磁粉检测标准导则英文版 ASTM E709-21 Standard Guide for Magnetic Particle Testing

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) CommitteeDesignation:E709-21
INTERNATIONAL
Standard Guide for
Magnetic Particle Testing
This standard is issued under the fixed designation E709; the number immediately following the designation indicates the year oforiginaladoptionor,inthecaseofrevisiontheyearoflastrevisionAnumberinparenthesesindicatestheyearoflastreapproval.superscriptepsilon(e)indicates aneditorial changesincethelastrevisionorreapproval.1.Scope*
1.1 This guide2 covers techniques for both dry and wetmagnetic particle testing, a nondestructive method for detect-ing cracks and other discontinuities at or near the surface inferromagnetic materials.Magnetic particle testing may beapplied to raw material, semifinished material (billets, blooms,castings,and forgings),finishedmaterial and welds,regardlessof heat treatment or lack thereof.It is useful for preventivemaintenance testing.
1.1.1 This guide is intended as a reference to aid in thepreparation of specifications/standards,procedures and tech-niques,
1.2 This guide is also a reference that may be used asfollows:
1.2.1 To establish a means by which magnetic particletesting,procedures recommended or required by individualorganizations, can be reviewed to evaluate their applicabilityand completeness.
1.2.2To aid in theorganization of the facilities and person-nel concerned in magnetic particle testing.1.2.3 To aid in the preparation of procedures dealing withthe examination of materials and partsThis guide describesmagneticparticletestingtechniquesthatarerecommendedfora great variety of sizes and shapes of ferromagnetic materialsand widely varying examination requirements. Since there aremany acceptable differences in both procedure and technique,the explicit requirements should be covered by a writtenprocedure (see Section 21)
1.3 This guide does not indicate, suggest, or specify acceptance standards for parts/pieces examined by these techniques.It should bepointed out, however,that after indications havebeen produced, they must be interpreted or classified and thenevaluated. For this purpose there should be a separate code,specification, ora specific agreement to define the type, size,location, degree of alignment and spacing, area concentration.I This guide is under the jurisdiction of ASTM Commitee E07 on Nondestruc-tive Testing and is the direct responsibiltity of Subcommittee E07.03 on LiquidPenetrant and Magnetic Particle Methods.Current edition approved June1,2021.Published July2021.Originally approvedin 1980. Last previous edition approved in 2015 as E709-15.DOI: 10.1520/E0709-21
2For ASME Boiler and Pressure Vessel Code Applications, see related GuideSE-709 in Section Il of that Code.and orientation ofindications that are unacceptable in a specificpart versus those which need not be removed before partacceptance.Conditionswhererework orrepairisnotpermittedshould be specified.
1.4 This guide describes the use of thefollowing magneticparticle method techniques.
1.4.1Drymagneticpowder (see8.4).1.4.2Wetmagnetic particle(see8.5)1.4.3 Magnetic slurry/paintmagnetic particle (see 8.5.7).and
1.4.4Polymermagneticparticle (see8.5.8).1.5PersonnelQualification-Personnelperformingexami-nations in accordance with this guide should be qualified andcertified in accordance withASNTRecommended Practice No.SNT-TC-1A,ANSI/ASNT Standard CP-189,NAS410,or asspecified in the contract or purchase order.1.6 Nondestructive Testing Agency-If a nondestructivetesting agency as described in Specification E543 is used toperform the examination, the nondestructive testing agencyshould meet the requirements of Specification E543.1.7 Units-The values stated in inch-pound units are to beregarded as standard. The values given in parentheses aremathematical conversions to SI units that are provided forinformation only and are not considered standard.1.8 Warning-Mercury has been designated by many regu-latory agencies as a hazardous material that can cause seriousmedical issues. Mercury, or its vapor, has been demonstratedto be hazardous to health and corrosive to materials.Cautionshould be taken when handling mercury and mercury contain-ing products. See the applicable product Safety Data Sheet(SDS)for additional information.Users should be aware thatselling mercury or mercury containing products, orboth, intoyour state or countrymay beprohibited bylaw.1.9 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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.1o This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for the*A Summary of Changes section appears at the end of this standardCopyrightASMIntemational.100BarrHarborDrve.POBoxC700,WestConshohocken,PA19428-2959.UnitedStates1
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Development of International Standards, Guides and Recommendations issued by the World Trade Organization TechnicalBarriersto Trade(TBT)Committee2.Referenced Documents
2.1 ASTM Standards.3
D93Test Methods for Flash Point by Pensky-MartensClosed CupTester
D445Test Method for Kinematic Viscosityof Transparentand Opaque Liquids(and Calculation of Dynamic Viscos-ity)
E165/E165MPractice forLiquid Penetrant Testing for GeneralIndustry
E543SpecificationforAgenciesPerformingNondestructiveTesting
E1316Terminologyfor Nondestructive ExaminationsE1444/E1444MPractice forMagnetic ParticleTestingE3024/E3024MPractice for Magnetic Particle Testing forGeneral Industry
2.2SAE:Aerospace Materials Specifications:+AMs2300Premium Aircraft Quality Steel CleanlinessMagnetic ParticleInspection ProcedureAMS2301Aircraft Quality SteelCleanliness MagneticPar-ticle Inspection Procedure
AMS2303Aircraft Quality SteelCleanliness MartensiticCorrosion Resistant Steels Magnetic Particle InspectionProcedure
AMS2641VehicleMagneticParticleInspectionAMS3040Magnetic Particles,Non-fluorescent,DryMethod
AMS304IMagnetic Particles,Non-fluorescent,WetMethod,OilVehicle,ReadytoUseAMS3042Magnetic Particles,Non-fluorescent,Wet
Method,DryPowder
AMS3043MagneticParticles,Non-fluorescent,OilVehicleAerosol Packaged
AMS3044Magnetic Particles,Fluorescent,Wet MethodDryPowder
AMS3045Magnetic Particles,Non-fluorescent,WetMethod Oil Vehicle,Readyto UseAMs3046Magnetic Particles.Non-fluorescent.Wet
Method,OilVehicle,Aerosol PackagedAMS5062Steel,Low Carbon Bars,Forgings,Tubing.Sheet,Strip,andPlate0.25Carbon,MaximumAMS5355InvestmentCastings
AMS-1-83387InspectionProcess,MagneticRubberAS 4792Water Conditioning Agents forAqueous MagneticParticle Inspection
AS5282Tool Steel Ring Standard for Magnetic ParticleInspection
AS5371ReferenceStandards Notched Shims for MagneticParticle Inspection
For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontactASTM CustomerService at [email protected] Book of ASTMStandardsvolume infomation,referto the standard'sDocumentSummarypageonthe ASTM website.
Available from Society of Automotive Engineers (SAE).400 CommonwealthDr.,Warrendale,PA15096-0001,htp://www.sae.org.2
2.3 ASNT Documents.:5
SNT-TC-IA Personnel Qualification and Certification inNondestructive Testing
CP-189ASNT Qualification and Certification of Nondestructive Testing Personnel
2.4 Federal Standards.6
A-A-59230Fluid.MagneticParticleInspection,SuspensionFED-STD-313Material Safety Data Sheets Preparation andthe Submission of
2.5OSHA Document:7
29CFR 1910.1200 Hazard Communication2.6 AIA Documents:8
NAS410 Nondestructive TestingPersonnel Qualificationand Certification
2.7 Iso Standard:9
ISO7810Identification Cards-Physical Characteristics3.Terminology
3.1 For definitions of terms used in the practice, refer toTerminology E1316
4.SummaryofGuide
4.1 Principle-The magnetic particle method is based onestablishing a magnetic field with high flux density in aferromagnetic material. The flux lines must spread out whenthey pass through non-ferromagnetic material such as air in adiscontinuity or an inclusion. Because flux lines can not cross.this spreading action may force some of the flux lines out of thematerial (flux leakage).Flux leakage is also caused by reduc-tion in ferromagnetic material (cross-sectional change),a sharpdimensional change, or the end of the part. If the flux leakageis strong enough, fine magnetic particles will be held in placeand an accumulation of particles will be visible under theproper lighting conditions. While there are variations in themagnetic particle method, they all are dependent on thisprinciple,that magnetic particleswill be retained at thelocations of magnetic flux leakage.The amount of flux leakageatdiscontinuities depends primarilyon thefollowingfactors:flux density in the material, and size, orientation,and proximityto the surface of a discontinuity.With longitudinal fields,all ofthe flux lines mustcomplete theirloops though airand anexcessively strong magnetic field may interfere with examina-tion near the flux entry and exit points due to the highflux-density present at these points.SAvailable from American Society for Nondestructive Testing (ASNT),P.O. Box28518,1711Arlingate Ln.,.Columbus,OH 43228-0518,http:/www.asnt.orgAvailable from Standardization Documents Order Desk,DODSSP, Bldg.4,Section D.700RobbinsAve.,Philadelphia,PA19111-5098.http://www.dodssp.daps.mil.
7Available from Occupational Safety and Health Administration (OSHA),200Constitution Ave.,NW,Washington,DC20210,http://www.osha.gov.\Available from Aerospace Industries Association of America, Inc. (AIA), 1o00wilsonBlvd.,Suite1700Arlington,VA22209-3928.http://www.aia-aerospace.orgAvailable from International Organization for Standardization (ISO).ISOCentral Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier. Geneva.Switzerland,https:/www.iso.org.PE709-21
4.2 Method-While this practice permits and describesmany variables in equipment, materials, and procedures, thereare three steps essential to the method:4.2.1 The part must be magnetized.4.2.2 Magnetic particles of the type designated in thecontract/purchase order/specification should be applied whilethe part is magnetized or immediately thereafter4.2.3 Any accumulation of magnetic particles must beobserved, interpreted, and evaluated.4.3Magnetization:
4.3.1WaystoMagnetize--Aferromagneticmaterial canbemagnetized either by passing an electric current through thematerial or by placing the material within a magnetic fieldoriginated by an external source. The entire mass or a portionof the mass can be magnetized as dictated by size andequipment capacity or need. As previously noted, in order tobedetectable,thediscontinuitymustinterruptthenormalpathofthe magnetic field lines. If a discontinuity is open to thesurface, the flux leakage attracting the particles will be at themaximum value for that particular discontinuity. When thatsame discontinuity is below the surface, flux leakage evidenton thesurfacewill be alesservalue.4.3.2FieldDirectionIfadiscontinuityisoriented parallelto the magnetic field lines, it may be essentially undetectable.Therefore, since discontinuities may occur in any orientation,itmay be necessary to magnetize the part or the area of interesttwice or more sequentially in different directions by the samemethod or a combination of different methods (see Section 13)to induce magnetic field lines in a suitable direction in whichto perform anadequate examination.4.3.3Field Strength-The magnetic field must be of sufi-cient strength to indicate those discontinuities which areunacceptable,yet must not be so strong that an excess oflocalparticle accumulation masks relevant indications (see Section14)
4.4 Types of Magnetic Particles and Their Use-There arevarious types ofmagneticparticles availableforuseinmagnetic particle testing, They are available as dry powders(fluorescent and nonfluorescent) ready for use as supplied (see8.4),powder concentrates (fluorescent and nonfluorescent)fordispersion in water or suspending in light petroleum distillates(see 8.5), magnetic slurries/paints (see 8.5.7), and magneticpolymerdispersions(see8.5.8)4.5 Evaluation of Indications-When the material to beexamined hasbeen properlymagnetized,the magneticparticleshavebeen properly applied,and the excess particles properlyremoved, there will be accumulations of magnetic particlesremaining at the points of flux leakage. These accumulationsshow the distortion of the magnetic field and are calledindications.Without disturbing the particles,the indicationsmust be examined, classified, compared with the acceptancestandards,and a decision made concerningthedisposition ofthe material that contains the indication4.6TypicalMagneticParticle Indications:4.6.1SurfaceDiscontinuities-Surfacediscontinuities,withfew exceptions,produce sharp, distinct patterns (see AnnexA.
4.6.2 Near-surface Discontinuities-Near-surface disconti-nuitiesproducelessdistinctindications thanthoseopentothesurface.The patterns tend to be broad, rather than sharp, andthe particles are less tightly held (see Annex Al).5.SignificanceandUse
5.1 The magnetic particle method of nondestructive testingindicates the presence of surface and near-surface discontinui-ties in materials that can be magnetized (ferromagnetic). Thismethod can be used for production examination of parts/components or structures and for field applications whereportability of equipment and accessibility to the area to beexaminedarefactors.Theabilityofthemethodtofind smalldiscontinuities can be enhanced by using fluorescent particlessuspended in a suitable vehicle and by introducing a magneticfield of the proper strength whose orientation is as close aspossible to 90° to the direction of the suspected discontinuity(see 4.3.2).A smoother surfaceorapulsed currentimprovesmobility of the magnetic particles under the influence of themagnetic field to collect on the surface where magnetic fluxleakageoccurs
6.Equipment
6.1 Types-There are a number of types of equipmentavailableformagnetizingferromagneticpartsandcomponents.FIG.1(a)Articulating Yoke Method of Part Magnetization3
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With the exception of a permanentmagnet,all equipmentrequires a power source capable of delivering the requiredcurrent levels to produce the magnetic field. The current useddictates the sizes of cables and the capability of relays,switching contacts,meters and rectifier if the power source isalternatingcurrent
6.2 Portability-Portability, which includes the ability tohand carry the equipment, can be obtained from yokes,portable coils with power supplies, and capacitor dischargepower supplies with cables: Generally,portable coils providehighmagnetizingforcesbyusinghighernumbersofturnstocompensate for theirlower current flow.Capacitor dischargeunits use high current storage capacity and provide these highcurrent levels for only a very short duration.6.3 Yokes-Yokes are usually C-shaped electromagnetswhich induce a magnetic fieldbetween the poles (legs)and areused for local magnetization (Fig.l(a)).Manyportableyokeshave articulated legs (poles) that allow the legs to be adjustedto contact irregular surfaces or two surfaces that join at anangle.
6.3.1PermanentMagnets—-Permanentmagnets (Fig.1(b))are available but their use may be restricted for many applica-tions.This restriction may be dueto application impracticality,or due to the specifications governing the examination.Permanent magnets can lose their magnetic field generating capacityby being partially demagnetized by a stronger flux field,beingdamaged,ordropped.Inaddition,theparticlemobilitycreatedby AC current or HW current pulsations produced by electro-magnetic yokes are not present. Particles, steel filings, chips,and scale clinging to the poles can create a housekeepingproblem.
6.4 ProdsProds are used for local magnetizations, see Fig2. The prod tips that contact the piece should be aluminum,copper braid,or copper pads rather than solid copper.Withsolidcoppertips,accidentalarcingduringprodplacementorremoval can cause copper penetration into the surface whichFIG.1 (b)Permanent Magnet Yoke Method of Part Magnetization(continued)
may result in metallurgical damage (softening, hardening,cracking,etc.).Open-circuit voltages should not exceed 25 V.6.4.1Remole Control SwitchA remote-control switch,whichmaybebuiltintotheprodhandles,shouldbeprovidedto permit the current to be turned on after the prods have beenproperly placed and to turn it off before the prods are removedinordertopreventarcing(arcburns).6.5 Bench Unit-Atypical benchtypeunit is shown inFig3.The unit normallyis furnished with a head/tailstock combi-nation alongwitha fixed coil (seeFig.4).6.6 UV-A Lamps,which areportable,hand-held,perma-nently mounted or fixed, and used to examine parts, should bechecked for output at the verification intervals specified inTable 2 and after bulb or filter replacement.Alongerperiodmaybeused if aplanjustifying thisextensionisprepared bythe NDT facility or its delegate.Minimum acceptable intensityis 1000 μW/cmattheexamination surface.Nore IWhen using a mercury vapor style lamp,a change in linevoltagegreaterthan±10 %can cause a change in outputand consequen-tial loss of inspection performance. A constant voltage transformer may beused where there is evidence of voltage changes greater than 10 %.6.6.1UV-A lamps thatuse a UV-ALED source shallproduce a peak wavelength at 360 to 370 nanometers asmeasured with a spectroradiaometer.When requested, themanufacturershallprovideacertificationthereof.6.6.2 Battery-powered UV-A lamps used to examine partsshall have their intensity measured prior to use and after eachuse.
6.7EquipmentVerification-SeeSection207.ExaminationArea
7.1 UV-A Intensityfor Examination-Magnetic indicationsfound using nonfluorescent particles are examined under vis-iblelight.Indicationsfound usingfluorescentparticlesmustbeexamined under UV-A irradiance. This requires a darkenedarea with accompanying control of thevisible light intensity.7.1.1 Visible Light Intensity-The intensity of the visiblelight at the surface of the part/work piece undergoing nonfluo-rescentparticleexamination is recommended to bea minimumof 100 foot candles (1076 lux).7.1.1.1 Field Examinations-For some field examinationsusingnonfluorescentparticles,visiblelightintensitiesaslowas50foot candles (538 lux)maybeusedwhenagreed on by thecontractingagency.
7.1.1.2Ambient Visible Light-The intensity of ambientvisible light in the darkened area where fluorescent magneticparticle testing is performed is recommended to not exceed 2foot candles (21.5 lux).
7.1.2UV-AIrradiance:
7.1.2.1 UV-A Intensiry-The UV-A irradiance at the exami-nationsurfaceisrecommendedtonotbelessthanloooμW/cmwhen measured with a suitable UV-Aradiometer.7.1.2.2 UV-A Lamp Warm-up-When using a mercury vaporbulb, allow the UV-A lamp to warm up for a minimum of fiveminutes prior to its use ormeasurement of the intensity of theultraviolet light UV-A emitted.When using LED UV-A lamps,TypicalSingleProdSet
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TypicalportablepowerpackforprodsTypicalDoubleProdSet
FIG.2Prods
prior to examining parts under UV irradiance. (WarningPhotochromic orpermanently tinted lenses should notbewornduringexamination.)
7.2 Housekeeping-The examination area should be keptfree of interfering debris. If fluorescent materials are involved,the area should also be kept free of fluorescent objects notrelated tothepart/piecebeing examined.8.MagneticParticleMaterials
8.1MagneticParticleProperties:8.1.1Dry Particle Properties-—AMS3040 describes thegenerally accepted properties of drymethod particles.8.1.2 Wet Particle Properties-The following documentsdescribe the generally accepted properties of wet methodFIG.3 Bench Unit
it isrecommendedtoallowthelampto stabilizein accordancewith the manufacturer's recommendations prior to use ormeasurement.
7.1.3DarkArea EyeAdaptation-Thegenerallyacceptedpractice is that an inspector be in the darkened area at least one() minute so that his or her eyes will adapt to dark viewing5
particles in their various forms:AMS3041Magnetic Particles,Non-fluorescent,WetMethod,OilVehicle,ReadytoUseAMS3042MagneticParticles,Non-fluorescent,WetMethod,DryPowder
AMS3043Magnetic Particles,Non-fluorescent,OilVehicle,AerosolPackaged
AMS3044MagneticParticles,Fluorescent,WetMethodDryPowder
Pinion gear in coil
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Conception showing flux distributionwithpart inthebottomof thecoilFIG.4BenchFixed Coil andFieldDistributionAMS3045MagneticParticles,Non-fluorescent,WetMethod, Oil Vehicle, Ready to UseAMS3046 Magnetic Particles,Non-fluorescent,WetMethod,OilVehicle,AerosolPackaged8.1.3 Suspension Vehicle-The suspension vehiclefor wet-method examination may be either a light oil distillate fluid(refertoAMS2641orA-A-52930)oraconditionedwatervehicle (refertoAS4792)
8.2 Particle Types-The particles used in either dry or wetmagnetic particle testing techniques are basically finely dividedferromagneticmaterials which have been treated to impartcolor(fluorescent and nonfluorescent)in ordertomakethemhighly visible (contrasting) against the background of thesurface being examined. The particles are designed for useeither as a freeflowingdry powder orfor suspension at a givenconcentrationinasuitableliquidmedium8.3 Particle CharacteristicsThe magnetic particles musthave highpermeability to allow ease of magnetizing andattraction to the site of the flux leakage and low retentivity sothey will not be attracted (magnetic agglomeration) to eachother. Control of particle size and shape is required to obtainconsistentresults.Theparticles shouldbenontoxic,freefromrust, grease, paint, dirt, and other deleterious materials thatmight interfere with their use; see 20.5 and 20.6.Both dry andwetparticles areconsidered safewhenused in accordancewiththe manufacturer's instructions. They generally afford a verylowhazard potential with regard toflammability and toxicity.8.4Dry Particles-Drymagnetic powders are designed tobe used as supplied and are applied by spraying or dustingdirectly onto the surface of the part being examined. They aregenerally used on an expendable basis because of the require-menttomaintainparticlesizeand controlpossiblecontamina-tion.Reuseisnotanormal practice.Drypowdersmayalsobeused under extreme environmental conditions.They are notaffectedbycold;thereforeexamination canbe carried outattemperatures that would thicken or freeze wet baths. They arealso heat resistant; some powders may be usable at tempera-turesup to 600F (315°C).Some colored,organic coatingsapplied to dry particles to improve contrast lose their color at6
temperatures this high, making the contrast less effective.Fluorescent dry particles cannot be used at this high atemperature; the manufacturer should be contacted for thetemperature limitations (see 15.1.2).8.4.1 Advantages-The dry magnetic particle technique isgenerally superior to the wet technique for detection ofnear-surface discontinuities on parts with a gross indicationsize,Refer to 8.5.l:(a)for large objects when using portableequipment for local magnetization; (b) superior particle mo-bility is obtained for relatively deep-seated flaws using half-waverectified currentas themagnetizing source;(c)ease ofremoval.
8.4.2 Disadvantages-The dry magnetic particle technique;(a)cannot beused in confined areas withoutpropersafetybreathing apparatus; (b) can be difficult to use in overheadmagnetizing positions; (c) does not always leave evidence ofcomplete coverage of part surface as with the wet technique;(d)is likelyto have lowerproduction rates thanthe wettechnique; and (e)is difficult to adapt to any type of automaticsystem
8.4.3Nonfluorescent Colors-Althoughdry magnetic par-ticle powder can be almost any color,the most frequentlyemployed colors are light gray,black,red, or yellow.Thechoice is generally based on maximum contrast with thesurface tobe examined.The examination is done under visiblelight.
8.4.4 Fluorescent-Fluorescent dry magnetic particles arealso available, but are not in general use primarily because oftheir higher cost and use limitations. They require a UV-Asource and a darkened work area. These requirements are notoften available in the field-type locations where dry magneticparticle examinations are especially suitable.8.4.5Dual Response-Dual responseparticles are availablethat are readily detectable in visible light and also displayfluorescence when viewed under UV-A or a combinationvisible and UV-A. Use in accordance with the manufacturer'srecommendations.
8.5 Wet ParticleSystems-Wetmagnetic particles are de-signed to be suspended in a vehicle such as water or lightE709-21
petroleum distillate at a given concentration forapplication tothe examination surfacebyflowing,spraying,or pouring.Theyare available in both fluorescent and nonfluorescent concen-trates.In some cases the particles are premixed with thesuspending vehicle by the supplier, but usually the particles aresupplied as a dry concentrate or paste concentrate which ismixed with the distillate or water by the user.The suspensionsare normally used in wet horizontal magnetic particle equip-ment in which the suspension is retained in a reservoir andrecirculated for continuous use. The suspension may also beused on an expendablebasis dispensedfroman aerosol orothersuitabledispensers
8.5.1Primary Use-Becausetheparticlesused are smallerwet method techniques are generally used to locate smallerdiscontinuities than the dry method is used for. The liquidvehicles used may not perform satisfactorily when their vis-cosity exceeds 5cSt (5mm/s)at the operating temperature.Ifthe suspension vehicle is a hydrocarbon, its flash point limitsthe top temperature of usage. Mixing equipment for bulkreservoirs or manual agitation for portable dispensers is usuallyrequired tokeep wetmethod particles uniformly in suspension.8.5.2 WhereUsed-The wet fluorescent method usually isperformed indoors or in areas where shelter and ambient lightlevel can be controlled and where proper application equip-mentisavailable.
8.5.3 ColorThecolor chosen forany given examinationshould be one that best contrasts with the test surface. Becausecontrast is invariably higher with fluorescent materials,theseare utilized in most wet process examinations.Fluorescent wetmethod particles normally glow a bright yellow-green whenviewed under UV-A irradiance, although other colors areavailable.Non-fluorescent particles are usually black or red-dishbrown,althoughother colors are available.Dualresponseparticles are available that are readily detectable in visible lightand also display fluorescence when viewed under UV-A or acombination visible illumination andUV-Airradiance.Referto8.5.5.
8.5.4 Suspension Vehicles-Generally the particles are sus-pended in alightpetroleum(low-viscosity)distillate or condi-tioned water.(lf sulfur orchlorine limits are specified,use TestMethods E165/E165M,AnnexA2orA4todeterminetheirvalues.
8.5.4.1Petroleum Distillates-Low-viscosity light petro-leumdistillatesvehicles(AMS2641TypeIor equal)areidealfor suspending both fluorescent and nonfluorescent magneticparticles and are commonly employed.(1)Advantages-Two significantadvantages forthe useofpetroleum distillate vehicles are:(a)themagnetic particles aresuspended and dispersed in petroleum distillate vehicles with-out the use of conditioning agents; and (b) the petroleumdistillate vehicles provide a measure of corrosion protection toparts and the equipmentused.(2)Disadvantages—Principal
disadvantages
flammability,fumes,and availability.It is essential,therefore,to select and maintain readily available sources of supply ofpetroleum distillate vehicles that have as high a flash point aspracticableto avoidpossibleflammabilityproblems andpro-vide a work area with proper ventilation.7
(3)Characteristics-Petroleum distillate vehicles to beused in wet magnetic particle testing should possess thefollowing:(a)viscosityshouldnotexceed3.0cSt (3mm*/s)at100°F(38C)andnotmorethan5.0cSt(5mm*/s)atthelowest temperature at which the vehicle will be used; whenverified in accordance withTestMethodD445,in ordernot toimpedeparticlemobility(see20.7.3),(b)minimum flashpoint,when verified in accordance with Test Methods D93,should be200°F(93°C)in order tominimize fire hazards(see 20.7.4),(c)odorless:notobjectionabletouser,(d)lowinherentfluorescence if used withfluorescent particles; that is, it shouldnot interfere significantly with the fluorescent particle indica-tions (see 20.6.4.1),and (e) nonreactive; should not degradesuspendedparticles.
8.5.4.2 Water Vehicles with Conditioning Agents-Watermay be used as a suspension vehicle for wet magnetic particlesprovided suitable conditioning agents are added which provideproper wetdispersing,inaddition to corrosion protection forthe parts being examined and the equipment in use.Plain waterdoes not disperse sometypes of magnetic particles,does notwet all surfaces, and is corrosive to parts and equipment. Onthe other hand, conditioned water suspensions of magneticparticles are safer to use since they are nonflammable.Theselection and concentration of the conditioning agent should beas recommended by the particle manufacturer.The followingare recommended properties for water vehicles containingconditioning agents for use with wet magnetic particle testing:(l)Wetting Characteristics-The vehicle should havegood wetting characteristics; that is, wet the surface to beexamined,give even, complete coverage without evidence ofdewetting the examination surface.The surface tension (cov-erage) should be observed independently under both UV-Airradiance and visible light.Smooth examination surfacesrequire that a greater percentage of wetting agent be added thanis required for rough surface. Nonionic wetting agents arerecommended(see20.7.5).
(2)Suspension Characteristics-Impartgood dispersibility; that is, thoroughly disperse the magnetic particles withoutevidenceofparticleagglomeration(3)Foaming—-Minimize foaming;that is,it should notproduceexcessivefoamwhich wouldinterfere withindicationformation or cause particles to form scum with the foam.(4)Corrosiveness-—Itshouldnot corrodeparts tobeexam-ined orthe equipment inwhich it isused.(5)Viscosity Limit-The viscosity of the conditioned watershouldnotexceed amaximumviscosityof 3cSt(3mm*/s)at100°F(38C)(see20.7.3)
(6)Fluorescence-The conditioned water should not pro-duce excessive fluorescence if intended for use with fluorescentparticles.
(7) Nonreactiveness-The conditioned water should notcause deterioration of the suspended magnetic particles.(8)WaterpH-ThepH of the conditioned water should notbelessthan7.0orexceed 10.5.
(9)OdorThe conditioned water should be essentiallyodorless.
8.5.5Concentrationof WetMagneticParticle SuspensionE709-21
ties.As with nonconductive coatings,itmust be demonstratedThe initial bath concentration of suspended magnetic particlesshould be as specified or as recommended by the manufacturerand should be checked by settling volumemeasurements andmaintained at the specified concentration on a daily basis.If theconcentration is not maintained properly, examination resultscan vary greatly.The concentration of dual response particlesin the wet-method bath suspension may be adjusted to bestperform in thedesired lighting environment.Higher particleconcentrationisrecommendedforvisiblelightareas andlowerparticle concentration is recommended for UV-A areas.Use inaccordance with theparticle manufacturers recommendations.8.5.6Applicationof WetMagneticParticles (see15.2).8.5.7 Magnetic Slurry/Paint Systems-Anothertype of ex-amination vehicle is the magnetic slurry/paint type consistingof a heavy oil in which flake-like particles are suspended.Thematerial is normallyapplied bybrush before the part ismagnetized. Because of the high viscosity, the material doesnot rapidlyrun off surfaces,facilitating theexamination ofvertical or overhead surfaces. The vehicles may becombustible,but thefire hazard is very low.Other hazards arevery similarto those of theoilandwater vehiclespreviouslydescribed.
8.5.8Polymer-BasedSystemsThevehicleused in themagneticpolymeris basicallya liquidpolymerwhichdispersesthemagneticparticlesandwhichcurestoanelastic solid inagiven period of time, forming fixed indications. Viscositylimits of standard wet technique vehicles do not apply.Careshould be exercised in handling these polymer materials.Usein accordance with manufacturer's instructions and precau-tions.This technique is particularly applicable to examinationareas of limited visual accessibility, such as bolt holes.9.PartPreparation
9.1 General-The surface of the ferromagnetic part to beexamined should be essentially clean, dry,and freeofcontami-nants such as dirt, oil,grease,loose rust,loose mill sand, loosemillscale,lint,thickpaint,weldingflux/slag,andweldsplatterthat might restrict particle movement. See 15.1.2 about apply-ing dry particles to a damp/wet surface.When examining alocal area,suchas a weld, the areas adjacentto the surfacetobe examined, as agreed by the contracting parties,mustalsobecleaned to the extent necessary to permit detection of indica-tions,SeeAppendixX6formoreinformation on steels.9.1.1 Nonconductive Coatings-Thin nonconductivecoatings, such as paint in the order of 1 or 2 mil (0.02 to 0.05mm) will not normally interfere with the formation ofindications, but they must be removed at all points whereelectrical contact is to be made for direct magnetization.Indirect magnetization does not require electrical contact withthepart/piece.SeeSection12.2.Ifanonconductingcoating/plating is left on the area to be examined that has a thicknessgreater than 2 mil (0.05 mm),it must be demonstrated thatunacceptablediscontinuities can bedetectedthroughthemaxi-mum thickness applied.
9.1.2 Conductive Coatings-A conductive coating (such aschrome plating and heavy mill scale on wrought productsresulting from hot forming operations) can mask discontinui-8
that the unacceptable discontinuities can be detected throughthe coating.
9.1.3 Residual Magnetic Fields-If the part/piece holds aresidual magnetic field from a previous magnetization that willinterfere with the examination, the part must be demagnetized.SeeSection18.
9.2Cleaning Examination Surface-Cleaning of the exami-nation surface may be accomplished by detergents, organicsolvents,or mechanical means.As-welded, as-rolled, as-cast,or as-forged surfaces are generally satisfactory, but if thesurface is unusually nonuniform, as with burned-in sand, a veryrough weld deposit, or scale, interpretation may be difficultbecauseofmechanicalentrapmentofthemagneticparticles.Incase of doubt, any questionable area should be recleaned andreexamined (see9.1)
9.2.1 Plugging and Masking Small Holes and Openings-Unless prohibited by the purchaser, small openings and oilholesleadingtoobscurepassagesorcavitiescanbepluggedormasked with a suitable nonabrasive material which is readilyremoved. In the case of engine parts, the material must besoluble in oil. Effective masking must be used to protectcomponents that may be damaged by contact with the particlesorparticlesuspension.
10.Sequence of Operations
10.1Sequencing Particle Application and EstablishingMagnetic Flux Field-The sequence of operation in magneticparticle examination applies to the relationship between thetiming and application of particles and establishing the mag-netizing flux field.Two basic techniques apply,that is,con-tinuous (see 10.1.1 and 10.1.2) and residual (see 10.1.3), bothof whicharecommonlyemployedin industry.10.1.I Continuous Magnetization-Continuousmagnetiza-tion is employed for most applications utilizing either dry orwet particles and will provide higher magnetic field strengths.to aid indication formation better, than residual magentic fields.The continuous method must be used when performing multi-directional magnetization. The sequence of operation for thedry and the wet continuous magnetization techniques aresignificantly different and are discussed separately in 10.1.1.1and 10.1.1.2.
10.1.1.1DryContinuousMagnetizationTechnique-Unlikea wet suspension, dry particles lose most of their mobilitywhen they contact the surface of a part. Therefore, it isimperative that the part/area of interest be under the influenceof the applied magnetic field while the particles are stillairborne and free to be attracted to leakage fields. This dictatesthat the flow of magnetizing current be initiated prior to theapplication of dry magnetic particles and terminated after theapplication of powder has been completed and any excess hasbeen blown off.Magnetizing withHW current andAC currentprovide additional particle mobility on the surface of the part.Examination with dry particles is usually carried out inconjunction with prod-type or yoke localized magnetizations,and buildup of indications is observed as the particles are beingapplied.
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10.1.1.2 Wet Continuous Magnetization Technique-Thewet continuous magnetization technique involves bathing thepart with the examination medium to provide an abundantsource of suspended particles on the surface of the part andterminating the bath application immediately prior to thetermination of themagnetizing current.Theduration of themagnetizing current is typically on the order of 0.5 second foreach magnetizing pulse (shot),with two or more shots given tothe part. To ensure that indications are not washed away, thesubsequent shots should follow the first while the particles arestill mobile on the surface of the part.10.1.1.3 Polymer or Slurry Continuous MagnetizationTechnique-Prolonged or repeated periods of magnetizationare often necessary for polymer-or slurry-base suspensionsbecause of slower inherent magnetic particle mobility in thehigh-viscosity suspension vehicles.10.1.2 True Continuous Magnetization Technique-In thistechnique, the magnetizing current is sustained throughoutboth theprocessing and examination of thepart.10.1.3Residual Magnetization Techniques:10.1.3.1Residual Magnetization-In this technique, the ex-amination medium is applied after the magnetizing force hasbeen discontinued. It can be used only if the material beingexamined has relatively highretentivity so the residual leakagefield will be of sufficient strength to attract and hold theparticlesand produce indications.This technique may beadvantageous for integration with production or handlingrequirements or when higher than residual field strengths arenot required to achieve satisfactory results, When inducingcircular fields and longitudinal fields of long pieces, residualfields arenormally sufficientto meet magnetizing requirementsconsistent with the requirements of Section 14.The residualmethod has found wide use examining pipe and tubular goods.For magnetization requirements of oilfield tubulars, refer toAppendixX8.Unless demonstrations with typical parts indi-cate that the residual field has sufficient strength to producerelevantindicationsofdiscontinuities(see20.8)whenthefieldis in proper orientation, the continuous method should be used.11.Types of Magnetizing CurrentsI1.1Basic CurrentTypes-The fourbasic types of currentused in magnetic particle testing to establish part magnetizationare alternating current (AC), half-wave rectified current (HW),full-wave rectified current (FW), and for a special application,DC.
11.1.1 Alternating Current (AC)Part magnetization withalternating current is preferred for those applications whererequirementscallforthedetectionexamination
discontinuities, such as fatigue cracks, that are open to thesurface to which the magnetizing force is applied. Associatedwith ACis a\skin effect\that confines the magneticfield at ornear to the surface of a part. In contrast, both HW current andFW current produce a magnetic field having penetratingcapabilities proportional to the amount of applied current,9
which should be used when near-surface or inside surfacediscontinuities areof concern11.1.2 Half-Wave Rectified Current (HW)-Half-wave cur-rent is frequently used in conjunction with wet and dryparticles because the current pulses provide more mobility tothe particles.This waveform is used with prods,yokes, mobileand bench units.Half-wave rectified current is used to achievedepth of penetration for detection of typical discontinuitiesfound in weldments, forgings, and ferrous castings. As with ACfor magnetization, single-phase current is utilized and theaverage value measured as\magnetizing current.\1l.1.3 Full-Wave Rectified Current (FW)-Full-wave cur-rent may utilize single- or three-phase current. Three-phasecurrent has the advantage of lower line amperage draws,whereas single-phase equipment is less expensive.Full-waverectified current is commonly used when the residual method isto be employed.Because particle movement, either dry or wetis noticeably less, precautions must be taken to ensure thatsufficient time is allowed for formation of indications.11.1.4DirectCurrent (DC)-Abank of batteries,full-waverectified AC filtered through capacitors or a DC generatorproduce direct magnetizing current.They have largely givenway to half-wave rectified or full-wave rectified DC except fora few specialized applications,primarily because of broadapplication advantages when using other types of equipment.11.1.5 CapacitorDischarge(CD)Current-Abank of ca-pacitors are used to store energy and when triggered the energyreaches high amperage with a very short duration (normallyless than25milliseconds).Becauseof the shortpulsedurationthe current requirements are affected by the amount of materialto be magnetized as well as the applied amperage. Thecapacitor discharge technique is widely used to establish aresidual magnetic field in tubing, casing,line pipe, and drillpipe.Forspecificrequirements,seeAppendixX8.12.Part Magnetization Techniques12.1Examination Coverage-All examinations shouldbeconducted with sufficient area overlap to assure the requiredcoverage at the specified sensitivity has been obtained.12.2 Direct and Indirect Magnetization-A part can bemagnetized either directly or indirectly. For direct magnetiza-tion the magnetizing current is passed directly through the partcreating a magnetic field oriented 90 degrees to current flow inthe part. With indirect magnetization techniques a magneticfield is induced in the part,which can create a circular/toroidal,longitudinal, or multidirectional magnetic field in the part.Thetechniques described in 20.8 for verifying that the magneticfields have the anticipated direction and strength should beemployed. This is especially important when using multidirec-tional techniques to examinecomplex shapes.12.3 Choosing Magnetization Technique-The choice ofdirect or indirect magnetization will depend on such factors assize,configuration, or ease of processing.Table I compares theadvantages and limitations of the various methods of partmagnetization,
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TABLE1Advantages and Limitationsof theVariousWays ofMagnetizingaPartMagnetizing Technique and Material FormI. Direct Contact Part Magnetization (see 12.3.1)Head/Tailstock Contact
Solid, relatively small parts (castings,forgings,machined pieces) that can beprocessedon a horizontal wetunitLarge castings and forgings
1. Fast, easy technique.
Advantages
Limitations
1. Possibility of arc burns if poor contact conditionsexist.
2. Circular magneltic field surrounds current path.Good sensitivity to surface and near-surface discontinuities.3.
4.Simpleaswellasrelativelycomplexpartscanusuallybeeasily processed with one ormore shots.2. Long parts should be examined in sections tofacilitatebathapplication withoutresorting toanoverly long current shot
5.Completemagneticpathisconducivetomaximizingresidualcharacteristics of material.1. Large surface areas can be processed andexamined inrelatively short time.
Cylindrical parts such as tubing, pipe, hollow1. Entire length can be circularly magnetized by contacting.shafts,etc.
end to end.
Long solid parts such as billets,bars, shafts, 1. Entire length can be circularly magnetized by contacting.end to end.
2. Current requirements are independent of length.3.No end loss
Prods: Welds
Large castings or forgings
IL IndirectPartMagnetization (see12.3.3)Internal Conductor
Miscellaneous parts having holes throughwhich a conductor can be placed such as:Bearingrace
Hollow cylinder
Large nut
Largeclevis
Pipe coupling, casing/tubing1. Circular field can be selectively directed to weld area byprodplacement.
1. High amperage requirements (16 000 to 20 000 A)dictate costly DC power supply.1. Effective field limited to outside surface and cannotbe used for inside diameter examination.2. Ends must be conductive to electrical contacts andcapable of carrying required current without excessiveheat.Cannotbe used on.oilfield tubularsbecause ofpossibility of arc burns.
1. Output voltage requirements increase as the partlength increases,dueto greatervalueoftheimpedance or resistance as the cables and partlength grows, or both.
2. Ends mustbe conductive to electrical contact andcapable of carryingrequired current without excessiveheat.
1. Only small area can be examined at one time.2.In conjunction with half-wave rectified altemating current.and2.Are burns due fo poor contact.dryowderprovidesecellentsnsiivityo subsuaediscontinuities as well as surface type.3.Flexible,inthatprods,cables,and powerpacks canbebrought to examination site.1. Entire surface area can be examined in smallincrementsusing nominal current values.2.Circularfield can be concentrated in specific areas thathistorically are prone to discontinuities.3.Equipment canbe broughtothelocation ofparts thatare3. Surface must be dry when dry powder is being used.4,Prod spacing mustbe in accordance withthemagneltizing current level.
1. Coverage of large surface area require a multiplicityof shots that can be very time-consuming.2.Possibility of arc burns due to poor contact Surfaceshould be dry when dry powder is being used.3.Largepowerpacks(over6000A)oftenrequirealarge capacity voltage source to operate.difficulttomove.
4. In conjunction with half-wave rectified altemafing current and4.When using HW current or FW current on retentivedrypowder,providesexcellentsensitivitytonearsurfacesubsurface type discontinuities that are difficult to locate byothermethods.
1.Whenusedproperly,noelectricalcontactismadewiththepartand possibility of arc bums eliminated2. Circumferentialy directed magnetic field is generated in allsurfaces, surrounding the conductor (inside diameter, faces,etc.).
3. Ideal for those cases where the residual method isapplicable
4. Light weightparts can be supported by the internalconductor.
5.Smaller internal conductorand multiple coil wraps maybeusedto reduce current requirements,10
materials, it isoftennecessarythat thepowerpackbe equipped with a reversing DC demagnetizingoption.
1.Sizeofconductormustbeampletocarryrequiredcurrent.
2.Largerdiameters require repeatedmagnetizationwith conductoragainst inside diameler androtationofpart between processes.Where continuousmagnetization technique is being employed,examination is required after each magnetizationstep.
Magnetizing Technique and Material FomTubular type parts such as:
Pipe/Casting
TubingbzxZ.net
Hollow shatt
Large valve bodies and similar partsE709-21
TABLE1
Continued
Advantages
Limitations
1.Whenused properly,no electricalcontactismade withthe1Outside surfacesensitivitymaybesomewhat lesspart and possiblity of arc bums eliminated.than that obtained on the inside surface for largediameter and extremelyheavy wall sections.2. Inside diameter as well as outside diameter examination.Entire length of part circularly magnetized.3.
1.Providesgood sensitivityfordetection ofdiscontinuitieslocated on intemal surfaces.1. All generally longitudinal surfaces are longitudinallyCoil/CableWrap
Miscellaneous medium-sized parts wherethemagnetized to effectively locate transverse discontinuitieslength predominates such as a crankshaftLarge castings, forgings, or shaftingMiscellaneous small parts
1. Longitudinal field easily attained by means of cablewrapping
1. Easy and fast, especially where residual magnetization isapplicable.
2. No electrical contact.
3.Relatively complexparts canusuallybeprocessed withsame ease as those with simple cross section.Induced Current Fixtures
Examination of ring-shaped part for circumfer-1.No electrical contactential-type discontinuities.Ball examination
Disksandgears
Yokes:
Examination of large surface areasforsurface-type discontinuities.1.Outsidesurfacesensitivitymaybe somewhatlessthan thal obtained on the inside diameter for heavywallsections.
1.Lengthmaydictatemultipleshotascoil isrepositioned
2.Longitudinalmagnetization ofcomplex parts withupsets suchascrankshafts willead todead spotswhere the magnetic field is cancelled out. Care mustbe taken to assure magnetizationof all areas inperpendiculardirections.
1,Multiple magnetization may be required due toconfiguration of part.
1. L/D (length/diameter) ratio important consideration indetermining adequacy of ampere-turns.2.Effective L/D ratio canbe alteredby utilizing piecesof similarcross-sectionalarea.3. Use smaller coilformore intense field.4. Sensitivity diminishes at ends of part due to generalleakage field pattern.
5.Quick breakdesirable tominimize endeffectonshort parts with low L/D ratio.1. Laminated core required through ring.2. All surface of part subjected to toroidal-type mag-netic field.2.Type of magnetizing current must be compatible withSingle process for100% coverage.3.
4. Can be automated.
1. No electrical contact.
2.100% coverage for discontinuities in any direction withthree-step process and proper orientation between steps.3. Can be automated.
1. No electrical contact.
Good sensitivity at or near periphery or rim.2.
3. Sensitivity in various areas can be varied by core or pole-piece selection.
1. No electrical contact.
2. Highly portable.
3. Can locate discontinuities in any direction with properorientation.
Miscellaneous parts requiring examinationof1.No electrical contactlocalizedareas.
2. Good sensitivity to direct surface discontinuities.Highlyportable
4. Wet or dry technique.
5.Alternating-current type can also serve as demagnetizer insome instances.
Magnetization-For
Direct
Contact
direct
magnetization,physical contact must be madebetween theferromagnetic part and the current carrying electrodes con-nectedtothepowersource.Bothlocalizedareamagnetizationand overall part magnetization are direct contact means of partmagnetization, and can be achieved through the use of prods,head and tailstock, clamps, and magnetic leeches.11
3. Other conductors encircling field must be avoided.4. Large diameters require special consideration.1. For small-diameter balls, limited to residualmagnetization.
1.100%coverage may require two-stepprocess withcore or pole-piece variation, or both.2.Typeof magnetizing currentmustbecompatiblewithpartgeometry.
1. Time consuming-
2. Must be systematically repositioned in vlew ofrandom discontinuity orientation.1.Mustbeproperlypositioned relativetoorientationofdiscontinuities
2. Relatively good contact must be established be-tween pant and poles.
3.Complex part geometry may cause difficulty.4. Poor sensitivity to subsurface-type discontinuifiesexcept in isolated areas.
12.3.2 Localized Area Magnetization:12.3.2.1ProdTechnique-Theprod electrodes are firstpressed firmly against the part under examination (see Fig. 2).The magnetizing current is then passed through the prods andinto the area of the part in contact with the prods. Thisestablishes a circular magnetic field in the part around andbetween each prod electrode, sufficient to carry out a local
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