend Jr., H. E., Met Trans, V6A, April, 1976Raymond, L., The Susceptibility of Fasteners to HydrogenEmbrittlement and Stress Corrosion Cracking: FastenerSyst

12、em Design. In J. H. Bickford, therefore, thespecimen bolts shall not have standard A490 markings so theywill not be identified as standard A490 bolts.5.1.2 Specimen bolts shall be one of two nominal inch sizes:3/4-10 UNC or 1-8 UNC. Alternatively, small specimen sizebolts, 1/2-13 UNC may be used, bu

13、t are subject to more severestrength requirements shown in 8.4.5.1.3 Specimen bolts shall for a lot that displays themaximum wedge tensile load condition permitted by Specifi-cation A490, when tested in accordance with Test MethodsF606. Table 1 gives the range of acceptable wedge tensile loadsfor ea

14、ch specimen bolt size.5.1.4 Specimen bolts shall be from homogeneous lots trace-able to given mill heats of steel alloy.5.1.5 Test results shall be provided by an ISO 17025accredited laboratory. Wedge tensile strengths for the specimenbolts must be within the range specified in Table 1 anddimensiona

15、l and compositional conformance to SpecificationA490 shall be provided by the supplier of each specimen lot.5.2 Coatings:5.2.1 The coating to be evaluated shall be applied to allspecimen bolts under normal production conditions.5.2.2 The process of coating specimen bolts shall include allpost-coatin

16、g processing under normal production conditions.6. Sample Quantities Required6.1 A minimum of fifteen (15) bolts from any specimen lotshall be used for evaluation and qualification. Ten (10) boltsshall be coated and the remaining five (5) bolts shall remainuncoated. Additional samples may be require

17、d for repeat testand shall be held in contingency.7. Test Procedures7.1 Open Circuit Potential (OCP):7.1.1 The freely corroding or Open Circuit Potential (OCP)shall be measured in 3.5% NaCl solution produced in accor-dance with Practice G44 to characterize the galvanic corrosionbehavior of the coati

18、ng relative to the steel bolt. The OCPmeasurement shall be made on a coated specimen bolt inaccordance with Practice G3. The OCP measurement shall betaken using a potentiostat capable of making measurementswith a resolution no less than 6 5mV.NOTE 1If the coating is a known material then the measure

19、d OCP canbe compared to the values described in Guide G82.7.1.2 A second OCP test shall be performed and the twotests shall be compared for consistency. If the OCP test is not6 5 mV with a known value for a known coating or with theother OCP test for an unknown coating, then a known materialother th

20、an the coating shall be used to test the accuracy of thereference electrode. If the electrode is accurate, then anotherbolt sample shall be tested to obtain consistency. Some reasonsfor inconsistency include dissimilar materials in the test setupor coating voids that can change the OCP value.7.2 Env

21、ironmental Hydrogen Embrittlement Testing:7.2.1 Mechanical Test Set-up:7.2.1.1 The test shall be conducted on bolts that have beentruncated by removal of the bolt head. Cut off the bolt headusing a water cooled cut off saw or other device that does notcause excessive heating of the bolt. The length

22、of the specimenbolt for testing shall be a minimum length of 1.5 inches and amaximum length of 4.0 inches. The truncated bolt specimenshall be adjusted to achieve the placement of a minimum oftwo threads between the gripping devices. The exposed threadsshall be equally spaced on each side of the min

23、or diameter ofthe threads. This placement of the bolt specimen in the grippingdevice is shown in Fig. 1.7.2.1.2 The loading method required for this test is afour-point (4 pt) bend, which produces constant moment alongthe gage section so that the stress may be calculated anywherealong the length of

24、the fastener. The test is conducted underdisplacement control. The loading method shall have a speci-fied load accuracy of 6 0.5%, programmable to increaseincrementally in steps of load and time. The loading methodshall be within the guidelines of calibration, force range,resolution, and verificatio

25、n of Practices E4.7.2.2 Fast Fracture Testing:7.2.2.1 The first step in the testing sequence shall be ameasurement of the fast fracture load of the specimen bolts inbending. Determine this value by performing a test in accor-dance with Test Method F1624, Section 8, as shown in Fig. 2A,using a fast f

26、racture protocol. Test a minimum of five uncoatedspecimen bolts and a minimum of five coated specimen bolts.TABLE 1 Specimen Bolt Sizes and Wedge Tensile Load ValuesNominalSizeMinimumLengthTensileStressAreaWedge TensileLoad(D) (in.)As(in.2)Min.(lb)Max.(lb)1/2-13 1-1/2 0.1419 25,600 27,6003/4-10 2-1/

27、2 0.3345 59,000 63,0001-8 5 0.6057 103,000 107,000F2660 122The average of these five test results shall determine the fastfracture strength of each condition.7.2.2.2 The average fast fracture strength in bending ofcoated bolts, FFS(B)coatedmust be within 6 5% of the averagefast fracture strength for

28、 uncoated bolts, FFS(B)uncoated.Ifthecoated bolts exhibit a fast fracture strength that is below 95%of the fast fracture strength for uncoated bolts, the coating isdisqualified from this test.NOTE 2Lower than 95% fast fracture strength for the coated samplesis an indication that the coating process

29、may have affected the strength ofthe specimen bolts.FIG. 1 Four-Point Bend Loading of Fasteners. Maximum Tensile Stress, t= 32Pb/d3FIG. 2F2660 1237.2.3 EHE Sample Testing:7.2.3.1 To measure the EHE susceptibility of the fastener/coating system, bolts are tested in the environment/setupdescribed in s

30、ection 7.1.1 and 7.2.3.3 using the step loadmethodology described in Test Method F1624, Section 8, tomeasure Pth.7.2.3.2 A galvanic condition (see Addendum) is created byinscribing a mark in the coating at the root of a bolt thread toexpose the steel substrate. This condition simulates a damagedcoat

31、ing, also referred to as “coating holiday.” The scribe markin the coating shall be located between the exposed threads (seeFig. 1) between the gripping devices and shall have a length ofone diameter and a width that exposes the thread count. Caremust be taken not to cause any damage in the form of a

32、 notchto the bolt itself. To this end an abrasive medium, lower inhardness than the bolt material is recommended.NOTE 3For example, a wire can be placed at the base of the exposedthread in scribing the coating circumferentially to a length of onediameter.7.2.3.3 To test at the OCP of the coating, th

33、e environmentalchamber shall be partially filled with 3.5% NaCl solutionproduced in accordance with Practice G44 with the level of thesolution being maintained below the threshold section of thebolt specimen. The reference electrode shall be placed in closevicinity to the scribe mark. An electrochem

34、ical potential equalto the measured OCP from section 7.1 shall be imposed on thespecimen during the test to negate the influence of anydissimilar metals in the environmental chamber, such as theloading pins and gripping devices. When the potential readingis stable, the remaining salt solution is add

35、ed to the chamber tofully immerse the bolt sample.(1) As an alternative to imposing an electrochemicalpotential, the test can be performed under freely corrodingconditions, provided the coated specimen is isolated from allmetal contacts. It should be verified that there is no conduc-tivity between t

36、he specimen and the adapters. The freelycorroding potential, or OCP (section 7.1), shall be measuredand recorded.7.2.3.4 The loading profile of the first coated sample boltshall be (10/5/2,4), or ten (10) steps tested with a hold time of2-hours followed by ten (10) steps at a hold time of 4-hours in

37、5% increments of FFS(B)coated, taken as the initial value ofPmax. Loading is not released during the transition from the2-hour to 4-hour hold requirement. The test proceeds until thesample experiences a load drop of more than 5% during anysingle step in the load rate. An example of the step loadingp

38、rofile is shown in Fig. 2B.7.2.3.5 Subsequent tests shall be at progressively decreasingloading rates by using the same (10/5/2,4) profile and loweringPmaxto the value of the previous threshold load therebylowering the Pfor each loading step.As Pmaxis decreased, theresolution is increased and the lo

39、ading rate is decreased. Thetest proceeds until the sample experiences a load drop of morethan 5% during any single step in the load rate.7.2.3.6 The threshold load for the coated bolts, Pth,isobtained when the threshold load for the subsequent test iswithin a value of 5% of Pmaxof the threshold loa

40、d measured onthe previous test at the higher loading rate. The minimum valueof the threshold load obtained through these measurementsshall be used in the calculation described in Section 8. Thelowest threshold value established by consecutive tests shall beconsidered the threshold load for the coate

41、d bolts, Pth. Theminimum number of samples to accomplish the establishmentof the threshold load shall be five (5) coated specimen bolts.8. EHE Acceptance Criterion for Coated ASTM A490Bolts8.1 Perform tests on fasteners to the same hydrogen em-brittlement acceptance criterion as the Test Method F519

42、, Type1a specimens that require a threshold stress equal in value tothat of 75% of the notch tensile strength (NTS = 1.6 UTS) ofthe Type 1a specimen, which is equal to or greater than 1.2UTS.8.2 To obtain the equivalent acceptance criterion for thecoatedASTM A490 bolt, the net tensile stress at the

43、root of thethread should also be equal to or greater than 1.2 UTS. Sinced/D for fasteners is always greater than 0.8, that is greater than0.7 used with Test Method F519 notched tensile specimen, thefastener must be tested in bending to attain the same stresslevel.8.3 The acceptance criterion for EHE

44、 shall be a thresholdload in bending, b, to produce the same stress or greater thanthe load in tension that produces a stress of 1.2 UTS or b 1.2UTS. Since the limit load of a bolt in bending equals2.3YS 2.0 UTS; the acceptance criterion for EHE is equiva-lent to 60% of the fast fracture load in ben

45、ding, FFS(B)coated.8.3.1 Therefore for acceptance of a coating system for A490bolts, the following condition must be met:Pth$0.6FFS(B)coated(1)8.4 Bolt Size EquivalenceBased on the Fastener AnalysisDiagram (see Note 4), a smaller diameter bolt size can betested to satisfy the acceptance criterion fo

46、r a larger bolt sizediameter if it attains a threshold load with a higher value thanthe minimum value of 60% of the fracture load in bending.This ratio is defined as the hydrogen susceptibility ratio, Hsr, inTerminology F2078. The acceptance criteria is based on Hsrbeing 1.2 or 60% FFS(B).8.4.1 From

47、 the references in Note 4, the relationship be-tween two diameters is defined by the following equation:Hsr0*f d0D0! =D05 Hsr1*f d1D1! =D1(2)8.4.2 Using the dimensional parameters for d1and D1for alarger size bolt and inputting a value of Hsr1= 1.2, theequivalent Hsr0value for the smaller sized test

48、ed bolt with d0and D0can be calculated. These are the minimum values for asmaller diameter bolt size to satisfy the acceptance criterion fora larger bolt size. The f(d/D) function is found in Tada, H.,Paris, P. and Irwin, G., Stress Analysis of Cracks Handbook,S 27.2.8.4.3 This equivalence among the

49、 different sizes is summa-rized in Table 2.NOTE 4For more detail see reference: Raymond, L., Handbook ofBolts and Bolted Joints, pp. 745-747. Calculations are based on dimen-sions given in ASME B1.1-2003, Table 6. Basic Dimensions for CoarseThread Series (UNC/UNRC).F2660 1248.4.4 For example, using a 1/2“D bolt, which needs 60%FFS(B) to satisfy its basic acceptance criterion requirement forEHE, would need to attain a threshold of 72% FFS(B) tosatisfy the acceptance criterion for a 3/4“D bolt, 82.2%FFS(B) to satisfy the acceptance criterion for a 1.0“D bol