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Pure silver (also called fine silver) exhibits the highest electrical and thermal conductivity of all metals. It is also resistant against oxidation. Major disadvantages are its low mechanical wear resistance, the low softening temperature, and especially its strong affinity to sulfur and sulfur compounds. In the presence of sulfur and sulfur containing compounds brownish to black silver sulfide layer are formed on its surface. These can cause increased contact resistance or even total failure of a switching device if they are not mechanically, electrically, or thermally destroyed. Other weaknesses of silver contacts are the tendency to weld under the influence of over-currents and the low resistance against material transfer when switching DC loads. In humid environments and under the influence of an electrical field silver can creep (silver migration) and cause electrical shorting between adjacent current paths.
<xr id="tab:Overview_of_the_Most_Widely_Used_Silver_Grades"/><!--(Table 2.11)--> shows the typically available quality grades of silver. In certain economic areas, i.e. China, there are additional grades with varying amounts of impurities available on the market. In powder form silver is used for a wide variety of silver based composite contact materials. Different manufacturing processes result in different grades of Ag powder as shown in <xr id="tab:Quality_Criteria_of_Differently_Manufactured_Silver_Powders"/><!--Table 2.12-->. additional properties of silver powders and their usage are described in [[ Precious Metal Powders and Preparations#Precious_Metal_Powders|Precious Metal Powders ]] und [[Precious_Metal_Powders_and_Preparations|TabTable Different Types of Silver Powders. 8.1]]<!--(Tab. 8.1.)-->
Semi-finished silver materials can easily be warm or cold formed and can be clad to the usual base materials. For attachment of silver to contact carrier materials welding of wire or profile cut-offs and brazing are most widely applied. Besides these mechanical processes such as wire insertion (wire staking) and the riveting (staking) of solid or composite contact rivets are used in the manufacture of contact components.
<xr id="fig:Strain hardening of Ag bei cold working"/> <!--Fig. 2.45: --> Strain hardening of Ag 99.95 by cold working
<xr id="fig:Softening of Ag after annealing after different degrees"/> <!--Fig. 2.46: --> Softening of Ag 99.95 after annealing for 1 hr after different degrees of strain hardening
</figtable>
<xr id="fig:Influence of 1 10 atom of different alloying metals"/> <!--Fig. 2.47: --> Influence of 1-10 atom% of different alloying metals on the electrical resistivity of silver
<xr id="fig:Electrical resistivity p of AgCu alloys"/> <!--Fig. 2.48: --> Electrical resistivity p of AgCu alloys
<div class="multiple-images">
<xr id="fig:Phase diagram of silver copper"/> <!--Fig. 2.52: --> Phase diagram of silver-copper
<xr id="fig:Phase diagram of silver cadmium"/> <!--Fig. 2.53: --> Phase diagram of silver-cadmium
<xr id="fig:Strain hardening of AgCu3 by cold working"/> <!--Fig. 2.54: --> Strain hardening of AgCu3 by cold working
<xr id="fig:Softening of AgCu3 after annealing"/> <!--Fig. 2.55: --> Softening of AgCu3 after annealing for 1 hr after 80% cold working
<xr id="fig:Strain hardening of AgCu5 by cold working"/> <!--Fig. 2.56: --> Strain hardening of AgCu5 by cold working
<xr id="fig:Softening of AgCu5 after annealing"/> <!--Fig. 2.57: --> Softening of AgCu5 after annealing for 1 hr after 80% cold working
<xr id="fig:Strain hardening of AgCu 10 by cold working"/> <!--Fig. 2.58: --> Strain hardening of AgCu 10 by cold working
<xr id="fig:Softening of AgCu10 after annealing"/> <!--Fig. 2.59: --> Softening of AgCu10 after annealing for 1 hr after 80% cold working
<xr id="fig:Strain hardening of AgCu28 by cold working"/> <!--Fig. 2.60: --> Strain hardening of AgCu28 by cold working
<xr id="fig:Softening of AgCu28 after annealing"/> <!--Fig. 2.61: --> Softening of AgCu28 after annealing for 1 hr after 80% cold working
<xr id="fig:Strain hardening of AgNiO15 by cold working"/> <!--Fig. 2.62: --> Strain hardening of AgNi0.15 by cold working
<xr id="fig:Softening of AgNiO15 after annealing"/> <!--Fig. 2.63: --> Softening of AgNi0.15 after annealing for 1 hr after 80% cold working
<xr id="fig:Strain hardening of ARGODUR 27"/> <!--Fig. 2.64: --> Strain hardening of ARGODUR 27 by cold working
<xr id="fig:Softening of ARGODUR 27 after annealing"/> <!--Fig. 2.65: --> Softening of ARGODUR 27 after annealing for 1 hr after 80% cold working
<div class="multiple-images">
<xr id="fig:Phase diagram of silver palladium"/> <!--Fig. 2.66: --> Phase diagram of silver-palladium
<xr id="fig:Strain hardening of AgPd30 by cold working"/> <!--Fig. 2.67: --> Strain hardening of AgPd30 by cold working
<xr id="fig:Strain hardening of AgPd50 by cold working"/> <!--Fig. 2.68: --> Strain hardening of AgPd50 by cold working
<xr id="fig:Strain hardening of AgPd30Cu5 by cold working"/> <!--Fig. 2.69: --> Strain hardening of AgPd30Cu5 by cold working
<xr id="fig:Softening of AgPd30 AgPd50 AgPd30Cu5"/> <!--Fig. 2.70: --> Softening of AgPd30, AgPd50, and AgPd30Cu5 after annealing of 1 hr after 80% cold working
<div class="multiple-images">
<figtable id="tab:Physical Properties of Silver-Palladium Alloys">
<caption>'''<!--Table 2.17:-->Physical Properties of Silver-Palladium Alloys'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
The most important applications for Ag/Ni contact materials are typically in relays, wiring devices, appliance switches, thermostatic controls, auxiliary switches, and small contactors with nominal currents > 20A <xr id="tab:Application Examples and Forms of Supply for Silver-Nickel (SINIDUR) Materials"/><!--(Table 2.24)-->.
<figtable id="tab:Physical Properties of Silver-Nickel (SINIDUR) Materials">
<xr id="fig:Strain hardening of AgNi9010 by cold working"/> <!--Fig. 2.71: --> Strain hardening of Ag/Ni 90/10 by cold working
<xr id="fig:Softening of AgNi9010 after annealing"/> <!--Fig. 2.72: --> Softening of Ag/Ni 90/10 after annealing for 1 hr after 80% cold working
<xr id="fig:Strain hardening of AgNi8020"/> <!--Fig. 2.73: --> Strain hardening of Ag/Ni 80/20 by cold working
<xr id="fig:Softening of AgNi8020 after annealing"/> <!--Fig. 2.74: --> Softening of Ag/Ni 80/20 after annealing for 1 hr after 80% cold working
<xr id="fig:Micro structure of AgNi9010"/> <!--Fig. 2.75: --> Micro structure of Ag/Ni 90/10 a) perpendicular to the extrusion direction b) parallel to the extrusion direction
<xr id="fig:Micro structure of AgNi 8020"/> <!--Fig. 2.76: --> Micro structure of Ag/Ni 80/20 a) perpendicular to the extrusion direction b) parallel t o the extrusion direction
==== Silver-Metal Oxide Materials Ag/CdO, Ag/SnO<sub>2</sub>, Ag/ZnO====
The family of silver-metal oxide contact materials includes the material groups: silver-cadmium oxide (DODURIT CdO), silver-tin oxide (SISTADOX), and silverzinc oxide (DODURIT ZnO). Because of their very good contact and switching properties like high resistance against welding, low contact resistance, and high arc erosion resistance, silver-metal oxides have gained an outstanding position in a broad field of applications. They mainly are used in low voltage electrical switching devices like relays, installation and distribution switches, appliances, industrial controls, motor controls, and protective devices <xr id="tab:tab2.31Application Examples of Silver–Metal Oxide Materials"/><!--(Table 2.31)-->.
*'''Silver-cadmium oxide (DODURIT CdO) materials'''
Using different silver powders and minor additives for the basic Ag and CdO starting materials can help influence certain contact properties for specialized applications.
<xr id="fig:Strain hardening of internally oxidized AgCdO9010"/> <!--Fig. 2.77: --> Strain hardening of internally oxidized Ag/CdO 90/10 by cold working
<xr id="fig:Softening of internally oxidized AgCdO9010"/> <!--Fig. 2.78: --> Softening of internally oxidized Ag/CdO 90/10 after annealing for 1 hr after 40% cold working
<xr id="fig:Strain hardening of AgCdO9010P"/> <!--Fig. 2.79: --> Strain hardening of Ag/CdO 90/10 P by cold working
<xr id="fig:Softening of AgCdO9010P after annealing"/> <!--Fig. 2.80: --> Softening of Ag/CdO 90/10 P after annealing for 1 hr after 40% cold working
<xr id="fig:Strain hardening of AgCdO8812"/> <!--Fig. 2.81: --> Strain hardening of Ag/CdO 88/12 WP
<xr id="fig:Softening of AgCdO8812WP after annealing"/> <!--Fig. 2.82: --> Softening of Ag/CdO 88/12WP after annealing for 1 hr after different degrees of cold working
<xr id="fig:Micro structure of AgCdO9010"/> <!--Fig. 2.83: --> Micro structure of Ag/CdO 90/10 i.o. a) close to surface b) in center area
<xr id="fig:Micro structure of AgCdO9010P"/> <!--Fig. 2.84: --> Micro structure of Ag/CdO 90/10 P: a) perpendicular to extrusion direction b) parallel to extrusion direction
<xr id="fig:Micro structure of AgCdO9010ZH"/> <!--Fig. 2.85: --> Micro structure of Ag/CdO 90/10 ZH: 1) Ag/CdO layer 2) AgCd backing layer
<xr id="fig:Micro structure of AgCdO8812WP"/> <!--Fig. 2.86: --> Micro structure of AgCdO 88/12 WP: a) perpendicular to extrusion direction b) parallel to extrusion direction
<div class="multiple-images">
*'''Silver–tin oxide (SISTADOX) materials'''
Over the past years, many Ag/CdO contact materials have been replaced by Ag/SnO<sub>2</sub> based materials with 2-14 wt% SnO<sub>2</sub> because of the toxicity of Cadmium. This changeover was further favored by the fact that Ag/SnO<sub>2</sub> contacts quite often show improved contact and switching properties such as lower arc erosion, higher weld resistance, and a significant lower tendency towards material transfer in DC switching circuits <xr id="tab:tab2.30Contact and Switching Properties of Silver–Metal Oxide Materials"/> <!--(Table 2.30)-->. Ag/SnO<sub>2</sub> materials have been optimized for a broad range of applications by other metal oxide additives and modification in the manufacturing processes that result in different metallurgical, physical and electrical properties<xr id="tab:tab2.28"/> <!--(Tab. 2.28) --> und <xr id="tab:tab2.29"/> <!--(Table 2.29)-->.
Manufacturing of Ag/SnO<sub>2</sub> by ''internal oxidation'' is possible in principle, but during heat treatment of alloys containing > 5 wt% of tin in oxygen, dense oxide layers formed on the surface of the material prohibit the further diffusion of oxygen into the bulk of the material. By adding Indium or Bismuth to the alloy the internal oxidation is possible and results in materials that typically are rather hard and brittle and may show somewhat elevated contact resistance and is limited to applications in relays. To make a ductile material with fine oxide dispersion (SISTADOX TOS F) <xr id="fig:Micro structure of Ag SnO2 88 12 TOS F"/> <!--(Fig. 2.114) --> it is necessary to use special process variations in oxidation and extrusion which lead to materials with improved properties in relays. Adding a brazable fine silver layer to such materials results in a semifinished material suitable for the manufacture as smaller weld profiles (SISTADOX WTOS F) <xr id="fig:Micro structure of Ag SnO2 92 8 WTOS F"/> <!--(Fig. 2.116)-->. Because of their resistance to material transfer and low arc erosion these materials find for example a broader application in automotive relays <xr id="tab:tab2.31Application Examples of Silver–Metal Oxide Materials"/> <!--(Table 2.31)-->.
:'''e) Powder blending based on chemically precipitated compound powders''' <br> A silver salt solution is added to a suspension of for example SnO<sub>2</sub> together with a precipitation agent. In a chemical reaction silver and silver oxide respectively are precipitated around the additive metal oxide particles who act as crystallization sites. Further chemical treatment then reduces the silver oxide with the resulting precipitated powder being a mix of Ag and SnO<sub>2</sub>.
Further processing of these differently produced powders follows the conventional processes of pressing, sintering and hot extrusion to wires and strips. From these contact parts such as contact rivets and tips are manufactured. To obtain a brazable backing the same processes as used for Ag/CdO are applied. As for Ag/CdO, larger contact tips can also be manufactured more economically using the press-sinter-repress (PSR) process <xr id="tab:Physical Properties of Powder Metallurgical Silver-Metal Oxide Materials with Fine Silver Backing Produced by the Press-Sinter-Repress Process"/> <!--(Table 2.27)-->.
<div id="figures">
<xr id="fig:Strain hardening of AgSNO2 92 8 PE"/> <!--Fig. 2.87: --> Strain hardening of Ag/SnO<sub>2</sub> 92/8 PE by cold working
<xr id="fig:Softening of AgSnO2 92 8 PE"/> <!--Fig. 2.88: --> Softening of Ag/SnO<sub>2</sub> 92/8 PE after annealing for 1 hr after 40% cold working
<xr id="fig:Strain hardening of Ag SnO2 88 12 PE"/> <!--Fig. 2.89: --> Strain hardening of Ag/SnO<sub>2</sub> 88/12 PE by cold working
<xr id="fig:Softening of Ag SnO2 88 12 PE after annealing"/> <!--Fig. 2.90: --> Softening of Ag/SnO<sub>2</sub> 88/12 PE after annealing for 1 hr after 40% cold working
<xr id="fig:Strain hardening of oxidized AgSnO2 88 12 PW4"/> <!--Fig. 2.91: --> Strain hardening of oxidized Ag/SnO<sub>2</sub> 88/12 PW4 by cold working
<xr id="fig:Softening of Ag SnO2 88 12 PW4 after annealing"/> <!--Fig. 2.92: --> Softening of Ag/SnO<sub>2</sub> 88/12 PW4 after annealing for 1 hr after 30% cold working
<xr id="fig:Strain hardening of Ag SnO2 98 2 PX"/> <!--Fig. 2.93: --> Strain hardening of Ag/SnO<sub>2</sub> 98/2 PX by cold working
<xr id="fig:Softening of Ag SnO2 98 2 PX after annealing"/> <!--Fig. 2.94: --> Softening of Ag/SnO<sub>2</sub> 98/2 PX after annealing for 1 hr after 80% cold working
<xr id="fig:Strain hardening of Ag SnO2 92 8 PX"/> <!--Fig 2.95: --> Strain hardening of Ag/SnO<sub>2</sub> 92/8 PX by cold working
<xr id="fig:Softening of Ag SnO2 92 8 PX after annealing"/> <!--Fig. 2.96: --> Softening of Ag/SnO<sub>2</sub> 92/8 PX after annealing for 1 hr after 40% cold working
<xr id="fig:Strain hardening of internally oxidized Ag SnO2 88 12 TOS F"/> <!--Fig. 2.97: --> Strain hardening of internally oxidized Ag/SnO<sub>2</sub> 88/12 TOS F by cold working
<xr id="fig:Softening of Ag SnO2 88 12 TOS F after annealing"/> <!--Fig. 2.98: --> Softening of Ag/SnO<sub>2</sub> 88/12 TOS F after annealing for 1 hr after 30% cold working
<xr id="fig:Strain hardening of internally oxidized Ag SnO2 88 12P"/> <!--Fig. 2.99: --> Strain hardening of internally oxidized Ag/SnO<sub>2</sub> 88/12P by cold working
<xr id="fig:Softening of Ag SnO2 88 12P after annealing"/> <!--Fig. 2.100: --> Softening of Ag/SnO<sub>2</sub> 88/12P after annealing for 1 hr after 40% cold working
<xr id="fig:Strain hardening of Ag SnO2 88 12 WPC"/> <!--Fig. 2.101: --> Strain hardening of Ag/SnO<sub>2</sub> 88/12 WPC by cold working
<xr id="fig:Softening of Ag SnO2 88 12 WPC after annealing"/> <!--Fig. 2.102: --> Softening of Ag/SnO<sub>2</sub> 88/12 WPC after annealing for 1 hr after different degrees of cold working
<xr id="fig:Strain hardening of Ag SnO2 86 14 WPC"/> <!--Fig. 2.103: --> Strain hardening of Ag/SnO<sub>2</sub> 86/14 WPC by cold working
<xr id="fig:Softening of Ag SnO2 86 14 WPC"/> <!--Fig. 2.104: --> Softening of Ag/SnO<sub>2</sub> 86/14 WPC after annealing for 1 hr after different degrees of cold working
<xr id="fig:Strain hardening of Ag SnO2 88 12 WPD"/> <!--Fig. 2.105: --> Strain hardening of Ag/SnO<sub>2</sub> 88/12 WPD by cold working
<xr id="fig:Softening of Ag SnO2 88 12 WPD after annealing"/> <!--Fig. 2.106: --> Softening of Ag/SnO<sub>2</sub> 88/12 WPD after annealing for 1 hr after different degrees of cold working
<xr id="fig:Softening of Ag SnO2 88 12 WPX"/> <!--Fig. 2.108: --> Softening of Ag/SnO<sub>2</sub> 88/12 WPX after annealing for 1 hr after different degrees of cold working
<xr id="fig:Strain hardening of Ag SnO2 88 12 WPX"/> <!--Fig. 2.107: --> Strain hardening of Ag/SnO<sub>2</sub> 88/12 WPX by cold working
<xr id="fig:Micro structure of Ag SnO2 92 8 PE"/> <!--Fig. 2.109: --> Micro structure of Ag/SnO<sub>2</sub> 92/8 PE: a) perpendicular to extrusion direction
b) parallel to extrusion direction
<xr id="fig:Micro structure of Ag SnO2 88 12 PE"/> <!--Fig. 2.110: --> Micro structure of Ag/SnO<sub>2</sub> 88/12 PE: a) perpendicular to extrusion direction
b) parallel to extrusion direction
<xr id="fig:Micro structure of Ag SnO2 88 12 PW"/> <!--Fig. 2.111: --> Micro structure of Ag/SnO<sub>2</sub> 88/12 PW: a) perpendicular to extrusion direction
b) parallel to extrusion direction
<xr id="fig:Micro structure of Ag SnO2 98 2 PX"/> <!--Fig. 2.112: --> Micro structure of Ag/SnO<sub>2</sub> 98/2 PX: a) perpendicular to extrusion direction
b) parallel to extrusion direction
<xr id="fig:Micro structure of Ag SnO2 92 8PX"/> <!--Fig. 2.113: --> Micro structure of Ag/SnO<sub>2</sub> 92/8 PX: a) perpendicular to extrusion direction
b) parallel to extrusion direction
<xr id="fig:Micro structure of Ag SnO2 88 12 TOS F"/> <!--Fig. 2.114: --> Micro structure of Ag/SnO<sub>2</sub> 88/12 TOS F: a) perpendicular to extrusion direction
b) parallel to extrusion direction
<xr id="fig:Micro structure of Ag SnO2 86 14 WPC"/> <!--Fig. 2.115: --> Micro structure of Ag/SnO<sub>2</sub> 86/14 WPC: a) perpendicular to extrusion direction
b) parallel to extrusion direction, 1) AgSnO<sub>2</sub> contact layer, 2) Ag backing layer
<xr id="fig:Micro structure of Ag SnO2 92 8 WTOS F"/> <!--Fig. 2.116: --> Micro structure of Ag/SnO<sub>2</sub> 92/8 WTOS F: a) perpendicular to extrusion direction
b) parallel to extrusion direction,1) AgSnO<sub>2</sub> contact layer, 2) Ag backing layer
<xr id="fig:Micro structure of Ag SnO2 88 12 WPD"/> <!--Fig. 2.117: --> Micro structure of Ag/SnO<sub>2</sub> 88/12 WPD: parallel to extrusion direction
1) AgSnO<sub>2</sub> contact layer, 2) Ag backing layer
<xr id="fig:Micro structure of Ag SnO2 88 12 WPX"/> <!--Fig. 2.118: --> Micro structure of Ag/SnO<sub>2</sub> 88/12 WPX:parallel to extrusion direction
1) AgSnO<sub>2</sub> contact layer, 2) Ag backing layer
<xr id="fig:Micro structure of Ag SnO2 86 14 WPX"/> <!--Fig. 2.119: --> Micro structure of Ag/SnO<sub>2</sub> 86/14 WPX: a) perpendicular to extrusion direction
b) parallel to extrusion direction, 1) AgSnO<sub>2</sub> contact layer, 2) Ag backing layer
</div>
<figtable id="tab:Physical Properties of Powder Metallurgical Silver-Metal Oxide Materials with Fine Silver Backing Produced by the Press-Sinter-Repress Process">
<caption>'''<!--Table 2.27: -->Physical Properties of Powder Metallurgical Silver-Metal Oxide Materials with Fine Silver Backing Produced by the Press-Sinter-Repress Process'''</caption>
<table class="twocolortable">
<tr><th rowspan="2"><p class="s11">Material/</p><p class="s11">DODUCO- Designation</p></th><th rowspan="2"><p class="s11">Additives</p></th><th rowspan="2"><p class="s11">Density</p><p class="s11">[ g/cm<sup>3</sup>]</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>
*'''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 Ag<sub>2</sub>WO<sub>4</sub> in the process b) as described in the preceding chapter on Ag/SnO<sub>2</sub> 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:tab2.30Contact and Switching Properties of Silver–Metal Oxide Materials"/> <!--(Tab. 2.30) --> and <xr id="tab:tab2.31Application Examples of Silver–Metal Oxide Materials"/> <!--(Tab. 2.31)-->.
<figtable id="tab:tab2.28">
<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>
{| class="twocolortable" style="text-align: left; font-size: 12px"
<div id="figures1">
<xr id="fig:Strain hardening of Ag ZnO 92 8 PW25"/> <!--Fig. 2.120: --> Strain hardening of Ag/ZnO 92/8 PW25 by cold working
<xr id="fig:Softening of Ag ZnO 92 8 PW25"/> <!--Fig. 2.121: --> Softening of Ag/ZnO 92/8 PW25 after annealing for 1 hr after 30% cold working
<xr id="fig:Strain hardening of Ag ZnO 92 8 WPW25"/> <!--Fig. 2.122: --> Strain hardening of Ag/ZnO 92/8 WPW25 by cold working
<xr id="fig:Softening of Ag ZnO 92 8 WPW25"/> <!--Fig. 2.123: --> Softening of Ag/ZnO 92/8 WPW25 after annealing for 1hr after different degrees of cold working
<xr id="fig:Micro structure of Ag ZnO 92 8 Pw25"/> <!--Fig. 2.124: --> Micro structure of Ag/ZnO 92/8 Pw25: a) perpendicular to extrusion direction
b) parallel to extrusion direction
<xr id="fig:Micro structure of Ag ZnO 92 8 WPW25"/> <!--Fig. 2.125: --> Micro structure of Ag/ZnO 92/8 WPW25:a) perpendicular to extrusion direction
b) parallel to extrusion direction, 1) Ag/ZnO contact layer, 2) Ag backing layer
</div>
<figtable id="tab:tab2.29">
<caption>'''<!--Table 2.29: -->Optimizing of Silver–Tin Oxide Materials Regarding their Switching Properties and Forming Behavior'''</caption>
<table class="twocolortable">
<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>
<figtable id="tab:tab2.30Contact and Switching Properties of Silver–Metal Oxide Materials"><caption>'''<!--Table 2.30: -->Contact and Switching Properties of Silver–Metal Oxide Materials'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
<figtable id="tab:tab2.31Application Examples of Silver–Metal Oxide Materials"><caption>'''<!--Table 2.31: -->Application Examples of Silver–Metal Oxide Materials'''</caption>
<table class="twocolortable">
<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>
====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: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.
Ag/C contact materials exhibit on the one hand an extremely high resistance to contact welding but on the other have a low arc erosion resistance. This is caused by the reaction of graphite with the oxygen in the surrounding atmosphere at the high temperatures created by the arcing. The weld resistance is especially high for materials with the graphite particle orientation parallel to the arcing contact surface. Since the contact surface after arcing consists of pure silver the contact resistance stays consistently low during the electrical life of the contact parts.
A disadvantage of the Ag/C materials is their rather high erosion rate. In materials with parallel graphite orientation this can be improved if part of the graphite is incorporated into the material in the form of fibers (GRAPHOR DF), <xr id="fig:Micro structure of Ag C DF"/> <!--(Fig. 2.133)-->. The weld resistance is determined by the total content of graphite particles.
Ag/C tips with vertical graphite particle orientation are produced in a specific sequence: Extrusion to rods, cutting of double thickness tips, burning out of graphite to a controlled layer thickness, and a second cutting to single tips. Such contact tips are especially well suited for applications which require both, a high weld resistance and a sufficiently high arc erosion resistance <xr id="tab:tab2.33"/> <!--(Table 2.33)-->. For attachment of Ag/C tips welding and brazing techniques are applied.
welding the actual process depends on the material's graphite orientation. For Ag/C tips with vertical graphite orientation the contacts are assembled with single tips. For parallel orientation a more economical attachment starting with contact material in strip or profile tape form is used in integrated stamping and welding operations with the tape fed into the weld station, cut off to tip form and then welded to the carrier material before forming the final contact assembly part. For special low energy welding the Ag/C profile tapes GRAPHOR D and DF can be pre-coated with a thin layer of high temperature brazing alloys such as CuAgP.
In a rather limited way, Ag/C with 2 – 3 wt% graphite can be produced in wire form and headed into contact rivet shape with low head deformation ratios.
The main applications for Ag/C materials are protective switching devices such as miniature molded case circuit breakers, motor-protective circuit breakers, and fault current circuit breakers, where during short circuit failures highest resistance against welding is required <xr id="tab:tab2.34"/> <!--(Table 2.34)-->. For higher currents the low arc erosion resistance of Ag/C is compensated by asymmetrical pairing with more erosion resistant materials such as Ag/Ni and Ag/W.
<div id="figures3">
<xr id="fig:Strain hardening of Ag C 96 4 D"/> <!--Fig. 2.126: --> Strain hardening of Ag/C 96/4 D by cold working
<xr id="fig:Softening of Ag C 96 4 D"/> <!--Fig. 2.127: --> Softening of Ag/C 96/4 D after annealing
<xr id="fig:Strain hardening of Ag C DF"/> <!--Fig. 2.128: --> Strain hardening of Ag/C DF by cold working
<xr id="fig:Softening of Ag C DF after annealing"/> <!--Fig. 2.129: --> Softening of Ag/C DF after annealing
</div>
<div id="figures4">
<xr id="fig:Micro structure of Ag C 97 3"/> <!--Fig. 2.130: --> Micro structure of Ag/C 97/3: a) perpendicular to extrusion direction
b) parallel to extrusion direction, 1) Ag/C contact layer, 2) Ag backing layer
<xr id="fig:Micro structure of Ag C 95 5"/> <!--Fig. 2.131: --> Micro structure of Ag/C 95/5: a) perpendicular to extrusion direction
b) parallel to extrusion direction, 1) Ag/C contact layer, 2) Ag backing layer
<xr id="fig:Micro structure of Ag C 96 4 D"/> <!--Fig. 2.132: --> Micro structure of Ag/C 96/4 D: a) perpendicular to extrusion direction
b) parallel to extrusion direction, 1) Ag/C contact layer, 2) Ag backing layer
<xr id="fig:Micro structure of Ag C DF"/> <!--Fig. 2.133: --> Micro structure of Ag/C DF: a) perpendicular to extrusion direction
b) parallel to extrusion direction, 1) Ag/C contact layer, 2) Ag/Ni 90/10 backing layer
</div>
<figtable id="tab:tab2.32">
<caption>'''<!--Table 2.32: -->Physical Properties of Silver–Graphite (GRAPHOR) Contact Materials'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
<figtable id="tab:tab2.33">
<caption>'''<!--Table 2.33: -->Contact and Switching properties of Silver–Graphite (GRAPHOR) Contact Materials'''</caption>
<table class="twocolortable">
<tr><th><p class="s12">Material/</p><p class="s12">DODUCO-Designation</p></th><th><p class="s11">Properties</p></th></tr><tr><td><p class="s12">Ag/C</p><p class="s12">GRAPHOR</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 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>
<figtable id="tab:tab2.34">
<caption>'''<!--Table 2.34: -->Application Examples and Forms of Supply of Silver– Graphite (GRAPHOR) Contact Materials'''</caption>
<table class="twocolortable">
<tr><th><p class="s12">Material/</p><p class="s12">DODUCO Designation</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">GRAPHOR 2</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></td></tr><tr><td><p class="s12">Ag/C 97/3</p><p class="s12">GRAPHOR 3</p><p class="s12">Ag/C 96/4</p><p class="s12">GRAPHOR 4</p><p class="s12">Ag/C 95/5</p><p class="s12">GRAPHOR 5</p><p class="s12">GRAPHOR 3D GRAPHOR 4D GRAPHOR 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><tr><td><p class="s12">Ag/C 97/3</p><p class="s12">GRAPHOR 3</p><p class="s12">Ag/C 96/4</p><p class="s12">GRAPHOR 4</p><p class="s12">Ag/C 95/5</p><p class="s12">GRAPHOR 5</p><p class="s12">GRAPHOR 3D GRAPHOR 4D GRAPHOR 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 profiles (weld tapes), Contact tips, brazed and welded contact parts</p></td></tr><tr><td/><td/></tr></table>
==References==
[[Contact Materials for Electrical Engineering#References|References]]
[[de:Werkstoffe_auf_Silber-Basis]]
