PRODUCTION AND EQUIPMENT
PROPERTIES AND STRUCTURE OF MAGNESIA MODIFIERS
FOR CONVERTER SLAGS
I. D. Kashcheev,
E. A. Terent’ev,
K. N. Demidov,
T. V. Borisova,
and I. D. Maryasev
Translated from Novye Ogneupory, No. 2, pp. 27 – 34, February, 2007.
Original article submitted June 25, 2006.
Recently with the aim of increasing the stability of converter linings there has been extensive use of a new
class of synthetic magnesia modifiers that are added directly to the converter melt during steel melting. The
chemical composition of modifiers and method for their preparation are provided. The basis of the magnesia
modifiers is MgO oxide and its compounds. Modifier properties (density, open porosity) are studied in relation
to a change in specimen heating and the mineral composition of modifiers of different chemical composition,
and the change in the structure of modifier specimens during heating is examined. The mechanism of modifier
dissolution in molten slag is suggested.
Processing iron in an oxygen converter is accompanied
by formation of slag saturated with a considerable amount of
iron oxides that have a negative effect on the converter lin-
ing. The corrosive nature of slag with respect to the converter
lining, and in fact the amount of MgO passing from the lining
into the molten slag in a unit of time is considerable at the
start of blowing, it decreases during the decarburizing period
and increases towards the end of blowing as a result of an in
crease in the solubility of refractory MgO in the iron slag .
The wear mechanism of periclase-carbon refractories is
accompanied by the following processes:
liquid-phase decarburization of the lining surface layer
by iron oxides and free oxygen;
infiltration of slag into the decarburized layer;
reaction between the refractory and slag that leads to
transfer of MgO into the slag.
Thus wear of periclase-carbon refractories of the con
verter lining is explained by the fact that iron oxide reacting
with the refractory at high temperature during blowing of the
metal (above 1600°C) by the reaction
C + 2(FeO) = CO
forms pores through which there is penetration of slag into
the decarburized layer.
Wear rate v,kg/sec, of the lining is generally described
by the equation :
where F is lining contact area with the slag, m
are the concentration of the diffusing component into the re
fractory and slag respectively, kg/m
; d is diffusion bound
ary layer effective thickness, m; D
are the diffusion
coefficients in the refractory and slag respectively, m
It follows from Eq. (1) that the lining wear rate is directly
proportional to the concentration of the diffusing component
into the solid and liquid phases, i.e. it depends on the concen
tration of iron and magnesium oxides in the slag. Therefore a
reduction in the corrosive action of high iron slag on the
lining may be provided by introducing magnesium-contain
ing materials into the melt.
As applied to the solubility of periclase refractory in con
verter slag Eq. (1) may be replaced by the expression :
– n), (2)
where dn/dt is magnesium oxide dissolution rate; t is time;
D is MgO diffusion coefficient in the slag; F is slag’ refrac
tory reaction surface; d is diffusion layer thickness at the in
Refractories and Industrial Ceramics Vol. 48, No. 1, 2007
1083-4877/07/4801-0017 © 2007 Springer Science+Business Media, Inc.
GOU VPO UGTU-UPI, Ural Institute of Metals Joint Stock
Company (OAO), Magnezit Plant OAO, Tormag Limited Liabi
lity Company (OOO), Russia.