Cuprothal® 49 has a number of special characteristics – some electrical, some mechanical – which make it a remarkably versatile alloy. For certain applications, its high specific resistance and negligible temperature coefficient of resistance are the most important attributes. For others, the fact that Cuprothal® 49 offers good ductility, is easily soldered and welded and has good resistance to atmospheric corrosion is more significant.
Although the range of applications of Cuprothal® 49 is so wide, its normally fall into four principal categories:
- An ideal alloy for winding heavy-duty industrial rheostats and electric motor starter resistance. High specific resistance, together with good ductility and resistance to corrosion are all important requirements in this category, and Cuprothal® 49 satisfies the most demanding specifications.
- Cuprothal® 49 is widely used in wire-wound precision resistors, temperature-stable potentiometers, volume control devices and strain gauges. In the resistor field, its high resistance and negligible temperature coefficient of resistance are main attractions.
- The third main category of application exploits another characteristic of Cuprothal® 49. This is the fact that it develops a high thermal EMF (electromotive force) against certain other metals.
- Low temperature resistance heating applications, such as heating cables.
Copper-nickel alloys with medium and low resistivity
Kanthal produces copper-nickel alloys with resistivity lower than those of Cuprothal 49. The main applications are in high current electrical resistances, fittings, heating cables, electric blankets, fuses, resistors but they are also used in many other applications.
Resistivity 30 μΩcm (180 Ω/cmf)
Resistivity 15 μΩcm (90 Ω/cmf)
Resistivity 10 μΩcm (60 Ω/cmf)
Resistivity 5 μΩcm (30 Ω/cmf)
|Nominal composition, %||Ni||44||21||11||6||2|
|Resistivity at 20°C||Ω mm2/m||0.49||0.30||0.15||0.10||0.05|
|Temperature factor of the resistivity, Ct|
|-55 – 150°C -67 – 300°F||±20 /±60|
|20 – 105°C (68 – 220°F)||250||400||700||1300|
|Temperature range||°C||-55 – 150||20 – 105||20 – 105||20 – 105||20 – 105|
|°F||-67 – 300||68 – 220||68 – 220||68 – 220||68 – 220|
|Linear thermal expansion coefficient α, × 10-6/K||14||16||16||16||16.5|
|20 – 100°C (68 – 210°F)|
|Thermal conductivity λ at 50°C||W/m K||21||35||60||90||130|
|at 122°F||Btu in/ft2 h °F||146||243||460||624||901|
|Specific heat capacity at 20°C||kJ/kg K||0.41||0.37||0.38||0.38||0.38|
|at 68°F||Btu/lb °F||0.098||0.088||0.091||0.091||0.091|
|Melting point (approx.)||°C||1280||1150||1100||1095||1090|
|Mechanical properties* (approx.)|
|Tensile strength, min||N/mm2||420||340||250||230||220|
|Tensile strength, max||N/mm2||690||690||540||680||440|
|Elongation at rupture||%||30||30||30||30||30|