Changes

!Material/DODUCO-Designation

!Material/DODUCO-Designation

The manufacturing of strips and wires by internal oxidation starts with a molten alloy of silver and cadmium. During a heat treatment below it's melting point in a an oxygen rich atmosphere in such a homogeneous alloy the oxygen diffuses from the surface into the bulk of the material and oxidizes the Cd to CdO in a more or less fine particle precipitation inside the Ag matrix. The CdO particles are rather fine in the surface area and are becoming larger further away towards the center of the material <xr id="fig:Micro structure of AgCdO9010"/><!--(Fig. 2.83)-->.

During the manufacturing of Ag/CdO contact material by internal oxidation the processes vary depending on the type of semi-finished material. For Ag/CdO wires a complete oxidation of the AgCd wire is performed, followed by wire-drawing to the required diameter <xr id="fig:Strain hardening of internally oxidized AgCdO9010"/><!--(Figs. 2.77)--> and <xr id="fig:Softening of internally oxidized AgCdO9010"/><!--(Fig. 2.78)-->. The resulting material is used for example in the production of contact rivets. For Ag/CdO strip materials two processes are commonly used: Cladding of an AgCd alloy strip with fine silver followed by complete oxidation results in a strip material with a small depletion area in the center of it's thickness and a an Ag backing suitable for easy attachment by brazing (sometimes called "Conventional Ag/CdO"). Using a technology that allows the partial oxidation of a dual-strip AgCd alloy material in a higher pressure pure oxygen atmosphere yields a composite Ag/CdO strip material that has besides a relatively fine CdO precipitation also a an easily brazable AgCd alloy backing <xr id="fig:Micro structure of AgCdO9010ZH"/><!--(Fig. 2.85)-->. These materials are mainly used as the basis for contact profiles and contact tips.

[[File:Strain hardening of AgCdO9010P.jpg|left|thumb|<caption>Strain hardening of powder metallurgical Ag/CdO 90/10 P by cold working</caption>]]

<tr><th rowspan="2"><p class="s11">Material/</p><p class="s11"></p></th><th rowspan="2"><p class="s11">Additives</p></th><th rowspan="2"><p class="s11">Density</p><p class="s11">[ g/cm³]</p></th><th rowspan="2"><p class="s11">Electrical</p><p class="s11">Resistivity</p><p class="s11">[µ<span class="s14">S ·</span>cm]</p></th><th colspan="2"><p class="s11">Electrical</p><p class="s11">Conductivity</p></th><th rowspan="2"><p class="s11">Vickers</p><p class="s11">Hardness</p><p class="s11">HV 10.</p></th></tr>

<tr><td><p class="s11">AgCdO 90/10</p><p class="s11"></p></td><td/><td><p class="s11">10.1</p></td><td><p class="s11">2.08</p></td><td><p class="s12">83</p></td><td><p class="s12">48</p></td><td><p class="s11">60</p></td></tr><tr><td><p class="s11">AgCdO 85/15 </p></td><td/><td><p class="s11">9.9</p></td><td><p class="s11">2.27</p></td><td><p class="s12">76</p></td><td><p class="s12">44</p></td><td><p class="s11">65</p></td></tr><tr><td><p class="s11">AgSnO² 90/10</p></td><td><p class="s11">CuO and</p><p class="s11">Bi² O³</p></td><td><p class="s11">9.8</p></td><td><p class="s11">2.22</p></td><td><p class="s12">78</p></td><td><p class="s12">45</p></td><td><p class="s11">55</p></td></tr><tr><td><p class="s11">AgSnO² 88/12EPX SISTADOX 12EPX12</p></td><td><p class="s11">CuO and</p><p class="s11">Bi² O³</p></td><td><p class="s11">9.6</p></td><td><p class="s11">2.63</p></td><td><p class="s12">66</p></td><td><p class="s12">38</p></td><td><p class="s11">60</p></td></tr></table>

*'''Silver–zinc oxide (DODURIT ZnO) materials'''Silver zinc oxide (DODURIT ZnO) contact materials with mostly 6 - 10 wt% oxide content including other small metal oxides are produced exclusively by powder metallurgy [[#figures1|(Figs. 76 – 81)]],<!--(Table 2.28)-->. Adding WO₃ or Ag₂WO₄ in the process b) as described in the preceding chapter on Ag/SnO₂ has proven most effective for applications in AC relays, wiring devices, and appliance controls. Just like with the other Ag metal oxide materials, semi-finished materials in strip and wire form are used to manufacture contact tips and rivets. Because of their high resistance against welding and arc erosion Ag/ZnO materials present an economic alternative to Cd free Ag-tin oxide contact materials <xr id="tab:Contact and Switching Properties of Silver–Metal Oxide Materials"/><!--(Tab. 2.30)--> and <xr id="tab:Application Examples of Silver–Metal Oxide Materials"/><!--(Tab. 2.31)-->.

<caption>'''<!--Table 2.28:--> Physical and Mechanical Properties as well as Manufacturing Processes and Forms of Supply of Extruded Silver-Zinc Oxide (DODURIT ZnO) Contact'''</caption>

!Material/<br />DODUCO-<br />Designation

<tr><th><p class="s12">Material/</p><p class="s12">Material Group</p></th><th><p class="s12">Special Properties<th colspan="2"></p></th></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2 </span>PE</p></td><td><p class="s12">Especially suitable for automotive relays</p><p class="s12">(lamp loads)</p></td><td><p class="s12">Good formability (contact rivets)</p></td></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2 </span>98/2 PX/PC</p></td><td><p class="s12">Especially good heat resistance</p></td><td><p class="s12">Easily riveted, can be directly welded</p></td></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2 </span>TOS F</p></td><td><p class="s12">Especially suited for high inductive</p><p class="s12">DC loads</p></td><td><p class="s12">Very good formability (contact rivets)</p></td></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2 </span>WPC</p></td><td><p class="s12">For AC-3 and AC-4 applications in motor</p><p class="s12">switches (contactors)</p></td><td/></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2 </span>WPD</p></td><td><p class="s12">Especially suited for severe loads (AC-4)</p><p class="s12">and high switching currents</p></td><td/></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2 </span>WPX</p></td><td><p class="s12">For standard motor loads (AC-3) and</p><p class="s12">Resistive loads (AC-1), DC loads (DC-5)</p></td><td/></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2 </span>WTOSF</p></td><td><p class="s12">Especially suitable for high inductive DC</p><p class="s12">loads</p></td><td/></tr></table>

!Material/DODUCO-Designation !Properties

|Ag/CdO<br />DODURIT CdO

|Ag/SnO₂<br />SISTADOX

|Ag/ZnO<br />DODURIT ZnO

<tr><th><p class="s12">Material</p></th><th><p class="s12">Application Examples</p></th></tr><tr><td><p class="s12">Ag/CdO</p></td><td><p class="s12">Micro switches, Network relays, Wiring devices, Appliance switches, Main switches, contactors, Small (main) power switches</p></td></tr><tr><td><p class="s12">Ag/SnO<span class="s48">2</span></p></td><td><p class="s12">Micro switches, Network relays, Automotive relays, Appliance switches,</p><p class="s12">Main switches, contactors, Fault current protection relays (paired against</p><p class="s12">Ag/C), (Main) Power switches</p></td></tr><tr><td><p class="s12">Ag/ZnO</p></td><td><p class="s12">Wiring devices, AC relays, Appliance switches, Motor-protective circuit</p><p class="s12">breakers (paired with Ag/Ni or Ag/C), Fault current circuit breakers paired againct Ag/C, (Main) Power switches</p></td></tr></table>

Ag/C (GRAPHOR) contact materials are usually produced by powder metallurgy with graphite contents of 2 – 5 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 (GRAPHOR) or parallel (GRAPHOR D) 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)-->.

Since the graphite particles in the Ag matrix of Ag/C materials prevent contact tips from directly being welded or brazed, a graphite free bottom layer is required. This is achieved by either burning out (de-graphitizing) the graphite selectively on one side of the tips or by compound extrusion of a Ag/C billet covered with a fine silver shell.