| Carpenter Super Invar 32-5, a magnetic, austenitic, solid solution alloy containing iron, nickel and cobalt, is designed to provide minimum thermal expansion at room temperatures. This alloy also exhibits austenite stability to service temperatures at least -67°F (-55°C) and thermal expansion properties less than those of Carpenter Invar "36"® alloy (36% nickel-iron) when used in the -67/203°F (-55/95°C) temperature range. Applications for Super Invar 32-5 have included structural components for supports and substrates in optical and laser systems requiring precision measurements. This alloy has also been used in wave guide tubes and other systems requiring metals in conjunction with low expansion glass/quartz assemblies. Fabricating practices such as machining, forming, and deep drawing introduce stresses in this alloy which promote variation in thermal expansion behavior. Consequently, parts should be heat treated at or as close to finish size as possible. Heat Treating for Lowest Thermal Expansion and Optimum Stability: The recommended heat treating practice for lowest thermal expansion and optimum stability is to heat at 1550°F (843°C) for 1 hour, water quench, followed by a stress relieving operation at 600°F (316°C) for 1 hour, air cool and age at 200°F (93°C) for 24 hours, then air cool. Because this alloy oxidizes readily at heat treating temperatures above about 1000°F (538°C), it is recommended parts be heat treated in a protective environment such as vacuum, hydrogen, dissociated ammonia, or inert gases. Heat to 1450°F (790°C) and hold at heat 30 minutes per inch of thickness, then air cool. Heating to temperatures above 1000°F (538°C) relieves the presence of cold work stresses. Data provided by Carpenter Technology Corporation. |
