MINERAL COMPOSITION AND PHASE TRANSFORMATIONS
IN THE REFRACTORY LINING OF THE BOTTOM
OF ALUMINUM ELECTROLYSIS CELLS. PART 1.
V. V. Sharapova,
I. I. Lishchuk,
D. Yu. Boguslavskii,
and V. V. Chesnyak
Translated from Novye Ogneupory, No. 3, pp. 13 – 17, March, 2005.
Original article submitted January 21, 2005.
Results for specimens of the refractory lining sampled from the bottom of an aluminum electrolysis cell with a
service life of 3.5 years examined by methods of petrography, chemical analysis, and electron probe x-ray
microanalysis are reported. The main products of conversion are sodium aluminosilicates, sodium silicates, a
glassy phase of variable composition, oxyfluoride glasses, and eutectics. Some of the specimens analyzed are
high in b-alumina (20 – 50%). Fluorides are represented by NaF (about 7%), cryolite Na
(2 – 5%),
(2%), and NaF × MgF
(1 – 2%), and the metallic phase, by aluminum (2 – 7%) and ferro-
silicon (3 – 10%). The apparent density of the used refractory material is 2.5 – 2.62 g/cm
Data have been reported [1 – 4] on the use of a-alumina
as a component of the cathode lining for aluminum electroly-
sis cells, on fluoride salts as impregnators for the lining, and
on the phase transformations in a-Al
involved. In [5, 6],
results of an inspection of a chamotte refractory specimen
sampled from the bottom lining of the base plate of a dis
mantled aluminum electrolysis cell were given.
Here we report results of a study of specimens sampled
from different parts of the chamotte refractory lining of the
bottom of an aluminum electrolysis cell that had been in ser
vice for 3.5 years. The lining of the bottom of the electrolysis
cell was composed of a heat-insulating vermiculite layer
100 mm thick, a layer of dry barrier mixture (DBM) 110 mm
thick, and a refractory layer of ShA-5-grade chamotte refrac
tory 65 mm thick.
Methods of petrography, chemical analysis, and electron
probe x-ray microanalysis (EPXMA) were used in our study.
The specimens were observed in reflected and transmitted
light under MBI-6 and MIN-8 microscopes at magnifications
of ´ 90 – 400, and in reflected light at magnifications of
´ 950 – 1800 using an immersion oil. The EPXMA was car
ried out on an MS-46 Cameca microprobe analyzer.
A total of 50 specimens were sampled from the disused
refractory lining. The sampling scheme is shown in Fig. 1.
Chemical analysis results are summarized in Table 1.
In this communication, results of a comparative analysis
of specimens of intact (pre-service) ShA-5 chamotte refrac
tory and six specimens of post-service chamotte 6-3m;
24-1m, 33-1t, 34-3m, 38-2m, and 40-1m are given.
The commercial ShA-5 chamotte refractory contained
(according to manufacturer’s specifications) 37 – 41% Al
with an open porosity of 22.4 – 24%. The apparent density of
post-service ShA was 2.50 – 2.62 g/cm
The inspected specimens of refractory layer were present
in a range of colors — green, gray, yellow-brown, occasion
ally milky in appearance, hard and stony to touch, in places
exhibiting a zonal pattern. Specimen 33-1t was powdery, of
gray-brown color. The surface of solid, powder-like, and
milky specimens, when tested with phenolphthalein, gave an
alkaline reaction. The characteristic crimson color took dif
ferent times to develop from specimen to specimen — either
instantly or in a matter of several minutes. On the surface or
in the interior of some specimens, cracks, winding or twisted
in appearance, could be observed. Inspection of fracture
specimens revealed the occurrence of porous zones and bub
Refractories and Industrial Ceramics Vol. 46, No. 3, 2005
1083-4877/05/4603-0165 © 2005 Springer Science+Business Media, Inc.
Ukrainian State Research Institute of Special Steels
(UkrNIISpetsstal’), Zaporozhe, Ukraine; Zaporozhye Aluminum
Production Kombinat, Zaporozhe, Ukraine.