Designation:B742−90(Reapproved2012)StandardSpecificationforFineSilverElectricalContactFabricatedMaterial1ThisstandardisissuedunderthefixeddesignationB742;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.1.Scope1.1Thisspecificationcoversfinesilvergrade99.9%infabricatedform.Theformscoveredaretubing,rod,wire,strip,andsheetforelectricalcontactapplications.1.2Theelectricalcontactpropertiesmayvarydependentuponthemethodofmanufacture(referto6.3).1.3Thevaluesstatedininch-poundunitsaretoberegardedasstandard.ThevaluesgiveninparenthesesaremathematicalconversionstoSIunitsthatareprovidedforinformationonlyandarenotconsideredstandard.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtobecomefamiliarwithallhazards,includingthoseidentifiedintheappropriateMaterialSafetyDataSheet(MSDS)forthisproduct/materialasprovidedbythemanufacturer,toestablishappropriatesafetyandhealthpractices,anddeterminetheapplicabilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2B413SpecificationforRefinedSilverB476SpecificationforGeneralRequirementsforWroughtPreciousMetalElectricalContactMaterials3.Classification3.1Thisspecificationpresentlydefinesonlyonegradeoffinesilver,99.90%minimumsilver.ItdiffersfromtheGrade99.90referredtoinSpecificationB413inthatthechemicallimitsareslightlydifferent.ThereasonforthisisthatSpeci-ficationB413refersto“refinedsilverincastbarform,”whereasthisSpecificationcoversfabricatedforms.Theprop-ertiesofsilveraregreatlydependentupontheamountandtypeofelementspresent,upto0.10%.3.2Othertypesofsilvercontainingappreciablylesseramountsofimpurities,andthosewithadditivesforspecialpurposes,arenotcoveredbythisspeci...
