1、Designation: E 566 99 (Reapproved 2004)e1Standard 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 y
2、ear of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made to provide consistent terminology in May 2004.1. Scope1.1 This practice covers the proce
3、dure for sorting ferrousmetals using the electromagnetic (eddy-current) method. Theprocedure relates 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 electro
4、magnetic or magnetic properties ofthe material. The selection of specimens to determine sortingfeasibility 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 thi
5、s 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:3E 105 Practice for Probability Sampling of MaterialsE 122 Practice for Calculating Sample Size to Estimate,with a Specif
6、ied Tolerable Error, the Average for Charac-teristic for a Lot or ProcessE 543 Practice for Agencies Performing NondestructiveTestingE 1316 Terminology for Nondestructive Examinations2.2 ASNT Documents:SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive Te
7、sting4ANSI/ASNT CP-189 Standard for Qualification and Certi-fication of Nondestructive Testing Personnel42.3 AIA Standard:NAS-410 Qualification and Certification of NondestructiveTesting Personnel53. Terminology3.1 Standard terminology relating to electromagnetic ex-amination may be found in Termino
8、logy E 1316, Section C:Electromagnetic Testing.4. Summary of Practice4.1 The two techniques that are primarily 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 by
9、empirical data. In the absolute-coil method, the equipment isstandardized by placing standards of known 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 specim
10、en iscompared with a reference specimen and the indication tellswhether the test specimen is within or outside of the requiredlimits.4.1.1 Absolute Coil MethodA specimen of known classi-fication is inserted in the test coil, and the controls of theinstrument are adjusted to obtain an indication. The
11、 method isthen continued by inserting the test specimens to be sorted intothe test coil, and observing the instrument indication.4.1.2 Comparative Coil MethodKnown reference speci-mens representing the minimum or maximum limits of accep-tance, or both, are inserted in the reference coil and test coi
12、l.The instrument controls are adjusted for appropriate indica-tions. The method is then continued by inserting the testspecimens 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 adj
13、ustedin the initial step that the anticipated deviations will berecognized within the range of readout according to whethertwo- or three-way sorts are to be accomplished.4.3 Both absolute and comparative methods require com-paring the test specimens with the reference specimen(s). Two1This practice
14、is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Methods.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1976. Last previous edition approved in 1999 as E 566 - 99.2Ge
15、neral information can be found in the Nondestructive Testing Handbook,(Second Edition), Vol IV: Electromagnetic Testing, Society for NondestructiveTesting, 1986.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book o
16、f ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from The American Society for Nondestructive Testing (ASNT), P.O.Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.5Available from Standardization Documents Order Desk, DODSSP, Bldg. 4
17、,Section D, 700 Robbins Ave., Philadelphia, PA 19111-50981Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.or more specimens representing the limits of acceptance maybe required. In the absolute method the electrical reference isgenera
18、ted by a test specimen. In the 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
19、 of manual insertion ofone specimen 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
20、are employed.5. Significance and 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
21、 testing is required. The advantage 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 sa
22、tisfactorily these types ofseparations 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 de
23、pending on their size and shape.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
24、the coupling between the test coil 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
25、order to minimize measurement drift.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 practice
26、or standard, such as ANSI/ASNT-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 N
27、ondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E 543. The applicableedition of Practice E 543 shall be specified in the contractualagreement.6.3 Acceptance CriteriaSince acceptance criteria are notspecified in thi
28、s practice, they shall 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 v
29、arious groups do notoverlap 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 fi
30、eldstrength, any influence 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
31、will permit awell-defined 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.
32、7.1.5 The geometry and 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 f
33、requencies and power levels 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 device
34、sor any suitable combination 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
35、test specimen.8.2.1 When 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
36、 complicated test specimen 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.8.3 Mechanical Ha
37、ndling ApparatusA mechanical devicefor feeding and sorting the test specimens may be used toautomate the particular application.E 566 99 (2004)e129. Sampling9.1 Sampling (see Practices E 105 and E 122) is a method toobtain assurance that materials are of satisfactory quality.Instead of 100 % inspect
38、ion, a portion of the material isexamined 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
39、assemblies while they are beingprocessed. 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 t
40、he sample meet the specification. 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 sam
41、pling table is designed for accept/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 orproce
42、ssing operations before they become 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. Thishel
43、ps prevent production of defective 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 ch
44、art is by far the most effective process 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
45、willbe accepted or rejected; (2) protection 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) cos
46、t required, that is,average inspection 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
47、coil (see 11.2) or comparative coil (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
48、sorting method is primarily one ofcomparison 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 s
49、tandard to a fixed position in or 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
