Super Invar® 32-5
CarTech® Super Invar 32-5 is an austenitic, magnetic iron-nickel-cobalt alloy with a chemistry consisting of nominal 32% nickel, 5% cobalt and balance iron. The alloy is manufactured to provide minimum thermal expansion at room temperature. The thermal expansion rates exhibited by this alloy is less than half of Invar 36 with narrower application temperature range due to a lower Curie temperature. The alloy exhibits austenite stability to service temperatures at least -67°F. ASTM F1684 and UNS K93500 are the specification references.
Although Super Invar has a substantially lower expansivity than Invar, it is susceptible to martensite transformation in the vicinity of -30 C. (-22 F.), due to its reduced nickel content.
The alloy has a very low coefficient of thermal expansion at temperatures from below -50 C. (-58 F.) up to about 100 C. (212 F.). It also exhibits thermal stability, a martensitic transformation inception point which is controlled, so as to fall well below the lowest temperature to be encountered in the particular application.
Super Invar is sometimes referred to as Invar 32-5 or Nickel 32-5 Alloy.