Kovar 952841 207370532 2008-04-22T14:59:59Z Chowbok 54304 clean up, Replaced: ® → , typos fixed: Km → km using [[Project:AutoWikiBrowser|AWB]] '''Kovar''' (trademark of Carpenter Technology Corporation) is a [[nickel]]-[[cobalt]] [[ferrous]] [[alloy]] designed to be compatible with the [[thermal expansion]] characteristics of [[borosilicate glass]] (~5×10<sup>-6</sup> /K between 30 and 200°C, to ~10×10<sup>-6</sup> /K at 800°C) in order to allow direct mechanical connections over a range of temperatures. It finds application in [[electroplate]]d conductors entering glass envelopes of electronic parts such as [[vacuum tubes]] (valves), X-ray and Microwave tubes and some [[lightbulb]]s. The name Kovar is often used as a general term for FeNi alloys with these particular thermal expansion properties. Note the related particular Fe-Ni alloy [[Invar]] which exhibits minimum thermal expansion. == Typical Composition == given in weight % {| class="wikitable" |- ! [[Fe]] ! [[Nickel|Ni]] ! [[Cobalt|Co]] ! [[Carbon|C]] ! [[Silicon|Si]] ! [[Manganese|Mn]] |- | balance | 29% | 17% | <0.01% | 0.2 % | 0.3 % |- |} == Properties == {| class="wikitable" |- ! Property ! [[Sintering|sintered]] ! [[hot isostatic pressing|HIP]]ed |- | [[Density]] / g cm<sup>3</sup> | 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 | colspan="2" align="center"| 17 |- |[[Curie point|Curie Temperature]] / °C | colspan="2" align="center"| 435 |- |[[electrical resistivity]] Ω mm<sup>2</sup> / m | colspan="2" align="center"| 0.49 |- |[[specific heat]] J/gK | colspan="2" align="center"| 0.46 |- |[[thermal expansion coefficient]]/10<sup>-6</sup> K<sup>-1</sup> (25 – 200°C) | colspan="2" align="center"| 5.2 |- | align="right"| (25 – 300°C) ||colspan="2" align="center"| 5.1 |- | align="right"| (25 – 400°C) ||colspan="2" align="center"| 4.9 |- | align="right"| (25 – 450°C) ||colspan="2" align="center"| 5.3 |- | align="right"| (25 – 500°C) ||colspan="2" align="center"| 6.2 |- |} ==External links== *[http://www.espimetals.com/tech/kovar.pdf Kovar specification sheet] [[Category:Ferrous alloys]] {{alloy-stub}} [[de:Kovar]] [[fr:Kovar]] [[ja:コバール]] [[sv:Kovar]] [[uk:Ковар]]