Kovar (Alloy K) is a nickel-iron-cobalt controlled-expansion alloy containing 29% nickel. Its coefficient of expansion, which decreases with rising temperature to the inflection point, matches the expansion rate of borosilicate glasses and alumina ceramics. Kovar (Alloy K) is used for glass-to-metal seals in applications requiring high reliability or resistance to thermal shock. Kovar (Alloy K) is used for high-power transmitting valves, transistor leads and headers, integrated-circuit lead frames, and photography flash bulbs. Kovar(Alloy K):UNS K94610,1.3981 Technical Data Sheet Kovar Chemical Composition (Basic Density 8.36) Weight % Ni Fe Co C Mn Si Al Cr Mg Zr Ti Cu Mo Alloy K Kovar 29.0 53.0 17.0 0.04 max 0.50 max 0.20 0.10 max 0.20 max 0.10 max 0.10 max 0.10 max 0.20 max 0.20 max Typical Mechanical Properties Material Condition Yield Strength (0.1% Offset) Tensile Strength Elongation % psi MPa psi MPa Alloy K Kovar Annealed 49,000 340 75,000 520 42 Availability Alloy K / Kovar is available in Bar, Rod, Tube, Sheet, Strip, Coil, Plate and Wire. For all stock availability contact Sales for further availability. Model GB ASTM DIN BS AFNOR New grades Old grades 4J36（Invar 36) UNS K93600 W.Nr.1.3912 X1NiCrMoCu Fe-Ni36 Kovar(Alloy K) UNS K94610 1.3981 Alloy 42 UNS K94100 1.3917