STUDY OF A HOT-CASTING TECHNOLOGY
TO FORM A PERMEABLE THIN-WALLED HIGH-POROSITY CERAMIC
B. L. Krasnyi
and V. A. Chernikov
Translated from Novye Ogneupory, No. 10, pp. 36 – 38, October, 2015.
Original article submitted May 18, 2015.
A comparative analysis is made of certain types of ceramic products and the processes that are chosen to make
them in order to ensure that they have a certain level of physico-mechanical properties. Some of the features
and capabilities of hot casting are examined in the fabrication of high-porosity and high-strength thin-walled
ceramic products of complex shape. Results are presented from experiments and studies of ceramic specimens
made by hot casting. It is shown how the strength properties and open porosity of the ceramics change in rela
tion to the parameters of the production process.
Keywords: hot casting, porous ceramic, thermoplastic slips, physico-mechanical properties of ceramics.
Recent years have a seen an expansion of the types of
technical ceramics that are made for the traditional industries
and the military. This includes ceramic products for aero-
space, where equipment is subjected to extremely high tem-
peratures and pressures. The growth of this segment of the
ceramics sector has led to the adoption of much more de-
manding requirements on the quality of the ceramics and the
values of the indices that characterize their physico-mechani-
The areas of application and service conditions of the
products are dictating the implementation of strictly defined
standards for ceramics, regardless of the manufacturing tech
nology that is used. Here, it must be taken into account that
the technology which is chosen must not only ensure that the
physico-mechanical property indices of the ceramic product
are at the prescribed level but that its surface is clean and it
has the requisite geometric parameters. The product may be
of relatively complex shape, include different internal cavi
ties and inclined surfaces, and be several meters in size.
Each of the main processes used to make ceramics can be
subjected to a comparative evaluation by taking the proper
ties (open porosity, etc.) of a ceramic product made by differ
ent methods from charge materials that are comparable
(based on their granulometric composition in the presence of
certain additives) and correlating them with the tempera
ture-time parameters of the product’s treatment.
The process of isostatic pressing can be used to make
products of relatively simple geometry, particularly solids of
revolution. These products may have good refractoriness and
strength but also have negligible open porosity. Open poros-
ity is usually within the range 17 – 23% and depends on the
pressing pressure and several other process parameters. In
addition, refractory products made by isostatic pressing do
not always have satisfactorily high resistance to heat.
With respect to the levels of the properties of the result
ing ceramics, dry pressing, vibropressing, and similar tech
nologies are comparable to isostatic pressing but produce ce
ramics with a higher open porosity (30 – 38%). All of the
processes just mentioned have serious shortcomings that are
related to the limited capabilities of the equipment which is
available for making large products.
In contrast to ceramics obtained by the above processes,
vibrocast ceramics make it possible to fabricate large ce
ramic products of complex shape with dimensions of
1500 mm or more. These products are distinguished by supe
rior refractoriness and strength, but their range of open po
rosity is only 20 – 26% [1 – 5].
Hot casting occupies a special place in the production of
ceramics. The term “hot casting” appeared after the advent of
injection molding technology for ceramics. Prior to that de
velopment, manufacturers cast thermoplastic slips by contin
uous casting, direct pour casting, permanent-mold casting,
freeze-casting, and other techniques . The term “hot cast
ing” is not entirely accurate if one is referring to injection
molding, since it does not reflect the physical essence of the
process itself. It would be more accurate to refer to this
Refractories and Industrial Ceramics Vol. 56, No. 5, January, 2016
1083-4877/16/05605-0530 © 2016 Springer Science+Business Media New York
”Bakor” Scientific-Technical Center, Shcherbinka, Moscow Re