NATURAL GRAPHITE AHES AND THEIR EFFECT ON THE PROPERTIES
OF CARBONIZED PERICLASE REFRACTORIES
S. A. Suvorov
and V. A. Musevich
Translated from Novye Ogneupory, No. 5, pp. 35 – 40, May, 2007.
Original article submitted January 29, 2007.
The properties of Chinese natural graphite of grades FG+194 and FG+198 and their ashes are investigated.
The extent of the effect of ash content in graphite on the technical parameters of carbonized periclase
refractories with an increased carbon content is demonstrated. The advisability of using low-ash graphite for
carbon-bearing refractories is justified.
The refractory lining in metallurgical aggregates func
tions under the intense impact of high temperatures, aggres-
sive gaseous media, and thermomechanical loads. The inten-
sification of metallurgical processes calls for new solutions
that could upgrade carbon-bearing refractories and extend
their service life.
The Department of Chemical Engineering of High-Tem-
perature Materials at the St. Petersburg Technological Insti-
tute has substantiated and keeps refining the parameters of
producing a new type of carbonized periclase refractory with
a wide spectrum of carbon content (6 – 22 wt.%), which en-
sures a high level of physicotechnical properties . Optimi
zation of the material and phase compositions, microstruc
ture, and technological parameters of functional carbonized
periclase refractories makes it possible to achieve high ther
momechanical properties and high resistance to degradation
processes . The most significant service characteristics of
such refractories exceed those of the existing analogs and of
fer a high competitive potential on the refractory market.
The developed promising carbonized periclase products
are intended to line steel-casting ladles, ladle-furnace plants,
bay window elements in electric steel-melting furnaces, and
combined brickwork for converter lining with an extended
service life. Depending on the quantity of the carbonaceous
additive, the properties of periclase carbonized refractories
vary within a wide range, which ought to be used in deter
mining the functional purpose of the product in the structure
of lining. For metallurgical aggregate zones with a high level
of mechanical loads the most suitable are refractories con
taining up to 12 wt.% carbon, whereas compositions with an
increased carbon content are preferable for high temperature
gradients and high slag loads. However, an increased content
of the graphite additive decreases the resistance of refrac-
tories to oxidation. Technologically, the production of car-
bonized periclase products (graphite content > 12 wt.%) is
the most difficult. Mixtures for such refractories involve
much air; therefore, the mold in the course of molding re-
quires special ventilation, in particular, vacuum treatment.
The choice of an appropriate composition of the main com-
ponents in the periclase-graphite mixture that would be justi-
fiable with respect to the cost/quality/properties ratio re-
mains a topical problem.
The production of carbonized periclase refractories
uses high-quality materials: melted periclase (MgO ³ 97%,
³ 2), high-purity coarse-scale natural graphite
(C ³ 94%). The carbon phase is dissolved in steel melts, but
significantly increases the resistance of the refractories to
melted pig iron and acid slag, decreases the seepage of the
melts into the refractory, increases the thermal conductivity,
high-temperature strength, and resistance to thermomechani
cal stresses, and lowers the coefficient of linear temperature
As the content of carbon in a carbonized periclase mix
ture grows, the concentration of ash impurities introduced
via the graphite component increases. The graphite ash (min
eral residue) decreases the corrosion resistance of carbonized
periclase refractories, As the content of ash impurities in
natural graphite grows (specific surface area being equal),
the oxidizability decreases and the strength of refractory
samples at room temperature increases. As the degree of
milling of graphite grows, the oxidizability increases .
The properties of periclase-carbon refractories with 20 wt.%
Refractories and Industrial Ceramics Vol. 48, No. 2, 2007
1083-4877/07/4802-000118 © 2007 Springer Science+Business Media, Inc.
St. Petersburg State Technological Institute (Technical Univer