Invar® Coil

Invar® Coil (Fe64/Ni36, UNS K93600) is the near-zero thermal expansion alloy supplied in a continuous strip format, combining a coefficient of thermal expansion of 1.7–2.0 × 10⁻⁶ K⁻¹ with the processing efficiency of a coiled feedstock suited to roll-to-roll fabrication, progressive-die stamping, and automated forming operations. The coil format provides the continuous, uninterrupted supply needed for high-throughput production of Invar components, including fine metal mask blanks for OLED display manufacture, thermal compensation strip elements embedded in precision electronic assemblies, and bimetallic thermostatic strip stock where Invar serves as the low-expansion layer. Its tensile strength of 450–590 MPa and elongation of 45% in the annealed condition support reliable forming behaviour across the dimensional range without the brittleness that characterises many high-modulus low-expansion alternatives. The Curie temperature of 279 °C defines the upper bound of the low-CTE behaviour: above this temperature the anomalous magnetovolume effect collapses and CTE returns toward normal ferrous alloy values, a parameter relevant to any application where service temperature approaches this limit. In aerospace tooling, Invar coil strip is used to fabricate face sheets and thermal management elements in composite lay-up moulds, where CTE matching to carbon fibre reinforced polymer is the design requirement. In research, it serves as a substrate strip for thin-film deposition and surface science experiments requiring a dimensionally stable metallic platform across cryogenic to near-ambient temperature ranges.