|
The CHA and CPA methods are
realized using a centrifugal
nozzle which is shown schematically
in Figure 1. Melt 1 is fed
under the excess pressure
of an inert gas to tangential
channel 2 and then to swirling
chamber 3 of the centrifugal
nozzle. The melt is spinned
in the channel and the swirling
chamber and subsequently is
directed to confuser 4, where
the rotational component of
the melt velocity further
increases.
The melt comes to the atomizing
coloumn through nozzle 5 in
the form of a spinning hollow
stream which widens under
the action of centrifugal
forces and transforms into
thinning conical film 6. The
film is unstable and desintegrates
into fine droplets. Capacity
of the CHA process is 100
to 1000 kg of powder or granules
per hour. Gas consumption
is on the average 0.005 nmç
per 1 kg of the product. The
mean dimension of the powder
particles is adjastable within
60 to 1000 mkm. The CHA method
realized either in vacuum
or in an inert gas medium.
If the melt and a gas under
pressure are tangentially
fed at a time to the swirling
chamber, the so-called method
of centrifugal-pneumatic atomizing
(CPA) is realized. This method
ensures production of powders
with the mean dimension of
particles from 10 to 60 mkm,
capacity of 20...60 kg/h,
and gas consumption no to
exceed 0.05 nmç/h.
The CHA method can be used
efficiently for production
of quick-hardened powders
with amorphous or mycrocrystalline
structure. Such powders provide
fro production of materials
featuring high service properties.
The prduction scheme of these
powders is given on the Figure
2. The melt 1 is force fed
from the crucible to centrifugal
nozzle 2 and is atomized to
from droplets 3. The droplets
get to rotating cooled crystallizer
4, where the droplets are
hardened at a rate of 105
107 K/s and a powder with
flaky shape particles is formed.
The plant is capable of producing
over 50 kg of quick-hardened
powder per hour. The mean
particel dimension is 0.75
to 2 mm.
|
