1、Designation: E 703 09Standard Practice forElectromagnetic (Eddy-Current) Sorting of NonferrousMetals1This standard is issued under the fixed designation E 703; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. 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 describes a procedure for sorting nonfer-rous metals using the electromagnetic (eddy-current) method.The procedure
3、is intended for use with instruments usingabsolute or comparator-type coils for distinguishing variationsin mass, shape, conductivity, and other variables such as alloy,heat treatment, or hardness that may be closely correlated withthe electrical properties of the material. Selection of samples toev
4、aluate sorting feasibility and to establish standards is alsodescribed.1.2 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 th
5、e applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 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 Specificati
6、on for Agencies Performing Nondestruc-tive TestingE 1316 Terminology for Nondestructive Examinations2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive TestingANSI/ASNT CP-189 Standard for Qualification and Certi-fication of Nondestruct
7、ive Testing Personnel2.3 AIA Standard:4NAS-410 Qualification and Certification of NondestructiveTesting Personnel3. Terminology Definitions3.1 Standard terminology relating to electromagnetic ex-amination may be found in Terminology E 1316, Section C:Electromagnetic Testing.4. Summary of Practice4.1
8、 The techniques that are primarily used in electromag-netic sorting employ the absolute (single-) and comparative(two-) coil methods using either encircling or probe coils. Thedecision of whether to use single-coil or two-coil operation isusually based on empirical data. In the absolute-coil method(
9、encircling or probe), the equipment is standardized by placingstandards of known properties in the test coil. The value of theexamined electrical parameter, which may be correlated withalloy, heat treatment temper, or hardness, is read on the displayof an indicator. In the comparative coil method (e
10、ncircling orprobe coils), the test specimen in one coil is compared with areference piece in a second coil to determine whether the testspecimen is within or outside of the required limits.4.1.1 Absolute Coil Method:4.1.1.1 Encircling CoilSamples of known classification(standards) are inserted conse
11、cutively in the test coil, and thecontrols of the instrument are adjusted to obtain an appropriateresponse. Typically, three samples would be used representingthe upper, lower, and mid-range for which standardization isrequired. The examination is then conducted by inserting thespecimens to be sorte
12、d into the test coil, and observing theinstrument response.4.1.1.2 Probe CoilThe probe coil is placed consecutivelyon the standards of known properties and the controls of theinstrument are adjusted for appropriate response (see 4.1.1.1).The examination is then conducted by placing the probe on thes
13、pecimens to be sorted and observing the instrument response.4.1.2 Comparative Coil Method: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.
14、Published June 2009. Originallyapproved in 1979. Last previous edition approved in 2004 as E 703 - 98(2004)1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the sta
15、ndards Document Summary page onthe ASTM website.3Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arli
16、ngton, VA22209-3928, http:/www.aia-aerospace.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.2.1 Encircling CoilKnown reference pieces (stan-dards) representing the minimum or maximum limits, or both,of acceptance or sorting
17、category are inserted in the referenceand test coil. The instrument controls are adjusted for appro-priate responses. The examination is then conducted by insert-ing specimens to be sorted in the test coil, leaving the knownreference in the reference coil and observing the instrumentresponse.4.1.2.2
18、 Probe CoilBoth probe coils are placed on thereference pieces (standard) representing the minimum or maxi-mum limits, or both, of acceptance or sorting category. Theinstrument controls are adjusted for appropriate responses. Theexamination is then conducted by placing the test probe on thespecimens
19、to be sorted (the other probe is left on the referencestandard) and observing the instrument response.4.2 The range of instrument response must be so adjusted inthe initial step that the anticipated deviations will be within therange of readout.4.3 Both absolute and comparative methods using encir-c
20、ling coil(s) require comparing the specimens to be examinedwith the reference piece(s). Two or more samples representingthe limits of acceptance may be required. In the absolutemethod, the electrical reference signal from the instrument isadjusted with the standard in the coil. In the comparativemet
21、hod, any electromagnetic condition, that is not common tothe test specimen and the standard, will produce an imbalancein the system. The comparative method is usually more stablesince it suppresses most of the interferences.4.4 The examination process may consist of manual inser-tion of one specimen
22、 after another into the test coil or anautomated feeding and classifying mechanism may be em-ployed. In automated setups, it is sometimes necessary toestablish empirically the time required for the test specimen toremain in the test coil while the reading is being taken,especially if low frequencies
23、 are employed.5. Significance and Use5.1 Absolute and comparative methods provide a measurefor sorting large quantities of nonferrous parts or stock withregard to composition or condition, or both.5.2 The comparative or two-coil method is used whenhigh-sensitivity examination is required. The advant
24、age of thismethod is that it almost completely suppresses interferences.5.3 The ability to accomplish these types of separationssatisfactorily is dependent upon the relation of the electriccharacteristics of the nonferrous parts to their physical condi-tion.5.4 These methods may be used for high-spe
25、ed sorting in afully automated setup where the speed of examination mayapproach many specimens per second depending on their sizeand shape.5.5 Successful sorting of nonferrous material dependsmainly on the variables present in the sample and the properselection of frequency and fill factor.5.6 The a
26、ccuracy of a sort will be affected greatly by thecoupling between the test coil field and the examined partduring the measuring period.6. Basis of Application6.1 Personnel QualificationIf specified in the contractualagreement, personnel performing examinations to this practiceshall be qualified in a
27、ccordance with a nationally recognizednondestructive testing (NDT) personnel qualification practiceor 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 revisi
28、on shall be identified in the contractualagreement between the using parties.6.2 Qualification of Nondestructive Testing AgenciesIfspecified in the contractual agreement, NDT agencies shall bequalified and evaluated as described in Practice E 543. Theapplicable edition of Practice E 543 shall be spe
29、cified in thecontractual agreement.6.3 Acceptance CriteriaSince acceptance criteria are notspecified in this practice, they shall be specified in thecontractual agreement.7. Interferences7.1 The influence of the following variables must be con-sidered for proper interpretation of the results:7.1.1 T
30、he correlation shall be established so that electricalproperties of various groups do not overlap and are welldefined in the standardization procedure used.7.1.2 The examination frequency must be selected to pro-vide a well-defined separation of variables.7.1.3 The temperature of the standard and te
31、st specimenshall be controlled within limits that will permit a well-definedrange of conductivity or permeability, or both, for which thecorrelation of the group or groups is valid. Cooling of thestandard when high field strengths are used or allowing testspecimens to cool or heat to an established
32、ambient range, orboth, may be required.7.1.4 The geometry, mass, and thickness of the standard andtest specimen shall be controlled within limits that will permitsorting.7.1.5 Magnetic permeability variations can interfere whensorting paramagnetic materials.7.1.6 Signal response can result from a ch
33、ange in relativemotion between the test specimen and the test coil, such as thelength of time the specimen is in a test coil (see 4.4).7.1.7 Conductivity has an unambiguous relationship tohardness for certain alloys. However, when alloys are mixed,identical conductivity does not necessarily indicate
34、 the samehardness.7.1.8 Care must also be exercised in using conductivity tosort overheated parts quenched at a high temperature as theconductivity reading for acceptable parts may repeat at a largeincrease in temperature.7.1.9 Lift-off can result in a change in the test system outputwith probe coil
35、s. This effect is a change in the magneticcoupling between the test specimen and probe coil. Care mustbe exercised to prevent this effect from interfering withexamination results; either mechanical or electronic compen-sation must be used.7.1.10 For certain heat-treatable (aluminum) alloys, conduc-t
36、ivity values can also repeat themselves during the aging cycleE703092at a constant temperature. Thus, for such alloys, conductivity isnot unique as a monitor of temper, etc.8. Apparatus8.1 Electronic ApparatusThe electronic apparatus shallbe capable of energizing the test coils with alternating curr
37、entsof suitable frequencies and power levels and shall be capable ofsensing changes in the electromagnetic response of the coils.Equipment may include any suitable signal-processing devices(phase discriminator, filter circuits, etc.) and the output may bedisplayed by meter, oscilloscope, recorder, s
38、ignaling devices,or 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 standard, and sensing changes in the electricor magnetic characteristics o
39、f the 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 examina-tions requiring high sensit
40、ivity.8.2.2 For complicated test specimen shapes, a correspond-ing insert shall be provided to ensure that each test specimencan be placed in the same position within the test coil. Theseinserts, as well as any other accessories, should consist ofnon-ferromagnetic, electrically nonconductive materia
41、l.8.3 Mechanical Handling Apparatus A mechanical de-vice for feeding and sorting the test specimens may be used toautomate a 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 % inspe
42、ction, a portion of the material isexamined to show evidence of the quality of the whole. Thereare two important needs for this approach: first, the finalinspection or examination is made to assure that productsdelivered are in conformance with specification requirements;second, to control parts and
43、 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
44、the 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 attributes basis and the usualacceptance sampli
45、ng table is designed for accept/reject.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 examinations.Many parts and materials are subjected to several successivemachining or processing
46、 operations before they become fin-ished units. Parts can be most effectively controlled duringproduction by examining small samples of these parts atfrequent regularly scheduled intervals. The object of thisprocess check is to provide a continuous picture of the qualityof parts being produced. This
47、 helps prevent production ofdefective parts by stopping and correcting the problem as soonas it begins to appear in the manufacturing process and therebykeeping the process in control. Sampling may be by attributesor by variables and process control sampling tables are used.The measurements (variabl
48、es) control chart is by far the mosteffective process control technique.9.4 Statistical sampling tables have four definite features:(1) specification of sampling datathat is, the size of thesamples to be selected, the conditions under which the samplesare to be selected, and the conditions under whi
49、ch the lot willbe accepted or rejected; (2) protection affordedthat is, theelement of risk that the sampling schedules in a given table willreject good lots or accept bad ones; (3) disposal procedurethat is, a set of rules that state what is to be done with lots aftersampling has been completed; and (4) cost requiredthat is,average inspection cost required to accept or reject a lot.10. Test Specimen or Sample (Standards)10.1 Two known samples of the precise size and configu-ration of the product to be examined are usually used to set upfor sorting by the absolute coil m
