High Precision Invar 36 Material Nickel Plate Type For Thermostats

Introduction of Invar alloy/4J36/UNS k93600

Invar 36 is a nickel-iron-chromium alloy with additions of copper and molybdenum. It also contains niobium for stabilization against sensitization and resultant intergranular corrosion. Invar 36 has excellent resistance to general corrosion, pitting, and crevice corrosion in chemicals containing chlorides and sulfuric, phosphoric and nitric acids. Invar 36 is used for tanks, piping, heat exchangers, pumps, valves and other process equipment. Standard product forms are round, flats, pipe,

This alloy has been used for applications where dimensional changes due to temperature variation must be minimized such as in radio and electronic devices, aircraft controls, optical and laser system, etc.
Invar 36 alloy has also been used in conjunction with high expansion alloys in applications where a motion is desired when the temperature changes, such as in bimetallic thermostats and in rod and tube assemblies for temperature regulators.

Forging
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.

Machinability
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.

Weldability
The alloy may be welded by conventional methods.