Thermocouple k-type KP KN chromel alumel alloy
1. Material Composition & Properties
Leg Alloy Designation Chemical Composition Key Characteristics
Positive (KP) Chromel Equivalent Ni 89-91%, Cr 9-10%, Si/Mn ≤1% Non-magnetic, resistivity 0.71 μΩ·m
Negative (KN) Alumel Equivalent Ni 94-97%, Al 1.5-2.5%, Mn 1.5-2.5%, Si ≤1% Magnetic, resistivity 0.23 μΩ·m
2. Performance Specifications
Parameter Value Standard/Notes
Temp Range (Wire Grade) Short-term: -200°C to 1,300°C Max 1,260°C per IEC 60584-1
Long-term:0°C to 1,100°C Optimal stability range
Temp Range (Extension) 0°C to 200°C Limited accuracy beyond 200°C
EMF Output 41 µV/°C at 1,000°C Vs. Platinum 67 reference
Accuracy (Class 1) ±1.5°C or ±0.4% (>0°C) Whichever greater
±2.5°C (-200°C to 0°C) Cryogenic tolerance
Oxidation Resistance Superior to Type J/T/E below 1,000°C Cr2O3 protective layer
3. Environmental Compatibility & Restrictions
Recommended Atmospheres:
- Oxidizing: Air, combustion exhausts (electric furnaces)
- Inert Gases: Argon, nitrogen (full performance up to 1,100°C)
Prohibited Conditions:
Scenario Failure Mechanism Mitigation
Sulfur-containing gases Sulfidation → brittle fracture Avoid H2S/SO2 environments
Alternating redox cycles Calibration drift >5°C Use Type N in cyclic apps
Vacuum >1 hour (>800°C) Chromium vaporization Max 60-min exposure
H2/CO atmospheres Green Rot corrosion (815-1040°C) Ceramic protection tubes
4. Competitive Advantages
- Cost Efficiency: 30–50% cheaper than noble-metal types (R/S/B)
- Radiation Hardness: Preferred in nuclear applications vs. Type J
- Lifetime: 5× longer than Type J at 900°C (Fe oxidation in J)
5. Precision Tolerance Standards
Class Tolerance Formula Application Context
Class 1 ±1.5°C or ±0.004×|t| (°C) Aerospace, calibration labs
Class 2 ±2.5°C or ±0.0075×|t| (°C) Industrial process control
|t| = Absolute temp in °C; Special Error Grade (±0.4%) available for high-precision needs
Supplemental Technical Notes
Connection Best Practices:
- Use MgO-insulated nickel-alloy extension wires for EMF stability
- Avoid copper terminals → galvanic corrosion in humid environments
Aging Prevention:
- Pre-aging at 850°C for 2 hrs reduces drift in precision sensors
Physical Properties:
Property KP Value KN Value
Density (g/cm³) 8.5 8.6
Tensile Strength ≥490 MPa ≥390 MPa
Elongation ≥10% ≥15%
Thermocouples are used in processes to sense temperature and is connected to the pyrometers for indication and control. The thermocouple and pyrometer are electrically conducted by thermocouple extension cables / thermocouple compensating cables. The conductors used for these thermocouple cables are required to have similar thermo-electric (emf) properties as that of the thermocouple used for sensing the temperature.
Our plant mainly manufacture thermocouple wire, strip, and cable, and they are used in temperature measurement instruments. Our thermocouple products are all made abiding by GB and also IEC584-3 (International standard).
Thermocouple strip can be used to produce thermocouple connector's hollow pin, thermocouple spade, and thermocouple connector's contacts.
| Chemical Composition |
| Conductor Name | Polarity | Code | Nominal Chemical Composition /% |
| Ni | Cr | Si |
| Ni-Cr | Positive | KP | 90 | 10 | -- |
| Ni- Si | Negative | KN | 97 | -- | 3 |
Application
• Heating – Gas burners for ovens
• Cooling – Freezers
• Engine protection – Temperatures and surface temperatures
• High temperature control – Iron casting
