Changes

===2.1 Introduction===The contact parts are important components in switching devices. They have tomaintain their function from the new state until the end of the functional life of thedevices.

The requirements on contacts are rather broad. Besides typical contact propertiessuch as

they They have to exhibit physical, mechanical, and chemical properties like high electricaland thermal conductivity, high hardness, high corrosion resistance, etc . and besidesthis , should have good mechanical workability, and also be suitable for good weld andbrazing attachment to contact carriers. In addition they must be made fromenvironmentally friendly materials.

Materials suited for use as electrical contacts can be divided into the following groupsbased on their composition and metallurgical structure:

*'''Pure metals''' Within this group, silver has the greatest importance for switching devices in the higher energy technology. Other precious metals such as gold and platinum are only used in applications for the information technology in the form of thin surface layers. As a nonprecious metal, tungsten is used for some special applications such as, for example, automotive horn contacts. In some rarer cases, pure copper is used, but mainly paired to a silver-based contact material. '''Alloys''' Besides these few pure metals, a larger number of alloy materials made by melt technology are available for the use as contacts. An alloy is characterized by the fact, that its components are completely or partially soluble in each other in the solid state. Phase diagrams for multiple metal compositions show the number and type of the crystal structure as a function of the temperature and composition of the alloying components.

Besides these few pure metals a larger number They indicate the boundaries of liquid and solid phases and define the parameters of alloy materials made by meltsolidification.technology are available for Alloying allows to improve the use as contacts. An alloy is characterized by properties of one material at the factthat its components are completely or partially soluble in each other in cost of changing them for the solid statesecond material.Phase diagrams for multiple metal compositions show As an example, the number and type hardness of a base metal may be increased while at thecrystal structure as a function of same time the temperature and composition electrical conductivity decreases with even small additions of the second alloying componentscomponent.

*Composite Materialsmaterials are a material group whose properties are of great importance for electrical contacts that are used in switching devices for higherelectrical currents.

Composite materials are a material group whose properties are of greatimportance for electrical contacts that are used in switching devices for higherelectrical currents.Those used in electrical contacts are heterogeneous materials , composed of twoor more uniformly dispersed components , in which the largest volume portionconsists of a metal.The properties of composite materials are determined mainly independent fromeach other by the properties of their individual components. Therefore it is forexample possible to combine the high melting point and arc erosion resistanceof tungsten with the low melting and good electrical conductivity of copper, orthe high conductivity of silver with the weld resistant metalloid graphite.

Figure 2The properties of composite materials are determined mainly independent from each other by the properties of their individual components.1 Therefore it is, for example, possible to combine the high melting point and arc erosion resistance of tungsten with the low melting and good electrical conductivity of copper or the high conductivity of silver with the weld resistant metalloid graphite. <xr id="fig:Powder metallurgical manufacturing of composite materials (schematic)"/> shows the schematic manufacturing processes from powderblending to contact material. Three basic process variations are typicallyapplied:

During sintering without a liquid phase <figure id="fig:Powder metallurgical manufacturing of composite materials (left side of schematic) the powder mix is">first densified by pressing, then undergoes a heat treatment [[File:Powder metallurgical manufacturing of composite materials (sinteringschematic), andeventually is re-pressed again to further increase the density. The sinteringatmosphere depends on the material components and later application; avacuum is used for example for the low gas content material Cu/Cr. Thisprocess is used for individual contact parts and also termed pressjpg|thumb|<caption>Powder-sinterrepressmetallurgical manufacturing of composite materials (PSRschematic). For materials with high silver content T_s = Melting point of the starting point atpressing is most a larger block (or billetlower melting component) which is then after sintering hotextruded into wire, rod, or strip form. The extrusion further increases the density</caption>]]of these composite materials and contributes to higher arc erosion resistance.Materials such as Ag</Ni, Ag/MeO, and Ag/C are typically produced by thisprocess. Sintering with liquid phase has the advantage of shorter process times due tothe accelerated diffusion and also results in near-theoretical densities of thefigure>

FigDuring ''sintering without a liquid phase'' (left side of schematic), the powder mix is first densified by pressing, then undergoes a heat treatment (sintering) and eventually is re-pressed again to further increase the density. 2The sintering atmosphere depends on the material components and later application; a vacuum is used for example for the low gas content material Cu/Cr.1: PowderThis process is used for individual contact parts and also termed press-metallurgical manufacturing of composite sinter-repress (PSR). For materials with high silver content, the starting point before pressing is mostly a large block (schematicor billet)T = Melting point which is then, after sintering, hot extruded into wire, rod or strip form. The extrusion further increases the density of the lower melting componentthese composite materials and contributes to higher arc erosion resistance. Materials such as Ag/Ni, Ag/MeO and Ag/C are typically produced by this process.

''Sintering with liquid phase'' has the advantage of shorter process times due to the accelerated diffusion and also results in near-theoretical densities of the composite material. To ensure the shape stability during the sintering process , it

As opposed to the liquid phase sintering , which has limited use for electricalcontact manufacturing, the ''Infiltration process '' as shown on the right side of theschematic , has a broad practical range of applications. In this process thepowder of the higher melting component , sometimes also as a powder mix witha small amount of the second material , is pressed into parts and . Then, right after sintering, the porous skeleton is infiltrated with liquid metal of the second material. Thefilling fill-up process of the pores happens through capillary forces. This process reaches, after the infiltration , near-theoretical density without subsequent pressing and iswidely used for Ag- and Cu-refractory contacts. For Ag/W or Ag/WC contacts,controlling the amount or excess on the bottom side of the contact of theinfiltration metal Ag , results in contact tips that can be easily attached to theircarriers by resistance welding. For larger Cu/W contacts , additional machining isoften used to obtain the final shape of the contact component. ===2.2 Gold Based Materials=== Pure Gold is besides Platinum the chemically most stable of all precious metals.In its pure form it is not very suitable for use as a contact material in electromechanical devices because of its tendency to stick and cold-weld at even low contact forces. In addition it is not hard or strong enough to resistmechanical wear and exhibits high materials losses under electrical arcingloads. This limits its use in form of thin electroplated or vacuum deposited layers. For most electrical contact applications gold alloys are used. Depending on thealloying metal the melting is performed either under in a reducing atmosphere orin a vacuum. The choice of alloying metals depends on the intended use of theresulting contact material. The binary Au alloys with typically <10 wt% of otherprecious metals such as Pt, Pd, or Ag or non-precious metals like Ni, Co, andCu are the more commonly used ones (Table 2.2). On one hand these alloyadditions improve the mechanical strength and electrical switching propertiesbut on the other hand reduce the electrical conductivity and chemical corrosionresistance (Fig. 2.2) to varying degrees. Under the aspect of reducing the gold content ternary alloys with a gold contentof approximately 70 wt% and additions of Ag and Cu or Ag and Ni resp., forexample AuAg25Cu5 or AuAg20Cu10 are used which exhibit for manyapplications good mechanical stability while at the same time have sufficientresistance against the formation of corrosion layers (Table 2.3). Other ternaryalloys based on the AuAg system are AuAg26Ni3 and AuAg25Pt6. These alloysare mechanically similar to the AuAgCu alloys but have significantly higheroxidation resistance at elevated temperatures (Table 2.4). Caused by higher gold prices over the past years the development of alloys withfurther reduced gold content had a high priority. The starting point has been theAuPd system which has continuous solubility of the two components. Besidesthe binary alloy of AuPd40 and the ternary one AuPd35Ag9 other multiplecomponent alloys were developed. These alloys typically have < 50 wt% Au andoften can be solution hardened in order to obtain even higher hardness andtensile strength. They are mostly used in sliding contact applications. Gold alloys are used in the form of welded wire or profile (also called weldtapes),segments, contact rivets, and stampings produced from clad stripmaterials. The selection of the bonding process is based on the cost for thejoining process, and most importantly on the economical aspect of using theleast possible amount of the expensive precious metal component. Besides being used as switching contacts in relays and pushbuttons, goldalloys are also applied in the design of connectors as well as sliding contacts forpotentiometers, sensors, slip rings, and brushes in miniature DC motors(Table 2.5). Table 2.3: Mechanical Properties of Gold and Gold-Alloys Table 2.1: Commonly Used Grades of Gold Table 2.2: Physical Properties of Gold and Gold-Alloys Fig. 2.2:Influence of 1-10 atomic% of differentalloying metals on the electrical resistivity of gold(according to J. O. Linde) Fig. 2.3:Phase diagramof goldplatinum Fig. 2.4:Phase diagramof gold-silver Fig. 2.5:Phase diagramof gold-copper Fig. 2.6: Phase diagram of gold-nickel Fig. 2.7: Phase diagram of gold-cobalt Fig. 2.8:Strain hardeningof Au by cold working Fig. 2.9:Softening of Au after annealingfor 0.5 hrs after 80%cold working Fig. 2.10:Strain hardening ofAuPt10 by cold working Fig. 2.11:Strain hardeningof AuAg20 by cold working Fig. 2.12:Strain hardening ofAuAg30 by cold working Fig. 2.13:Strain hardening of AuNi5by cold working Fig. 2.14:Softeningof AuNi5 after annealingfor 0.5 hrs after 80%cold working Fig. 2.15:Strain hardeningof AuCo5 by cold working Fig. 2.16:Precipitation hardening ofAuCo5 at 400°C hardeningtemperature Fig. 2.17:Strain hardeningof AuAg25Pt6 by cold working Fig. 2.18:Strain hardeningof AuAg26Ni3 by cold working Fig. 2.19:Softeningof AuAg26Ni3 afterannealing for 0.5 hrsafter 80% coldworking Fig. 2.20:Strain hardening ofAuAg25Cu5by cold working Fig. 2.21:Strain hardening ofAuAg20Cu10by cold working Fig. 2.22:Softeningof AuAg20Cu10 afterannealing for 0.5 hrsafter 80% cold working Fig. 2.23:Strain hardening ofAuCu14Pt9Ag4by cold working Fig. 2.24:Precipitationhardening ofAuCu14Pt9Ag4at differenthardeningtemperaturesafter 50%cold working Table 2.4: Contact and Switching Properties of Gold and Gold Alloys Table 2.5: Application Examples and Forms of Gold and Gold Alloys ===2.3 Platinum Metal Based Materials=== The platinum group metals include the elements Pt, Pd, Rh, Ru, Ir, and Os (Table2.6). For electrical contacts platinum and palladium have practical significanceas base alloy materials and ruthenium and iridium are used as alloying components.Pt and Pd have similar corrosion resistance as gold but because of theircatalytical properties they tend to polymerize adsorbed organic vapors on contactsurfaces. During frictional movement between contact surfaces the polymerizedcompounds known as “brown powder” are formed which can lead to significantlyincrease in contact resistance. Therefore Pt and Pd are typically used as alloys andnot in their pure form for electrical contact applications. Rhodium is not used as a solid contact material but is applied for example as aelectroplated layer in sliding contact systems. Ruthenium is mostly used as an alloyingcomponent in the material PdRu15. The metals osmium and iridium have no practicalapplications in electrical contacts. Since Pd was for the longest time rather stable in price it was looked at as a substitutefor the more expensive gold. This was followed by a steep increase in the Pd pricewhich caused a significant reduction in its use in electrical contacts. Today (2011) thePd price again is lower than that of gold. Alloys of Pt with Ru, Ir, Ni, and W were widely used in electromechanical componentsin the telecommunication industry and in heavy duty automotive breaker points (Table2.7). Today these components have been replaced in many applications by solidstate technology and the usage of these materials is greatly reduced. Pd alloyshowever have a more significant importance. PdCu15 is widely used for example inautomotive flasher relays. Because of their resistance to sulfide formation PdAg alloysare applied in various relay designs. The ability to thermally precipitation harden somemulti component alloys based on PdAgAuPt they find special usage in wear resistantsliding contact applications. Pd44Ag38Cu15PtAuZn is a standard alloy in this group. Platinum and palladium alloys are mainly used similar to the gold based materials inthe form of welded wire and profile segments but rarely as contact rivets. Because ofthe high precious metal prices joining technologies are used that allow the mosteconomic application of the contact alloy in the area where functionally needed.Because of their resistance to material transfer they are used for DC applications anddue to their higher arc erosion resistance they are applied for medium electrical loadsup to about 30W in relays and switches (Table 2.10). Multi-component alloys basedon Pd with higher hardness and wear resistance are mainly used as spring arms insliding contact systems and DC miniature motors. Table 2.6: Properties, Production Processes, and Application Forms for Platinum Metals Table 2.7: Physical Properties of the Platinum Metals and their Alloys Table 2.8: Mechanical Properties of the Platinum Metals and their Alloys Fig. 2.25:Influence of 1-20 atom% ofdifferent additivemetals on theelectricalresistivity p ofplatinum(Degussa) Fig. 2.26:Influence of 1-22 atom% of differentadditive metals on the electricalresistivityp of palladium Fig. 2.27:Phase diagram ofplatinum-iridium Fig. 2.28:Phase diagram ofplatinum-nickel Fig. 2.29:Phase diagramof platinum-tungsten Fig. 2.30:Phase diagram ofpalladium-copper Fig. 2.31:Strainhardeningof Pt by coldworking Fig. 2.32:Softening of Pt afterannealing for 0.5 hrsafter 80%cold working Fig. 2.33:Strain hardening of PtIr5by cold working Fig. 2.34:Softening of PtIr5 after annealing for 1 hrafter different degrees of cold working Fig. 2.35:Strain hardeningof PtNi8 by cold working Fig. 2.36:Softening of PtNi8 afterannealingfor 1 hr after80% cold working Fig. 2.37:Strain hardeningof PtW5 by cold working Fig. 2.38:Softeningof PtW5 afterannealing for 1hrafter 80% coldworking Fig. 2.39:Strain hardeningof Pd 99.99 by cold working Fig. 2.40:Strain hardeningof PdCu15 by cold working Fig. 2.41:Softeningof PdCu15 afterannealingfor 0.5 hrs Fig. 2.42:Strain hardeningof PdCu40 by cold working Fig. 2.43:Softeningof PdCu40after annealingfor 0.5 hrs after 80%cold working Fig. 2.44:Electrical resistivity pof PdCu alloys with and without anannealing step for forming an orderedphase Table 2.9: Contact and Switching Propertiesof the Platinum Metals and their Alloys Table 2.10: Application Examples and Formof Supply for Platinum Metals and their Alloys ===2.4 Silver Based Materials=== ===2.4.1 Pure Silver===Pure silver (also called fine silver) exhibits the highest electrical and thermalconductivity of all metals. It is also resistant against oxidation. Major disadvantagesare its low mechanical wear resistance, the low softening temperature,and especially its strong affinity to sulfur and sulfur compounds. In the presenceof sulfur and sulfur containing compounds brownish to black silver sulfide layerare formed on its surface. These can cause increased contact resistance oreven total failure of a switching device if they are not mechanically, electrically,or thermally destroyed. Other weaknesses of silver contacts are the tendency toweld under the influence of over-currents and the low resistance againstmaterial transfer when switching DC loads. In humid environments and underthe influence of an electrical field silver can creep (silver migration) and causeelectrical shorting between adjacent current paths. Table 2.11 shows the typically available quality grades of silver. In certaineconomic areas, i.e. China, there are additional grades with varying amounts ofimpurities available on the market. In powder form silver is used for a widevariety of silver based composite contact materials. Different manufacturingprocesses result in different grades of Ag powder as shown in Table 2.12.additional properties of silver powders and their usage are describedin chapter 8.1.Semi-finished silver materials can easily be warm or cold formed and can beclad to the usual base materials. For attachment of silver to contact carriermaterials welding of wire or profile cut-offs and brazing are most widely applied.Besides these mechanical processes such as wire insertion (wire staking) andthe riveting (staking) of solid or composite contact rivets are used in themanufacture of contact components. Contacts made from fine silver are applied in various electrical switchingdevices such as relays, pushbuttons, appliance and control switches forcurrents < 2 A (Table 2.16). Electroplated silver coatings are widely used toreduce the contact resistance and improve the brazing behavior of other contactmaterials and components. Table 2.11: Overview of the Most Widely Used Silver Grades Table 2.12: Quality Criteria of Differently Manufactured Silver Powders Fig. 2.45:Strain hardeningof Ag 99.95 by cold working Fig. 2.46:Softening of Ag 99.95after annealing for 1 hr after differentdegrees of strain hardening ===2.4.2 Silver Alloys===To improve the physical and contact properties of fine silver melt-metallurgicalproduced silver alloys are used (Table 2.13). By adding metal components themechanical properties such as hardness and tensile strength as well as typicalcontact properties such as erosion resistance, and resistance against materialtransfer in DC circuits are increased (Table 2.14). On the other hand however,other properties such as electrical conductivity and chemical corrosionresistance can be negatively impacted by alloying (Figs. 2.47 and 2.48). ===2.4.2.1 Fine-Grain Silver===Fine-Grain Silver (ARGODUR-Spezial) is defined as a silver alloy with an additionof 0.15 wt% of Nickel. Silver and nickel are not soluble in each other in solidform. In liquid silver only a small amount of nickel is soluble as the phase diagram(Fig. 2.51) illustrates. During solidification of the melt this nickel addition getsfinely dispersed in the silver matrix and eliminates the pronounce coarse graingrowth after prolonged influence of elevated temperatures (Figs. 2.49 and 2.50. Fine-grain silver has almost the same chemical corrosion resistance as finesilver. Compared to pure silver it exhibits a slightly increased hardness andtensile strength (Table 2.14). The electrical conductivity is just slightly decreasedby this low nickel addition. Because of its significantly improved contactproperties fine grain silver has replaced pure silver in many applications. ===2.4.2.2 Hard-Silver Alloys===Using copper as an alloying component increases the mechanical stability ofsilver significantly. The most important among the binary AgCu alloys is that ofAgCu3, known in europe also under the name of hard-silver. This material stillhas a chemical corrosion resistance close to that of fine silver. In comparison topure silver and fine-grain silver AgCu3 exhibits increased mechanical strengthas well as higher arc erosion resistance and mechanical wear resistance(Table 2.14). Increasing the Cu content further also increases the mechanical strength ofAgCu alloys and improves arc erosion resistance and resistance againstmaterial transfer while at the same time however the tendency to oxide formationbecomes detrimental. This causes during switching under arcing conditions anincrease in contact resistance with rising numbers of operation. In specialapplications where highest mechanical strength is recommended and a reducedchemical resistance can be tolerated, the eutectic AgCu alloy with 28 wt% ofcopper (Fig. 2.52) is used. AgCu10 also known as coin silver has beenreplaced in many applications by composite silver-based materials while sterlingsilver (AgCu7.5) has never extended its important usage from decorative tablewear and jewelry to industrial applications in electrical contacts. Besides these binary alloys, ternary AgCuNi alloys are used in electrical contactapplications. From this group the material ARGODUR 27, an alloy of 98 wt% Agwith a 2 wt% Cu and nickel addition has found practical importance close to thatof AgCu3. This material is characterized by high resistance to oxidation and lowtendency to re-crystallization during exposure to high temperatures. Besideshigh mechanical stability this AgCuNi alloy also exhibits a strong resistanceagainst arc erosion. Because of its high resistance against material transfer thealloy AgCu24.5Ni0.5 has been used in the automotive industry for an extendedtime in the North American market. Caused by miniaturization and the relatedreduction in available contact forces in relays and switches this material hasbeen replaced widely because of its tendency to oxide formation. The attachment methods used for the hard silver materials are mostly close tothose applied for fine silver and fine grain silver. Hard-silver alloys are widely used for switching applications in the informationand energy technology for currents up to 10 A, in special cases also for highercurrent ranges (Table 2.16). Dispersion hardened alloys of silver with 0.5 wt% MgO and NiO (ARGODUR 32)are produced by internal oxidation. While the melt-metallurgical alloy is easy tocold-work and form the material becomes very hard and brittle after dispersionhardening. Compared to fine silver and hard-silver this material has a greatlyimproved temperature stability and can be exposed to brazing temperatures upto 800°C without decreasing its hardness and tensile strength.Because of these mechanical properties and its high electrical conductivity Table 2.13: Physical Properties of Silver and Silver Alloys ARGODUR 32 is mainly used in the form of contact springs that are exposed tohigh thermal and mechanical stresses in relays, and contactors for aeronauticapplications. Fig. 2.47:Influence of 1-10 atom% of differentalloying metals on the electrical resistivity ofsilver Fig. 2.48:Electrical resistivity pof AgCu alloys with 0-20 weight% Cuin the soft annealedand tempered stagea) Annealed and quenchedb) Tempered at 280°C Fig. 2.49: Coarse grain micro structureof Ag 99.97 after 80% cold workingand 1 hr annealing at 600°C Fig. 2.50: Fine grain microstructureof AgNi0.15 after 80% cold workingand 1 hr annealing at 600°C Fig. 2.51:Phase diagramof silver-nickel Fig. 2.52:Phase diagramof silver-copper Fig. 2.53:Phase diagram ofsilver-cadmium Table 2.14: Mechanical Properties of Silver and Silver Alloys Fig. 2.54:Strain hardeningof AgCu3by cold working Fig. 2.55:Softening of AgCu3after annealing for 1 hrafter 80% cold working Fig. 2.56:Strain hardening of AgCu5 by coldworking Fig. 2.57:Softening of AgCu5 afterannealing for 1 hr after 80% coldworking Fig. 2.58:Strain hardening of AgCu 10by cold working Fig. 2.59:Softening of AgCu10 afterannealing for 1 hr after 80% coldworking Fig. 2.60:Strain hardening of AgCu28 bycold working Fig. 2.61:Softening of AgCu28after annealing for 1 hr after80% cold working Fig. 2.62:Strain hardening of AgNi0.15by cold working Fig. 2.63:Softening of AgNi0.15after annealing for 1 hr after 80%cold working Fig. 2.64:Strain hardening ofARGODUR 27by cold working Fig. 2.65:Softeningof ARGODUR 27 after annealingfor 1 hr after 80% cold working Table 2.15: Contact and Switching Properties of Silver and Silver Alloys Table 2.16: Application Examples and Forms of Supply for Silver and Silver Alloys ===2.4.2.3 Silver-Palladium Alloys===The addition of 30 wt% Pd increases the mechanical properties as well as theresistance of silver against the influence of sulfur and sulfur containingcompounds significantly (Tables 2.17 and 2.18).Alloys with 40-60 wt% Pd have an even higher resistance against silver sulfideformation. At these percentage ranges however the catalytic properties ofpalladium can influence the contact resistance behavior negatively. Theformability also decreases with increasing Pd contents. AgPd alloys are hard, arc erosion resistant, and have a lower tendency towardsmaterial transfer under DC loads (Table 2.19). On the other hand the electricalconductivity is decreased at higher Pd contents. The ternary alloy AgPd30Cu5has an even higher hardness which makes it suitable for use in sliding contactsystems. AgPd alloys are mostly used in relays for the switching of medium to higher loads(>60V, >2A) as shown in Table 2.20. Because of the high palladium price theseformerly solid contacts have been widely replaced by multi-layer designs suchas AgNi0.15 or AgNi10 with a thin Au surface layer. A broader field of applicationfor AgPd alloys remains in the wear resistant sliding contact systems. Fig. 2.66: Phase diagram of silver-palladium Fig. 2.67:Strain hardeningof AgPd30 by cold working Fig. 2.68:Strain hardeningof AgPd50 by cold working Fig. 2.69:Strain hardeningof AgPd30Cu5by cold working Fig. 2.70:Softening of AgPd30, AgPd50,and AgPd30Cu5 after annealing of 1 hrafter 80% cold working Table 2.17: Physical Properties of Silver-Palladium Alloys Table 2.18: Mechanical Properties of Silver-Palladium Alloys Table 2.19: Contact and Switching Properties of Silver-Palladium Alloys Table 2.20: Application Examples and Forms of Suppl for Silver-Palladium Alloys ===2.4.3 Silver Composite Materials=== ===2.4.3.1 Silver-Nickel (SINIDUR) Materials===Since silver and nickel are not soluble in each other in solid form and in the liquidphase have only very limited solubility silver nickel composite materials withhigher Ni contents can only be produced by powder metallurgy. During extrusionof sintered Ag/Ni billets into wires, strips and rods the Ni particles embedded inthe Ag matrix are stretched and oriented in the microstructure into a pronouncedfiber structure (Figs. 2.75. and 2.76) The high density produced during hot extrusion aids the arc erosion resistanceof these materials (Tables 2.21 and 2.22). The typical application of Ag/Nicontact materials is in devices for switching currents of up to 100A (Table 2.24).In this range they are significantly more erosion resistant than silver or silveralloys. In addition they exhibit with nickel contents <20 wt% a low and over theiroperational lifetime consistent contact resistance and good arc movingproperties. In DC applications Ag/Ni materials exhibit a relatively low tendencyof material transfer distributed evenly over the contact surfaces (Table 2.23). Typically Ag/Ni (SINIDUR) materials are usually produced with contents of 10-40wt% Ni. The most widely used materials SINIDUR 10 and SINIDUR 20- and alsoSINIDUR 15, mostly used in north america-, are easily formable and applied bycladding (Figs. 2.71-2.74). They can be, without any additional welding aids,economically welded and brazed to the commonly used contact carriermaterials.The (SINIDUR) materials with nickel contents of 30 and 40 wt% are used inswitching devices requiring a higher arc erosion resistance and where increasesin contact resistance can be compensated through higher contact forces. The most important applications for Ag/Ni contact materials are typically inrelays, wiring devices, appliance switches, thermostatic controls, auxiliaryswitches, and small contactors with nominal currents >20A (Table 2.24). Table 2.21: Physical Properties of Silver-Nickel (SINIDUR) Materials Table 2.22: Mechanical Properties of Silver-Nickel (SINIDUR) Materials Fig. 2.71:Strain hardeningof Ag/Ni 90/10 by cold working Fig. 2.72:Softening of Ag/Ni 90/10after annealingfor 1 hr after 80% cold working Fig. 2.73:Strain hardeningof Ag/Ni 80/20 by cold working Fig. 2.74:Softening of Ag/Ni 80/20after annealingfor 1 hr after 80% cold working Fig. 2.75: Micro structure of Ag/Ni 90/10 a) perpendicular to the extrusion directionb) parallel to the extrusion direction Fig. 2.76: Micro structure of Ag/Ni 80/20 a) perpendicular to the extrusion directionb) parallel t o the extrusion direction Table 2.23: Contact and Switching Properties of Silver-Nickel (SINIDUR) Materials Table 2.24: Application Examples and Forms of Supplyfor Silver-Nickel (SINIDUR) Materials ===2.4.3.2: Silver-Metal Oxide Materials Ag/CdO, Ag/SnO , Ag/ZnO===The family of silver-metal oxide contact materials includes the material groups:silver-cadmium oxide (DODURIT CdO), silver-tin oxide (SISTADOX), and silverzincoxide (DODURIT ZnO). Because of their very good contact and switchingproperties like high resistance against welding, low contact resistance, and higharc erosion resistance, silver-metal oxides have gained an outstanding positionin a broad field of applications. They mainly are used in low voltage electricalswitching devices like relays, installation and distribution switches, appliances,industrial controls, motor controls, and protective devices (Table 2.13). *Silver-cadmium oxide (DODURIT CdO) materials Silver-cadmium oxide (DODURIT CdO) materials with 10-15 wt% are producedby both, internal oxidation and powder metallurgical methods (Table 2.25). The manufacturing of strips and wires by internal oxidation starts with a moltenalloy of silver and cadmium. During a heat treatment below it's melting point in aoxygen rich atmosphere in such a homogeneous alloy the oxygen diffuses fromthe surface into the bulk of the material and oxidizes the Cd to CdO in a more orless fine particle precipitation inside the Ag matrix. The CdO particles are ratherfine in the surface area and are becoming larger further away towards the centerof the material (Fig. 2.83). During the manufacturing of Ag/CdO contact material by internal oxidation theprocesses vary depending on the type of semi-finished material.For Ag/CdO wires a complete oxidation of the AgCd wire is performed, followedby wire-drawing to the required diameter (Figs. 2.77 and 2.78). The resultingmaterial is used for example in the production of contact rivets. For Ag/CdO stripmaterials two processes are commonly used: Cladding of an AgCd alloy stripwith fine silver followed by complete oxidation results in a strip material with asmall depletion area in the center of it's thickness and a Ag backing suitable foreasy attachment by brazing (sometimes called “Conventional Ag/CdO”). Usinga technology that allows the partial oxidation of a dual-strip AgCd alloy materialin a higher pressure pure oxygen atmosphere yields a composite Ag/CdO stripmaterial that has besides a relatively fine CdO precipitation also a easily brazableAgCd alloy backing (Fig. 2.85). These materials (DODURIT CdO ZH) are mainlyused as the basis for contact profiles and contact tips. During powder metallurgical production the powder mixed made by differentprocesses are typically converted by pressing, sintering and extrusion to wiresand strips. The high degree of deformation during hot extrusion produces auniform and fine dispersion of CdO particles in the Ag matrix while at the sametime achieving a high density which is advantageous for good contact properties(Fig. 2.84). To obtain a backing suitable for brazing, a fine silver layer is appliedby either com-pound extrusion or hot cladding prior to or right after the extrusion(Fig. 2.86). For larger contact tips, and especially those with a rounded shape, the single tipPress-Sinter-Repress process (PSR) offers economical advantages. Thepowder mix is pressed in a die close to the final desired shape, the “green” tipsare sintered, and in most cases the repress process forms the final exact shapewhile at the same time increasing the contact density and hardness.

FigPure Gold is besides Platinum the chemically most stable of all precious metals. In its pure form, it is not very suitable for use as a contact material in electromechanical devices because of its tendency to stick and cold-weld at even low contact forces. 2In addition, it is not hard or strong enough to resist mechanical wear and exhibits high material losses under electrical arcing loads.77:Strain hardening This limits its use in form of internally oxidizedAg/CdO 90/10 by cold workingthin electroplated or vacuum deposited layers.

Fig. 2.78Main Article:Softening of internally oxidizedAg/CdO 90/10 after annealingfor 1 hr after 40% cold working[[Gold Based Materials| Gold Based Materials]]

Table 2.25: Physical and Mechanical Properties as well as Manufacturing Processes andForms of Supply of Extruded Silver Cadmium Oxide(DODURIT CdO) Contact ==Platinum Metal Based Materials==

FigThe platinum group metals include the elements Pt, Pd, Rh, Ru, Ir and Os ([[Platinum_Metal_Based_Materials|Table 1]]<!--(Table 2.6)-->). For electrical contacts, platinum and palladium have practical significance as base alloy materials and ruthenium and iridium are used as alloying components. Pt and Pd have similar corrosion resistance as gold but due to their catalytical properties, they tend to polymerize adsorbed organic vapors on contact surfaces. 2During frictional movement between contact surfaces, the polymerized compounds known as “brown powder” are formed, which can lead to a significant increase in contact resistance. Therefore Pt and Pd are typically used as alloys and are rather not used in their pure form for electrical contact applications.79:Strain hardening ofAg/CdO 90/10 P by cold working

Fig. 2.80Main Article: Softeningof Ag/CdO 90/10 P after annealingfor 1 hr after 40% cold working[[Platinum Metal Based Materials| Platinum Metal Based Materials]]

Fig. 2.82Main Article:Softening of Ag/CdO 88/12WP after annealingfor 1 hr after different degrees ofcold working[[Silver Based Materials| Silver Based Materials]]

Fig. 2.84Main Article: Micro structure of Ag/CdO 90/10 P:a) perpendicular to extrusion directionb) parallel to extrusion direction[[Tungsten and Molybdenum Based Materials| Tungsten and Molybdenum Based Materials]]

FigThe low gas content contact materials are developed for the use in vacuum switching devices. 2.86: Micro structure of AgCdO 88/12 WP: a) perpendicular to extrusion directionb) parallel to extrusion direction

*Silver–tin oxide(SISTADOX)materialsOver the past years, many Ag/CdO contact materials have been replaced byAg/SnO₂ based materials with 2-14 wt% SnO₂ because of the toxicity ofCadmium. This changeover was further favored by the fact that Ag/SnO₂contacts quite often show improved contact and switching properties such aslower arc erosion, higher weld resistance, and a significant lower tendencytowards material transfer in DC switching circuits ''(Table 2.30)''. Ag/SnO₂materials have been optimized Main Article: [[Contact Materials for a broad range of applications by other metaloxide additives and modification in the manufacturing processes that result indifferent metallurgical, physical and electrical properties ''(Table 2.29)''.Vacuum Switches| Contact Materials for Vacuum Switches]]

''Powder metallurgy'' plays a significant role in the manufacturing of Ag/SnO₂contact materialsVinaricky, E. Besides SnO₂ a smaller amount (<1 wt%Hrsg.) of one or more: Elektrische Kontakte, Werkstoffe und Anwendungen.other metal oxides such as WO₃Springer-Verlag, MoO₃Berlin, CuO and/or Bi₂O₃ are added. Theseadditives improve the wettability of the oxide particles and increase the viscosityof the Ag melt. They also provide additional benefits to the mechanical andarcing contact properties of materials in this group ''(Table 2.26)''Heidelberg etc.2002

In the manufacture the initial powder mixes different processes are appliedwhich provide specific advantages of the resulting materials in respect to theircontact properties ''(FigsLindmayer, M. 2.87 – 2.119)'': Schaltgeräte-Grundlagen, Aufbau, Wirkungsweise. Some of them are described here asfollows::'''a) Powder blending from single component powders''' <br> In this common process all components including additives that are part of the powder mix are blended as single powders. The blending is usually performed in the dry stage in blenders of different design.Springer-Verlag, Berlin, Heidelberg, New York, Tokio, 1987

Rau, G.:'''b) Powder blending on the basis of doped powders''' <br> For incorporation of additive oxides in the SnO₂ powder the reactive spray process (RSV) has shown advantages. This process starts with a waterbased solution of the tin and other metal compounds. This solution is nebulized under high pressure and temperature in a reactor chamber. Through the rapid evaporation of the water each small droplet is converted into a salt crystal and from there by oxidation into a tin oxide particle in which the additive metals are distributed evenly as oxides. The so created doped AgSnO2 powder is then mechanically mixed with silver powderMetallische Verbundwerkstoffe.WerkstofftechnischeVerlagsgesellschaft, Karlsruhe 1977

Schreiner, H.:'''c) Powder blending based on coated oxide powders''' <br> In this process tin oxide powder is blended with lower meting additive oxides such as for example Ag₂ MoO₄ and then heat treated. The SnO₂ particles are coated in this step with a thin layer of the additive oxidePulvermetallurgie elektrischer Kontakte.Springer-VerlagBerlin, Göttingen, Heidelberg, 1964

Hansen. M.; Anderko, K.:'''d) Powder blending based on internally oxidized alloy powders''' <br> A combination Constitution of powder metallurgy and internal oxidation this process starts with atomized Ag alloy powder which is subsequently oxidized in pure oxygen. During this process the Sn and other metal components are transformed to metal oxide and precipitated inside the silver matrix of each powder particleBinary Alloys.New York:Mc Graw-Hill, 1958

Shunk, F.A.:'''e) Powder blending based on chemically precipitated compound powders''' <br> A silver salt solution is added to a suspension Constitution of for example SnO₂ together with a precipitation agentBinary Alloy. 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 SnO₂Suppl.New York; Mc Graw-Hill, 1969

Further processing of these differently produced powders follows theconventional processes of pressingEdelmetall-Taschenbuch. ( Herausgeber Degussa AG, sintering and hot extrusion to wires andstripsFrankfurt a. From these contact parts such as contact rivets and tips aremanufacturedM. To obtain a brazable backing the same processes as used for),Ag/CdO are applied. As for Ag/CdOHeidelberg, larger contact tips can also bemanufactured more economically using the pressHüthig-sinter-repress (PSR) process''(Table 2.27).''Verlag, 1995

FigRau, G. 2: Elektrische Kontakte-Werkstoffe und Technologie.87:Eigenverlag G. RauStrain hardening ofAg/SnO₂ 92/8 PE by cold workingGmbH & Co., Pforzheim, 1984

FigHeraeus, W. 2C.88:Softening ofAg/SnO₂ 92/8 PE after annealingfor 1 hr after 40% cold workingWerkstoffdaten. Eigenverlag W.C. Heraeus, Hanau, 1978

Table 2Linde, J.O.26: Physical and Mechanical Properties as well as Manufacturing Processes andElektrische Widerstandseigenschaften der verdünnten LegierungenForms of Supply of Extruded Silver-Tin Oxide (SISTADOX) Contact Materialsdes Kupfers, Silbers und Goldes. Lund: Hakan Ohlsson, 1938

FigGroßmann, H. 2Saeger, K. E.; Vinaricky, E.90:Gold and Gold Alloys in ElectricalSoftening of Ag/SnO₂ 88/12 PEafter annealing forEngineering. in: Gold, Progress in Chemistry, Biochemistry and Technology. John1 hr after 40% cold workingWiley & Sons, Chichester etc, (1999) 199-236

FigGehlert, B. 2: Edelmetall-Legierungen für elektrische Kontakte.91:Strain hardening of oxidizedAg/SnO₂ 88/12 PW4 by cold workingMetall 61 (2007) H. 6, 374-379

FigAldinger, F. 2; Schnabl, R.92:Edelmetallarme Kontakte für kleine Ströme.Softening of Ag/SnO₂ 88/12 PW4 afterannealing for 1 hrafter 30% cold workingMetall 37 (1983) 23-29

FigBischoff, A. 2; Aldinger, F.93:Einfluss geringer Zusätze auf die mechanischenStrain hardening ofEigenschaften von Au-Ag/SnO₂ 98/2 PXby cold working-Pd-Legierungen. Metall 36 (1982) 752-765

FigWise, E. 2M.94: Palladium, Recovery, Properties and Uses. New York, London:Softening ofAg/SnO₂ 98/2 PXafter annealingfor 1 hr after 80%cold workingAcademic Press 1968

Fig 2Savitskii, E.M.; Polyakova, V.P.; Tylina, M.A.95:Palladium Alloys, Primary Sources.Strain hardeningof Ag/SnO₂ 92/8 PXby cold workingNew York: Publishers 1969

FigGehlert, B. 2.96:Lebensdaueruntersuchungen von Edelmetall Kontaktwerkstoff-Softening ofAg/SnO₂ 92/8 PXafter annealing for 1 hrafter 40% cold workingKombinationen für Schleifringübertrager. VDE-Fachbericht 61, (2005) 95-100

FigHolzapfel,C. 2.97:Verschweiß und elektrische Eigenschaften vonStrain hardening of internallyoxidizedAg/SnO₂ 88/12 TOS Fby cold workingSchleifringübertragern. VDE-Fachbericht 67 (2011) 111-120

FigSchnabl, R. 2; Gehlert, B.98:Lebensdauerprüfungen von Edelmetall-Softening ofAg/SnO₂ 88/12 TOS F afterannealing for 1 hr after 30%Schleifkontaktwerkstoffen für Gleichstrom Kleinmotoren.cold workingFeinwerktechnik & Messtechnik (1984) 8, 389-393

FigKobayashi, T. 2; Koibuchi, K.; Sawa, K.; Endo, K.; Hagino, H.99:A Study of LifetimeStrain hardening ofAu-plated Slip-Ring and AgPd Brush System for Power Supply.internally oxidizedAg/SnO₂ 88/12Pby cold workingth Proc. 24 Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 537-542

FigHarmsen, U. 2; Saeger K.E.100:Über das Entfestigungsverhalten von SilberSoftening ofAg/SnO₂ 88/12Pafter annealing for 1 hr after40% cold workingverschiedener Reinheiten. Metall 28 (1974) 683-686

FigBehrens, V. 2; Michal, R.; Minkenberg, J.N.; Saeger, K.E.101:Abbrand undStrain hardening ofKontaktwiderstandsverhalten von Kontaktwerkstoffen auf Basis von Silber-Ag/SnO_{Nickel. e.& i. 107. Jg. (1990), 2} 88/12 WPCby cold working, 72-77

FigBehrens, V. 2.102:Softening of AgSilber/SnO<sub>2<Nickel und Silber/sub> 88/12 WPC after annealingGrafit- zwei Spezialisten auf dem Gebietfor 1 hr after different degrees of cold workingder Kontaktwerkstoffe. Metall 61 (2007) H.6, 380-384

FigRieder, W. 2.103:Strain hardening ofAg/SnO₂ 86Silber /14 WPCMetalloxyd-Werkstoffe für elektrische Kontakte,by cold workingVDE - Fachbericht 42 (1991) 65-81

FigHarmsen,U. 2: Die innere Oxidation von AgCd-Legierungen unterSauerstoffdruck.104:Softening of Ag/SnO_{Metall 25 (1991), H.2} 86/14 WPC after annealingfor 1 hr after different degrees of cold working, 133-137

FigMuravjeva, E. 2M.; Povoloskaja, M.D.105:Verbundwerkstoffe Silber-Zinkoxid undStrain hardening ofAg/SnO₂ 88/12 WPDSilber-Zinnoxid, hergestellt durch Oxidationsglühen.by cold workingElektrotechnika 3 (1965) 37-39

FigBehrens, V. 2; Honig Th.; Kraus, A.; Michal, R.; Saeger, K.-E.; Schmidberger, R.;Staneff, Th.106:Softening of Ag/SnOEine neue Generation von AgSnO₂ 88/12 WPD afterannealing for 1 hr after different degrees-Kontaktwerkstoffen.of cold workingVDE-Fachbericht 44, (1993) 99-114

FigBraumann, P. 2; Lang, J.108:Softening of Kontaktverhalten von Ag/SnO₂ 88/12 WPX after-Metalloxiden für den Bereichannealing for 1 hr after different degreesof cold workinghoher Ströme. VDE-Fachbericht 42, (1991) 89-94

FigHauner, F. 2; Jeannot, D.; Mc Neilly, U.; Pinard, J.107:Advanced AgSnO Contact 2Strain hardening ofth Materials for High Current Contactors. Proc. 20 Int. Conf. on Electr. ContactAg/SnO₂ 88/12 WPXby cold workingPhenom., Stockholm 2000, 193-198

FigWintz, J. 2-L.; Hardy, S.; Bourda, C.109: Micro structure Influence on the Electrical Performances of Ag/SnOAssembly Process, Supports Materials and Production Means for AgSnO₂ 92.Proc.24<sub>th</8 PE: a) perpendicular to extrusion directionb) parallel to extrusion directionsub> Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 75-81

FigBehrens, V. 2; Honig, Th.; Kraus, A.; Michal, R.110: Micro structure of Ag/SnO₂ 88/12 PE: a) perpendicular to extrusion directionSchalteigenschaften vonverschiedenen Silber-Zinnoxidwerkstoffen in Kfz-Relais. VDE-Fachbericht 51b(1997) parallel to extrusion direction51-57

FigSchöpf, Th. 2.111: Micro structure of Ag/SnO₂ 88Silber/12 PW: a) perpendicular to extrusion directionZinnoxid und andere Silber-Metalloxidwerkstoffe inbNetzrelais. VDE-Fachbericht 51 (1997) parallel to extrusion direction41-50

FigSchöpf, Th. 2; Behrens, V.; Honig, Th.; Kraus, A.112: Micro structure Development of Ag/SnO₂ 98/2 PX: a) perpendicular to extrusion directionSilver Zincth Oxide for General-Purpose Relays. Proc. 20 Int. Conf. on Electr. Contacts,b) parallel to extrusion directionStockholm 2000, 187-192

FigBraumann, P. 2; Koffler, A.113: Micro structure of Einfluss von Herstellverfahren, Metalloxidgehalt undWirkzusätzen auf das Schaltverhalten von Ag/SnO_{in Relais. 2} 92/8 PX: a) perpendicular to extrusion directionbVDE-Fachbericht 59, (2003) parallel to extrusion direction133-142

FigKempf, B. 2; Braumann, P.; Böhm, C.; Fischer-Bühner, J.114: Micro structure of Ag/SnO₂ 88/12 TOS FSilber-Zinnoxid-Werkstoffe: aHerstellverfahren und Eigenschaften. Metall 61(2007) perpendicular to extrusion directionb) parallel to extrusion directionH. 6, 404-408

FigLutz, O. 2; Behrens, V.; Finkbeiner, M.; Honig, T.; Späth, D.115: Micro structure of Ag/SnO₂ 86/14 WPC: a) perpendicular to extrusion directionCdO-Ersatz inb) parallel to extrusion directionLichtschaltern. VDE-Fachbericht 61, 1(2005) AgSnO₂ contact layer, 2) Ag backing layer165-173

FigLutz, O.; Behrens, V.; Wasserbäch, W.; Franz, S.; Honig, Th.; Späth,D. 2; Heinrich, J.116: Micro structure of Ag/SnO₂ 92Improved Silver/8 WTOS F: a) perpendicular to extrusion directionTin Oxide Contact Materials for Automotiveb) parallel to extrusion directionth Applications. Proc.24 Int. Conf. on Electr. Contacts, Saint Malo,1) AgSnO₂ contact layerFrance 2008, 2) Ag backing layer88-93

FigLeung, C. 2; Behrens, V.117: Micro structure A Review ofAg/SnO_{Contact Materials and Arc Erosion. 2} 88/12 WPD: parallel to extrusion direction1) AgSnO₂ contact layerth Proc.24 Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 2) Ag backing layer82-87

FigChen, Z.K.; Witter, G. 2J.118: Micro structure ofComparison in Performance for Silver–Tin–IndiumAg/SnO₂ 88/12 WPX:parallel to extrusion directionOxide Materials Made by Internal Oxidation and Powder Metallurgy.1) AgSnO₂ contact layerth Proc. 55 IEEE Holm Conf. on Electrical Contacts, Vancouver, BC, Canada, 2(2009) Ag backing layer167 – 176

FigRoehberg, J.; Honig, Th. 2; Witulski, N.; Finkbeiner, M.; Behrens, V.119: Micro structure Performanceof AgDifferent Silver/SnO₂ 86/14 WPX: a) perpendicular to extrusion directionTin Oxide Contact Materials for Applications in Low Voltageth Circuit Breakers. Proc. 55 IEEE Holm Conf. on Electrical Contacts, Vancouver,b) parallel to extrusion directionBC, 1) AgSnO₂ contact layerCanada, 2(2009) Ag backing layer187 – 194

Table 2Muetzel, T.; Braumann, P.; Niederreuther, R.27: Physical Properties Temperature Rise Behavior of Powder Metallurgical Silver-Metal Oxide th Ag/SnO Contact Materialsfor Contactor Applications. Proc. 55 IEEE Holm 2with Fine Silver Backing Produced by the Press-Sinter-Repress ProcessConf. on Electrical Contacts, Vancouver, BC, Canada, (2009) 200 – 205

*'''Silver–zinc oxide (DODURIT ZnO) materials'''Silver zinc oxide (DODURIT ZnO) contact materials with mostly 6 - 10 wt% oxidecontent including other small metal oxides are produced exclusively by powdermetallurgy ''(FigsLutz, O. 2et al.120 : Silber/Zinnoxid – 2.125)'' ''(Table 2.28)''. Adding Ag₂WO₄ in the process b)Kontaktwerkstoffe auf Basis der Innerenas described in the preceding chapter on Ag/SnO₂ has proven most effectivefor applications in Oxidation fuer AC relays, wiring devices, and appliance controls. Just likewith the other Ag metal oxide materials, semi-finished materials in strip and wireform are used to manufacture contact tips and rivets– und DC – Anwendungen.Because of their high resistance against welding and arc erosion Ag/ZnOmaterials present an economic alternative to Cd free Ag-tin oxide contactmaterials ''VDE Fachbericht 65 (Tables 2.30 and 2.312009)''.167 – 176

Table 2Harmsen, U.; Meyer, C.L.28: Physical and Mechanical Properties as well as Manufacturing Processes andMechanische Eigenschaften stranggepresster Silber-Forms of Supply of Extruded SilverGraphit-Zinc Oxide Verbundwerkstoffe. Metall 21 (DODURIT ZnO1967) Contact, 731-733

FigBehrens, V. 2: Mahle, E.; Michal, R.; Saeger, K.E.120: Strain hardening ofAn Advanced Silver/GraphiteAg/ZnO 92/8 PW25 by cold workingth Contact Material Based on Graphite Fibre. Proc. 16 Int. Conf. on Electr.Contacts, Loghborough 1992, 185-189

FigSchröder, K. 2-H.; Schulz, E.-D.121: Softening of Ag/ZnO 92/8 PW25Über den Einfluss des Herstellungsverfahrensth auf das Schaltverhalten von Kontaktwerkstoffen der Energietechnik. Proc. 7 Int.after annealing for 1 hr after 30% cold workingConf. on Electr. Contacts, Paris 1974, 38-45

FigMützel, T. 2: Niederreuther, R.122: Strain hardening ofAg/ZnO 92/8 WPW25Kontaktwerkstoffe für Hochleistungsanwendungen.by cold workingVDE-Bericht 67 (2011) 103-110

FigLambert, C. 2; Cambon, G.123: Softening The Influence ofManufacturing Conditions andAg/ZnO 92/8 WPW25 after annealing forMetalurgical Characteristics on the Electrical Behaviour of Silver-Graphiteth Contact Materials. Proc. 9 Int. Conf.on Electr. Contacts,1hr after different degrees of cold workingChicago 1978, 401-406

FigVinaricky, E. 2.115: Micro structure of Grundsätzliche Untersuchungen zum Abbrand- undSchweißverhalten von Ag/ZnO 92/8 Pw25: aC-Kontaktwerkstoffen. VDE-Fachbericht 47 (1995) perpendicular to extrusion directionb) parallel to extrusion direction159-169

FigAgte, C. 2; Vacek, J.116: Micro structure of Ag/ZnO 92/8 WPW25Wolfram und Molybdän. Berlin:a) perpendicular to extrusion directionb) parallel to extrusion direction, 1) Ag/ZnO contact layer, 2) Ag backing layerAkademie-Verlag 1959

Table 2Keil, A.; Meyer, C.-L.29: Optimizing of Silver–Tin Oxide Materials Regarding their SwitchingDer Einfluß des Faserverlaufes auf die elektrischeProperties and Forming BehaviorVerschleißfestigkeit von Wolfram-Kontakten. ETZ 72, (1951) 343-346

Table 2Slade, P. G.30: Electric Contacts for Power Interruption. A Review. Proc. 19 Int.Conf. on Electric Contact and Switching Properties of Silver–Metal Oxide MaterialsPhenom. Nuremberg (Germany) 1998, 239-245

Table 2Slade, P. G.31: Application Examples of Silver–Metal Variations in Contact Resistance Resulting from Oxide MaterialsFormationand Decomposition in AgW and Ag-WC-C Contacts Passing Steady Currentsfor Long Time Periods. IEEE Trans. Components, Hybrids and Manuf. Technol.CHMT-9,1 (1986) 3-16

===2Slade, P.4G.3.3 Silver–Graphite (GRAPHOR)-Materials===Ag/C (GRAPHOR) contact materials are usually produced by powder metallurgywith graphite contents : Effect of 2 – 5 wt% ''(Table 2.32)''. The earlier typicalthe Electric Arc and the Ambient Air on the Contactmanufacturing process Resistance of single pressed tips by pressing Silver, Tungsten and Silver- sintering - repressingTungsten Contacts.J.Appl.Phys. 47, 8 (PSR1976) has been replaced in Europe for quite some time by extrusion. In NorthAmerica and some other regions however the PSR process is still used to someextend mainly for cost reasons.3438-3443

The extrusion Lindmayer, M.; Roth, M.: Contact Resistance and Arc-Erosion of sintered billets is now the dominant manufacturing method forW-Ag andsemiWC-finished AgC materials ''(FigsAg. 2IEEE Trans components, Hybrids and Manuf.126 – 2Technol.129)''. The hot extrusion processresults in a high density material with graphite particles stretched and oriented inthe extrusion direction ''(Figs. 2.130 – CHMT-2.133)''. Depending on the extrusionmethod in either rod or strip form the graphite particles can be oriented in thefinished contact tips perpendicular , 1 (GRAPHOR1979) or parallel (GRAPHOR D) to theswitching contact surface ''(Figs. 2.131 and 2.132)''.70-75

Since the graphite particles in the Leung, C.-H.; Kim, H.J.: A Comparison of Ag matrix of /W, Ag/WC and Ag/C materials prevent contactMo Electricaltips from directly being welded or brazedContacts. IEEE Trans. Components, Hybrids, Manuf. Technol., a graphite free bottom layer isrequiredVol. This is achieved by either burning out CHMT-7, 1 (de1984) 69-graphitizing) the graphiteselectively on one side of the tips or by compound extrusion of a Ag/C billetcovered with a fine silver shell.75

Ag/C contact materials exhibit Allen, S.E.; Streicher, E.: The Effect of Microstructure on the one hand an extremely high resistance toElectricalcontact welding but on the other have a low arc erosion resistanceth Performance of Ag-WC-C Contact Materials. Proc. This iscaused by the reaction of graphite with the oxygen in the surroundingatmosphere at the high temperatures created by the arcing44 IEEE Holm Conf. The weld resistanceis especially high for materials with the graphite particle orientation parallel to thearcing contact surfaceon Electr. Since the contact surface after arcing consists of puresilver the contact resistance stays consistently low during the electrical life of thecontact parts.Contacts, Arlington, VA, USA (1998), 276-285

A disadvantage of the Ag/C materials is their rather high erosion rateHaufe, W. In materialswith parallel graphite orientation this can be improved if part of the graphite isincorporated into the material in the form of fibers (GRAPHOR DF); Reichel, ''(FigW.; Schreiner H. 2: Abbrand verschiedener W/Cu-Sinter-Tränkwerkstoffe an Luft bei hohen Strömen.133)''Z.The weld resistance is determined by the total content of graphite particlesMetallkd.63 (1972) 651-654

Ag/C tips with vertical graphite particle orientation are produced in a specificsequence: Extrusion to rodsAlthaus, cutting of double thickness tipsB.; Vinaricky, burning out ofE.: Das Abbrandverhalten verschieden hergestelltergraphite to a controlled layer thickness, and a second cutting to single tipsWolfram-Kupfer-Verbundwerkstoffe im Hochstromlichtbogen.Such contact tips are especially well suited for applications which require both,a high weld resistance and a sufficiently high arc erosion resistance ''Metall 22 (Table 2.331968)''.For attachment of Ag/C tips welding and brazing techniques are applied.697-701

welding the actual process depends on the material's graphite orientationGessinger, G. ForAg/C tips with vertical graphite orientation the contacts are assembled withsingle tipsH. For parallel orientation a more economical attachment starting withcontact material in strip or profile tape form is used in integrated stamping andwelding operations with the tape fed into the weld station; Melton, cut off to tip form andthen welded to the carrier material before forming the final contact assemblypartK.N. For special low energy welding the Ag/C profile tapes GRAPHOR D and DFcan be pre: Burn-coated with a thin layer off Behaviour of high temperature brazing alloys such asWCu Contact Materials in anCuAgPElectric Arc. Powder Metall. Int.9 (1977) 67-72

In a rather limited wayMagnusson, Ag/C with 2 – 3 wt% graphite can be produced in wireM.: Abbrandverhalten und Rißbildung bei WCu-Tränkwerkstoffenform and headed into contact rivet shape with low head deformation ratiosunterschiedlicher Wolframteilchengröße.ETZ-A 98 (1977) 681-683

The main applications for Ag/C materials are protective switching devices suchas miniature molded case circuit breakersHeitzinger, F.; Kippenberg, motor-protective circuit breakersH.; Saeger,and fault current circuit breakersK.E.; Schröder, where during short circuit failures highestresistance against welding is required ''(Table 2K.34)''H. For higher currents the low: Contact Materials forarc erosion resistance of Ag/C is compensated by asymmetrical pairing withmore erosion resistant materials such as Ag/Ni and Ag/WVacuum Switching Devices. Proc.XVth ISDEIV, Darmstadt 1992, 273-278

FigGrill, R. 2; Müller, F.126:Verbundwerkstoffe auf Wolframbasis fürStrain hardeningof Ag/C 96/4 Dby cold workingHochspannungsschaltgeräte. Metall 61 (2007) H. 6, 390-393

FigSlade, P. 2: G.127:The Vacuum Interrupter- Theory; Design; and Application. CRCSoftening of Ag/C 96/4 D afterannealingPress, Boca Raton, FL (USA), 2008

FigFrey, P. 2; Klink, N.; Saeger, K.E.128: Strain hardeningUntersuchungen zum Abreißstromverhalten vonof Ag/C DF by cold workingKontaktwerkstoffen für Vakuumschütze. Metall 38 (1984) 647-651

FigFrey, P. 2; Klink, N.; Michal, R.; Saeger, K.E.129: SofteningMetallurgical Aspects of Contactof Ag/C DF after annealingMaterials for Vacuum Switching Devices. IEEE Trans. Plasma Sc. 17, (1989) 743-740

FigSlade, P.: Advances in Material Development for High Power Vacuum Interrupterth Contacts. Proc.16 Int. Conf. 2on Electr.130: Micro structure of Ag/C 97/3: a) perpendicular to extrusion directionContact Phenom.,b) parallel to extrusion directionLoughborough 1992, 1) Ag/C contact layer, 2) Ag backing layer-10

FigBehrens, V.; Honig, Th. 2; Kraus, A.; Allen, S.131: Micro structure Comparison of Ag/C 95/5: a) perpendicular to extrusion directionDifferent Contactth Materials for Low Voltage Vacuum Applications. Proc.19 Int. Conf. on Electr.b) parallel to extrusion directionContact Phenom., 1) Ag/C contact layerNuremberg 1998, 2) Ag backing layer247-251

FigRolle, S. 2; Lietz, A.132: Micro structure of Ag/C 96/4 ; Amft, D.; Hauner, F.: a) perpendicular to extrusion directionCuCr Contact Material for Low Voltageth Vacuum Contactors. Proc. 20 int. Conf. on Electr. Contact. Phenom. Stockholmb) parallel to extrusion direction, 1) Ag/C contact layer2000, 2) Ag backing layer179-186

FigKippenberg, H. 2.133: Micro structure of Ag/C DF: CrCu as a) perpendicular to extrusion directionContact Material for Vacuum Interrupters.b) parallel to extrusion direction, 1) Ag/C contact layerth Proc.13 Int. Conf. on Electr. Contact Phenom. Lausanne 1986, 2) Ag/Ni 90/10 backing layer140-144

Table 2Hauner, F.; Müller, R.; Tiefel, R.32: Physical Properties of Silver–Graphite CuCr für Vakuumschaltgeräte-Herstellungsverfahren, Eigenschaften und Anwendung.Metall 61 (GRAPHOR2007) Contact MaterialsH. 6, 385-389

Table 2.33: Contact and Switching properties of Silver–Graphite Manufacturing Equipment for Semi-Finished Materials(GRAPHORBild) Contact Materials

Table 2.34[[de: Application Examples and Forms of Supply of Silver–Graphite (GRAPHOR) Contact MaterialsKontaktwerkstoffe_für_die_Elektrotechnik]]