MANUFACTURING AND EQUIPMENT
QUASI-ISOSTATIC PRESSING TECHNIQUE
FOR POWDERED MATERIALS
M. I. Timokhova
Translated from Novye Ogneupory, No. 11, pp. 31 – 34, November, 2003.
A simple and economical method of quasi-static pressing, based on standard hydraulic or mechanical pressure
molding facilities, is developed. The pressurizing medium for conveying isostatic uniform pressure is an elas
tic synthetic rubber. A technology for pressure molding of powdered materials into a wide range of engineer
ing components is developed.
Currently, the isostatic pressing technique in which pres-
sure is applied to the press-powder isostatically, i.e. equally
in all directions, has gained wide acceptance in the produc-
tion of ceramic components, in the treatment of graphite and
metallic powders, abrasive materials and, specifically, in the
production of refractory materials. As the pressurizing me-
dium, a range of materials — liquid, inert gas, molten metal,
glass, or graphite (hot isostatic pressing) — can be used.
In practice, hydrostatic pressing has been the most popu-
lar technique. Using this technique, one can mold compo
nents of any size and of high and uniform density. Still, hy
drostatic pressing, for all its benefits, suffers from shortcom
ings that pose problems for its wider uses in the domestic in
dustry. For example, the hydrostatic pressing method re
quires the support of an arsenal of auxiliary facilities: a
hydrostat made of high-strength steels, hydraulic pumps, a
vessel for keeping the pressurizing liquid, a quite intricate
system of high-pressure pipelines, and a sizeable amount of
measuring instrumentation. All this requires large production
areas and rather high capital costs. Because of the large mass
of the isostat and the sealing joints in pipelines, the vibratory
compaction of the powder transferred to the isostat is diffi
cult (if possible altogether) to perform. Usually, the vibratory
operation is done outside the isostat, which results in a sharp
decrease of productivity of the process. Furthermore, prob
lems arise with vacuum degassing of the press-powder dur
ing pressing .
In recent years, a simple technique, the quasi-isostatic
pressing, has been developed, which is based on the use of
standard hydraulic or mechanical pressing equipment (avail
able from domestic manufacturers) and press molds which in
design, installation, and operational conditions do not differ
much from conventional techniques.
The principle of quasi-isostatic pressing is based on the
use of an elastic material (synthetic rubber) as the pressuriz-
ing medium to convey isostatic uniform pressure. In a ring
press mold, the elastic element is a core which shapes the in-
ner cavity of the ring pressed.
A variant of the press mold for quasi-isostatic pressing is
shown in Fig. 1. The press mold is composed of a floating
steel die 1, an elastic element, press buffer 2, a cavity 3
(which is filled with press powder), a steel punch 4, a pusher
5, and vibrators 6.
The powder is pressed by means of the top punch which
conveys pressure to the powder and to the elastic press-
Refractories and Industrial Ceramics Vol. 44, No. 6, 2003
1083-4877/03/4406-0364$25.00 © 2003 Plenum Publishing Corporation
Reméko Co., Moscow, Russia.
Fig. 1. Schematic diagram of a press mold for quasi-isostatic