Invar 42
Invar 42 is a 41% nickel-iron controlled expansion alloy that has been used in a variety of glass-to-metal sealing applications.
The expansion properties of this alloy are most similar to that of 1075 glass, but it is also used for seals on 0120 and 0010 glasses. It can also be used with hard glass if thin edged tubular seals are used. For sealants that have not been hydrogen annealed before sealing, a gas-free sealing property was achieved by using a modification of this alloy containing Glass Sealing 42 Gas-Free, a small amount of titanium additive.
Type Analysis
Applications
Invar 42 has been used in glass-to-metal seals for electronic tubes, automotive and industrial lamps, transformer and capacitor bushings, and other glass-to-metal and ceramic-to-metal applications.
Heat Treatment
Annealing
Heat to 1450°F (788°C), hold heat for at least 30 minutes per inch, and allow air to cool.
workability
Forging
Forging temperature should be 2150/2200°F (1177/1204°C). Do not soak for a long time to avoid absorption of sulfur from the furnace atmosphere.
Cold Heading
Glass sealing 42 can be swaged or cold relaxed.
Blanking or forming
For clean blanking of Glass Sealing 42, a Rockwell hardness of approximately B90 is suggested. When forming finished parts from strips or rods that involve sharp bending, hardness not exceeding Rockwell B93 is suitable.
Grinding
Preferably a silicon carbide wheel, preferably a soft wheel with no load wear. For finish grinding, a satisfactory grade starting from grit 80.
Welding
Any conventional welding method can be used. Glass sealing 42 is recommended if an inlet rod is required.
