PRODUCTION AND EQUIPMENT
COMPACTION METHODS AND THEIR EFFECT
ON COKE-PITCH COMPOSITE PROPERTIES
N. A. Lobastov
and A. N. Chernyavets
Translated from Novye Ogneupory, No. 10, pp. 36 – 39, October 2007.
Original article submitted April 16, 2007.
Different methods are considered for compacting materials, including “green” graphite billets. It is shown that
the majority of these methods, in particular compaction of powder mixes, are used for this class of powder
bodies. A considerable future is noted for the use of hydrostatic pressing in order to prepare fine-grained iso
tropic graphites that are used most widely in the national economy, in particular in the production of electronic
technology. The main pioneers in Russia for preparation of isotropic graphite, prepared by hydrostatic press
ing, are shown.
Compaction is a process of changing the shape and di-
mensions of an original mass due to reducing the volume
with action of external forces, and also giving a billet a spe-
cific strength required for retaining it shape during subse-
quent production treatment. Methods for compacting billets
are very varied [1, 2]. With respect to the time of action they
may be separated into continuous and interrupted. According
to the principle of pressure application they may be separated
into gradually increasing, instantaneously increasing, and
vibration, according to the scheme of increasing load they
may be separated into unidirectional, two-directional,
all-round and centrifugal, according to applied temperature
they may be separated into cold compaction at room temper
ature (surrounding temperature) and hot, i.e. at elevated tem
perature, with respect to atmosphere they may be separated
into compaction in air, in a vacuum and in an inert medium.
Each of these compaction methods has its own features. We
consider each method briefly.
The continuous method relates to the majority of com
paction cases when there is piecewise preparation of billets:
compaction by a different class of presses (hydraulic, me
chanical, vibration), and also different forms of isostatic
(all-round) compaction: hydrostatic in thin shells, isostatic in
thin-walled elastic shells, hot isotatic, and explosive.
The discontinuous method, by means of which it is pos
sible to obtain billets of significant length, relates to: com
paction by extrusion, wedge compaction, rolling of powders,
and also the new method of continuous compaction of billets
from a hot coke-pitch mix with continuous extrusion of indi-
vidual portions of material into the main formable mix.
In order to prepare carbon-graphite materials the most
widespread methods used are compaction in a die and extru-
sion (nozzle compaction). Comparative evaluation of com-
paction by extrusion points to the following advantages: the
possibility of preparing billets of uniform density with a high
ratio of length to cross sectional area, high productivity and
economy of the method. The first advantage is achieved by
uniform compaction of material by forces that arise in over
coming resistance caused by the walls of the nozzle, and the
possibility of continuous occurrence of extrusion. Absence
of damage at the nozzle surface, having a friction coefficient
for the mix over the nozzle walls, and also with an un
changed compaction rate the extrusion resistance should be
kept constant, which provides uniform compression of the
material emerging through the nozzle opening.
Compaction in a die limits the manufacture of billets of
large sizes over the compaction axis as a result of nonuni
form deformation, i.e. non-compactability over the billet
height . The second advantage of the nozzle method of
compaction compared with that in a die is connected with
shortening of a number of operations. First, it is only neces
sary to charge the material and extrude it with simultaneous
cutting to the required size. In the second case additional
time is expended in the operation of pressing itself, prepara
tion of the die for removal of the pressed billet and loading of
a new portion of mix (powder).
Refractories and Industrial Ceramics Vol. 48, No. 5, 2007
1083-4877/07/4805-0342 © 2007 Springer Science+Business Media, Inc.
FGUP (Federal State Unitary Enterprise) NIIgrafit, Russia.