1、Designation:B26707(Reapproved 2013)Standard Specification forWire for Use In Wire-Wound Resistors1This standard is issued under the fixed designation B267;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A nu
2、mber in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This specification covers round wire and ribbon withcontrolled electrical properties for use in wire-wound resis-tance units and similar appl
3、ications,but not for use as electricalheating elements.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 purp
4、ort to address all of thesafety 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 appropriateMaterial Safety Data Sheet(MSDS)for this product/materialas provided by the manufacturer,to est
5、ablish appropriatesafety and health practices,and determine the applicability ofregulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B63 Test Method for Resistivity of Metallically ConductingResistance and Contact MaterialsB77 Test Method for Thermoelectric Power of Electric
6、al-Resistance AlloysB84 Test Method for Temperature-Resistance Constants ofAlloy Wires for Precision Resistors3.Significance and Use3.1 This specification on wire and ribbon contains thegeneric chemistry and requirements for resistivity,temperaturecoefficient of resistance,thermal emf versus copper
7、resistancetolerances,and mechanical properties of bare wire,as well asthe wire enamels and insulations of alloys normally used in themanufacture of wound resistors.4.Alloy Classes4.1 Fifteen classes of alloys are covered by this specificationas listed in Table 1.5.Elongation5.1 The wire shall confor
8、m to the requirements for elonga-tion as prescribed in Table 1,when tested on a 10-in.(254-mm)length.6.Resistivity6.1 The bare wire shall conform to the requirements fornominal resistivity as prescribed in Table 1.6.2 Actual resistivity shall not vary from nominal resistivityby more than 65%for Allo
9、y Classes 1 to 4 inclusive,and610%for Alloy Classes 5 to 11 inclusive.7.Nominal Electrical Resistance per Unit Length7.1 The nominal resistance per unit length for round wireshall be calculated from the nominal resistivity and the nominalcross-sectional area.NOTE1When ribbon or flat wire is produced
10、 by rolling from roundwire,the cross section departs from that of a true rectangle by an amountdepending on the width-to-thickness ratio and the specific manufacturingpractice.The conventional formula for computing ohms per foot and feetper pound is to consider the cross section as 17%less than a tr
11、ue rectanglewhen width is more than 15 times the thickness and 6%less than a truerectangle in other cases.This is not valid in view of modern rollingequipment and practices,but still is widely used as a basis of description.Ribbon actually is made to a specified resistance per foot,and no tolerancei
12、s specified for thickness.An alternative and a closer approximation wouldbe that for ribbon rolled round wire,the electrical resistance would becalculated on a cross 6%less than a true rectangle.8.Temperature Coefficient of Resistance8.1 The change in resistance with change in temperature,expressed
13、as the mean temperature coefficient of resistancebased on the reference temperature of 25C,shall be within thelimits specified in Table 1,Columns 4 and 6,over thecorresponding temperature ranges specified in Columns 5 and7.The mean temperature coefficient of resistance referred to25C is defined as t
14、he slope of a chord of an arc.This slope isdetermined from the following equation:m5R/R25T!31061This specification 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 Heat
15、ing Materials.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 1952.Last previous edition approved in 2007 as B267 07.DOI:10.1520/B0267-07R13.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual B
16、ook 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 Conshohocken,PA 19428-2959.United States1 where:m=mean temperature coefficient of resistance,ppm/C,Table 1,Columns 4 and 6,R=change in resistance over temperature range indicatedin Table 1,Columns 5 and 7,R25=resistance at 25C,T=temperature range indicated in Table 1,Columns 5and 7.8.2 ForAlloy Classes 1,2,and 5,the temperatur
