What is constantan an alloy of

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Constantan
composition53… 57% copper
43… 45% nickel
0.5 ... 1.2% manganese
<0.5% iron (remainder)
Specific electrical resistance

ρ = 4.9 · 10−7 Ω m (20 ° C)
ρ = 5.1 10−7 Ω m (600 ° C)

densityρ = 8.9 g cm−3
Specific heat capacity\ ({\ displaystyle c = 410 ~ {\ tfrac {\ rm {J}} {\ rm {kg \ cdot K}}}} \)
Resistance temperature coefficient\ ({\ displaystyle \ alpha = 0 {,} 00001 ~ {\ rm {K ^ {- 1}}}} \) (20 ° C)
Thermal conductivity\ ({\ displaystyle \ lambda = 23 ~ {\ tfrac {\ rm {W}} {\ rm {m \ cdot K}}}} \)
Electric conductivity\ ({\ displaystyle \ kappa = 2 ~ {\ tfrac {\ rm {m}} {\ Omega \ cdot {\ rm {mm ^ {2}}}}}} \)
Linear expansion coefficient\ ({\ displaystyle \ alpha = 13 {,} 5 \ cdot 10 ^ {- 6} \, {\ rm {K}} ^ {- 1}} \) (100 ° C)
\ ({\ displaystyle \ alpha = 14 \ cdot 10 ^ {- 6} \, {\ rm {K}} ^ {- 1}} \) (200 ° C)
\ ({\ displaystyle \ alpha = 14 {,} 5 \ cdot 10 ^ {- 6} \, {\ rm {K}} ^ {- 1}} \) (300 ° C)
\ ({\ displaystyle \ alpha = 15 \ cdot 10 ^ {- 6} \, {\ rm {K}} ^ {- 1}} \) (400 ° C)
\ ({\ displaystyle \ alpha = 16 \ cdot 10 ^ {- 6} \, {\ rm {K}} ^ {- 1}} \) (600 ° C)
modulus of elasticity\ ({\ displaystyle E = 180 \, {\ tfrac {\ rm {kN}} {\ rm {mm ^ {2}}}}} \)
Melting point1280 ° C
boiling pointapprox. 2400 ° C

Constantan is a brand name of VDM Metals (formerly ThyssenKrupp VDM GmbH[1]) for an alloy that generally consists of 55% copper, 44% nickel and 1% manganese. It is characterized by an approximately constant specific electrical resistance over a wide temperature range. Other alloys with similarly low (e.g. Manganin, CuMn12Ni) or even lower temperature coefficients such as Isaohm are known.

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The brand name


The brand name was registered with the German Patent and Trademark Office on December 14, 1952 and has since become common language as the name for this copper-nickel alloy. In the English-speaking world, the name is in the spelling Constantan protected. Another brand name for a very similar alloy is Isotane from the Isabellenhütte Heusler.

Background and usage


The rather low temperature dependence of the specific electrical resistance of constantan is almost exclusively due to the fact that this alloy has a high density of impurities within its crystal structure over a wide temperature range. This means that the density of the imperfections in this material also depends on the temperature and increases slowly with increasing temperature, but because of the large number of imperfections in the crystal structure, these mainly influence the electron scattering on them and not, for example, that also on the temperature dependent electron-electron or electron-phonon scattering. The Kanthal alloy has similar properties.

Because of the small temperature coefficient of the specific resistance, constantan is used for precision and measuring resistors. Sliding and heating resistors are also made from constantan.

Another numerical value


According to another source, constantan with 60% copper and 40% nickel has a linear expansion coefficient of \ ({\ displaystyle \ alpha = 12.22 \ cdot 10 ^ {- 6} \ over the temperature range −161 ° C to +16 ° C , {\ rm {K}} ^ {- 1}} \) [2].

Constantan has an unobtrusive coefficient of expansion, similar to that of some other metals, such as nickel, iron and steel. There are pure metals with only about half (e.g. tantalum) and special alloys with only less than one twentieth the thermal expansion of constantan, such as Invar.

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  1. ↑ https: //www.vdm-metals.com/de/unternehmen/ueber-vdm-metals/historie/
  2. ↑ Hübschmann / Links: Tables for Chemistry, Verlag Handwerk und Technik GmbH, Hamburg, 1991, ISBN 3-582-01234-4, p. 35: Coefficients of expansion of metal alloys (materials), glasses and inorganic chemicals.

Web links


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Categories:Electrotechnical material | Copper alloy | Electric heat | nickel




Status of information: 02/23/2021 4:04:49 AM CET

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