ASTM A717 A717M-2012(2018) Standard Test Method for Surface Insulation Resistivity of Single-Strip Specimens.pdf

1、Designation: A717/A717M 12 (Reapproved 2018)Standard Test Method forSurface Insulation Resistivity of Single-Strip Specimens1This standard is issued under the fixed designation A717/A717M; the number immediately following the designation indicates the yearof original adoption or, in the case of revi

2、sion, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a means of testing the surfaceinsulation resistivity of single strips or pun

3、chings of flat-rolledelectrical steel under predetermined conditions of voltage,pressure, and temperature.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall b

4、e used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 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-pri

5、ate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelop

6、ment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2A34/A34M Practice for Sampling and Procurement Testingof Magnetic Materials3. Terminology3.1 Definitions of Terms

7、Specific to This Standard:3.1.1 surface insulation resistivityrefers to the effectiveresistivity of a single insulative layer tested between appliedbare metal contacts and the base metal of the insulated testspecimen. It is not the same as the terms interlaminar resistivityand stack resistivity, whi

8、ch refer to the average resistivity oftwo adjacent insulative surfaces in contact with each other.3.1.2 The apparatus is popularly known as a Franklin tester.4. Summary of Test Method4.1 Ten metallic contacts of fixed area are applied to one ofthe surfaces of the specimen and electrical contact is m

9、ade withthe base metal by two drills. The effectiveness of the surfaceinsulation is then indicated by a measurement of averageelectrical current flowing between the contacts and the basemetal under specified applied voltage. This measurement canbe used directly as an indicator of insulation quality

10、or may beconverted to an apparent surface insulation resistivity value.5. Significance and Use5.1 This test method is particularly suitable for qualitycontrol in the application of insulating coatings.5.2 Surface insulation resistivity is evaluated from a dccurrent that can range from 0 (perfect ins

11、ulator) to 1 A (perfectconductor).5.3 Single readings should not be considered significantsince the nature of the test device and specimen are such thatsuccessive measurements of a specimen often yield differentvalues.6. Apparatus6.1 The apparatus, as shown in Fig. 1 and Fig. 2, shallconsist of a co

12、ntact unit or test head which is attached to thehead of a hydraulic press. Its associated measuring equipment,which may be remotely located, includes an ammeter,voltmeter, and voltage regulated dc power supply. Whenmeasurements are to be made at elevated temperatures, theplaten beneath the specimen

13、is heated and controlled. Detaileddescriptions of the various components are given in Annex A1.7. Sampling7.1 Samples shall be representative of the steel and shall becut in a manner to assure representative sampling as describedin Practice A34/A34M.1This test method is under the jurisdiction of AST

14、M Committee A06 onMagnetic Properties and is the direct responsibility of Subcommittee A06.01 on TestMethods.Current edition approved May 1, 2018. Published June 2018. Originallyapproved in 1975. Last previous edition approved in 2012 as A717/A717M 12.DOI: 10.1520/A0717_A0717M-12R18.2For referenced

15、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 standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consho

16、hocken, PA 19428-2959. United StatesThis 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 Orga

17、nization Technical Barriers to Trade (TBT) Committee.18. Test Specimen8.1 The width and length of a specimen strip shall be greaterthan the width and length respectively of the assembly ofcontacts. The suggested minimum specimen size is 2 by 5 in.50 by 130 mm.8.2 A minimum of five specimen strips is

18、 recommended.8.3 By mutual agreement between the producer and theuser, tests may be run on Epstein test strips. The Epsteinspecimens may be less satisfactory than the minimum sizespecimen suggested in 8.1 because of the tilting effect due toburrs, shearing strains, and disturbances in the coating.9.

19、 Procedure9.1 To ensure correct contact button conditions, make ashort circuit test occasionally by testing a bare metal surface.When the short circuit current is less than 0.99 A, clean thecontacts. The use of solvents for cleaning is preferred toabrasives because the latter can result in rounded t

20、ips withreduced contact areas.9.2 The recommended standard pressure for purpose ofcomparative tests shall be 300 psi 2.1 MPa. Other pressures,depending upon the application, may be agreed upon by theproducer and the user. If more than one test pressure is to beused, apply the pressures in ascending

21、order. During testing,apply the pressures only once, but an applied pressure may beincreased to a higher value.9.3 If both sides of the specimen are coated, do not use thesame area to test both sides.9.4 The recommended standard test temperatures are roomtemperature and 300F 150C. Other temperatures

22、 and thesequence of temperatures, depending upon the application,may be agreed upon by the producer and the user.9.5 When tests are made at elevated temperatures allowsufficient time (usually 30 s) to heat the specimen to thespecified temperature.9.6 When the insulation may be hygroscopic, a conditi

23、oningprocedure immediately prior to testing should be mutuallyagreed upon by the producer and the user.9.7 Place the specimen on the platen beneath the test headand position it so that all contacts are within the test area whenthe test head is brought in contact with the specimen.Apply thespecified

24、pressure. Check that the voltage is 0.50 V and readthe ammeter.10. Calculations10.1 The average of electrical current measurements isusually acceptable for evaluating surface insulation. Averagethe current readings for each surface. The reported value for asample shall be the average of both surface

25、s.10.2 The two surface insulation resistivity of the test sample(two surfaces in series), Ri, may be calculated from I, theaverage ammeter reading in A, as follows:Ri5 6.451/I! 2 1! incm2/lamination, (1)orRi5 6451/I! 2 1! inmm2/lamination.10.3 The equations in 10.2 may be derived as shown inAnnex A2

26、.11. Precision and Bias11.1 Even with the best practices in design, instrumentation,maintenance, and operation, the repeatability and reproducibil-ity of the test method are greatly influenced by the nature of thesurfaces of the test specimens. Hence it is not consideredFIG. 1 Apparatus of Surface I

27、nsulation Resistivity MeasurementFIG. 2 Diagram of Connections for Contacts and ResistorsA717/A717M 12 (2018)2possible to state meaningful values for repeatability andreproducibility that are universally applicable.12. Keywords12.1 coating; electrical steel; Franklin tester; insulation;resistivity;

28、single-strip specimens; surface insulation resistivityANNEXES(Mandatory Information)A1. APPARATUSA1.1 Test HeadThe test head shall consist of a mountingblock on which are assembled:A1.1.1 Two parallel longitudinal rows of five verticallymounted steel rods free to move axially against surroundingspir

29、al springs or other means to apply equal pressure.A1.1.2 Brass, stainless steel, or other suitable metalliccontact button on each rod, but insulated from it. Articulationof tips improves contact by compensating for minor misalign-ments. Avoid soft metals, poor conductors, or metals subject tooxidati

30、on or attack by solvents used in cleaning. Due tolow-voltage circuitry (0.5 V) all contacting surfaces must bekept clean. Full area contact of tips to coreplate is needed toavoid decreases in Franklin amperage. Check with knownsamples or standard test blocks. The contact area of each of theten conta

31、ct buttons shall be 0.645 cm264.5 mm2.A1.1.3 A 5- (60.1 %) resistor connected to each contactbutton. Contacts with their individual resistors shall be con-nected in parallel as shown in Fig. 2.A1.1.4 Electrical contact with the base metal is madethrough two18 in. 3 mm diameter twist drills (preferab

32、lycarbide-tipped) or hardened and pointed rods. These arevertically mounted and spring loaded in spiral slotted sleeves toimpart a twist while piercing the coating.A1.2 Hydraulic PressThe hydraulic press shall have acapacity of 2000 lb 10 000 N, with mountings to accommo-date the test head, test spe

33、cimens or punchings, and a hot plate.The press or hot plate must provide a smooth, flat, and rigidsupport for the test specimen.A1.3 Hot PlateThe hot plate, when used, shall be suitablefor heating to the temperature of test with automatic control tomaintain the test temperature.A1.4 Test Head Power

34、SupplyThe voltage regulated dcpower supply should be capable of voltage regulation of atleast 0.5 % at 0.5 V during load changes from zero to 1.0Aandline voltage variations of 610 %. This maintains the voltageadequately accurate during test and eliminates the necessity formanual voltage adjustment.A

35、1.5 AmmeterThe dc ammeter should be a low imped-ance 0 to 1Adigital type rated for 0.1 % or better accuracy andhave resolution of 0.01 A.A1.6 VoltmeterThe dc voltmeter should be a high imped-ance 0 to 1 V digital type rated for 0.1 % or better accuracy andhave resolution of 0.01 V.A1.7 Hot Plate Pow

36、er SupplyThe plate power supply andtemperature control equipment should be capable of automatictemperature control and variable setting features. It may usethermocouples or other temperature sensing elements, but mustbe able to maintain temperature of the hot plate within 10F5C of the set temperatur

37、e.A717/A717M 12 (2018)3A2. DERIVATIONA2.1 The equations in 10.2 may be derived as follows:I 5 E(n51101/Rs1 Rn!5 10E/Rs1Rj/Ab!Rj5 Ab10 E I! 2 Rs! (A2.1)Ri5 2 Rj5 2Ab10 E/I! 2 Rs!where:I = ammeter reading in A,E = applied voltage in V,= 0.5V,Rs= resistance of resistor in series with each contact butto

38、nin ,=5,Rn= resistance of surface between single contact button andbase metal of the test specimen in ,Rj= surface insulation resistivity of one surface of testsample in cm2/surface or mm2/surface,Ab= area of each contact button in cm2or mm2= 0.645 cm2or 64.5 mm2,Ri= two surface insulation resistivi

39、ty of test sample (twosurfaces in series) in cm2/lamination ormm2/lamination.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validi

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42、t 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 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple cop

43、ies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 12 (2018)4