RESEARCH IN THE FIELD OF PREPARING MOLDED
AND UNMOLDED REFRACTORIES BASED ON HIGH-ALUMINA HCBS.
PART 2. PROPERTIES OF STARTING COMPONENTS AND CASTINGS
BASED ON COMPOSITE COMPOSITION HCBS. STUDY OF THE INITIAL
STAGE OF SINTERING AND MULLITIZATION
Yu. E. Pivinskii
and P. V. Dyakin
Translated from Novye Ogneupory, No. 10, pp. 50 – 57, October 2015.
Original article submitted June 19, 2015.
The initial stages of sintering and mullite formation are studied for specimens based on HCBS of complex
composition prepared by combined wet milling of high-alumina bauxite and fuzed quartz. The starting materi
als have a different ratio of components and solid phase particle fineness. The initial sintering stage is in the
range 900 – 950°C, and mullite formation 1100 – 1150°C. In the range 1150 – 1200°C there are simulta-
neously both sintering and mullite formation. Depending on fineness and fuzed quartz HCBS content the max-
imum amount of shrinkage is 0.35 – 0.60%. An increase in firing temperature to above 1200°C is accompa-
nied by specimen growth and an increase in porosity. Even with an insignificant level of the proportion of
sintering pores (0.09 – 0.11) materials have an ultimate strength in bending of 100 – 130 MPa and open poros-
ity of 14 – 16%.
Keywords: bauxite, corundum, very fine quartz glass, HCBS, silicate modulus, mullite, secondary mullite
formation, isothermal and nonisothermal sintering, shrinkage, growth, porosity, ultimate strength in bending.
STARTING MATERIALS, COMPOSITE HCBS
COMPOSITION AND PROPERTIES
The main starting material used for preparing composite
HCBS in a bauxite – very fine quartz glass (VFQG) system
was Chinese bauxite chamotte (BCh) Rota HD  fraction
1 – 3 mm, whose apparent density is 3.23 g/cm
, true density
, open porosity 9.6%, overall porosity about 12%.
The oxide content in bauxite chamotte was, wt.%: Al
1.32, CaO + MgO 0.35,
O 0.2; phase composition, %: 82 corundum,
10 – 11 mullite,5–6titanium compound,2–4glass phase.
As an additional solid phase component for HCBS of
mixed composition there has been use of previously prepared
finely dispersed suspension of fuzed quartz previously pre
pared by wet milling [2 – 4] with an SiO
content of 98.9%
and 0.7% Al
. A suspension (VFQG) from calculation of
quartz content of 5.5 – 15 wt.% (dry) was introduced into a
charge composition for milling together with granular baux
ite and a required amount of water, proceeding from a re
quirement for achieving a suspension density of
2.75 – 2.78 g/cm
, which corresponds to C
» 0.68 – 0.70 or
a moisture content of about 11%. The thinner added in an in
significant amount (about 0.01 wt.%) was liquid water glass
with a silicate modulus m = 3.0. HCBS of the mixed compo
sition was prepared by wet milling in an industrial ball mill
with a volume of 3.5 m
with single-stage loading. High-alu
mina (uralite) milling bodies (density 3.15 – 3.20 g/cm
were used, and the same mill lining [2 – 4, 10]. The contents
within them were 75 – 78 and 15 – 18%
respectively. Grinding of milling bodies and lining was
1 – 3% depending on the amount of them and prescribed
fineness, and did not have a marked effect on HCBS solid
phase final chemical composition.
Refractories and Industrial Ceramics Vol. 56, No. 5, January, 2016
1083-4877/16/05605-0544 © 2016 Springer Science+Business Media New York
Part 1 of the article published in Novye Ogneupory No. 8 (2015).
OOO NVF Kerambet-Ogneupor, St. Petersburg, Russia.
FGBOU VPO St. Petersburg State Technological University
(Technical University), St. Petersburg, Russia.