Invar 36 Alloy

Chemical Analysis
C Carbon
Mn Manganese
Si Silicon
Ni Nickel
Fe Iron

General characteristics of Invar 36 Alloy

Invar 36 is a 36 percent nickel-iron alloy with a rate of thermal expansion approximately one tenth that of carbon steel at temperatures up to 400ºF (205ºC)


This alloy is used where dimensional changes due to temperature variations must be minimized, e.g. in radio and electronic devices, aircraft controls and optical and laser systems. It is also used in conjunction with high-expansion alloys in applications where motion with temperature change is desired such as in bimetallic thermostats and in rod and tube assemblies for temperature regulators.


Quick heating to forging temperature, 2000/2150ºF (1100/1180ºC), is suggested to minimize length of time exposed to sulfur and oxygen, hence to minimize sulfide and
oxide penetration from the furnace atmosphere, Forging should not be performed below 1700/1800ºF (925/980ºC), but advice should be taken on actual finishing temperatures and their effects on material properties.

Heat treatment

For optimum dimensional stability – cold work causes very slight changes in dimensional stability – heat to 1500ºF (815ºC), hold for 30 minutes per inch of section and water quench, then reheat to 600ºF (315ºC) for 1 hour and air cool.

A simple annealing treatment is carried out at 1450ºF (790ºC) for 30 mins per section inch and air cooling.


The alloy is not easy to machine, and gumminess may result from the alloy’s high work- hardening rate. Positive feeds and overpowered equipment are recommended.
A free-machining variety of Invar 36, containing nominally 0.20 percent selenium, is available.


The alloy may be welded by conventional methods.

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