Type K (Chromel/Alumel or NiSi)
Type K is the most common thermocouple type. It has a broad operating range up to 1260°C and has good corrosion resistance. Do not use in low Oxygen or reducing atmospheres at higher temperatures. Typically use is above 550°C in Oxygen or Inert atmospheres.
Chemical Composition, %
| Type | Ni | Cr | Si | Al |
| KP (Chromel) | 90 | 10 | – | – |
| KN | 97 | – | 3 | – |
| *KN (Alumel) | 95 | – | – | 5 |
Specification (IEC 60584-1)
| Type | EMF Versus Pt.67(mV) |
| 100℃ | 200℃ | 400℃ | 600℃ | 800℃ |
| KP | 2.826-2.886 | 5.937-6.017 | 12.729-12.821 | 19.532-19.676 | 26.064-26.246 |
| KN | 1.224-1.256 | 2.140-2.180 | 3.600-3.644 | 5.271-5.331 | 7.080-7.160 |
| KP-KN | 4.050-4.187 | 8.077-8.197 | 16.329-16.465 | 24.803-25.007 | 33.144-33.46 |
Physical and Mechanical Properties (RT, Annealed)
| Type | Density, g/cm³ | Melting Point, ℃ | Tensile Strength, MPa | Elongation, % | Resistivity, μΩ.m |
| KP | 8.5 | 1427 | ≥490 | ≥10 | 0.71 |
| KN | 8.6 | 1399 | ≥390 | ≥15 | 0.30 |
Features
- Strong resistance to oxidation than other base metal thermocouples
- High EMF against Platinum 67
- Excellent temperature accuracy, sensitivity and stability
- Low cost
Applications
Type K Thermocouple Alloy is used in many industrial, scientific, and OEM applications.It is recommended for oxidation or inert atmospheres, but can’t be used directly in the following cases:
- Alternatively oxidizing and reducing atmosphere
- Atmosphere with sulphur gases
- Long time in vacuum
- Low oxidizing atmosphere such as hydrogen and carbon monoxide atmosphere
