Low Expansion Alloys
Invar, Alloy 36 & 42 Alloy
Low expansion alloys are iron-nickel alloys with face-centered cubic crystal structure. These alloys have very low coefficients of thermal expansion over certain temperature ranges, which are related to ferromagnetism. Each low expansion alloy’s Curie temperature, the temperature below which it is ferromagnetic, results in a low thermal expansivity anomaly, often referred to as the “Invar Effect.”
Thanks to a very high magnetic permeability, low expansion alloys are useful in transformers, cores, laminations for efficient motors, relays and solenoids. They are used extensively where changes in mechanical properties with temperature could be a problem.
Invar: Also called Alloy 36 or Invar 36, Invar is a low expansion alloy whose name is derived from “invariable” because it won’t react to thermal expansion. Invar is used predominantly in precision instruments like stencils, fine line etching and laser cutting, as well as scientific instruments, physics laboratory devices and motor valves.
42 Alloy: Very similar to Invar, 42 Alloy has a slightly different coefficient of thermal expansion. 42 Alloy is well-suited for the lid, lead frames, stencil/etching and aircraft industries. Easily machined and formed hot or cold, 42 Alloy is also used extensively in the medical, electronics and automotive industries.