ASTM B844-98(2021)
(Guide)Standard Guide for Silver-Tin Oxide Contact Material
Standard Guide for Silver-Tin Oxide Contact Material
SIGNIFICANCE AND USE
4.1 The methods for manufacture (proprietary or otherwise) of these materials vary significantly among suppliers, and these methods influence such properties as arc erosion, contact resistance, and tendency to weld in service. Since the performance of contacts in a device depends on numerous factors outside the contact itself (opening speed, closing speed, contact pressure, contact bounce, environmental variations, assembly technique and variations, etc.) this guide cannot ensure performance control in the application. As part of the qualification on initial samples it is recommended that the user electrically test the materials in a functional manner for all devices applicable to the material’s use. This guide will provide a means for the contact manufacturer and contact user to reach agreement on the details of material to be supplied for a specific use and how to provide reasonable assurance that future lots will be similar in properties and microstructure to the initial test of sample contacts supplied.
SCOPE
1.1 This standard provides guidelines for users and manufacturers of silver-tin oxide material produced in strip, rod, wire, and part form for electrical contact applications.
1.2 Silver-tin oxide refers to contact material containing silver, tin oxide, and other metal oxide which may be used for either improving the processing or performance of the material.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Safety Data Sheet (SDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental practices, and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B844 − 98 (Reapproved 2021)
Standard Guide for
1
Silver-Tin Oxide Contact Material
This standard is issued under the fixed designation B844; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 lot, n—(usage involving discrete manufactured
parts)—all parts of the same form, and dimensions, from the
1.1 This standard provides guidelines for users and manu-
same alloy melt or batch of particulate (if manufactured by
facturers of silver-tin oxide material produced in strip, rod,
consolidation), processed under the same conditions, and
wire, and part form for electrical contact applications.
submitted for inspection at the same time.
1.2 Silver-tin oxide refers to contact material containing
silver, tin oxide, and other metal oxide which may be used for
4. Significance and Use
eitherimprovingtheprocessingorperformanceofthematerial.
4.1 The methods for manufacture (proprietary or otherwise)
1.3 This standard does not purport to address all of the
ofthesematerialsvarysignificantlyamongsuppliers,andthese
safety concerns, if any, associated with its use. It is the
methods influence such properties as arc erosion, contact
responsibility of the user of this standard to become familiar
resistance, and tendency to weld in service. Since the perfor-
with all hazards including those identified in the appropriate
mance of contacts in a device depends on numerous factors
Safety Data Sheet (SDS) for this product/material as provided
outsidethecontactitself(openingspeed,closingspeed,contact
by the manufacturer, to establish appropriate safety, health,
pressure, contact bounce, environmental variations, assembly
and environmental practices, and determine the applicability
technique and variations, etc.) this guide cannot ensure perfor-
of regulatory limitations prior to use.
mance control in the application.As part of the qualification on
1.4 This international standard was developed in accor-
initial samples it is recommended that the user electrically test
dance with internationally recognized principles on standard-
the materials in a functional manner for all devices applicable
ization established in the Decision on Principles for the
to the material’s use. This guide will provide a means for the
Development of International Standards, Guides and Recom-
contact manufacturer and contact user to reach agreement on
mendations issued by the World Trade Organization Technical
the details of material to be supplied for a specific use and how
Barriers to Trade (TBT) Committee.
to provide reasonable assurance that future lots will be similar
in properties and microstructure to the initial test of sample
2. Referenced Documents
contacts supplied.
2
2.1 ASTM Standards:
B311 Test Method for Density of Powder Metallurgy (PM) 5. Materials and Manufacture
Materials Containing Less Than Two Percent Porosity
5.1 Various processes may be utilized to produce silver-tin
B476 Specification for General Requirements for Wrought
oxide contact materials. Internal oxidation of a silver-tin alloy
Precious Metal Electrical Contact Materials
is a viable method. However, if oxidized at relatively low
pressures, a binary silver-tin alloy develops a stable layer of tin
NOTE 1—Test Method B311 is applicable to fully dense forms.
Specification B476 is applicable to strip, rod, or wire only. Test Method is
oxide at the surface which inhibits further oxidation of the
applicable to forms less than 99 % dense.
material. Because of this phenomenon, usually at least a third
element (such as indium) is added to the alloy in order to
3. Terminology
promoteinternaloxidation.Oxidationmaybecarriedoutunder
3.1 Definitions of Terms Specific to This Standard:
elevated oxygen pressure and also at various temperatures;
oxidation conditions determine size and distribution of the
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This guide is under the jurisdiction of ASTM Committee B02 on Nonferrous
resultingoxideparticles.Othermanufacturingprocessesutilize
Metals and Alloys and is the direct responsibility of Subcommittee B02.05 on
powder metallurgical techniques. Silver- and tin-oxide pow-
Precious Metals and Electrical Contact Materials.
ders may be blended and consolidated by heat or pressure, or
Current edition approved Nov. 1, 2021. Published December 2021. Originally
both, into wire or strip suitable for further processing, or may
approved in 1993. Last previous edition approved in 2016 as B844 – 98 (2016).
DOI: 10.1520/B0844-98R21.
be
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