What is Composition of Constantan – 45Ni-55Cu - Definition

Composition of Constantan – 45Ni-55Cu. Constantan consist usually from 55% copper and 45% nickel and specific minor amounts of additional elements.

Constantan is a copper–nickel alloy consisting usually of 55% copper and 45% nickel and specific minor amounts of additional elements to achieve precise (almost constant) values for the temperature coefficient of resistivity. That means, its main feature is the low thermal variation of its resistivity, which is constant over a wide range of temperatures. Other alloys with similarly low temperature coefficients are known, such as manganin.

This alloy has high electrical resistivity (4.9 x 10⁻⁷ Ω·m), high enough to achieve suitable resistance values in even very small grids, the lowest temperature coefficient of resistance, and the highest thermal EMF (also known as the Seebeck effect) against platinum of any of the copper-nickel alloys. Because of the first two of these properties, it is used for electrical resistors, and because of the latter property, for thermocouples. Thermocouples are electrical devices consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature.

For example, constantan is the negative element of the type J thermocouple with iron being the positive. The type J thermocouples are used in heat treating applications. Also, Constantan is the negative element of the type T thermocouple with copper the positive. These thermocouples are used at cryogenic temperatures.

In nuclear reactors, the thermocouples are positioned at preselected locations to measure fuel assembly coolant outlet temperature for use in monitoring the core radial power sharing and coolant. But in this case, thermocouples must withstand neutron irradiation, thus type E (chromel-alumel) or other special thermocouples are preferred.

References:

Materials Science:

U.S. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.
U.S. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 2 and 2. January 1993.
William D. Callister, David G. Rethwisch. Materials Science and Engineering: An Introduction 9th Edition, Wiley; 9 edition (December 4, 2013), ISBN-13: 978-1118324578.
Eberhart, Mark (2003). Why Things Break: Understanding the World by the Way It Comes Apart. Harmony. ISBN 978-1-4000-4760-4.
Gaskell, David R. (1995). Introduction to the Thermodynamics of Materials (4th ed.). Taylor and Francis Publishing. ISBN 978-1-56032-992-3.
González-Viñas, W. & Mancini, H.L. (2004). An Introduction to Materials Science. Princeton University Press. ISBN 978-0-691-07097-1.
Ashby, Michael; Hugh Shercliff; David Cebon (2007). Materials: engineering, science, processing and design (1st ed.). Butterworth-Heinemann. ISBN 978-0-7506-8391-3.
J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.

See above:
Nickel Alloys

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