RESEARCH IN THE FIELD OF PREPARING MOLDED
AND UNMOLDED REFRACTORIES BASED ON HIGH-ALUMINA HCBS.
PART 6. MULLITIZATION AND THERMAL EXPANSION OF MATERIALS
BASED ON COMPOUND COMPOSITION HCBS
Yu. E. Pivinskii,
P. V. Dyakin,
and A. Yu. Kolobov
Translated from Novye Ogneupory, No. 6, pp. 31 – 38, June 2016.
Original article submitted November 4, 2015.
Sintering and mullitization are studied for specimens prepared on the basis of compound composition HCBS
in the system bauxite – very fine quartz glass (VFQG), and also with addition of refractory clay. The nature of
sintering and mullitization is governed to a considerable extent by SiO
content in the original composition
(VFQG + clay). Dilatometric studies of specimens previously fired at 1600°C established that depending on
composition thermal expansion values in the range 20 – 1000°C are within the limits of 0.5 – 0.6%, which is
close or comparable with similar data for pure mullite.
Keywords: bauxite, corundum, mullite, mullitization, HCBS, VFQG, refractory clay, sintering, thermal
The significant practical interest in production and appli-
cation of various refractories of mullite and mullite-contain-
ing compositions is due to a large extent to their good ther-
mal shock resistance. To a considerable extent the latter is
determined by mullite relatively low thermal expansion
[1 – 7]. According to different publications the linear thermal
expansion index for mullite and materials based on it at
1000°C varies within the limits 0.39 – 0.60%. Compared
with materials based on Al
and MgO used extensively the
thermal expansion of mullite is lower by almost factors of
two and three respectively.
Marked scatter of data should be noted for the linear
thermal expansion coefficient (LTEC) provided in various
publications. In a monograph [1, p. 95] for mullite and
mullite-corundum materials (85 – 95% Al
) LTEC (a)is
provided in the range 25 – 1000°C of 5.06 ´ 10
7.91 ´ 10
respectively. In  for mullite ceramic in
the same temperature range a is from 4.5 ´ 10
5.5 ´ 10
. According to  the value of a for mullite
and corundum ceramics in the same temperature range is
5.3 ´ 10
and 8.8 ´ 10
. These values of a are pro
vided in contemporary textbooks [4, 5]. In a handbook 
a different value of a is provided for fuzed mullite
(6.0 ´ 10
) and mullitized raw material (5.0 ´ 10
Thus, it follows from the data provided that the LTEC index
or equivalent relative linear thermal expansion (TE) for ma
terials of mullite composition at 1000°C is predominantly in
ranges from 0.45 to 0.55% [1 – 7].
The quite wide range of thermal expansion data for
mullite provided in publications is due to presence of impuri
ties (glass phase) and in a number of cases manufacturing
technology. In particular, in  as applied to preparation of
refractory pipes for steel-pouring based on mullite three
molding methods were studied: isostatic compaction, extru
sion, and ramming by means pneumatic tamping. It was es
tablished that the TE index at 1000°C for materials prepared
by these methods comprises 0.40, 0.39, and 0.44% respec
In the present work, taking account of results published
in previous articles of the series [9 – 13], the problem is set
of studying the effect of nonisothermal heating temperature
Refractories and Industrial Ceramics Vol. 57, No. 3, September, 2016
1083-4877/16/05703-0297 © 2016 Springer Science+Business Media New York
Parts 1 – 3 of the article published in Novye Ogneupory Nos. 8,
10, and 12 (2015) and parts 4 and 5 in Nos. 2 and 4 (2016).
OOO NVF Kerambet-Ogneupor, St. Petersburg, Russia.
FGBOU VPO St. Petersburg State Technological University
(Technical University), St. Petersburg, Russia.
OAO Dinur, Pervoural’sk, Sverdlov Region, Russia.