Thermothal® KM is an austenitic nickel-chromium alloy (NiCr alloy) used for the positive leg of thermocouples type K. Thermothal® KM is an alloy optimized for manufacturing of mineral insulated cable. In standard condition the Thermothal® KM is delivered in stabilized condition. The tabulated list describes the temperature characteristic in standard condition. Thermocouples of type K have good resistance to oxidation, and better than other base metal combinations.
Thermothal KM cannot be exposed to reducing or alternately oxidizing and reducing atmospheres or vacuum.
Chemical composition
Ni % | Cr % | Si % | |
---|---|---|---|
Nominal composition | Bal. | 10.0 | 0.5 |
Mechanical properties
Wire size | Yield strength | Tensile strength | Elongation | Hardness |
---|---|---|---|---|
Ø | Rp0.2 | Rm | A | |
mm | MPa | MPa | % | Hv |
2.0 | 220 | 580 | 35 | 140 |
Mechanical properties at elevated temperature
Temperatur | Yield strength | Tensile strength | Elongation |
---|---|---|---|
Rp0.2 | Rm | A50 | |
°C | MPa | MPa | % |
100 | 272 | 596 | 41 |
300 | 244 | 594 | 39 |
500 | 217 | 563 | 39 |
Ultimate tensile strength - deformation rate 6.2 x 10-6 min-1
Physical properties
Density g/cm3 | 8.72 |
---|---|
Electrical resistivity at 20°C Ω mm2/m | 0.706 |
Temperature coefficient of resistance between 20°C and 100°C x 10-6/ K | 300 |
Temperature °C | 20 | 100 | 300 | 500 |
---|---|---|---|---|
GPa | 200 | 132 | 68 | 48 |
Temperature °C | Thermal Expansion x 10-6/ K |
---|---|
20 - 100 | 17 |
Temperature °C | 100 |
---|---|
W m-1 K-1 | 19.2 |
Temperature °C | 20 |
---|---|
kJ kg-1 K-1 | 0.448 |
Melting point °C | 1430 |
---|---|
Magnetic properties | The material is non-magnetic |
Wire size Ø | 3.26 | 1.63 | 1.00 | 0.50 | 0.25 |
---|---|---|---|---|---|
Bare wire °C | 1050 | 930 | 900 | 800 | 710 |
Protected wire °C | 1150 | 1080 | 1050 | 910 | 820 |
Note that the indicated temperatures should be considered as guide values
Thermoelectric properties
°C | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 | 1100 | 1200 |
---|---|---|---|---|---|---|---|---|---|---|---|---|
mV | 2.814 | 5.970 | 9.323 | 12.764 | 16.214 | 19.618 | 22.951 | 26.205 | 29.386 | 32.499 | 35.544 | 38.508 |
Reference junction 0°C
°C | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 | 1100 | 1200 |
---|---|---|---|---|---|---|---|---|---|---|---|---|
mV | 4.096 | 8.139 | 12.209 | 16.397 | 20.644 | 24.906 | 29.129 | 33.275 | 37.326 | 41.276 | 45.119 | 48.839 |
(ITS 90) - Reference junction 0°C