FERRITIC (FeCrAl) ALLOYS

Catégories: Matériaux chauffants , Matériaux de résistance

These alloys are known for their high electrical resistivity and exceptional resistance to hightemperature oxidation, making them ideal for use as electric heating elements and resistance materials in electronic equipment. Our range of FeCrAl alloys, branded as Kanthal®, can also be effectively utilized in non-electrical environments, such as ignitors or flame probes for gas burners.

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.CaptionComparison 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.
(element temperature in air)

°C
(°F)

1,425
(2,600)

1,400
(2,550)

1,300
(2,370)

1,300
(2,370)

1,100
(2,010)

Nominal composition (See Note), %

Cr
Al
Fe
Ni

22
5.8
balance
22
5.8
balance
22
5.3
balance
22
4.8
balance
15
4.3
balance
Density ρ

g/cm3
Ib/in3

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***
at 800°C
at 1,470°F
at 1,000°C
at 1,830°F
at 1,100°C
at 2,010°F
at 1,200°C
at 2,190°F

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®