PRESS-MOLDING OF HIGH-ALUMINA CERAMIC CASTABLES.
1. COMPACTION AND PROPERTIES OF MATRIX SYSTEMS BASED
ON MIXED HCBS OF COMPOSITION: BAUXITE, QUARTZ GLASS,
AND COMMERCIAL ALUMINA
Yu. E. Pivinskii,
Pavel V. Dyakin,
S. V. Vikhman,
and Petr V. Dyakin
Translated from Novye Ogneupory, No. 5, pp. 39 – 44, May, 2005.
Original article submitted January 25, 2005.
Preparation of powders based on bauxite HCBS (Highly Concentrated Ceramic Binding Suspensions) con
taining high-disperse quartz glass and plasticized with refractory clay is described. The powders, molded at
moderate pressure (50 – 100 MPa), give a high-density material with an initial porosity of 20 – 25%. Mixes
containing 10 to 43% commercial alumina are tested. The materials can be used as matrices for press-molded
high-alumina ceramic castables which, when sintered, show a high mechanical strength and volume constancy.
Among high-alumina ceramic castables commercially
available from the Pervouralsk Dinas Plant JSC [1, 2], there
has recently been an increased output of press-molded
refractories based on mixed HCBS in the system bauxite
(90%) – quartz glass (10%). Formerly, the traditional product
was mixed brick (mostly shaped by friction pressing techno-
logy) with a long service life (capable of sustaining as many
as two thousand pouring cycles); currently, the production of
pressed refractories of mullite-corundum composition
(MKTP-85 grade) for the lining of steel ladles has been
launched . The HCBS-based refractories, when compared
to their compositional analogs of grades MK, MKS, MKT or
MKB, show a substantially lower porosity, higher mechani
cal strength and thermal stability (by a factor of 2 – 3), and
smaller production costs . Economy has been achieved
owing to the fact that the HCBS-based refractories require
lower sintering temperatures in comparison to the products
prepared by the conventional technology.
An advantage of the HCBS-based refractories is their en
hanced operational stability . Furthermore, these refrac
tories may be a convenient alternative to conventional refrac
tories of similar composition currently used in many sectors
of industry. One would attempt a suggestion, not without rea
son, that the new technology for production of aluminosili
cate components (with 50 – 95% Al
) will play, in the
near future, a leading role in the field. Viewed in this light,
further development of the technology of press-molded ce-
ramic castables based on Al
-containing composites and
study of their structure and properties are at present a chal-
lenging task. The properties of press-molded ceramic
castables, like those of monolithic and vibrocast castables
, are mainly controlled by the composition and properties
of their matrix composed of HCBS and plasticizing, thin
ning, or strengthening additives. In our study, the composi
tions of both matrix and refractory fillers were varied over a
wide concentration range.
In step 1 of our work, the matrix systems were studied
for compaction and the properties of the finely dispersed
component of press-molded ceramic castables were examined.
Starting materials. Compaction and properties of matrix
systems based on a wet-ground mixture of bauxite HCBS
and 10% quartz glass were studied . The HCBS-based ma
trices are exceptionally efficient owing to the involvement of
a low-temperature mullitization mechanism which imparts
enhanced thermomechanical properties to ceramic castables.
The matrix concentration of Al
(up to 43%) was con
trolled by adding GÉF-grade commercial alumina which was
prepared by calcining aluminum hydroxide in a rotary kiln at
1200 – 1300°C. The alumina used had an acicular-laminated
structure, of composition 99.4% Al
and 0.3% Na
Refractories and Industrial Ceramics Vol. 46, No. 3, 2005
1083-4877/05/4603-0220 © 2005 Springer Science+Business Media, Inc.
Kerambet-Ogneupor R&D Co., St. Petersburg, Russia; St. Peters
burg State Technological Institute (Technical University), St. Pe