Content:
Types of Kanthal® alloys
Advantages of Kanthal® alloys
Physical and mechanical properties
Summary
Product varieties
Types of Kanthal® alloys
Kanthal® APM: Up to 1,425°C (2,600°F)
Kanthal® APM is an electric resistance material that can improve performance at high temperatures. It addresses issues like bunching, creeping, sagging and oxide spallation that conventional metallic elements often face. Additionally, it can be used to explore new applications where metallic elements are currently not utilized.
Advantages of Kanthal® APM:
Improved hot strength, providing:
- Better form stability of the heating element
- Reduced need for element support
- Minimal resistance change (aging)
- Extended element life
Excellent oxide, providing:
- Effective protection in most atmospheres
- Minimal scaling and impurities
- Extended element lifespan
Kanthal® A-1: Up to 1,400°C (2,550°F)
The alloy is known for its high resistivity and excellent oxidation resistance.
Kanthal® A-1 is a high-temperature alloy used in applications involving ceramics, glass, steel, and electronics.
Kanthal® AF: Up to 1,300°C (2,370°F)
This alloy grade has improved creep strength and oxidation properties.
It is especially recommended where good form stability properties are required, particularly at high temperatures.Comparison between Kanthal® APM (top) and conventional FeCrAl (bottom) after 1,250 hours at max 1,225°C element temperature.
Kanthal® D: Up to 1,300°C (2,370°F)
Employed mainly in home appliances and industrial furnaces.
Its high resistivity and low density, combined with better heat resistance than austenitic alloys, make it suitable for many applications.
Alkrothal®: Up to 1,100°C (2,010°F)
It is commonly specified for rheostats, braking resistors, etcetera.
It is also used as a heating wire for lower temperatures, such as heating cables.
Performance metrics of ferritic alloys
Creep rupture strength, sagging resistance, and elongation across Kanthal® APM and Kanthal® A-1 at high temperatures.
Creep rupture strengh for industrial wire 4 mm
Time, H | Temperature 1,000°C, MPA |
100 | 5.6 |
1,000 | 3.4 |
10,000 | 2.2 |
Time, H | Temperature 1,200°C, MPA |
100 | 3.3 |
1,000 | 1.6 |
10,000 | 0.7 |
Time, H | Temperature 1,400°C, MPA |
100 | 1.3 |
1,000 | 0.5 |
10,000 | 0.5 |
Elongation at 1,300°C element temperature
Sagging test diameter 9.5mm, 1,300°C and 1,400°C, 300 mm between supports
Advantages of Kanthal® alloys
Higher maximum operating temperature
Kanthal® A-1 can withstand temperatures up to 1,400°C (2,550°F) in air, compared to Nikrothal® 80, which can only handle up to 1,200°C (2,190°F).
Higher surface load capacity
Due to higher maximum temperature, Kanthal® alloys can endure higher surface loads.
Extended lifespan
Kanthal® elements offer 2–4 times the lifespan of Nikrothal® alloys when operated in the air at the same temperature.
Higher electrical resistivity
The greater resistivity of Kanthal® alloys allows for the use of materials with a larger cross-section, especially for thin wire applications. Additionally, Kanthal® alloys’ resistivity is less affected by cold-working and heat treatment than that of Nikrothal® alloys.
Higher yield strength
The higher yield strength of Kanthal® alloys results in less deformation during wire coiling.
Superior oxidation properties
The aluminum oxide (Al₂O₃) formed on Kanthal® alloys adheres better, is less contaminating, and serves as a more effective diffusion barrier and electrical insulator. It is also more resistant to carburizing atmospheres compared to the chromium oxide (Cr₂O₃) formed on Nikrothal® alloys.
Lower density
Kanthal® alloys have a lower density than Nikrothal® alloys, allowing them to produce more elements from the same weight of material.
Significant savings
The combination of lower density and higher resistivity means that less material is required to achieve the same power output when using Kanthal® alloys instead of Nikrothal®. When converting from Nikrothal® to Kanthal®, either the wire diameter can remain constant while adjusting the surface load, or the surface load can remain constant while changing the wire diameter. This flexibility often leads to substantial weight and cost savings in various applications.
Enhanced sulfur resistance
Kanthal® alloys demonstrate superior corrosion resistance in hot conditions when exposed to sulfuric compounds or sulfur-containing contaminants on the wire surface, whereas Nikrothal® alloys are highly susceptible to damage under these conditions.
Physical and mechanical properties
Kanthal® APM | Kanthal® A-1 | Kanthal® AF | Kanthal® D | Alkrothal® | ||
---|---|---|---|---|---|---|
Max continuous operating temp. |
°C |
1,425 |
1,400 |
1,300 |
1,300 |
1,100 |
Nominal composition (See Note), % |
Cr |
22 5.8 balance – |
22 5.8 balance – |
22 5.3 balance – |
22 4.8 balance – |
15 4.3 balance – |
Density ρ |
g/cm3 |
7.10 (0.256) |
7.10 (0.256) |
7.15 (0.258) |
7.25 (0.262) |
7.28 (0.263) |
Resistivity at 20°C at 68°F |
Ω mm2/m Ω/cmf |
1.45 (872) |
1.45 (872) |
1.39 (836) |
1.35 (812) |
1.25 (744) |
Temperature factor of the resistivity, Ct 250°C (480°F) 500°C (930°F) 800°C (1,470°F) 1,000°C (1,830°F) 1,200°C (2,190°F) |
1.00 1.01 1.03 1.04 1.05 |
1.00 1.01 1.03 1.04 1.04 |
1.01 1.03 1.05 1.06 1.06 |
1.01 1.03 1.06 1.07 1.08 |
1.02 1.05 1.10 1.11 – |
|
Linear thermal expansion coefficient α, × 10-6/K 20 – 100°C (68 – 210°F) 20 – 250°C (68 – 480°F) 20 – 500°C (68 – 930°F) 20 – 750°C (68 – 1,380°F) 20 – 1,000°C (68 – 1,840°F) |
– 11 12 14 15 |
– 11 12 14 15 |
– 11 12 14 15 |
– 11 12 14 15 |
– 11 12 14 15 |
|
Thermal conductivity λ at 50°C at 122°F |
W/m K (Btu in/ft2 h °F) |
11 (76) |
11 (76) |
11 (76) |
11 (76) |
16 (110) |
Specific heat capacity at 20°C at 68°F |
kJ/kg K (Btu/lb °F) |
0.46 (0.110) |
0.46 (0.110) |
0.46 (0.110) |
0.46 (0.110) |
0.46 (0.110) |
Melting point (approx.) | °C (°F) |
1,500 (2,730) |
1,500 (2,730) |
1,500 (2,730) |
1,500 (2,730) |
1,500 (2,730) |
Mechanical properties* (approx.) |
||||||
Tensile strength | N/mm2 (psi) |
680** (98,600**) |
680 (98,600) |
700 (101,500) |
670 (97,200) |
630 (91,400) |
Yield point | N/mm2 (psi) |
470** (68,200**) |
545 (79,000) |
500 (72,500) |
485 (70,300) |
455 (66,000) |
Hardness | Hv | 230 | 240 | 230 | 230 | 220 |
Elongation at rupture | % | 20** | 20 | 23 | 22 | 22 |
Tensile strength at 900°C | N/mm2 (psi) |
40 (5,800) |
34 (4,900) |
37 (5,400) |
34 (4,900) |
30 (4,300) |
Creep strength*** |
N/mm2 (psi) N/mm2 (psi) N/mm2 (psi) N/mm2 (psi) |
8.2 (1190) – – – – – – |
1.2 (170) 0.5 (70) – – – – |
– – – – 0.7 (100) 0.3 (40) |
1.2 (170) 0.5 (70) – – – – |
1.2 (170) 1 (140) – – – – |
Magnetic properties | 1) | 1) | 1) | 1) | 1) | |
Emissivity, fully oxidized condition | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 |
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 1,000 hours
1) Magnetic (Curie point approx. 600°C (1,100°F)) 2) Non-magnetic 3) Slightly magnetic
Summary
Kanthal® alloys are designed for high temperatures: for oxidation resistance and longevity.
Maximum operatin temperature per alloy
Resistivity vs. temperature
Product varieties
Kanthal® and Nikrothal® alloys are available in specialized forms such as wire, strips (0.10–3.5 mm thick, 4–195 mm wide), rods, and straightened wire. These versatile forms ensure adaptability for high-temperature and resistance needs.
Rod | Wire | Strip |
Straightned wire |
|
Kanthal® APM | • | • | • | • |
Kanthal® A-1 | • | • | • | • |
Kanthal® D | • | • | • | • |
Kanthal® AF | • | • | • | |
Alkrothal® | • | • | • | • |