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→Silver–Graphite (GRAPHOR)-Materials
====Silver–Graphite (GRAPHOR)-Materials====
Ag/C (GRAPHOR) contact materials are usually produced by powder metallurgy with graphite contents of 2 – 5 wt% ''<xr id="tab:tab2.32"/> (Table 2.32)''. The earlier typical manufacturing process of single pressed tips by pressing - sintering - repressing (PSR) has been replaced in Europe for quite some time by extrusion. In North America and some other regions however the PSR process is still used to some extend mainly for cost reasons.
The extrusion of sintered billets is now the dominant manufacturing method for semi-finished AgC materials <!--[[#figures3|(Figs. 82 – 85)]](Figs. 2.126 – 2.129)-->. The hot extrusion process results in a high density material with graphite particles stretched and oriented in the extrusion direction [[#figures4|(Figs. 86 – 89)]](Figs. 2.130 – 2.133)''. Depending on the extrusion method in either rod or strip form the graphite particles can be oriented in the finished contact tips perpendicular (GRAPHOR) or parallel (GRAPHOR D) to the switching contact surface <xr id="fig:fig2.131"/> (Fig. 2.131) and <xr id="fig:fig2.132"/> (Fig. 2.132).
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<figtable id="tab:tab2.32">
'''Table 2.32: Physical Properties of Silver–Graphite (GRAPHOR) Contact Materials'''