Constantan – thermostable alloy based on copper (about 59%) and Nickel (39-41%) with the addition of manganese (1-2%).
Constantan (lat. constans – “constant”, “constant”) – thermostable alloy based on copper (Cu) (about 59%) and Nickel (Ni) (39-41%) with the addition of manganese (Mn) (1-2%).
Constantan is used as the heaters of electric furnaces with operating temperatures up to 400-500 °C, the electrodes thermocouples and extension wires, measuring instruments of high accuracy class, the active element of the strain gage resistors.
– has soft yellow-silver color
– melting point +1260 °C
– 8 800-8 density 900 kg/m3,
– high electrical resistivity, which is 0,45-0,52 μω*m,
– responds well to machining and welding and soldering,
– easily deformed,
– a high degree of plasticity,
– hardness 155 HB and HB 75-90 (after annealing),
– small temperature coefficient of electrical resistanceranging from -0,02·10-3 to +0.06·10-3 °C-1. Alloy practically does not change its electric resistance with temperature change,
– develops a high thermal electromotive force (thermal EMF) paired with some metals (e.g. copper and iron) and alloys (e.g., chromel). Heating of the alloy contacts in a closed circuit consisting of series-connected conductors of Constantan in a pair with the specified metals and alloysleads to the appearance in it of an electric current,
– temperature coefficient of linear expansion in the range of 20-100 °C, which is 14.4·10-6 °C-1 ,
– high corrosion resistance,
– after heat treatment the surface alloy is covered with a strong oxide film with excellent electrical insulation characteristics.