1、Designation: B63 07 (Reapproved 2018)Standard Test Method forResistivity of Metallically Conducting Resistance andContact Materials1This standard is issued under the fixed designation B63; the number immediately following the designation indicates the year of originaladoption or, in the case of revi
2、sion, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test meth
3、od covers the determination, to a precisionof 2 %, of the electrical resistivity of materials used inresistors, heating elements, and electrical contacts, as well asproducts of powder metallurgy processes which are used forother purposes.NOTE 1For determining the resistivity of electrical conductors
4、 seeTest Method B193.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety
5、concerns, if any, associated with its use. It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateSafety Data Sheet (SDS) for this product/material as providedby the manufacturer, to establish appropriate safety, health,an
6、d environmental practices, and determine the applicabilityof 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 theDevelopment of International S
7、tandards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B193 Test Method for Resistivity of Electrical ConductorMaterials3. Terminology3.1 Definitions:3.1.1 resistivity, nthat property of a mat
8、erial which deter-mines its resistance to the flow of an electric current, expressedas: 5 RA/L (1)where R is the resistance in ohms of a specimen of thematerial of uniform cross section A and of a length L.Inreporting values of resistivity under this test A shall be ex-pressed in square centimeters
9、and L in centimeters. Resistiv-ity is measured in micro ohm-meter. English units of ohmscircular mil per foot are expressed as: 5 12 3106RA/0.7854 L (2)where:R = resistance in ohmsA = uniform cross section area in square inchesL = length in inches4. Significance and Use4.1 In the case of materials f
10、or resistors and heatingelements, a knowledge of resistivity is important in determin-ing whether wire or strip of a specified area of cross section andlength will have a required resistance. It serves as one basis forthe selection of materials for specific applications and itsmeasurement is a neces
11、sary acceptance test for resistancematerials.4.2 In the case of materials for electrical contacts, themeasurement of resistivity can serve as a test for uniformity ofmaterials of nominally the same composition and structure.5. Apparatus5.1 Means for applying current and voltage terminals to thespeci
12、men are specified in Section 9. An optional suitablespecimen holder for nonductile materials is shown in Fig. 1.5.2 A suitable bridge, potentiometer, digital ohmmeter, orequivalent, with necessary accessories for making resistancemeasurements with a limit of error of less than 0.5 %.1This test metho
13、d is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.10 on Thermostat Metals and Electrical Resistance Heating Materials.Current edition approved Nov. 1, 2018. Published November 2018. Originallyapproved in 1926. Last pr
14、evious edition approved in 2013 as B63 07 (2013). DOI:10.1520/B0063-07R18.2For 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 standards Document Summary page onthe
15、ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelop
16、ment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15.3 Means for measuring the dimensions of the specimen,adequate to determine its length and its mean area of crosssection, each within 0.5 %.6. Test Specime
17、n6.1 Ductile MaterialsThe test specimen for ductilematerials, including those used for contacts, shall be in theform of a wire or a strip. In order to determine the resistivitywith a precision of 2 %, it is necessary that the resistance,cross-sectional area, and length shall be measured with a limit
18、of error within 0.5 %. To ensure this limit of error each testspecimen shall conform to the following:6.1.1 It shall have a length of at least 0.5 ft (15 cm) betweenpotential probes.6.1.2 It shall have a resistance of at least 0.001 .6.1.3 If the cross section is to be determined by directmeasuremen
19、t, the diameter of a wire specimen or the thicknessof a strip specimen shall not be less than the limits defined bythe 0.5 % criteria of 6.1, and this dimension throughout thelength of the specimen shall not vary by more than 3 %.6.1.4 It shall show no surface cracks or other defectsobservable with
20、normal vision, and shall be free from surfaceoxide.6.2 Nonductile MaterialsThe test specimen for nonductilematerials shall be made in accordance with Fig. 2 if thematerial is readily machinable. For materials which are notreadily machinable, such as those containing graphite, a flatstrip may be used
21、 as a test specimen. In order to determine theresistivity with a precision of 2 %, each specimen shallconform to the following:6.2.1 The diameter of a specimen (Fig. 2), or the thicknessand width of a strip specimen, shall be uniform within 1 %.6.2.2 It shall show no surface cracks or other defectso
22、bservable with normal vision, and shall be free from surfaceoxide.Item Description Dimensions, in. (mm) MaterialNumberRequired1 Base block12 by 3 by 4 (12.7 by 76.2 by 101.6) micarta 12 Clamp block34 by 1 by 1 (19.0 by 25.4 by 25.4) copper 23 Current lead clamp screw, knurled head1032 by316 brass 24
23、 Specimen clamp screw, knurled head14 in.by40by1in. brass 25 Pivot bracket12 by1516 by 1716 (12.7 by 23.8 by 36.5) steel 26 Pivot . steel 27 Pivot block12 by 2332 by 3 (12.7 by 53.2 by 76.2) micarta 18 Potential knife-edge . steel 2 sets9 Specimen being tested . . .NOTE 1Contact surfaces must be cle
24、an and free of visible oxide.FIG. 1 Specimen Holder for Nonductile MaterialsB63 07 (2018)27. Length Measurements7.1 The length may be measured by any scale which willgive an accuracy of 0.5 % in the length measured. In casepotential leads are used, the length shall be taken between thepotential cont
25、acts. In the direction of the length of specimen,the dimension of each potential contact, including solderingsurface or clamp contact area, shall not be more than 0.5 % ofthe distance between the potential contacts. In the case of thespecimen holder for nonductile materials shown in Fig. 1, thedista
26、nce between the potential contacts may be found bymeasuring from the outside flat of one potential knife edge tothe outside flat of the other. A micrometer or other suitablemeans shall be used for measuring this length.8. Cross-Sectional Area Measurements8.1 In general, the diameter of a specimen of
27、 circular crosssection, or the thickness and width of a strip specimen, shall bedetermined by micrometer measurements, and a sufficientnumber of measurements shall be made to obtain the meancross section to within 0.5 %.8.2 In case the diameter of the cylinder or the thickness ofthe strip cannot be
28、measured to give the above accuracy withthe micrometer available, determine the cross section from theweight, density, and length of specimen.8.3 When the density is unknown, it may be determined asfollows:8.3.1 For nonporous materials first weigh a sample of atleast 10 g in air and then in water. T
29、he density in grams percubic centimetre is equivalent to the weight in air divided bythe loss of weight due to submergence in water. The water shallbe at room temperature to avoid errors due to convectioncurrents. For the accuracy required, no corrections are neces-sary for the temperature of the wa
30、ter or for the buoyancy of theair. However, exercise care to remove all air bubbles from thespecimen when weighing it in water. To remove air bubblesfrom a specimen of fine wire, dip the wire, in the form of aloosely wound coil, in alcohol and rinse in water beforeimmersing it in the water to be use
31、d in weighing. Thencalculate the density from the following equation:D 5 B/B 2 E! (3)where:D = density, g/cm3B = weight of specimen in air, gE = weight of specimen in water, gThe cross-sectional area, A, in square centimeters, may befound from the equation:A 5 B 2 E!/L (4)8.3.2 For porous materials
32、such as products of powdermetallurgy, weigh a specimen of at least 10 g in air. Immersethe specimen for at least4hinoil(viscosity of approximately200 SUS at 37.8C (100F), held at a temperature of 82.2 65.5C (180 6 10F). Then cool the specimen to room tem-perature by immersing it in oil at room tempe
33、rature. Afterremoving excess oil from the specimen by means of a softcloth, weigh the specimen in air and then in water. Calculatethe density from the equation:D 5 B/C 2 E! (5)where:D = density, g/cm3B = weight of the unimpregnated specimen in air, gC = weight of the specimen impregnated with oil (i
34、n air), gE = weight of the impregnated specimen in water, gThe cross-sectional area, A, in square centimetres, may befound from the equation:A 5 C 2 E!/L (6)9. Leads9.1 Specimens with a resistance of less than 10 shall beprovided with both current and potential leads. The minimumdistance between eac
35、h potential contact and the adjacentcurrent lead shall be at least three times the diameter of thewire or the width of the strip. Current shall be introduced intothe specimen with current leads amply large to minimizeheating of the specimen. Specimens with a resistance greaterthan 10 do not require
36、potential leads, though they may beused, if desired.10. Resistance Measurements10.1 Resistance of specimens provided with potential leadsshall be measured with a Kelvin bridge, potentiometer, digitalohmmeter, or equivalent capable of measuring the resistancebetween the potential contacts with a limi
37、t of error within0.5 %. Specimens with a resistance of more than 1 may bemeasured with a limit of error within 0.5 % by means of asuitable Wheatstone bridge.11. Heating of Specimen11.1 In all resistance measurements, the measuring currentraises the temperature of the specimen above that of thesurrou
38、nding medium. If this is sufficient to change the resis-tance by 0.5 %, a correction shall be made. In general, thesmallest current that will give the sensitivity necessary toNOTE 1Metric equivalents are as follows.in. mm in. mm0.010 0.25 0.438 11.120.012 0.30 2.000 50.800.187 4.75 2.375 60.320.188
39、4.78 3.250 82.550.237 6.01FIG. 2 Resistivity Test Specimen for MachinableNonductile MaterialsB63 07 (2018)3measure to 0.5 % of the resistance shall be used. A convenienttest to determine whether a correction should be applied is toincrease the current to 1.4 times the value it had when themeasuremen
40、t was made (Note 2) and then to measure theresulting change in resistance. If this change is as large as0.5 % of the measured value, a correction should be made. Fora material which has a positive temperature coefficient ofresistance, the resistance at the temperature of the surroundingmedium shall
41、be obtained by subtracting the measured changefrom the resistance as measured with the smaller current. Formaterial with a negative temperature coefficient, this differenceshall be added to the resistance obtained by measurements withthe smaller current.NOTE 2Increasing the current to 1.4 times the
42、value it had when themeasurement was made serves to very nearly double the heating effect,and, for small changes in temperature, the rise in temperature.11.2 Measurements are to be in a controlled temperatureenvironment.12. Report12.1 Report the following information:12.1.1 Identification of test sp
43、ecimen,12.1.2 Material type,12.1.3 Temperature of surrounding medium,12.1.4 Length of specimen used,12.1.5 Method of obtaining cross-sectional area:12.1.5.1 If by micrometer, a record of all micrometerreadings, including average values and calculated cross-sectional area,12.1.5.2 If by weighing, a r
44、ecord of length, mass and densitydeterminations and calculated cross-sectional area,12.1.6 Method of measuring resistance,12.1.7 Value of resistance,12.1.8 Calculated value of electrical resistivity, and12.1.9 Previous mechanical and thermal treatments. (Sincethe resistivity of a material usually de
45、pends upon them, theseshall be stated whenever the information is available.)13. Precision and Bias13.1 The precision of this test method is within 2 %.13.2 The bias of this test method is less than 1 %.14. Keywords14.1 contact materials; electrical conductors; heating ele-ments; resistivity; resist
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