A THEORETICAL AND COMPUTATIONAL MODEL FOR THE BUILDUP
OF THE WALL THICKNESS OF A CERAMIC MOLDING LAYER CAST
FROM AN AQUEOUS SLIP INTO A POROUS MOLD
E. I. Suzdal’tsev
and V. I. Kurakin
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 10, pp.8–11,October, 2001.
Based on available data on the kinetics of the buildup of the wall thickness of the ceramic molding layer cast
from an aqueous slip into a porous mold, a theoretical computational model is proposed that makes it possible
to predict the casting process for different slips and differently designed molds. The model is tested for mold
ing layers cast from aqueous slips based on quartz and lithium aluminosilicate glasses and can be used to cast
molds from other materials. The model provides ways toward effective control of the molding process by the
use of properly designed molds.
It was established in a study of the technology of fabrica-
tion of large-size components by casting aqueous slips into
porous molds that the moisture content of slip cast in a mold
decreases owing to the uptake of water by the mold walls un-
der the action of capillary forces. The movement of the fluid
toward the wall of the mold involves transportation of solid
particles, which leads to the buildup of a deposit on the wall
surface. Simultaneously, deposition of larger particles under
the pull of gravity takes place, which results in an increased
wall-buildup rate in the bottom section of the casting. Fur
thermore, the height of the slip column is an important factor
for the wall-buildup rate: the higher the slip column, the
higher the wall-buildup rate in the bottom section of the cast
ing [1, 2].
Thus, in the course of formation of the wall of a large-
size cast product by an aqueous-slip casting technology, the
cavity of the mold gradually becomes filled in the “bottom
up” direction with a solid precipitate. This behavior is com
mon to all aqueous-slip casting technologies, the only differ
ence being that, depending on the material used, the solid-
particle mobility may be different and the wall buildup may
proceed at different rates. After the wall-buildup process as
described above has been completed, the process of water
uptake from the casting by the mold material continues, that
is, the casting becomes dried-off, which results in its shrink
age onto the hard mold core and, eventually, in its fracture.
We propose here a theoretical computational model that
allows one to predict the wall-buildup rate from an aqueous
slip allowing for specific features of the technology, aque-
ous-slip parameters, and casting equipment used (Fig. 1).
Our model is based on the following assumptions:
– the slip is a homogeneous mixture of hydrated solid
– solid particles near the surface of the mold (made up of
a porous material, for example, gypsum) move normally to
this surface under the action of all forces involved whose re-
sultant is the equivalent pressure applied at the interface slip
— built-up surface of the cast product;
Refractories and Industrial Ceramics Vol. 42, Nos. 9 – 10, 2001
Tekhnologiya Research and Production Enterprise, Obninsk, Ka
luga Region, Russia.
Fig. 1. Schematic diagram of the molding layer of a shell: 1 ) cast
ing chamber, 2 ) “sequestered” water, 3 ) gypsum boundary, 4 )de
posited molding layer, 5 ) slip.
1083-4877/01/0910-0347$25.00 © 2001 Plenum Publishing Corporation