THE SLAG REGIME OF EQUIPMENT
USED FOR THE SECONDARY TREATMENT OF STEEL
AND THE DURABILITY OF ITS REFRACTORIES
O. Yu. Sheshukov,
I. V. Nekrasov,
M. A. Mikheenkov,
D. K. Egiazar’yan,
L. A. Ovchinnikova,
A. A. Metelkin,
I. D. Kashcheev,
and V. S. Tsepelev
Translated from Novye Ogneupory, No. 8, pp. 7 – 12, August, 2015.
Original article submitted March 19, 2015.
The composition of the ladle slag in units designed for the secondary treatment of steel needs to be optimized
in order to increase the service life of the units’ linings. On the one hand, the slag subjects the refractories to
chemical wear. On the other hand, under certain conditions the slag is capable of forming a protective crust in
side the units. The Nizhniy Tagil Metallurgical Combine has chosen certain refractories for the most heavily
worn part of the lining of its vacuum chambers, since only the installation of a lining of a differentiated design
that equalizes the rate of wear around the lining’s perimeter will allow the desired effect to be obtained from
optimizing the composition of the slag. An efficient composition for the slag was also chosen, the slag having
high contents of MgO and Al
. The use of such a slag helps form a protective slag crust of the composition
on spinel refractories having the compositions MgO·Cr
Keywords: lining design, vacuum chamber, slag crust, spinel, slag temperature.
The importance of the work being done to make the lin
ings of steelmaking furnaces more durable is beyond dispute.
The service life of the refractories that are used for the lin
ings in large part determines the profitability and safety of
the steelmaking operation .
At large modern factories such as the Nizhniy Tagil Met
allurgical Combine (OAO EVRAZ NTMK), the cost of ac
quiring refractories for the secondary (ladle) treatment of
steel accounts for more than 30% of the total expenditure on
refractory materials [2, 3]. The importance of improving the
durability of secondary steel-treatment units stems from the
decisive effect that these pieces of equipment have on the
quality of the finished steel [3, 4]. In ladle-furnace units
(LFUs) and vacuum-degassing units (VDUs), liquid steel is
treated by a refining slag that rids the steel of sulfur, oxygen,
and nonmetallic inclusions (NIs).
Experience shows that the composition of the refining
slag affects the durability of the refractories [2, 3, 5]. It has
this effect because most (roughly 2/3) of the wear of refrac
tory products occurs chemically — by dissolution of the re
fractory in the slag . This makes it necessary to use ladle
refining slags that are less aggressive toward refractories.
The choice of slag is obviously made more difficult by the
fact that the slag still has to have satisfactory refining proper
ties. Optimizing the slag regime of secondary steel-treatment
units is a complex problem.
However, optimization of the composition of the slag
will have a lasting effect only if the treatment unit is de
signed so as to alleviate the problem of “hot zones” about the
perimeter of the lining. The slag will otherwise affect the du
rability of the least heavily stressed zones — the zones in
which wear is controlled solely by the chemical interaction
of the slag with the refractory. The slag will have less of an
effect in the zones where wear is accelerated thermally or
mechanically. The service life of the treatment unit as a
whole is in fact determined by the “hot zones” referred to
above. Thus, it is best to first explore the ways in which the
design of the lining might be improved.
Refractories and Industrial Ceramics Vol. 56, No. 4, November, 2015
1083-4877/15/05604-0327 © 2015 Springer Science+Business Media New York
Institute of Metallurgy, Ural Branch of the Russian Academy of
Sciences, Ekaterinburg, Russia.
Ural Federal University, Nizhniy Tagil, Russia.
Ural Federal University, Ekaterinburg, Russia.