1、Designation: B742 90 (Reapproved 2012)Standard Specification forFine Silver Electrical Contact Fabricated Material1This standard is issued under the fixed designation B742; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This specification covers fine silv
3、er grade 99.9 % infabricated form. The forms covered are tubing, rod, wire, strip,and sheet for electrical contact applications.1.2 The electrical contact properties may vary dependentupon the method of manufacture (refer to 6.3).1.3 The values stated in inch-pound units are to be regardedas standar
4、d. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 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 stand
5、ard to become familiarwith all hazards, including those identified in the appropriateMaterial Safety Data Sheet (MSDS) for this product/materialas provided by the manufacturer, to establish appropriatesafety and health practices, and determine the applicability ofregulatory limitations prior to use.
6、2. Referenced Documents2.1 ASTM Standards:2B413 Specification for Refined SilverB476 Specification for General Requirements for WroughtPrecious Metal Electrical Contact Materials3. Classification3.1 This specification presently defines only one grade offine silver, 99.90 % minimum silver. It differs
7、 from the Grade99.90 referred to in Specification B413 in that the chemicallimits are slightly different. The reason for this is that Speci-fication B413 refers to “refined silver in cast bar form,”whereas this Specification covers fabricated forms. The prop-erties of silver are greatly dependent up
8、on the amount and typeof elements present, up to 0.10 %.3.2 Other types of silver containing appreciably lesseramounts of impurities, and those with additives for specialpurposes, are not covered by this specification, because themechanical properties can be appreciably different.4. Ordering Informa
9、tion4.1 Orders for material under this specification shall includethe following information:4.1.1 Quantity (weight usually in troy ounces, or number ofunits).4.1.2 Name of material (fine silver).4.1.3 Temper.4.1.4 Dimensions; thickness, width, length, diameter, coilsize, or other pertinent sizes.4.1
10、.4.1 Form of Material: sheet, strip, disks, blanks, wire,shaped wire, or other.4.1.4.2 Form Furnished: flat lengths, coils, rod, straightlengths, or other.4.1.5 ASTM designation and date of issue.4.1.6 Additions to the specification and supplementary re-quirements, if required.1This specification is
11、 under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.05 on Precious Metals and Electrical Contact Materials.Current edition approved May 1, 2012. Published May 2012. Originallyapproved in 1985. Last previous edition approved
12、 in 2006 as B742 90 (2006).DOI: 10.1520/B0742-90R12.2For 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 ASTM website.TABLE 1 C
13、hemical CompositionAElement Weight %Silver 99.90 min (by difference)Silver and copper 99.95 minCopper 0.10 maxNickel 0.002 maxCadmium 0.005 maxZinc 0.005 maxLead 0.025 maxIron 0.005 maxAluminum 0.002 maxBismuth 0.001 maxTotal others 0.05 maxTotal of all impurities 0.10 maxAElements, such as phosphor
14、us, sodium, and lithium are not natural impuritiesin this grade of silver and thus are not normally found in any appreciable quantities.However, since they may be detrimental for certain electrical contact applications,limits for these and other elements may be established by agreement between thepu
15、rchaser and manufacturer. Refer to 7.2.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. General Requirements5.1 The provisions of Specification B476 shall apply to allmaterials produced to this specification.6. Manufacture6.1 The m
16、aterials used for making this product shall be ofsuch quality and purity that the finished material will conformto the requirements and properties prescribed in this specifica-tion.6.2 The material shall be produced by either hot or coldworking operations. It should be finished by such cold workinga
17、nd annealing as may be necessary to meet the propertiesspecified.6.3 After the initial shipment and approval has been made,the supplier must notify the purchaser prior to making anysignificant changes in process techniques, basic formulation, orother factors that might affect the quality or the elec
18、tricalcontact characteristics, such as weld resistance or erosion. Suchchanges in process shall be immediately brought to theattention of the purchaser for determination of the necessity forrequalification.7. Chemical Composition7.1 Material produced under this specification shall meet therequiremen
19、ts of chemical composition prescribed in Table 1.7.2 By agreement between the purchaser and the manufac-turer, analysis may be required and limits established forelements or compounds not specified in the table of chemicalcomposition.8. Mechanical Properties8.1 The material shall conform to the mech
20、anical propertiesprescribed in Table 2 or Table 3.8.2 Since it is not always possible to tension test some partsand shapes, the user and supplier should reach an agreementwith respect to the type of hardness tests and the acceptablerange that should be applicable.8.3 All test specimens shall be full
21、 size when practical.8.4 All tests shall be conducted at room temperature, 65 to85F (18 to 29C).9. Inspection and Testing9.1 All material produced to this specification shall beinspected as detailed in the provisions of Specification B476.10. Certification10.1 When specified in the purchase order or
22、 contract, aproducers or suppliers certification shall be furnished to thepurchaser that the material was manufactured, sampled, tested,and inspected in accordance with this specification and hasbeen found to meet the requirements. When specified in thepurchase order or contract, a report of the tes
23、t results shall befurnished.11. Keywords11.1 contact; electrical contact; fine silver; silver; wroughtTABLE 2 Mechanical Properties of Sheet and StripNOTE 1These hardness values are listed as “Typical,” because of the difficulty in establishing a range meaningful for all the thicknesses possible.If
24、the purchaser desires hardness specifications, rather than tensile strengths, he shall reach agreement with the supplier as to the proper and suitablehardness scale and range for the particular size and form ordered.TemperReductioninB or through the ASTM website(www.astm.org). Permission rights to p
25、hotocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).3Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/dodssp.daps.dla.mil.4For further information, refer to Symposium on Evolution of the InternationalPractical Temperature Scale of 1968, ASTM STP 565, ASTM, 1968.B742 90 (2012)3
