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.
Chemical composition
|
C % |
Si % |
Mn % |
Cr % |
Al % |
Fe % |
| Nominal composition |
|
|
|
|
5.8 |
Bal. |
| Min |
- |
- |
- |
20.5 |
- |
|
| Max |
0.08 |
0.7 |
0.4 |
23.5 |
- |
|
Mechanical properties
| 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.
Physical properties
| 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
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.
