Invar® (UNS K93600) is a unique nickel-iron controlled expansion alloy.

With a composition of 36% nominal nickel and the balance Iron, Invar Alloy has the lowest thermal expansion of any known alloy. Another key factor is that Invar exhibits a very low expansivity below its Curie Temperature. This anomaly has been termed “The Invar Effect”. For this reason, Invar Alloy is particularly beneficial in applications that require minimum thermal expansion and high dimensional stability.