ABSTRACT
Silver-graphite is a popular brush material (see Table 1112, and for broader detail, Tables 21.3 and 21.12 in Chapter 21) as a result of its anti-welding and electrical resistance properties (see Chaps. 17-19). In this section the discussion is limited to these materials used for arcing contact applications. For these applications the composition range of 2-5% graphite by weight, 9-20% by volume, is the most popular. Since graphite is very low in density compared to silver the volume percentage range compared to the weight percentage range is quite different. Silver-graphite is a composite matrial, like previously discussed silver metal oxides. It is also manufactured by powder metallurgical methods since silver and graphite do not form any alloys. It is manufactured by a variety of powder metallurgical methods, including pressing, sintering, and extrusion of ingots to form wrought silver-graphite strip and wire and also the conventional press, sinter, and repress method. One of the differences in processing of silver-graphite from silver metal oxides is that it must be sintered in a protective atmosphere to prevent oxidation of the graphite.
