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Main Articel: [[Naturally Hard Copper Alloys| Naturally Hard Copper Alloys]]
===<!--5.1.5 -->Other Naturally Hard Copper Alloys===
Main Articel: [[Other Naturally Hard Copper Alloys| Other Naturally Hard Copper Alloys]]
===<!--5.1.6 -->Precipitation Hardening Copper Alloys===
Besides the naturally hard copper materials precipitation hardening copper alloys play also an important role as carrier materials for electrical contacts. By means of a suitable heat treatment finely dispersed precipitations of a second phase can be achieved which increase the mechanical strength of these copper alloys significantly.
Main Articel: [[Precipitation Hardening Copper Alloys| Precipitation Hardening Copper Alloys]]
===<!--5.1.7 -->Application Properties for the Selection of Copper Alloys===
Important for the usage as spring contact components are besides mechanical strength and electrical conductivity mainly the typical spring properties such as the maximum spring bending limit and the fatigue strength as well as the bendability. During severe thermal stressing the behavior of spring materials is determined by their softening and relaxation. The following briefly describes these material properties.
Main Articel: [[Application Properties for the Selection of Copper Alloys| Application Properties for the Selection of Copper Alloys]]
===<!--5.1.8 -->Selection Criteria for Copper-Based Materials===
The selection of copper-based materials from the broad spectrum of available materials must be based on the requirements of the application. First an application profile should be established which can be used to define the material properties. Usually there is however no single material that can fulfill all requirements to the same degree. A compromise must be found as for example between electrical conductivity and spring properties.
The increasing requirements on spring components in connectors, especially for use in automotive applications, such as higher surrounding temperatures, increased reliability, and the trend towards miniaturization led to a change of materials from traditionally CuZn30 and CuSn4 to CuNiSi alloys, for example. These CuNiSi alloys and the newer heavy duty copper alloys like CuNi1Co1 are significantly improved with regards to mechanical strength, relaxation behavior, and electrical conductivity.
==<!--5.2 -->Nickel and Nickel Alloys==
===<!--5.2.1 -->Technical Grade Pure Nickel===
Technical grade pure nickel commonly contains 99.0 to 99.8 wt% Ni and up to 1 wt% Co. Other ingredients are iron and manganese <xr id="tab:Physical Properties of Nickel and Nickel Alloys"/> <!--(Tab. 5.21) --> and <xr id="tab:Mechanical Properties of Nickel and Nickel Alloys"/> <!--(Tab. 5.22)-->. Work hardening and softening behavior of nickel are shown in [[#figures11|(Figs. 5 – 6)]] <!--Figs. 5.45 and 5.46-->.
One of the significant properties of nickel is its modulus of elasticity which is almost twice as high as that of copper. At temperatures up to 345°C nickel is ferro-magnetic.
<div id="figures11">
<xr id="fig:Strain hardening of technical pure nickel by cold working"/> <!--Fig. 5.45: --> Strain hardening of technical pure nickel by cold working
<xr id="fig:Softening of technical grad nickel after annealing for 3 hrs"/> <!--Fig. 5.46; --> Softening of technical grad nickel after annealing for 3 hrs after 50% cold working
</div>
<div class="clear"></div>
===<!--5.2.2 -->Nickel Alloys===
Because of its low electrical conductivity NiCu30Fe is besides pure Ni and CuNi alloys the most widely used backing material for weldable contact components. With 1 – 2 wt% additives of Fe as well as 0.5 – 1 wt% Mn and Co the mechanical strength of the binary alloy NiCu30 can be increased.
The strength values of NiCu30Fe are significantly higher than those of the copper rich CuNi alloys [[#figures12|(Figs. 7 – 8)]] <!--(Figs. 5.47 and 5.48)-->. The good spring properties and thermal stability of NiCu30Fe make it a suitable material for the use as thermally stressed contact springs.
<div id="figures12">
<xr id="fig:Strain hardening of NiCu30Fe by cold working"/> <!--Fig. 5.47: --> Strain hardening of NiCu30Fe by cold working
<xr id="fig:Softening of NiCu30Fe after annealing for 0.5 hrs"/> <!--Fig. 5.48: --> Softening of NiCu30Fe after annealing for 0.5 hrs and after 80% cold working
</div>
</div>
<div class="clear"></div>
<figtable id="tab:Physical Properties of Nickel and Nickel Alloys">
<caption>'''<!--Table 5.21: -->Physical Properties of Nickel and Nickel Alloys'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
<figtable id="tab:Mechanical Properties of Nickel and Nickel Alloys">
<caption>'''<!--Table 5.22: -->Mechanical Properties of Nickel and Nickel Alloys'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
<sup>c</sup>solution annealed, cold rolled, and precipitation hardened at mill (mill hardened)
===<!--5.2.3 -->Nickel-Beryllium Alloys===
Because of decreasing solubility of beryllium in nickel with decreasing temperature NiBe can be precipitation hardened similar to CuBe <xr id="fig:Phase diagram of nickel beryllium"/> <!--(Fig. 5.49)-->. The maximum soluble amount of Be in Ni is 2.7 wt% at the eutectic temperature of 1150°C. to achieve a high hardness by precipitation hardening NiBe, similar to CuBe, is annealed at 970 - 1030°C and rapidly quenched to room temperature. Soft annealed material is easily cold formed and after stamping and forming an hardening anneal is performed at 480 to 500°C for 1 to 2 hours.
<figure id="fig:Phase diagram of nickel beryllium">
</figure>
Commercial nickel-beryllium alloys contain 2 wt% Be. Compared to CuBe2 the NiBe2 materials have a significantly higher modulus of elasticity but a much lower electrical conductivity. The mechanical strength is higher than that of CuBe2 <xr id="fig:Precipitation hardening of NiBe2 soft at 480C"/> <!--(Fig. 5.50)-->, the spring bending force limit can exceed values of over 1400 MPa and the fatigue strength reaches approximately 400 MPa.
<figure id="fig:Precipitation hardening of NiBe2 soft at 480C">
Nickel-beryllium alloys are recommended for mechanically and thermally highly stressed spring components. For some applications their ferro-magnetic properties can also be advantageous.
==<!--5.3 -->Triple-Layer Carrier Materials==
Manufacturing of triple-layer carrier materials is usually performed by cold rollcladding. The three materials cover each other completely. The advantage of this composite material group is that the different mechanical and physical properties of the individual components can be combined with each other.
The thickness ratios of the components can be selected according to the application requirements. The two outer layers usually have the same thickness.
==<!--5.4 -->Thermostatic Bimetals==
Thermostatic bimetals are composite materials consisting of two or three layers of materials with different coefficients of thermal expansion. They are usually bonded together by cladding. If such a material part is heated either directly through current flow or indirectly through heat conduction or radiation, the different expansion between the active (strong expansion) and passive (low expansion) layer causes bending of the component part.
*'''Stamped and formed parts''' for special designs and applications
The wide variety of thermostatic bimetal types is specified mostly through DIN 1715 and/or applicable ASTM standards <xr id="tab:Partial Selection from the Wide Range of Available Thermo-Bimetals"/> <!--(Table 5.23)-->. The different types have varying material compositions for the active and passive side of the materials. The mostly used alloys are iron-nickel and manganese-copper-nickel. Mainly used in circuit protection switches (i.e. circuit breakers) some thermo-bimetals include an intermediate layer of copper or nickel which allows to design parts with a closely controlled electrical resistance.
<figtable id="tab:Partial Selection from the Wide Range of Available Thermo-Bimetals">
<caption>'''<!--Table 5.23: -->Partial Selection from the Wide Range of Available Thermo-Bimetals'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
</figtable>
===<!--5.4.1 -->Design Formulas=== For the design and calculation of the most important thermostatic-bimetal parts formulas are given in <xr id="tab:Design Formulas for Thermostatic Bimetal Components"/><!--Table 5.24-->. The necessary properties can be extracted for the most common materials from <xr id="tab:Partial Selection from the Wide Range of Available Thermo-Bimetals"/><!--Table 5.23-->. The values given are valid only for a temperature range up to approximately 150°C. For higher temperatures data can be obtained from the materials manufacturer.
<figtable id="tab:Design Formulas for Thermostatic Bimetal Components">
<caption>'''<!--Table 5.24: -->Design Formulas for Thermostatic Bimetal Components'''</caption>
{| class="twocolortable" style="font-size:1em;"
|}
===<!--5.4.2 -->Stress Force Limitations===
For all calculations according to the formulas in <xr id="tab:Design Formulas for Thermostatic Bimetal Components"/> <!--Table 5.24 --> one should check if the thermally or mechanically induced stress forces stay below the allowed bending force limit. The following formulas are applicable for calculating the allowable load (Force P<sub>max</sub> or momentum M<sub>max</sub>):
Kreye, H.; Nöcker, H.; Terlinde, G.: Schrumpfung und Verzug beim Aushärten von Kupfer-Beryllium-Legierungen. Metall 29 (1975) 1118-1121
[[de:Trägerwerkstoffe]]
