Active Standard ASTM B844 | Developed by Subcommittee: B02.05
Book of Standards Volume: 02.04
Historical (view previous versions of standard)
Significance and Use
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.
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 Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
B311 Test Method for Density of Powder Metallurgy (PM) Materials Containing Less Than Two Percent Porosity
B476 Specification for General Requirements for Wrought Precious Metal Electrical Contact Materials
ICS Number Code 77.120.99 (Other non-ferrous metals and their alloys)