Kovar Alloy: Materials, Properties and Heat Treatments for Oxidation
Kovar Alloy: Materials, Properties and Heat Treatments for Oxidation
KOVAR
HEAT TREATMENT
Decarburization is used for reducing carbon,
absorbed gases, and removing surface contaminants.
It is intended as a final cleaning treatment
for part being sealed, plated or brazed.
1. Degrease and chemically
clean.
2. Heat treat in we hydrogen
or dissociated ammonia.
3. Firing Temperature
– 900°C to 1100°C.
(Use water bubbler at room temperature)
Typical
Cycle
950°C
15 minutes
Semiconductor parts
1000°C
30 minutes
Electron tube parts
to be plated or glass sealed.
1000°C
45 minutes
Heavy bar or plate
parts
1050°C
20 minutes
For parts intended
to be brazed at equivalent temperatures
Heat
Treatment for Oxidation
1. Make sure that proper methods are used
to clean, degrease, and bright dip parts.
2. Oxidation – Heat treat in an electric
air furnace to
850°C to 900°C, until parts are
cherry red (dull red
heat). The length of heat cycle is approximately
3
minutes, but due to differences in humidity
and furnaces, the
proper cycle has to be varied. Then reduce
heat approximately
10 degrees °C per minute. When parts
are cooled, oxide will be
formed. The Black is normally considered
to be over oxidation
and is not necessarily desirable for a good
glass to metal seal.
KOVAR
MAGNETIC PROPERTIES
Material will be magnetic at all temperatures
below the Curie Point. Magnetic Properties
depend upon Heat Treatment. The softer the
material, the higher the Permeability Values
and lower Hysteresis Loss. Examples of Permeability
are as follows…
Flux Density
Permeability (Treatment
1830°F(999°C)30min-FC)
Permeability (Treatment
2010°F(1099°C)20min-FC
5000
1000
1900
1000
1400
3500
2000
2000
5800
5000
2300
10000
10000
3400
8200
12000
3000
5000
Flux
Density: Magnetic, Electric or Radiant
Flux per unit area normal to the direction
of the flux.
