Categories: Heating materials , Resistance materials

Nickel-iron (NiFe) alloys for up to 600°C (1110°F): Nifethal® 70 and Nifethal® 52 are alloys with low resistivity and high temperature coefficient of resistance. The positive temperature coefficient allows heating elements to reduce power as temperature increases. Typical applications are in low temperature tubular elements with self-regulating features.

Physical and mechanical properties

Nifethal®70 Nifethal®52
Max continuous operating temp. °C 600 600
(element temperature in air) °F 1110 1110
Nominal composition (See Note), % Cr
Al
Fe balance balance
Ni 72 52
Density ρ g/cm3 8.45 8.20
Ib/in3 0.305 0.296
Resistivity at 20°C Ω mm2/m 0.20 0.376
at 68°F Ω/cmf 120 220
Temperature factor of the resistivity, Ct
250°C (480°F) 2.19 1.93
500°C (930°F) 3.66 2.77
800°C (1470°F)
1000°C (1830°F)
1200°C (2190°F)
Linear thermal expansion coefficient α, × 10-6/K
20 – 100°C (68 – 210°F) 10
20 – 250°C (68 – 480°F)
20 – 500°C (68 – 930°F) 13
20 – 750°C (68 – 1380°F)
20 – 1000°C (68 – 1840°F) 15
Thermal conductivity λ at 50°C W/m K 17 17
at 122°F Btu in/ft2 h °F 120 120
Specific heat capacity at 20°C kJ/kg K 0.52 0.52
at 68°F Btu/lb °F 0.120 0.120
Melting point (approx.) °C 1430 1435
°F 2610 2620
Mechanical properties* (approx.)
Tensile strength N/mm2 640 610
psi 92800 88500
Yield point N/mm2 340 340
psi 49300 49300
Hardness Hv
Elongation at rupture % 30
Tensile strength at 900°C N/mm2
at 1650°F psi
Creep strength***
at 800°C N/mm2
at 1470°F psi
at 1000°C N/mm2
at 1830°F psi
at 1100°C N/mm2
at 2010°F psi
at 1200°C N/mm2
at 2190°F psi
Magnetic properties 4) 5)
Emissivity, fully oxidized condition 0.88 0.88

1) Magnetic (Curie point approx. 600°C (1100°F))

2) Non-magnetic

3) Slightly magnetic

4) Magnetic up to 610°C (1130°F) (Curie point)

5) Magnetic up to 530°C (990°F) (Curie point)

6) ± 10%