It is a nickel-iron low-expansion alloy containing 36% nickel. It maintains nearly constant dimensions over the range of normal atmospheric temperatures, and has a low coefficient of expansion from cryogenic temperatures to about 260°C. The alloy also retains good strength and toughness at cryogenic temperatures. Used for tanks and piping for storing and transporting liquefied gases. Consumable designed to have very low thermal expansion providing freedom to solidification and reheat cracking.