Silver wire - 009

Silver and pure silver possess very high electric and thermal conductivity, low and
stable contact resistance and good processing and welding performance. Because
of a little nickel added into silver, pure silver has higher intensity and thermal-
resistant performance than silver under same contact resistance. Therefore,
its fusion resistance and arc burning resistance are better than that of silver.
Under the same application condition, pure silver can take the place of silver.

AgNi material with 10-40% of high melting-point metal nickel has high electric
conductivity, low contact resistance and little burning loss. This material has little
transfer when connecting and breaking direct current. To be widely used in AC and
DC low-voltage devices, such as relays, instruction switches, can switches, breaker,
assisting contactors. Instrument switches, optical control switches, temperature
controller and washing machine timers.

AgZnO has higher thermal stability than AgCdO, therefore, has better fusion
resistance and arc burning resistance. But its contact resistance is high. Since
AgZnO is innoxiously and has no pollution to the environment. It is one of the ideal
materials to substitute AgCdO at present.

AgCdO is the most commonly used contact material at present. CdO obviously
increase the fusion resistance or cohesive resistance of the contacts at the moment
of getting through big current. The sublimation of CdO cools the contact surface
and lowers the arc energy and extinguishes the arc. Therefore AgCdO can meet the
main requirements of low-voltage apparatus to contacts. Such as arc burning
resistance at big-current switching-on, low and stable contact resistance under
various loads and good arc extinguishing performance. Since Cd pollutes the
environment, other materials are substituting it. It is used to low-voltage
apparatus with medium or high load, typically used to micro switches, relays,
protection switches, contactors and auto-switches.

AgSnO2 and AgSnO2 In2O3 are the ideal environment-protective materials for
substituting AgCdO. Since SnO2 has better thermal stability and higher hardness
than CdO, AgSbO2 ABD AgSnO2 In2O3 is higher and it is more difficult to processing
these two materials. It is used to substitute AgCdO material in the low-voltage
apparatus field, such as breakers, contactors and relays, etc. Especially being used
to DC apparatus for automobiles, such contactors, starters and photo switches.

The AgC contact material containing 3-5% graphite bears the highest fusion
resistance, low contact resistance and small temperature rise in switching on short
circuit current. It is self-lubricated when being used as a sliding contact .The
AgC contact material manufactured by sintering and extrusion process not only has
high density, but also has a lower burning loss rate under arc action due to the
fiber-oriented graphite particles. It is usually used with Cu or AgNi in pairs.

AgW is a W-based sintered contact material containing silver. The good thermal
and electric conductivities of silver and the high melting point and burning-loss
resistance of tungsten are combined together for AgW. And besides, the hardness
of AgW is high. Therefore the mechanical wear of AgW in the make and break process
is small and its fusion resistance when making current is good. But the oxide
produced in the make and break process makes its contact resistance high.

AgWC contact material containing 12-65% high-65% high-melting-point and high-
hardness WC has high hardness, high wear resistance, small fusion tendency, and
stable contact resistance which however, is higher than AgW. Since when electric
arc is in action, the dissociated carbons or AgWC have the function of deoxidization
which preventing the contact surface from forming an oxidized layer. AgWC is used
with AgNi in asymmetrical pairs sometimes.