1、Designation: E977 05 (Reapproved 2014)Standard Practice forThermoelectric Sorting of Electrically Conductive Materials1This standard is issued under the fixed designation E977; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the procedure for sorting materialsusing the thermoelectric method, which is based on theSe
3、ebeck effect. The procedure relates to the use of direct- andcomparator-type thermoelectric instruments for distinguishingvariations in materials which affect the thermoelectric proper-ties of those materials.1.2 While the practice is most commonly applied to thesorting of metals, it may be applied
4、to other electricallyconductive materials.1.3 Thermoelectric sorting may also be applied to thesorting of materials on the basis of plating thickness, casedepth, and hardness.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibi
5、lity of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Descriptions of Terms:2.1.1 acceptance limitsthe thermoelectric response thatestablishes the group into which the material
6、 being examinedbelongs.2.1.2 comparative instrumentationa system that uses elec-trode assemblies (probes), associated electronics, and knownstandards to measure a thermoelectric response from anelectrically-conductive material. This response is comparedwith that of the reference standard.2.1.3 direc
7、t instrumentationa system that specificallymeasures and displays the voltage (or an arbitrary unit)generated between the electrodes when they are at differenttemperatures and in contact with the material.2.1.4 electrodethe conductors used in thermoelectric sort-ing instruments used to generate the S
8、eebeck effect with thematerial under test.2.1.5 Seebeck effectthe thermoelectric electromotive force(emf) produced in a circuit connecting two dissimilar conduc-tors at two points of different temperatures. The magnitude ofthis emf is a function of the chemistry of the materials, surfacemetallurgica
9、l structure, and the temperature at the junctions.See Fig. 1.3. Summary of Practice3.1 The two techniques that are primarily used in thermo-electric sorting are direct and comparative instrumentation. Inthe direct instruments, equipment is standardized by placingmaterials with known chemistry and me
10、tallurgical structure inthe test system. The value of the thermoelectric voltage (orarbitrary unit) is read on the scale of an indicator. In thecomparative instruments, the thermoelectric response of thetest piece is compared with that of a known standard(s) and theresponse indicates whether the pie
11、ce is within the acceptancelimits.3.1.1 Both kinds of instrumentation require comparing thepieces to be examined with the known standard(s). Two ormore samples representing the acceptance limits may berequired.3.1.2 Direct Thermoelectric Instrumentationa knownstandard(s) is inserted in the system an
12、d the controls of theinstrument are adjusted to obtain a voltage (or arbitrary unit)reading(s). The process is then continued by inserting thepieces to be sorted into the system, and observing the instru-ment reading(s).3.1.3 Comparative InstrumentationKnown standards rep-resenting the acceptance li
13、mits are inserted into the system.The instrument controls are adjusted for appropriate response.The process is then continued by inserting the pieces to besorted in the system, and observing the instrument response.3.2 In both instruments, the range of the instrument re-sponse must be adjusted durin
14、g standardization so that anyanticipated deviation from the known standard(s) will berecognized as within the required acceptance limits.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.10 onSpecialized NDT
15、 Methods.Current edition approved June 1, 2014. Published July 2014. Originally approvedin 1984. Last previous edition approved in 2008 as E977 - 05 (2008). DOI:10.1520/E0977-05R14.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.3 T
16、he examination process may consist of manual inser-tion of one piece after another into the system, or an automatedfeeding and classifying mechanism may be employed.4. Application4.1 Thermoelectric techniques provide a method for sortinglarge quantities of conductive materials. The ability to accom-
17、plish satisfactorily these types of separations is dependent uponthe relation of the thermoelectric voltages with regard tocomposition, condition, structure, and processing.4.2 Comparative instrumentation is used when high-sensitivity testing is required. The advantage of this method isthat it reduc
18、es internal or external disturbances such astemperature variations of the material or probes, or both.4.3 The success of an attempted sort will be affected byinstrument factors such as electrode composition, electrodetemperature differential, and electrode contact.4.4 The degree of reliability of in
19、strument readings will beaffected greatly by the coupling between the electrodes and thepart and the accuracy with which the temperature is heldconstant during the measuring period. The surface of thematerials and of both electrodes must be kept free of anyinsulating materials such as surface oxide,
20、 dirt, paint, or otherforeign material.5. Interference5.1 The specific influence of the following variables must beconsidered for proper interpretation of the results obtained:5.1.1 A correlation shall be established so that if thethermoelectric properties of the various groups overlap, auxil-iary m
21、ethods are used for supplementary examination.5.1.2 In sorting materials, a temperature differential must beused that will result in a well-defined separation of thethermoelectric properties.5.1.3 Contaminates that will electrically insulate materialbeing examined, such as rust, grease, oil, mill sc
22、ale; or surfacecoatings such as paint, plastic, and so forth, must be removedto ensure clean contact between the material and the electrodesof the device.5.1.4 Extreme temperature differences between the stan-dard(s) and the pieces will alter the emf generated. Knownstandard(s) should be at the same
23、 temperature as the piecesbeing examined.5.1.5 The geometry and mass of the standard and part neednot be a consideration to permit sorting. Fixturing may berequired where the part mass is insufficient to provide anadequate heat sink (for example, thin foil, small-diameter wire,small bearings, etc.).
24、5.1.6 Interference may be caused by radio frequency pro-duced by devices such as arc welders or radio and radartransmitters. This interference may be observed when theequipment is used in proximity to the above mentioned r-fsources.5.1.7 If changes in the surface chemistry of the material arebrought
25、 about due to buildup or depletion of the constituents,the affected surface should be removed by grinding or othermeans; or a known standard containing the same surfaceconstituents should be used as comparison materials.6. Apparatus6.1 Electronic ApparatusThe electronic apparatus shall becapable of
26、maintaining a sufficient temperature differentialacross the electrodes to produce a suitable thermoelectricvoltage. Equipment to process this voltage may include anysuitable signal-processing devices (d-c amplifiers, nulldetectors, potentiometers, etc.) and the output may be dis-played by meter, sco
27、pe, recorder, signaling devices, or anysuitable combination required for the particular application. Atypical circuit is illustrated in Fig. 1.FIG. 1 Typical Circuit Used in Thermoelectric Material Sorting InstrumentsE977 05 (2014)26.2 Electrodes may be two or more separate electrodes orone multiple
28、 electrode probe. They may both contact the samesurface of the test sample or different surfaces.6.3 A mechanical device for feeding and sorting the speci-mens may be used to automate the particular application.7. Procedure7.1 Known Reference StandardsSelect samples represen-tative of known material
29、s to be sorted that will provide a rangeof instrument readings representative of the known materialgroup.7.2 Standardization:7.2.1 The thermoelectric sorting method is primarily one ofcomparison between pieces. Empirical data and physical testsare used to determine classification. The standardizatio
30、n pro-cedure is governed by the properties of the sample requiringseparation. Consult the individual users manual for specificcalibration information7.2.2 Standardization is governed by the characteristics ofthe materials to be sorted. In accordance with manufacturersinstructions, adjust the instrum
31、ent controls so that the readingsare representative of the known standard(s) and are within therange of instrument display.7.2.3 Perform restandardization at the start and finish ofeach run and at least once during every hour of continuousoperation.7.2.4 Restandardize whenever the following conditio
32、ns ex-ist:7.2.4.1 Operator variables that influence examination re-sults.7.2.4.2 Improper functioning of the system is suspected.7.2.4.3 Ambient conditions change or are suspected ofinfluencing results.7.2.5 If restandardization results in a change affecting thesort since the last standardization, r
33、etest all material testedsince the last standardization.7.3 Operation:7.3.1 Connect the required test electrode or electrodes to theinstrument.7.3.2 Switch on the instrument and allow it to warm up forat least the length of time recommended by the manufacturer.7.3.3 Make all necessary setup and cont
34、rol adjustments inaccordance with the manufacturers recommendations.7.3.4 Standardize in accordance with the manufacturersrecommendations.7.3.5 Position the electrodes on the piece to be examined.7.3.6 Observe the instrument output on the indicator.7.3.7 Sort the piece based on the acceptance limit(
35、s) set.7.4 Interpretation of Results:7.4.1 The results of any nondestructive testing procedureare based on the comparison of an unknown with a standard.Unless all of the significant interrelationships of material orproduct properties are understood and measurable for bothstandard and unknown samples
36、, the results may be meaning-less.7.4.2 Thermoelectric sorting is best used for repetitiveexamination of materials identical in composition and inmetallurgical structure.7.4.3 Interpretation of data depends upon the degree towhich the materials compare with either established data orreference materi
37、als. Results can often be interpreted by aprocessing change, such as changes in temperature,composition, or surface condition.7.4.4 The characteristics of different material(s) in differingconditions may produce identical or similar emf outputs. If anydoubt exists about the validity of a sort, a sec
38、ond method orprocedure such as changing electrode composition can be usedto further define the separation of materials. A chemical spottest, eddy current, or permeability exam using a magnet mayalso show the effect of other variables.8. Report8.1 A written report shall be supplied to the purchaser u
39、ponrequest indicating that a thermoelectric examination has beenperformed.9. Keywords9.1 electrode; electronic device; metal sorting; nondestruc-tive; Seebeck effect; standardization; thermoelectricASTM International takes no position respecting the validity of any patent rights asserted in connecti
40、on with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible
41、 technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consi
42、deration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Ba
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