| Studies of Alkali Attack by Molten Salts on
Alumino-Silicate Refractory Compositions:
!-Preparation and Properties of Sintered
Refractory Samples |
A. V. SUBRAHMANYAM*, V. A. ALTEKAR** AND
M. D. NARASIMHAN***
Pages : 46-54
DOI : 10.1080/0371750X.1978.10840669 |
| Abstract |
| Alkali attack, a vital factor contributing to the failure of
illuniino-silicate refractory materials, has been studied
using molten alkaline salts, and laboratory prepared and
field samples of refractory compositions. This study deals
with among other topics, the optimum temperatures for
the sintering of various alumino-silicate compositions,
prepared from mixtures of pure alumina and silica, as well
as naturally occurring silica sand or bauxite and china
clay, to obtain dense and impervious refractory samples.
It has been observed that the ratio of optimum sintering
temperature with the fusion temperature were in the range
0.87-0.95. Mullite contents as represented by hydrofluoric
acid insoluble residues, were 30-84% for sintered silica
sand or bauxite and china clay mixtures, compared with
30-77% for sintered pure almnina and silica mixes. It was
difficult to obtain by sintering, dense mullite samples using
pure almnina and pure silica, as this temperature (1770°C)
was very sharp and even then the samples had some porosity
(14. 7 %). Large number of porous samples having
almnina contents in the range of 28.8 to 68.12% and porosities
in the range of 2.5 to 31.4% were prepared to study
the effect of porosity on the rate of alkali attack. A field
sample of blast furnace stack brick of around 14% porosity,
containing predominantly alumino-silicates with 43.1 %
almnina was also collected for the study. The microstructural
studies were also done, using X-ray diffraction
and microscopic methods. |
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