Silver Graphite

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Scope

This information refers to silver graphite profiles and contact tips manufactured by blending of silver and graphite powder, compacting, sintering, extruding and rolling. The deformation results in the alignment of graphite particles along the direction of the extrusion and rolling. A brazeable silver side is produced by decarburization. Profiles clad with a brazing alloy and presoldered contact tips are available.

DESIGNATION OF STANDARD COMPOSITIONS

Profiles show a parallel orientation of the graphite to the contact surface and can be produced with 2 and 3 weight percent graphite. contact tips with 2,3,4 and 5% are available either with the parallel orientation (AgC II) or with a perpendicular orientation of the graphite to the contact surface (AgC!)

Applications

  • circuit breakers
  • earth leakage breakers
  • miniature circuit breakers

CHARACTERISTICS

  • best anti-welding properties of all contact materials on make with C-contents of 3% and higher (better with graphite particle alignment parallel to contact side)
  • best protection against contact welding of closed contacts under short ciruit currents
  • low erosion on make
  • low contact resistance
  • reduced erosion on break with perpendicular graphite particle alignment to contact surface
  • inferior are migration properties; compensated by asymmetrical material combinations:
  • Cu counter-contact with low currents
  • AgNi counter-contact with high currents

MICROSTRUCTURE

The directional deformation of the material during the manufacturing process causes a strong displacement of the graphite particles into graphite layers.
Longitudinal Sectional
(parallel to the diretion of extrusion)
AgC3
Cross Section
AgC5
Cross Section

Physical Properties

Material AgC2 AgC3 AgC4 AgC5
Density [g/cm3] 9.4 9.1 8.8 8.6
Electrical Conductivity [m/(Ω.mm2)] 47 47 44 43.5
Hardness Soft [HV1] 35 35 35 35