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Alloy K 
1.3981 – K94610

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Material description

Material 1.3981 (Alloy K) is a nickel-iron-cobalt alloy with controlled thermal expansion. The nickel content is around 29% and the cobalt content is around 17%. The coefficient of expansion of the alloy corresponds to the thermal expansion of borosilicate glass and (alumina) ceramics, which enables the combination of these materials. The coefficient of expansion decreases with rising temperature to the inflection point.  

Thanks to its material properties, 1.3981 is used for applications which require high reliability and resistance to thermal shock.  

An overview of the properties of 1.3981: 

  • High resistance to thermal shock 
  • Controlled expansion properties to 450°C

Applications

  • Glass/metal seals 
  • High-performance transmitter tubes 
  • Transistor leads and sockets 
  • IC lead frames  
  • Flashbulbs

Material data

Material no.: 1.3981
Name: Alloy K
UNS no.: K94610
ASTM: F 15
VdTÜV: —
Other: SEW 385, DIN 17745
Material type: Expansion alloy
Data sheet

Chemical composition in %

ASTM F15SEW 385DIN 17745
C≤ 0.04< 0.05≤ 0.05
Si≤ 0.20< 0.30≤ 0.30
Mn≤ 0.50< 0.50≤ 0.50
Co≈ 1717.0 – 18.016.0 – 18.0
Ni≈ 2928.0 – 30.028.0 – 30.0
Fe≈ 53Remainder
Al≤ 0.10
Mg≤ 0.10
Zr≤ 0.10
Ti≤ 0.10
Al + Mg + Zr + Ti≤ 0.30
Cu≤ 0.20
Cr≤ 0.20
Mo≤ 0.20

Mechanical properties

Annealed
Rm (MPa)
≤ 585440 – 640
A (%)≥ 25

AVERAGE LINEAR COEFFICIENT OF THERMAL EXPANSION

α10-6/K10-6/K10-6/K
20°C – 100°C6.3 +/- 0.3
20°C – 150°C6.0 +/- 0.3
20°C – 200°C5.8 +/- 0.3
20°C – 300°C5.4 +/- 0.3
20°C – 400°C5.1 +/- 0.34.6 – 5.6
20°C – 500°C6.4 +/- 0.3
20°C – 600°C8.0 +/- 0.3
30°C – 400°C4.6 – 5.2
30°C – 450°C5.1 – 5.5

The specified values are non-binding guide values.

Data sheet

13981Download