Kovar alloy Bar Factory, 4J29 Bar, ASTM F15, Nilo-K, FeNi29Co17, UNS K94610

A Nickel-Iron-Cobalt, controlled expansion alloy containing 29% Nickel. It’s coefficient of expansion (which decreases with rising temperature to the inflection point), matches the expansion rate of borosilicate glasses and aluminia ceramics. Applications include glass to metal seals in applications requiring high reliability or resistance to thermal shock, ie. high-power transmitting valves, transistor leads and heaters and photography flash bulbs.