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Silver Based Materials

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<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|Table Different Types of Silver Powders.]]<!--(Tab. 8.1.)-->
Semi-finished silver materials can easily be warm or cold formed and can be clad to the usual base materials(<xr id="fig:Strain hardening of Ag bei cold working"/> and <xr id="fig:Softening of Ag after annealing after different degrees"/>). 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.
Contacts made from fine silver are applied in various electrical switching devices such as relays, pushbuttons, appliance and control switches for
|80
|-
|AgNi 0,AgNi0.15<br />ARGODUR-Spezial
|99.85
|10.5
|85
|-
|AgCu24,.5Ni0,.5
|75
|10.0
|92
|-
|AgCd10|89 - 91|10.3|910 - 925|4.35|23|150|1Ag99.4|60|-|Ag99,5NiMg<br />ARGODUR 32<br />Not heat treated
|99.5
|10.5
<caption>'''<!--Table 2.14:-->Mechanical Properties of Silver and Silver Alloys'''</caption>
<table class="twocolortable">
<tr><th><p class="s12">Material</p></th><th><p class="s12">Hardness</p><p class="s12">Condition</p></th><th><p class="s12">Tensile Strength</p><p class="s12">R<span class="s31">m </span>[MPa]</p></th><th><p class="s12">Elongation A [%] min.</p></th><th><p class="s12">Vickers Hardness</p><p class="s12">HV 10</p></th></tr><tr><td><p class="s12">Ag</p></td><td><p class="s12">R 200</p><p class="s12">R 250</p><p class="s12">R 300</p><p class="s12">R 360</p></td><td><p class="s12">200 - 250</p><p class="s12">250 - 300</p><p class="s12">300 - 360</p><p class="s12">&gt; 360</p></td><td><p class="s12">30</p><p class="s12">8</p><p class="s12">3</p><p class="s12">2</p></td><td><p class="s12">30</p><p class="s12">60</p><p class="s12">80</p><p class="s12">90</p></td></tr><tr><td><p class="s12">AgNi 0,AgNi0.15</p><p class="s12">ARGODUR Special</p></td><td><p class="s12">R 220</p><p class="s12">R 270</p><p class="s12">R 320</p><p class="s12">R 360</p></td><td><p class="s12">220 - 270</p><p class="s12">270 - 320</p><p class="s12">320 - 360</p><p class="s12">&gt; 360</p></td><td><p class="s12">25</p><p class="s12">6</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">40</p><p class="s12">70</p><p class="s12">85</p><p class="s12">100</p></td></tr><tr><td><p class="s12">AgCu3</p></td><td><p class="s12">R 250</p><p class="s12">R 330</p><p class="s12">R 400</p><p class="s12">R 470</p></td><td><p class="s12">250 - 330</p><p class="s12">330 - 400</p><p class="s12">400 - 470</p><p class="s12">&gt; 470</p></td><td><p class="s12">25</p><p class="s12">4</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">45</p><p class="s12">90</p><p class="s12">115</p><p class="s12">120</p></td></tr><tr><td><p class="s12">AgCu5</p></td><td><p class="s12">R 270</p><p class="s12">R 350</p><p class="s12">R 460</p><p class="s12">R 550</p></td><td><p class="s12">270 - 350</p><p class="s12">350 - 460</p><p class="s12">460 - 550</p><p class="s12">&gt; 550</p></td><td><p class="s12">20</p><p class="s12">4</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">55</p><p class="s12">90</p><p class="s12">115</p><p class="s12">135</p></td></tr><tr><td><p class="s12">AgCu10</p></td><td><p class="s12">R 280</p><p class="s12">R 370</p><p class="s12">R 470</p><p class="s12">R 570</p></td><td><p class="s12">280 - 370</p><p class="s12">370 - 470</p><p class="s12">470 - 570</p><p class="s12">&gt; 570</p></td><td><p class="s12">15</p><p class="s12">3</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">60</p><p class="s12">95</p><p class="s12">130</p><p class="s12">150</p></td></tr><tr><td><p class="s12">AgCu28</p></td><td><p class="s12">R 300</p><p class="s12">R 380</p><p class="s12">R 500</p><p class="s12">R 650</p></td><td><p class="s12">300 - 380</p><p class="s12">380 - 500</p><p class="s12">500 - 650</p><p class="s12">&gt; 650</p></td><td><p class="s12">10</p><p class="s12">3</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">90</p><p class="s12">120</p><p class="s12">140</p><p class="s12">160</p></td></tr><tr><td><p class="s12">Ag98CuNi</p><p class="s12">ARGODUR 27</p></td><td><p class="s12">R 250</p><p class="s12">R 310</p><p class="s12">R 400</p><p class="s12">R 450</p></td><td><p class="s12">250 - 310</p><p class="s12">310 - 400</p><p class="s12">400 - 450</p><p class="s12">&gt; 450</p></td><td><p class="s12">20</p><p class="s12">5</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">50</p><p class="s12">85</p><p class="s12">110</p><p class="s12">120</p></td></tr><tr><td><p class="s12">AgCu24,5Ni0,5</p></td><td><p class="s12">R 300</p><p class="s12">R 600</p></td><td><p class="s12">300 - 380</p><p class="s12">&gt; 600</p></td><td><p class="s12">10</p><p class="s12">1</p></td><td><p class="s12">105</p><p class="s12">180</p></td></tr><tr><td><p class="s12">AgCd10</p></td><td><p class="s12">R 200</p><p class="s12">R 280</p><p class="s12">R 400</p><p class="s12">R 450</p></td><td><p class="s12">200 - 280</p><p class="s12">280 - 400</p><p class="s12">400 - 450</p><p class="s12">&gt; 450</p></td><td><p class="s12">15</p><p class="s12">3</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">36</p><p class="s12">75</p><p class="s12">100</p><p class="s12">115</p></td></tr><tr><td><p class="s12">Ag99,5NiMg</p><p class="s12">ARGODUR 32</p><p class="s12">Not heat treated</p></td><td><p class="s12">R 220</p><p class="s12">R 260</p><p class="s12">R 310</p><p class="s12">R 360</p></td><td><p class="s12">220</p><p class="s12">260</p><p class="s12">310</p><p class="s12">360</p></td><td><p class="s12">25</p><p class="s12">5</p><p class="s12">2</p><p class="s12">1</p></td><td><p class="s12">40</p><p class="s12">70</p><p class="s12">85</p><p class="s12">100</p></td></tr><tr><td><p class="s12">ARGODUR 32 Heat treated</p></td><td><p class="s12">R 400</p></td><td><p class="s12">400</p></td><td><p class="s12">2</p></td><td><p class="s12">130-170</p></td></tr></table>
</figtable>
====Fine-Grain Silver====
Fine-Grain silver (ARGODUR-Spezial) is defined as a silver alloy with an addition of 0.15 wt% of nickel. Silver and nickel are not soluble in each other in solid form. In liquid silver, only a small amount of nickel is soluble as the phase diagram illustrates (<xr id="fig:Phase diagram of silver nickel"/> <!--(Fig. 2.51)--> illustrates). During solidification of the melt, this nickel addition gets finely dispersed in the silver matrix and eliminates the pronounce coarse grain growth after prolonged influence of elevated temperatures (<xr id="fig:Coarse grain micro structure of Ag"/><!--(Fig. 2.49)--> and <xr id="fig:Fine grain microstructure of AgNiO"/><!--(Fig. 2.50)-->).
<div class="multiple-images">
<div class="clear"></div>
Fine-Grain silver has almost the same chemical corrosion resistance as fine silver. Compared to pure silver, it exhibits a slightly increased hardness and tensile strength (<xr id="tab:Mechanical Properties of Silver and Silver Alloys"/><!--(Table 2.14)-->). The electrical conductivity is just slightly decreased by this low nickel addition. Because of its significantly improved contact properties, fine grain silver has replaced pure silver in many applications.
====Hard-Silver Alloys====
Using copper as an alloying component increases the mechanical stability of silver significantly(<xr id="fig:Strain hardening of AgCu3 by cold working"/>, <xr id="fig:Softening of AgCu3 after annealing"/> and <xr id="fig:Strain hardening of AgCu5 by cold working"/>). The most important among the binary AgCu alloys is that of AgCu3, in europe also known as hard-silver. This material still has a chemical corrosion resistance close to that of fine silver. In comparison to pure silver and fine-grain silver, AgCu3 exhibits increased mechanical strength as well as higher arc erosion resistance and mechanical wear resistance.
Increasing the Cu content further also increases the mechanical strength of AgCu alloys and improves arc erosion resistance and resistance against material transfer while simultaneously the tendency to oxide formation becomes detrimental. This causes - during switching under arcing conditions - an increase in contact resistance with rising numbers of operation. In special applications, where highest mechanical strength is recommended and a reduced chemical resistance can be tolerated, the eutectic AgCu alloy with 28 wt% of copper is used (<xr id="fig:Phase diagram of silver copper"/>)<!--(Fig. 2.52)-->. AgCu10, also known as coin silver, has been replaced in many applications by composite silver-based materials while sterling silver (AgCu7.5) has never extended its important usage from decorative table wear and jewelry to industrial applications in electrical contacts.
<figure id="fig:Phase diagram of silver copper">
[[File:Phase diagram of silver copper.jpg|left|thumb|<caption>Phase diagram of silver-copper</caption>]]
</figure>
 
<figure id="fig:Phase diagram of silver cadmium">
[[File:Phase diagram of silver cadmium.jpg|left|thumb|<caption>Phase diagram of silver-cadmium</caption>]]
</figure>
</figure>
<figure id="fig:Strain hardening of AgNiO15 AgNi0.15 by cold working">
[[File:Strain hardening of AgNiO15 by cold working.jpg|left|thumb|<caption>Strain hardening of AgNiO15 by cold working</caption>]]
</figure>
<figure id="fig:Softening of AgNiO15 AgNi0.15 after annealing">
[[File:Softening of AgNiO15 after annealing.jpg|left|thumb|<caption>Softening of AgNiO15 after annealing</caption>]]
</figure>
!colspan="2" | Properties
|-
|Ag<br />AgNi0,.15<br />ARGODUR-Special
|Highest electrical and thermal conductivity, high affinity to sulfur (sulfide formation), low welding resistance, low contact resistance, very good formability
|Oxidation resistant at higher make currents, limited arc erosion resistance, tendency to material transfer in DC circuits, easy to braze and weld to carrier materials
!Form of Supply
|-
|Ag<br />AgNi0,.15<br />ARGODUR-Spezial<br />AgCu3<br />AgNi98NiCu2<br />ARGODUR 27<br />AgCu24,5Ni0,5
|Relays,<br />Micro switches,<br />Auxiliary current switches,<br />Control circuit devices,<br />Appliance switches,<br />Wiring devices (&le; 20A),<br />Main switches
|'''Semi-finished Materials:''' <br />Strips, wires, contact profiles, clad contact strips, toplay profiles, seam- welded strips<br />'''Contact Parts:'''<br />Contact tips, solid and composite rivets, weld buttons; clad, welded and riveted contact parts
|'''Semi-finished Materials:'''<br />Strips, wires, contact profiles, clad contact strips, seam-welded strips<br />'''Contact parts:'''<br />Contact tips, solid contact rivets, weld buttons; clad, welded and riveted contact parts
|-
|Ag99, .5NiOMgO<br />ARGODUR 32
|Miniature relays, aerospace relays and contactors, erosion wire for injection nozzles
|Contact springs, contact carrier parts
*'''Silver-cadmium oxide materials'''
Silver-cadmium oxide materials with 10-15 wt% are produced by both, internal oxidation and powder metallurgical methods (<xr id="tab:Physical and Mechanical Properties"/>)<!--(Table 2.25)-->. <figtable id="tab:Physical and Mechanical Properties">[[File:Physical and Mechanical Properties.jpg|right|thumb|Physical and Mechanical Properties as well as Manufacturing Processes and Forms of Supply of Extruded Silver Cadmium Oxide Contact Materials]]</figtable>
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 an oxygen rich atmosphere of 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 getting larger towards the center of the material (<xr id="fig:Micro structure of AgCdO9010"/>)<!--(Fig. 2.83)-->.
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. Adding a brazable fine silver layer to such materials results in a semifinished material, suitable for the manufacture as smaller weld profiles (<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:Application Examples of Silver–Metal Oxide Materials"/>)<!--(Table 2.31)-->.
 
''Powder metallurgy'' plays a significant role in the manufacturing of Ag/SnO<sub>2</sub> contact materials. Besides SnO<sub>2</sub> a smaller amount (<1 wt%) of one or more other metal oxides such as WO<sub>3</sub>, MoO<sub>3</sub>, CuO and/or Bi<sub>2</sub>O<sub>3</sub> are added. These
additives improve the wettability of the oxide particles and increase the viscosity of the Ag melt. They also provide additional benefits to the mechanical and arcing contact properties of materials in this group (<xr id="tab:Physical Mechanical Properties as Manufacturingtab2.26"/>). <!--(Download Table 2.26 as PDF: [[File:Physical Mechanical properties)-->.pdf|Physical and Mechanical Properties as well as Manufacturing Processes andForms of Supply of Extruded Silver-Tin Oxide (SISTADOX) Contact Materials]])''
<figtable id="tab:tab2.26">
<caption>'''<!--Table 2.26:--> Physical and Mechanical Properties as well as Manufacturing Processes and Forms of Supply of Extruded Silver-Tin Oxide Contact Materials'''</caption>
<figtable id{| class="twocolortable" style="tabtext-align: left; font-size:Physical Mechanical Properties as Manufacturing12px"|-!Material !Silver Content<br />[wt%]!Additives!Theoretical<br />Density<br />[g/cm<sup>3</sup>]!Electrical<br />Conductivity<br />[MS/m]!Vickers<br />Hardness<br />[HV0,1]!Tensile<br />Strength<br />[MPa]!Elongation (soft annealed)<br />A[File:Physical Mechanical Properties as %]min.!Manufacturing<br />Process!Form of Supply|-|Ag/SnO<sub>2</sub> 98/2 SPW|97 - 99|WO<sub>3</sub>|10,4|59 ± 2|57 ± 15|215|35|Powder Metallurgy|1|-|Ag/SnO<sub>2</sub> 92/8 SPW|91 - 93|WO<sub>3</sub>|10,1|51 ± 2|62 ± 15|255|25|Powder Metallurgy|1|-|Ag/SnO<sub>2</sub> 90/10 SPW|89 - 91|WO<sub>3</sub>|10|47 ± 5||250|25|Powder Metallurgy|1|-|Ag/SnO<sub>2</sub> 88/12 SPW|87 - 89|WO<sub>3</sub>|9.9|46 ± 5|67 ± 15|270|20|Powder Metallurgy|1|-|Ag/SnO<sub>2</sub> 92/8 SPW4|91 - 93|WO<sub>3</sub>|10,1|51 ± 2|62 ± 15|255|25|Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 90/10 SPW4|89 - 91|WO<sub>3</sub>|10|||||Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 88/12 SPW4<br />|87 - 89|WO<sub>3</sub>|9,8|46 ± 5|80 ± 10|||Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 88/12 SPW6|87 - 89|MoO<sub>3</sub>|9.8|42 ± 5|70 ± 10|||Powder Metallurgy|2|-|Ag/SnO<sub>2</sub> 97/3 SPW7|96 - 98|Bi<sub>2</sub>O<sub>3</sub> and WO<sub>3</sub>||||||Powder Metallurgy|2|-|Ag/SnO<sub>2</sub> 90/10 SPW7|89 - 91|Bi<sub>2</sub>O<sub>3</sub> and WO<sub>3</sub>|9,9|||||Powder Metallurgy|2|-|Ag/SnO<sub>2</sub> 88/12 SPW7|87 - 89|Bi<sub>2</sub>O<sub>3</sub> and WO<sub>3</sub>|9.jpg8|42 ± 5|70 ± 10|||Powder Metallurgy|2|right-|thumbAg/SnO<sub>2</sub> 98/2 PMT1|97 - 99|Physical Bi<sub>2</sub>O<sub>3</sub> and Mechanical Properties as well as Manufacturing Processes CuO|10,4|57 ± 2||215|35|Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 96/4 PMT1|95 - 97|Bi<sub>2</sub>O<sub>3</sub> and CuO||||||Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 94/6 PMT1|93 - 95|Bi<sub>2</sub>O<sub>3</sub> and CuO||||||Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 92/8 PMT1|91 - 93|Bi<sub>2</sub>O<sub>3</sub> and CuO|10|50 ± 2|62 ± 15|240|25|Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 90/10 PMT1|89 - 91|Bi<sub>2</sub>O<sub>3</sub> and CuO|10|48 ± 2|65 ± 15|240|25|Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 88/12 PMT1|87 - 89|Bi<sub>2</sub>O<sub>3</sub> and CuO|9,9|46 ± 5||260|20|Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 90/10 PE|89 - 91|Bi<sub>2</sub>O<sub>3</sub> and CuO|9,8|48 ± 2|55 - 100|230 - 330|28|Powder Metallurgy|1|-|Ag/SnO<sub>2</sub> 88/12 PE|87 - 89|Bi<sub>2</sub>O<sub>3</sub> and CuO|9,7|46 ± 5|60 - 106|235 - 330|25|Powder Metallurgy|1|-|Ag/SnO<sub>2</sub> 88/12 PMT2|87 - 89|CuO|9,9||90 ± 10|||Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 86/14 PMT3|85 - 87|Bi<sub>2</sub>O<sub>3</sub> and CuO|9,8||95 ± 10|||Powder Metallurgy|2|-|Ag/SnO<sub>2</sub> 94/6 LC1|93 - 95|Bi<sub>2</sub>O<sub>3</sub> andIn<sub>2</sub>O<sub>3</sub>|9,8|45 ± 5Forms of Supply of Extruded Silver|55 ± 10|||Powder Metallurgy|2|-|Ag/SnO<sub>2</sub> 90/10 POX1|89 - 91|In<sub>2</sub>O<sub>3</sub>|9,9|50 ± 5|85 ± 15|310|25|Internal Oxidation|1,2|-|Ag/SnO<sub>2</sub> 90/10 POX1|87 - 89|In<sub>2</sub>O<sub>3</sub>|9,8|48 ± 5|90 ± 15|325|25|Internal Oxidation|1,2|-|Ag/SnO<sub>2</sub> 90/10 POX1|85 - 87 |In<sub>2</sub>O<sub>3</sub>|9,6|45 ± 5|95 ± 15|330|20|Internal Oxidation|1,2|-Tin Oxide Contact Materials]]|}
</figtable>
 
1 = Wires, Rods, Contact rivets, 2 = Strips, Profiles, Contact tips
 
In the manufacture for the initial powder mixes, different processes are applied which provide specific advantages of the resulting materials in respect to their contact properties <!--[[#figures|(Figs. 43 – 75)]]-->. Some of them are described here as follows:
*'''Silver–zinc oxide materials'''
Silver zinc oxide contact materials with mostly 6 - 10 wt% oxide content, including other small metal oxides, are produced exclusively by powder metallurgy [[#figures1|(Figs. 76 58 – 8163)]]<!--(Table 2.28)-->. Adding WO<sub>3</sub> or Ag<sub>2</sub>WO<sub>4</sub> in the process - 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: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)-->.
!Form of<br />Supply
|-
|Ag/ZnO 92/8P<br />ZnO 8P
|91 - 93
|
|1
|-
|Ag/ZnO 94/6PW25<br />ZnO 6PW25|93 - 95|Ag<sub>2</sub>WO<sub>4</sub>|9.7|2.0|86|50|60 - 100|200 - 320|30|Powder Metallurgy<br />c) coated|1|-|Ag/ZnO 92/8PW25<br />ZnO 8PW25
|91 - 93
|Ag<sub>2</sub>WO<sub>4</sub>
|1
|-
|Ag/ZnO 90/10PW25<br />ZnO 10PW25
|89 - 91
|Ag<sub>2</sub>WO<sub>4</sub>
|1
|-
|Ag/ZnO 92/8WP<br />ZnO 8WP
|91 - 93
|
|2
|-
|AgZnO 94/6WPW25<br />ZnO 6WPW25|93 - 95|Ag<sub>2</sub>WO<sub>4</sub>|9.7|2.0|86|50|60 - 95|||Powder Metallurgy<br />c) coated|2|-|Ag/ZnO 92/8WPW25<br />ZnO 8WPW25
|91 - 93
|Ag<sub>2</sub>WO<sub>4</sub>
|2
|-
|Ag/ZnO 90/10WPW25<br />ZnO 10WPW25
|89 - 91
|Ag<sub>2</sub>WO<sub>4</sub>
</figure>
<figure id="fig:Micro structure of Ag ZnO 92 8 Pw25PW25"> [[File:Micro structure of Ag ZnO 92 8 Pw25.jpg|left|thumb|<caption>Micro structure of Ag/ZnO 92/8 Pw25PW25: a) perpendicular to extrusion direction b) parallel to extrusion direction</caption>]]
</figure>
{| class="twocolortable" style="text-align: left; font-size: 12px"
|-
|-!Material|Ag/CdO<br />|High resistance against welding during current-on-switching for currents up to<br />5kA especially for powder metallurgical materials,<br />Weld resistance increases with higher oxide contents,<br />Low and stable contact resistance over the life of the device and good<br />temperature rise properties,<br />High arc erosion resistance and contact life at switching currents<br />of 100A – 5kA,<br />Very good arc moving properties for materials produced by internal oxidation,<br />Good arc extinguishing properties,<br />Formability better than the one of Ag/SnO2 and Ag/ZnO materials,<br />Use of Ag/CdO in automotive components is prohibited because of Cd toxicity,<br />Prohibition of use in consumer products and appliances in the EU.!Properties
|-
|Ag/SnO<sub>2</sub><br />
<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/SnO<sub>2</sub><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>
</figtable>
Ag/C 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 64 – 8567)]]<!--(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 68 – 8971)]]<!--(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)-->.
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 burning out (de-graphitizing) the graphite selectively on one side of the tips.
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 consistantly 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 a part of the graphite is incorporated into the material (GRAPHOR Ag/C DF) in the form of fibers (<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.
|40 - 60
|-
|AgCDFAgC DF<br />GRAPHOR DF*)[[#text-reference1|<sup>1</sup>]]
|95.7 - 96.7
|8.7 - 8.9
|69 - 76
|40 - 44
|-
|}
<div id="text-reference1"><sub>1</sub> Graphite content 3.8 wt%, Graphite particles and fibers parallel to switching surface</div>
</figtable>
<nowiki>*)</nowiki> Graphite content 3.8 wt%, Graphite particles and fibers parallel to switching surface
<caption>'''<!--Table 2.34:-->Application Examples and Forms of Supply of Silver– Graphite Contact Materials'''</caption>
<table class="twocolortable">
<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><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<sub>2</sub><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>
</figtable>
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