1、Designation: B 781 93a (Reapproved 2006)Standard Guide forSilver-Cadmium Oxide Contact Material1This standard is issued under the fixed designation B 781; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide provides guidelines for users and manufac-turers of silver-cadmium oxide material produced in strip, rod,wire, and part fo
3、rm for electrical contact applications.1.2 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 become familiarwith all hazards including those identified in the appropriateMaterial Safety Data S
4、heet (MSDS) for this product/materialas provided by the manufacturer, to establish appropriatesafety and health practices , and determine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B311 Test Method for Density Determination for PowderMetallurgy
5、 (P/M) Materials Containing Less Than TwoPercent PorosityB 476 Specification for General Requirements for WroughtPrecious Metal Electrical Contact MaterialsC 914 Test Method for Bulk Density and Volume of SolidRefractories by Wax ImmersionNOTE 1Test Method B311 is applicable to fully dense forms.Spe
6、cification B 476 is applicable to strip, rod, or wire only. Test MethodC 914 is applicable to forms less than 99 % dense.3. Terminology3.1 lot, n(usage involving discrete manufactured parts)all parts of the same form, and dimensions, from the same alloymelt or batch of particulate (if manufactured b
7、y consolidation),processed under the same conditions, and submitted for inspec-tion at the same time.4. Significance and Use4.1 Silver-cadmium oxide is a popular contact material thathas been used in a wide range of applications in switches,relays and contactors for switching lamps, motors and resis
8、tiveloads. Silver-cadmium oxide is a composite material consistingof a metal matrix, silver, with a metal oxide, cadmium oxide,dispersed throughout the matrix. Compositions of up to 30 %cadmium are made, but most applications use silver-cadmiumoxide in the range of 10 to 15 % cadmium oxide by weight
9、.Several different processes are used for manufacturing silver-cadmium oxide material and it should be understood that themanufacturing method has an influence on the properties of thematerial such as arc erosion resistance, welding resistance, arcmobility and contact resistance. Since the performan
10、ce ofcontacts in a device is dependent on numerous factors outsidethe contact itself (opening speed, closing speed, contact pres-sure, contact bounce and many more device parameters), theguide cannot ensure performance in specific applications.4.2 Arc erosion resistance and welding resistance are im
11、-proved by the addition of cadmium oxide to the silver matrix.The contact resistance is raised by this addition but still is low.Cadmium oxide and silver do not alloy so the silver matrixretains its high conductivity. Silver-cadmium oxide contactsare used in current ranges of a few amperes to severa
12、l hundredamperes.4.3 Silver-cadmium oxide contact material is available aswire, silver-clad wire, sheet, strip, toplay, inlay and overlaysheet or strip, discrete contact parts, brazed contact assemblies,solid and composite rivet contacts and clad contact tapes.4.4 Materials with higher cadmium oxide
13、 contents havelower material costs but may have higher processing costs dueto lower formability.5. Manufacture5.1 Since the manufacturing method has a significant influ-ence on the properties and microstructure of silver-cadmiumoxide materials, it is important to understand some basicinformation on
14、the types of manufacturing. Silver-cadmiumoxide manufacturing can be first divided in two categories:Internal Oxidation and Power Metallurgy.5.1.1 Internal oxidation means that the cadmium oxideparticles are formed by diffusion of oxygen into the silver alloyto combine with cadmium atoms to form cad
15、mium oxideparticles. This process can be further divided into the catego-ries of post and pre-oxidized materials. The post-oxidizedprocess consists of performing the diffusion process after thefinished parts have been formed. The pre-oxidized process1This guide is under the jurisdiction of ASTM Comm
16、ittee B02 on NonferrousMetals and Alloys and is the direct responsibility of Subcommittee B02.05 onPrecious Metals and Electrical Contact Materials.Current edition approved June 1, 2006. Published June 2006. Originallyapproved in 1987. Last previous edition approved in 1999 as B 781 93a (1999).2For
17、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
18、 West Conshohocken, PA 19428-2959, United States.consists of oxidation of slugs and the forming of wire or stripfrom the oxidized slugs and then forming the final parts. Thecadmium oxide particle size distribution is dependent upon thegrain structure of the silver cadmium alloy, any additiveconcentr
19、ation, and oxidation conditions (for example, tempera-ture, oxygen partial pressure).5.1.2 For powder metallurgy silver-cadmium oxide, thematerial is made from a blend of silver and cadmium oxidepowder or other cadmium compounds such as cadmiumcarbonate, which can be thermally decomposed to cadmiumo
20、xide in a subsequent step. There are two basic types of thisprocess, one in which the contacts are pressed and sintered andrepressed into the final shape, and the other where a billet ismade from blended powder which is then formed into strip andwire and made into the final contact shapes.5.1.3 All
21、of these processes have many variations. There arealso hybrid processes such as internally oxidized powderswhich are then processed by powder metallurgy. The usershould obtain the basic information as to the type of materialbeing purchased.5.1.4 For purposes of attachment to bare metal supports,silv
22、er-cadmium oxide contact material is often produced with aconductive or brazable layer of material or backing. Incorpo-ration of such a layer is often an integral part of the silver-cadmium oxide manufacturing process.5.1.5 Silver-cadmium oxide materials vary from full theo-retical density to about
23、95 % of theoretical density dependingon the specific manufacturing method.5.1.6 The flexibility of the silver-cadmium oxide materialssystem allows many additional manufacturing methods to beintroduced, and those mentioned here are not a comprehensivelisting. The cadmium-oxide particle size, distribu
24、tion, anduniformity in combination with the contact density and chemi-cal composition (see 6.2 Additives and Impurities) determinethe performance characteristics of the electrical contacts inservice. It may be of importance to specify the type ofmicrostructure, in which case, it is recommended that
25、photo-graphs of acceptable microstructures be agreed upon betweenthe producer and the user, as well as photographs illustratingunacceptable types of microstructures. It is highly recom-mended that these attributes be considered in making selectionor replacement decisions and that full qualification
26、tests beperformed by the user or purchaser including functionalelectrical tests for new or altered selections and manufacturingsources.5.2 No substantive change shall be made in the manufac-turing processes or materials, or both, of the silver-cadmiumoxide contact material without notification to an
27、d approval bythe user.6. Chemical Composition6.1 Material produced under this guide shall meet thecomposition of silver and cadmium oxide agreed upon by thevendor and user. Popular compositions and suggested toler-ances are given in Table 1. In the case of material supplied witha distinct brazable o
28、r conductive backing, such backing shallnot be considered to be included in the silver-cadmium oxidematerial composition.6.2 Additives and Impurities:6.2.1 A wide variety of chemical additives have been madeto silver-cadmium oxide materials for processing and perfor-mance purposes. The merits of the
29、se additions remain a pointof contention. Additionally, various impurities may remain inthese materials from raw materials or processing which havebeen found to be either detrimental or helpful depending on theresidual level and the individual application. Chemical require-ments for such elements an
30、d analytical methods to be em-ployed shall be mutually agreed to by the producer and user.6.3 No substantive change shall be made to additives orimpurities without notification to and approval by the user.7. Other Properties7.1 Mechanical properties of silver-cadmium oxide contactmaterials are very
31、dependent on the manufacturing method.For this reason, only guideline properties are given.7.1.1 Table 2 indicates guideline properties for some dis-crete part contacts of popular silver-cadmium oxide composi-tions in the annealed state.7.1.2 Properties in coined, repressed, headed, or other statesw
32、ill vary due to the effects of coldworking. Additives andoxidation method also alter these properties.7.1.3 Guideline properties are given in Table 3 for popularsilver-cadmium oxide compositions in wire and strip form.7.2 Specific properties and tolerances shall be establishedand agreed to between t
33、he producer and user for any particularcommercial designation of silver-cadmium oxide material andtemper required.8. Sampling and Inspection8.1 Material or parts furnished under this guide shall beinspected by the producer listed as follows. Results of suchinspection shall conform to values agreed t
34、o between theproducer and user.8.1.1 Strip and Wire Procured to Temper shall be sampledand tested in accordance with Specification B 476 (whenspecified and applicable).8.1.1.1 Such other properties as are required to verify thequality of the material produced under this guide.8.1.2 Discrete Contact
35、Parts produced under this guideshall be sampled and tested on a lot basis. For the purpose ofthis guideline, a lot is defined in 3.1.8.1.2.1 For Dimensional Conformance.8.1.2.2 Other Properties as are required to verify thequality of the material produced under this guide.TABLE 1 Suggested Chemistri
36、es and Theoretical Densities90 Silver/10Cadmium-Oxide86.5 Silver/13.5Cadmium-Oxide85 Silver/15Cadmium-Oxide80 Silver/20Cadmium-OxideChemistryCadmium-Oxideweight %10.0 6 1.0 13.5 6 1.0 15.0 6 1.0 20.0 6 1.0Silver weight % ,min89.0 85.5 84.0 79.0Other elements (see 6.2)Theoretical Densities at Nominal
37、 Composition:Mg/m310.2 10.1 10.1 9.92troy oz./in.35.37 5.32 5.30 5.23B 781 93a (2006)29. Rejection and Rehearing9.1 Material that fails to conform to the requirements of thisguide may be rejected. Rejection should be reported to theproducer or supplier promptly within 30 days of the receipt ofthe sh
38、ipment and in writing. When results of the test are notsatisfactory, the producer or supplier may make claim for arehearing.10. Keywords10.1 cadmium oxide; cadmium; contacts; internal oxidation;powder metallurgy; silver-cadmium oxide; silver; wroughtTABLE 2 Typical Part Properties Made by Powder Met
39、allurgy(AnnealedAState)NOTE 1Due to lack of commercially available information, somevalues are not listed.90 Silver/10Cadmium-Oxide86.5 Silver/13.5Cadmium- Ox-ide85 Silver/15Cadmium- Ox-ide80 Silver/20Cadmium- Ox-ideType A: Parts processed so as to be “full dense.”Density:Mg/m3,mintroy oz/in.39.965.
40、259.895.219.825.179.735.13Electricalresistivity:nVm, minnVm, max19.223.920.323.921.026.922.427.4Electricalconductivity:% IACS, min% IACS, max7290728564826377Hardness:BHR30T, minHR30T, max1751205120522553Type B: Parts processed to conventional repressed densities and annealed.Density:Mg/m3,mintroy oz
41、/in.39.464.989.334.92Electricalresistivity:nVm, minnVm, max20.324.624.634.5Electricalconductivity:% IACS, min% IACS, max70855070HardnessBHR30T, minHR30T, max43572845AAnnealed state achieved by heating 600C min, for 20 min minimum.BRanges indicate values reported by many different manufacturing metho
42、dsand are much broader than would be expected for any specific product.B 781 93a (2006)3TABLE 3 Properties (Strip and Wire)NOTE 1Due to a lack of commercially available information, some values are not listed. %IACS is volume basis and “red,” equals reduction.90 Silver/10Cadmium-Oxide86.5 Silver/13.
43、5Cadmium-Oxide85 Silver/15Cadmium-Oxide80 Silver/20Cadmium-OxideDensity:Mg/m3,mintroy oz/in.39.995.269.895.219.865.199.735.13Typical Ranges Typical Ranges Typical Ranges Typical Rangesmin max min max min max min maxWire:Ultimate tensile:Annealed, MPa(0% red), ksi2073031045221323314824135345502764035
44、05414 hard, MPa(21 % red), ksi2904238055303444146031746427623314844065hard, MPa(60 % red), ksi3455044865355504646838055496723905549672Elongation:Annealed % (2 in.) (0 % red) 25 14 14 13 14 hard%(2in.)(21 % red)3 3 2 1hard%(2in.)(60 % red)1Electrical resistivity:Annealed nVm(0 % red) 19.2 20.8 14 har
45、d nVm(21 % red) 19.2 21.6 hard nVm(60 % red) 19.2 Electrical conductivity:Annealed MS/m(0 % red)% IACS43.57539.46814 hard MS/m(21 % red)% IACS41.87237.765 hard MS/m(60 % red)% IACS40.069Strip:Hardness:Annealed HR30T(0 % red)20 51 23 52 25 52 28 5514 hard HR30T(11 % red)45 65 45 65 46 66 48 70hard HR
46、30T(37 % red)50 72 52 72 53 73 55 75Electrical resistivity:Annealed nVm(0 % red) 19.2 21.6 14 hard nVm(11 % red) 20.3 21.6 hard nVm(37 % red) 20.8 21.8 Electrical conductivity:Annealed MS/m(0 % red)% IACS41.87237.76514 hard MS/m(11 % red)% IACS40.67037.164hard MS/m(37 % red)% IACS406936.563B 781 93a
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