CARBONATED PERICALSE REFRACTORIES
WITH FUNCTIONAL ADDITIVES
S. A. Suvorov,
V. A. Musevich,
and F. R. Iksanov
Translated from Novye Ogneupory, No. 6, pp. 58 – 62, June, 2007.
Original article submitted April 13, 2007.
Functional additives have been developed constituting an integrated multiphase ingredient in the form of
finely dispersed powder obtained by sintering the components of the B
–C–Al system at temperatures up to
1450°C. The introduction of such additives into the composition of carbonated periclase refractories improves
the level of their functional parameters.
The continuing upgrade of technology and parameters of
carbon-bearing refractories contributes to extending the pe-
riod of failure-free service of metallurgical furnace lining.
The oxidation of the carbonaceous component consisting
of graphite and coke formed in polymerization of the plasti-
cizing binder (tar, pitch, etc.) started in the interval of 400 –
600°C. The processes of gasification of the carbon compo-
nent at higher temperatures are accompanied by decarboniz-
ing of the refractory in the working layer of the lining, which
produces loss of strength of the microstructure, degradation
of the physicotechnical properties, and shearing in refractory
products due to thermal stresses under thermomechancical
To decrease the gasification of carbon under the effect of
the oxidizing gaseous medium and carbothermal reactions,
antioxidants that have high affinity to oxygen are introduced
into carbon-bearing refractories: aluminum, boron, magne
sium, boron compounds, silicon, silicon carbide, and others
changing the direction of chemical reactions. The added met
als are oxidized faster than the carbonaceous residue of the
plasticizer and graphite . The oxidation of metals in
creases the volume of the phase, which may reduce the po
rosity and gas permeability of the refractory. Such metal ad
ditives facilitate an increase in slag resistance, strength and
other parameters .
The most common antioxidant additives are aluminum
and magnesium. It is especially effective to use several me
tals simultaneously .
The formation of the phases and their stability in firing
periclase-carbon refractories with metal aluminum additives
were investigated in the interval of 600 – 1200°C in an argon
medium. At the initial firing stage, a liquid phase containing
aluminum and magnesium is formed at a temperature below
the melting point of metallic aluminum (660°C). The emerg-
ing liquid phase coexists with MgO and C at temperatures up
to 850°C, above this temperature it slowly dissociates. With
the progress of the reaction, melted aluminum reacts with
carbon and forms Al
in the form of thin plates, whereas
sublimed magnesium associates with oxygen in the surface
layers of the refractory and forms MgO in the form of “nibs”.
At temperatures above 1000°C, Al
reacts with MgO and
forms spinel MgAl
. Since MgAl
coexists with MgO
and C, no further reaction takes place in the refractory .
Samples containing Al+Si additive have higher oxidation re
sistance at high temperatures (above 1200°C), whereas at
low temperatures the more effective is the Al additive. The
use of Mg-containing alloys ensures high slag resistance and
resistance to hydration in samples .
The use of Al additive can significantly improve the
quality of carbonated periclase refractories. However, in this
case the refractory acquires some defects. One of them is in
creased porosity of the refractory. The Al grains enter into a
reaction with graphite and in the course of heating form
. Later Al evaporates from the grains, as a conse
quence, pores are formed, which decrease the corrosion re
sistance of the refractory. The Al
formed on the surface of
Al grains is easily hydrated in the presence of moisture. The
temperature of furnace lining during repairs or idle time be
Refractories and Industrial Ceramics Vol. 48, No. 2, 2007
1083-4877/07/4802-000133 © 2007 Springer Science+Business Media, Inc.
St. Petersburg State Technological Institute (Technical Univer
Reactions with formation of carbides at certain temperatures and
in certain gaseous media.