Content:
Nikrothal® advantages
Physical and mechanical properties
Kanthal® resistance heating alloys - summary
NICKEL-IRON ALLOYS (NiFe)
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.
AUSTENITIC ALLOYS (NiCr, NiCrFe)
Up to 1200°C (2190°F): Nikrothal® 80 is the austenitic alloy with the highest nickel content. Because of its good workability and high-temperature strength, Nikrothal® 80 is widely used for demanding applications in the electric appliance industry.
Up to 1200°C (2190°F): Nikrothal® TE has been developed for use in metal sheathed tubular elements operating at red hot temperatures. Suitable electrical properties and a relatively low nickel content makes Nikrothal® TE an attractive alternative to alloys of higher nickel content, such as Nikrothal® 80.
Up to 1250°C (2280°F): Nikrothal® 70 is normally used in furnace applications.
Up to 1150°C (2100°F): Nikrothal® 60 has good corrosion resistance, good oxidation properties and very good form stability. The corrosion resistance is good except in sulfur containing atmospheres. Typical applications for Nikrothal® 60 are in tubular heating elements and as suspended coils.
Up to 1100 °C (2010°F): Nikrothal® 40 is used as electric heating element material in domestic appliances and other electric heating equipment.
Up to 1050°C (1920°F): Nikrothal® 20 will be produced on volume based request.
NIKROTHAL® ADVANTAGES
Higher hot and creep strength
Nikrothal® alloys have higher hot and creep strength than Kanthal® alloys. Kanthal® APM, Kanthal® AF and Kanthal® AE are better in this respect than the other Kanthal® grades and have a very good form stability, however, not as good as that of Nikrothal®.
Better ductility after use
Nikrothal® alloys remain ductile after long use.
Higher emissivity
Fully oxidized Nikrothal® alloys have a higher emissivity than Kanthal® alloys. Thus, at the same surface load the element temperature of Nikrothal® is somewhat lower.
Non-magnetic
In certain low-temperature applications a non-magnetic material is preferred. Nikrothal® alloys are non-magnetic (except Nikrothal® 60 at low temperatures). Kanthal® alloys are non-magnetic above 600°C (1100°F).
Better wet corrosion resistance
Nikrothal® alloys generally have better corrosion resistance at room temperature than non-oxidized Kanthal® alloys. (Exceptions: atmospheres containing sulphur and certain controlled atmospheres).
Physical and mechanical properties
| Nikrothal® 80 | Nikrothal® TE | Nikrothal® 70 | Nikrothal® 60 | Nikrothal® 40 | Nikrothal® 20 | ||
|---|---|---|---|---|---|---|---|
| Max continuous operating temp. | °C | 1200 | 1200 | 1250 | 1150 | 1100 | 1050 |
| (element temperature in air) | °F | 2190 | 2190 | 2280 | 2100 | 2010 | 1920 |
| Nominal composition (See Note), % | Cr | 20 | 22 | 30 | 16 | 20 | 24 |
| Al | – | – | – | – | – | – | |
| Fe | – | 9 | – | balance | balance | balance | |
| Ni | 80 | balance | 70 | 60 | 35 | 20 | |
| Density ρ | g/cm3 | 8.30 | 8.10 | 8.10 | 8.20 | 7.90 | 7.80 |
| Ib/in3 | 0.300 | 0.293 | 0.293 | 0.296 | 0.285 | 0.281 | |
| Resistivity at 20°C | Ω mm2/m | 1.09 | 1.19 | 1.18 | 1.11 | 1.04 | 0.95 |
| at 68°F | Ω/cmf | 655 | 716 | 709 | 668 | 626 | 572 |
| Temperature factor of the resistivity, Ct | |||||||
| 250°C (480°F) | 1.02 | 1.04 | 1.02 | 1.04 | 1.08 | 1.12 | |
| 500°C (930°F) | 1.05 | 1.06 | 1.05 | 1.08 | 1.15 | 1.21 | |
| 800°C (1470°F) | 1.04 | 1.06 | 1.04 | 1.10 | 1.21 | 1.28 | |
| 1000°C (1830°F) | 1.05 | 1.07 | 1.05 | 1.11 | 1.23 | 1.32 | |
| 1200°C (2190°F) | 1.07 | 1.07 | 1.06 | – | – | – | |
| Linear thermal expansion coefficient α, × 10-6/K | |||||||
| 20 – 100°C (68 – 210°F) | – | – | – | – | – | – | |
| 20 – 250°C (68 – 480°F) | 15 | 14 | 14 | 16 | 16 | 16 | |
| 20 – 500°C (68 – 930°F) | 16 | 15 | 15 | 17 | 17 | 17 | |
| 20 – 750°C (68 – 1380°F) | 17 | 16 | 16 | 18 | 18 | 18 | |
| 20 – 1000°C (68 – 1840°F) | 18 | 17 | 17 | 18 | 19 | 19 | |
| Thermal conductivity λ at 50°C | W/m K | 15 | 14 | 14 | 14 | 13 | 13 |
| at 122°F | Btu in/ft2 h °F | 104 | 97 | 97 | 97 | 90 | 90 |
| Specific heat capacity at 20°C | kJ/kg K | 0.46 | 0.46 | 0.46 | 0.46 | 0.50 | 0.50 |
| at 68°F | Btu/lb °F | 0.110 | 0.110 | 0.110 | 0.110 | 0.119 | 0.119 |
| Melting point (approx.) | °C | 1400 | 1380 | 1380 | 1390 | 1390 | 1380 |
| °F | 2550 | 2515 | 2515 | 2535 | 2535 | 2515 | |
| Mechanical properties* (approx.) | |||||||
| Tensile strength | N/mm2 | 810 | 800 | 820 | 730 | 675 | 675 |
| psi | 117500 | 116000 | 118900 | 105900 | 97900 | 97500 | |
| Yield point | N/mm2 | 420 | 390 | 430 | 370 | 340 | 335 |
| psi | 60900 | 56600 | 62400 | 53700 | 49300 | 48600 | |
| Hardness | Hv | 180 | 190 | 185 | 180 | 180 | 160 |
| Elongation at rupture | % | 30 | 30 | 30 | 35 | 35 | 30 |
| Tensile strength at 900°C | N/mm2 | 100 | – | 120 | 100 | 120 | 120 |
| at 1650°F | psi | 14500 | – | 17400 | 14500 | 17400 | 17400 |
| Creep strength*** | |||||||
| at 800°C | N/mm2 | 15 | 15 | – | 15 | 20 | 20 |
| at 1470°F | psi | 2160 | 2160 | – | 2160 | 2900 | 2900 |
| at 1000°C | N/mm2 | 4 | 4 | – | 4 | 4 | 4 |
| at 1830°F | psi | 560 | 560 | – | 560 | 560 | 560 |
| at 1100°C | N/mm2 | – | – | – | – | – | – |
| at 2010°F | psi | – | – | – | – | – | – |
| at 1200°C | N/mm2 | – | – | – | – | – | – |
| at 2190°F | psi | – | – | – | – | – | – |
| Magnetic properties | 2) | 2) | 2) | 3) | 2) | 2) | |
| Emissivity, fully oxidized condition | 0.88 | 0.88 | 0.88 | 0.88 | 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%
Note: Composition listed is nominal. Actual composition may vary to meet standard electrical resistance and dimensional tolerances.
* The values given apply for sizes of approx. 1.0 mm diameter (0.039 in)
** 4.0 mm (0.157 in) Thinner gauges have higher strength and hardness values while the corresponding values are lower for thicker gauge
*** Calculated from observed elongation in a Kanthal standard furnace test. 1% elongation after 1000 hours
**** Composition listed is nominal. Actual composition may vary to meet standard electrical resistance and dimensional tolerances.
Kanthal® resistance heating alloys – summary
Resistivity vs. temperature
