1、Designation: E 566 09Standard Practice forElectromagnetic (Eddy-Current) Sorting of Ferrous Metals1This standard is issued under the fixed designation E 566; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. 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 practice covers the procedure for sorting ferrousmetals using the electromagnetic (eddy-current) method. Theprocedure relates
3、to instruments using absolute or comparator-type coils for distinguishing variations in mass, shape, conduc-tivity, permeability, and other variables such as hardness andalloy that affect the electromagnetic or magnetic properties ofthe material. The selection of specimens to determine sortingfeasib
4、ility and to establish standards is also included.21.2 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
5、regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E 105 Practice for Probability Sampling Of MaterialsE 122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or ProcessE 543 Specification for Agencies Perf
6、orming Nondestruc-tive TestingE 1316 Terminology for Nondestructive Examinations2.2 ASNT Documents:SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive Testing4ANSI/ASNT-CP-189 Standard for Qualification and Certi-fication of Nondestructive Testing Personne
7、l42.3 AIA Standard:NAS-410 Qualification and Certification of NondestructiveTesting Personnel53. Terminology3.1 Standard terminology relating to electromagnetic ex-amination may be found in Terminology E 1316, Section C:Electromagnetic Testing.4. Summary of Practice4.1 The two techniques that are pr
8、imarily used in electro-magnetic sorting employ the absolute (single-) and compara-tive (two-) coil methods. The decision of whether to usesingle-coil or two-coil operation is usually determined byempirical data. In the absolute-coil method, the equipment isstandardized by placing standards of known
9、 properties in thetest coil. The value of the tested parameter (for instance,hardness, alloy, or heat treatment) is read on the scale of anindicator. In the comparative-coil method, the test specimen iscompared with a reference specimen and the indication tellswhether the test specimen is within or
10、outside of the requiredlimits.4.1.1 Absolute Coil MethodA specimen of known classi-fication (standard) is inserted in the test coil, and the controlsof the instrument are adjusted to obtain an indication. Themethod is then continued by inserting the test specimens to besorted into the test coil, and
11、 observing the instrument indica-tion.4.1.2 Comparative Coil MethodKnown reference speci-mens (standards) representing the minimum or maximumlimits of acceptance, or both, are inserted in the reference coiland test coil. The instrument controls are adjusted for appro-priate indications. The method i
12、s then continued by insertingthe test specimens to be sorted in the test coil, leaving a knownreference in the reference coil, and observing the instrumentindication.4.2 The range of instrument indication must be so adjustedin the initial step that the anticipated deviations will berecognized within
13、 the range of readout according to whethertwo- or three-way sorts are to be accomplished.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Method.Current edition approved June 1, 2009. P
14、ublished June 2009. Originallyapproved in 1976. Last previous edition approved in 2004 as E 566 - 99(2004)1.2General information can be found in the Nondestructive Testing Handbook,(Second Edition), Vol IV: Electromagnetic Testing, Society for NondestructiveTesting, 1986.3For referenced ASTM standar
15、ds, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Ar
16、lingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.5Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/www.dodssp.daps.mil.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
17、19428-2959, United States.4.3 Both absolute and comparative methods require com-paring the test specimens with the reference specimen(s). Twoor more specimens representing the limits of acceptance maybe required. In the absolute method the electrical reference isgenerated by a test specimen. In the
18、comparative method anyelectromagnetic condition that is not common to the testspecimen and the reference specimen will produce an imbal-ance in the system. The comparative method usually is morestable, as it normally suppresses noise.4.4 The testing process may consist of manual insertion ofone spec
19、imen after another into the test coil, or an automatedfeeding and classifying mechanism may be employed. Inautomated setups, it is sometimes necessary to stop eachspecimen momentarily in the test coil while the reading isbeing taken, especially if low test frequencies are employed.5. Significance an
20、d Use5.1 Absolute and comparative methods provide a means forsorting large quantities of ferrous parts of stock with regard tocomposition, condition, structure, or processing, or a combi-nation thereof.5.2 The comparative or two-coil method is used whenhigh-sensitivity testing is required. The advan
21、tage of thismethod is that it almost completely suppresses all internal orexternal disturbances such as temperature variations or straymagnetic fields. The two-coil method is normally used whenharmonic evaluation is employed for sorting.5.3 The ability to accomplish satisfactorily these types ofsepa
22、rations is dependent upon the relation of the magneticcharacteristics of the ferromagnetic parts to their physicalcondition.5.4 These methods may be used for high-speed sorting in afully automated setup where the speed of testing may approachten specimens per second depending on their size and shape
23、.5.5 The success of sorting ferromagnetic material dependsmainly on the proper selection of magnetic field strength andfrequency of signal in the test coil, fill factor, and variablespresent in the sample.5.6 The degree of accuracy of a sort will be affected greatlyby the coupling between the test c
24、oil field and the test specimenand the accuracy with which the specimen is held in the testcoil field during the measuring period.5.7 When high currents are used in the test coil, a meansshould be provided to maintain a constant temperature of thereference specimen in order to minimize measurement d
25、rift.6. Basis of Application6.1 Personnel QualificationIf specified in the contractualagreement, personnel performing examinations to this practiceshall be qualified in accordance with a nationally recognizednondestructive testing (NDT) personnel qualification practiceor standard, such as ANSI/ASNT-
26、CP-189, SNT-TC-1A, NAS-410, or a similar document and certified by the employer orcertifying agency, as applicable. The practice or standard usedand its applicable revision shall be identified in the contractualagreement between the using parties.6.2 Qualification of Nondestructive Testing AgenciesI
27、fspecified in the contractual agreement, NDT agencies shall bequalified and evaluated as described in Practice E 543. Theapplicable edition of Practice E 543 shall be specified in thecontractual agreement.6.3 Acceptance CriteriaSince acceptance criteria are notspecified in this practice, they shall
28、be specified in thecontractual agreement.7. Interferences7.1 The specific influence of the following variables must beconsidered for proper interpretation of the results obtained:7.1.1 The correlation shall be established so that magneticor electrical properties, or both, of various groups do notove
29、rlap and are well defined in the standardization procedureused.7.1.2 In sorting magnetic materials, a magnetic fieldstrength and test frequency must be used that will result in awell-defined separation of variables being tested.7.1.3 When examining magnetic materials at low fieldstrength, any influe
30、nce from the previous magnetic history ofthe test specimen (residual magnetism) shall be negated bydemagnetization of the specimen if it restricts the electromag-netic sort.7.1.4 The temperature of the reference specimen and testspecimen shall be controlled within limits that will permit awell-defin
31、ed range of conductivity or permeability, or both, forwhich the correlation of the group or groups is valid. Coolingof the reference specimens when high field strengths are usedor allowing test specimens to cool or heat to an establishedambient range, or both, may be required.7.1.5 The geometry and
32、mass of the reference standard andtest specimen shall be controlled within limits that will permitsorting.7.1.6 Speed EffectsSee 4.4.8. Apparatus8.1 Electronic ApparatusThe electronic apparatus shallbe capable of energizing the test coils with alternating currentsof suitable frequencies and power le
33、vels and shall be capable ofsensing the changes in the electromagnetic response of the testcoils. Equipment may include any suitable signal-processingdevices (phase discriminator, filter circuits, etc.) and the outputmay be displayed by meter, scope, recorder, signaling devicesor any suitable combin
34、ation required for the particular appli-cation.8.2 Test Coils may be of the encircling or probe-coil typeand shall be capable of inducing an electromagnetic field in thetest specimen and reference specimen and sensing changes inthe electric and magnetic characteristics of the test specimen.8.2.1 Whe
35、n selecting the test coil, the objective should be toobtain a coil fill factor as large as possible. This means that theinside of the test coil should be filled by the test specimen asmuch as possible. This is of primary importance for testsrequiring high sensitivity.8.2.2 For complicated test speci
36、men shapes, a correspond-ing insert shall be provided to ensure that each specimen can beplaced in the same position within the test coil. These inserts,as well as any other accessories, should consist of nonferro-magnetic, electrically nonconductive material.E5660928.3 Mechanical Handling Apparatus
37、A mechanical devicefor feeding and sorting the test specimens may be used toautomate the particular application.9. Sampling9.1 Sampling (see Practices E 105 and E 122) is a method toobtain assurance that materials are of satisfactory quality.Instead of 100 % inspection, a portion of the material ise
38、xamined to show evidence of the quality of the whole. Thereare two important needs for this approach: first, in the finalinspection or examinations made to ensure that productsdelivered are in conformance with specification requirements;second, to control parts and assemblies while they are beingpro
39、cessed. Statistical acceptance sampling tables and statisticalprocess-control sampling tables have been developed to meetthese needs.9.2 Acceptance sampling may be conducted on an accept/reject (or attributes) basis, that is, determining whether or notthe units of the sample meet the specification.
40、Examination ofthe samples may also be conducted on a measurements (orvariables) basis, that is, determining actual readings on theunits in the sample. The majority of acceptance sampling iscarried out on a sampling by the attributes basis and the usualacceptance sampling table is designed for accept
41、/reject criteria.9.3 Process control sampling may be conducted on materialduring the course of production to prevent large quantities ofdefective parts being found in the acceptance tests. Many partsand materials are subjected to several successive machining orprocessing operations before they becom
42、e finished units. Partscan be most effectively controlled during production by exam-ining small samples of these parts at regularly scheduledintervals. The object of this process check is to provide acontinuous picture of the quality of parts being produced. Thishelps prevent production of defective
43、 parts by stopping andcorrecting the problem as soon as it begins to appear in themanufacturing process and thereby keeping the process incontrol. Sampling may be by attributes or by variable andprocess control sampling tables. The measurements (variables)control chart is by far the most effective p
44、rocess controltechnique.9.4 Statistical sampling tables have four definite features:(1) specifications of sampling data, that is, the size of thesamples to be selected, the conditions under which the samplesare to be selected, and the conditions under which the lot willbe accepted or rejected; (2) p
45、rotection afforded, that is, theelement of risk that the sampling schedules in a given table willreject good lots or accept bad ones; (3) disposal procedure, thatis, a set of rules that state what is to be done with lots aftersampling has been completed; and (4) cost required, that is,average inspec
46、tion cost required to accept or reject a lot.10. Test Specimen or Sample (Standards)10.1 A known acceptable specimen and known unaccept-able specimen of the precise size and configuration of theproduct to be tested shall be used to set up for sorting by theabsolute coil (see 11.2) or comparative coi
47、l (see 11.3) method.10.2 Three known specimens are required for a three-waymix (see 11.4).10.3 The specimen should be selected to represent theextremes of acceptable and unacceptable groups to assure nooverlap in the sort.11. Standardization11.1 The electromagnetic sorting method is primarily one of
48、comparison between specimens. Empirical data and physicaltests determine classification. The standardization procedureshall be governed by the properties of the material requiringseparation.11.2 When using the absolute coil method, insert the accept-able reference standard to a fixed position in or
49、relative to thetest coil and adjust the instrument to get an on-scale meter orscope reading, or both. Replace the reference standard with anunacceptable reference specimen in the same exact positionand adjust the sensitivity of the instrument to maximize theindicator difference reading without exceeding 90 % of theavailable scale range.11.3 When using the comparative coil method, select areference specimen (usually one that falls within the acceptablelimits of the specimens being tested) and place it in thereference coil in such a way that it will not be disturbed, and setth
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