Kovar

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For the Romanian village of Cetate, called Kővár in Hungarian, see Remetea Chioarului.
For the village and municipality in Azerbaijan, see Kövər.
For the Czech surname, see Kovář.

Kovar (trademark of CRS Holdings, inc., Delaware[1]) is a nickelcobalt ferrous alloy compositionally identical to Fernico 1, designed to be compatible with the thermal expansion characteristics of borosilicate glass (~5 × 10−6 /K between 30 and 200 °C, to ~10 × 10−6 /K at 800 °C) in order to allow direct mechanical connections over a range of temperatures. It finds application in electroplated conductors entering glass envelopes of electronic parts such as vacuum tubes (valves), X-ray and microwave tubes and some lightbulbs.

The name Kovar is often used as a general term for Fe–Ni alloys with these particular thermal expansion properties. Note the related particular Fe–Ni alloy Invar which exhibits minimum thermal expansion.

Typical composition[edit]

Given in weight %

Fe Ni Co C Si Mn
balance 29% 17% < 0.01% 0.2% 0.3%

Properties[edit]

Property sintered HIPed
Density / g cm3 8.0 8.35
Hardness / HV1 160 150
Youngs Modulus / GPa 159 159
reduction of area at fracture / % 30 30
yield strength / MPa 270 270
thermal conductivity / W/Km 17
Curie Temperature / °C 435
electrical resistivity Ω mm2 / m 0.49
specific heat J/gK 0.46
thermal expansion coefficient/10−6 K−1 (25 – 200 °C) 5.5
(25–300 °C) 5.1
(25–400 °C) 4.9
(25–450 °C) 5.3
(25–500 °C) 6.2

References[edit]

  1. ^ USPTO United States Patent and Trademark Office (1993). "Trademark Assignment Abstract". Retrieved 18 June 2014. 

External links[edit]