Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for materials under the trademark Kanthal®.
Kanthal® APM Tubes are an advanced powder metallurgical, dispersion strengthened, ferritic iron-chromium-aluminium alloy (FeCrAl alloy) for use at tube temperatures up to 1250°C (2280°F).
Kanthal® APM tubes have good form stability at high temperature. Kanthal APM forms an excellent, non-scaling surface oxide, which gives good protection in most furnace environments, i.e. oxidizing, sulphurous and carburizing, as well as against deposits of carbon, ash, etc. The combination of excellent oxidation properties and form stability makes the alloy unique.
Typical applications for Kanthal® APM are as radiant tubes in electrically or gas fired furnaces such as continuous galvanizing furnaces, seal quench furnaces, holding furnaces and dosing furnaces in the aluminium, zinc, lead industries, thermocouple protection tubes, furnace muffles for sintering applications.
C %
Si %
Mn %
Cr %
Al %
Fe %
Nominal composition
5.8
Bal.
Min
-
-
-
20.5
-
Max
0.08
0.7
0.4
23.5
-
Yield strength
Tensile strength
Elongation
Hardness
Rp0.2
Rm
A
MPa (ksi)
MPa (ksi)
%
Hv
450 (65)
670 (97)
27
225
Remark: The samples are taken in the longitudinal direction.
Mechanical properties at elevated temperature
Creep data from tests on tube in delivery state with load applied in the longitudinal direction. Typical initial average grain size is 30-50μm.
Creep strength
Temperature °C
900
1000
1100
1200
Temperature °F
1652
1832
2012
2192
MPa
5.9
2.0
0.7
0.3
psi
860
290
100
44
1% elongation in 1000 h
Secondary creep rate at various stress levels
Creep rate
Temperature / Stress
900°C (1652°F)
1000°C (1832°F)
1100°C (2012°F)
1200°C (2192°F)
s-1
MPa (psi)
MPa (psi)
MPa (psi)
MPa (psi)
1.0e-10
4.0 (580)
1.5 (220)
0.9 (130)
0.7 (100)
1.0e-8
6.8 (990)
3.1 (220)
1.1 (160)
0.8 (120)
1.0e-6
11.0 (1600)
6.7 (450)
3.1 (450)
1.9 (280)
1.0e-4
20.0 (2900)
13.0 (1900)
11.0 (1600)
6.0 (870)
Creep rupture strength
Time
Temperature / Stress
900°C (1652°F)
1000°C (1832°F)
1100°C (2012°F)
1200°C (2192°F)
h
MPa (psi)
MPa (psi)
MPa (psi)
MPa (psi)
100
10.0 (1500)
5.2 (750)
3.0 (440)
2.0 (290)
1000
7.0 (1000)
3.4 (490)
1.7 (250)
1.0 (150)
10000
4.5 (650)
2.1 (300)
0.9 (130)
0.5 (73)
Maximum recommended unsupported length for Kanthal APM tube
Distance between supports m (in)
Tube Ø mm (Tube Ø in)
Tube Ø mm (Tube Ø in)
Tube Ø mm (Tube Ø in)
Tube Ø mm (Tube Ø in)
Tube Ø mm (Tube Ø in)
Tube Ø mm (Tube Ø in)
100/90 (3.94/3.54)
128/117 (5.04/4.61)
146/134 (7.75/5.28)
154/142 (6.06/5.59)
178/162 (7.01/6.38)
198/182 (7.80/7.17)
800
2.2 (86.6)
2.5 (98.4)
2.5 (98.4)
2.5 (98.4)
2.5 (98.4)
2.5 (98.4)
900
2.2 (86.6)
2.3 (90.6)
2.5 (98.4)
2.5 (98.4)
2.5 (98.4)
2.5 (98.4)
1000
2.0 (78.7)
2.2 (86.6)
2.5 (98.4)
2.5 (98.4)
2.5 (98.4)
2.5 (98.4)
1100
1.5 (59.1)
1.8 (70.9)
2.2 (86.6)
2.2 (86.6)
2.3 (90.6)
2.3 (90.6)
1200
1.2 (47.2)
1.4 (55.1)
1.5 (59.1)
1.5 (59.1)
1.6 (63.0)
1.7 (66.9)
If the Kanthal APM is equipped with electrical resistance elements, the distance between the supports must be shortened.
Density g/cm3 (lb/in3)
7.10 (0.257)
Electrical resistivity at 20°C Ω mm2/m (Ω circ. mil/ft)
1.45 (872)
Poisson's ratio
0.30
Young's modulus
Temperature °C
20
100
200
400
600
800
1000
Temperature °F
68
212
392
752
1112
1472
1832
GPa
220
210
205
190
170
150
130
Msi
32
30
30
28
25
22
19
Temperature factor of resistivity
Temp. °C
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
Temp. °F
212
392
572
752
932
1112
1292
1472
1652
1832
2012
2192
2372
2552
Ct
1.00
1.00
1.00
1.00
1.01
1.02
1.02
1.03
1.03
1.04
1.04
1.04
1.04
1.05
Coefficient of thermal expansion
Temperature °C (°F)
Thermal Expansion x 10-6/K (10-6 /°F)
20 - 250 (68-482)
11 (6.1)
20 - 500 (68-932)
12 (6.7)
20 - 750 (68-1382)
14 (7.8)
20 - 1000 (68-1832)
15 (8.3)
20 - 1200 (68-2192)
16 (8.9)
20 - 1400 (68-2552)
16 (8.9)
Thermal conductivity
Temperature °C
50
600
800
1000
1200
1400
Temperature °F
122
1112
1472
1832
2192
2552
W m-1 K-1
11
20
22
26
27
35
Btu h-1ft-1°F-1
6.4
11.6
12.7
15.0
15.6
20.2
Specific heat capacity
Temperature °C
20
200
400
600
800
1000
1200
1400
Temperature °F
68
392
752
1112
1472
1832
2192
2552
kJ kg-1 K-1
0.46
0.56
0.63
0.75
0.71
0.72
0.74
0.80
Btu lb-1 °F-1
0.11
0.13
0.15
0.18
0.17
0.17
0.18
0.19
Melting point °C (°F)
1500 (2732)
Max continuous operating temperature in air °C (°F)
1250 (2282)
Magnetic properties
The material is magnetic up to approximately 600°C (1112°F) (Curie point).
Emissivity - fully oxidized material
0.70
Welding of Kanthal APM tube to NiCr(Fe)
Pre-heat the tube to approximately 200-300°C (392-572°F).
Use TIG welding.
Use 25Cr/20Ni low carbon, low silicon material as filler material. (As an alternative Nikrothal 40B - low silicon material can be used).
Stress relieve the welded component at approximately 700°C (1292°F)for one (1) hour, followed by slow cooling in the furnace to obtain a minimum of stresses in the welded goods.
Remark: Stress relieving is not absolutely necessary to perform if the handling and installation is done with care.
Welding of Kanthal APM tube to Kanthal APM bottom
Heat up the tube and the bottom plate to 300-500°C (572-932°F) using a gas torch or in a furnace.
Carry out the welding while the tube and the bottom plate are still hot. Finish off the welding before the temperature has fallen below approximately 200°C (392°F).
Spot weld the bottom plate to the tube.
Weld the bottom plate to the tube until the gap is completely filled up with material (3-4 passes). Use TIG welding equipment and Kanthal A-1 wire, Ø 1-3 mm, as filler material.
Put the welded tube into a furnace for stress relieving. This must be done before the temperature of the material has fallen below approximately 150°C (302°F). Raise the temperature to 900-1000°C (1652-1832°F) and maintain this temperature for two (2) hours.
Welding of Kanthal APM tube to mild steels
Use TIG welding
Use the same type of filler material, i.e. type of mild steel.
Stress relieve the welded component at approximately 700°C (1292°F) for one (1) hour, followed by slow cooling in the furnace to obtain a minimum of stresses in the welded goods.
Remark: Stress relieving is not absolutely necessary to perform if the handling and installation is done with care.
Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for materials under the trademark Kanthal®.
