Changes

====Silver–Graphite (GRAPHOR)-Materials====Ag/C (GRAPHOR) contact materials are usually produced by powder metallurgy with graphite contents of 2 – 6 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 or parallel to the switching contact surface (<xr id="fig:Micro structure of Ag C 95 5"/><!--(Fig. 2.131)--> and <xr id="fig:Micro structure of Ag C 96 4 D"/>)<!--(Fig. 2.132)-->.

<caption>'''<!--Table 2.33:-->Contact and Switching properties of Silver–Graphite (GRAPHOR) Contact Materials'''</caption>

<tr><th><p class="s12">Material</p></p></th><th><p class="s11">Properties</p></th></tr><tr><td><p class="s12">Ag/C</p></p></td><td><p class="s12">Highest resistance against welding during make operations at high currents,</p><p class="s12">High resistance against welding of closed contacts during short circuit,</p><p class="s12">Increase of weld resistance with higher graphite contents, Low contact resistance,</p><p class="s12">Low arc erosion resistance, especially during break operations, Higher arc erosion with increasing graphite contents, at the same time carbon build-up on switching chamber walls increases, GRAPHOR silver-graphite with vertical orientation has better arc erosion resistance, parallel orientation has better weld resistance,</p><p class="s12">Limited arc moving properties, therefore paired with other materials,</p><p class="s12">Limited formability,</p><p class="s12">Can be welded and brazed with decarbonized backing, GRAPHOR DF is optimized for arc erosion resistance and weld resistance</p></td></tr></table>

<caption>'''<!--Table 2.34:-->Application Examples and Forms of Supply of Silver– Graphite (GRAPHOR) Contact Materials'''</caption>

<tr><th><p class="s12">Material/</p><p class="s12"></p></th><th><p class="s12">Application Examples</p></th><th><p class="s12">Form of Supply</p></th></tr><tr><td><p class="s12">Ag/C 98/2</p><p class="s12"></p></td><td><p class="s12">Motor circuit breakers, paired with Ag/Ni</p></td><td><p class="s12">Contact tips, brazed and welded contact parts, some contact rivets </p><p class="s12">Contact profiles (weld tapes), Contact tips, brazed and welded contact parts</p></td></tr><tr><td><p class="s12">Ag/C 97/3</p><p class="s12"></p><p class="s12">Ag/C 96/4</p><p class="s12"></p><p class="s12">Ag/C 95/5</p><p class="s12"></p><p class="s12">Ag/C DF</p></td><td><p class="s12">Circuit breakers, paired with Cu, Motor-protective circuit breakers, paired with Ag/Ni,</p><p class="s12">Fault current circuit breakers, paired with Ag/Ni, Ag/W, Ag/WC, Ag/SnO<span class="s45">2</span>, Ag/ZnO,</p><p class="s12">(Main) Power switches, paired with Ag/Ni, Ag/W</p></td><td><p class="s12">Contact tips, brazed and welded contact</p><p class="s12">parts, some contact rivets with</p><p class="s12">Ag/C97/3</p><td/></tr></table>