REFRACTORIES IN HEATING UNITS
DESIGN OF A POROUS ANNULAR REFRACTORY INJECTION BLOCK
FOR THE TUNDISH REFINING OF STEEL
A. N. Smirnov,
V. G. Efimova,
and A. V. Kravchenko
Translated from Novye Ogneupory,No.6,pp.3–8,June, 2014.
Original article submitted March 24, 2014.
A new annular injection block containing pores of the optimum size has been developed. Use of the block
maximizes the removal of nonmetallic inclusions from the tundish bath. The efficiency of the block has been
confirmed by theoretical calculations, data obtained from physical modeling, and factory tests.
Keywords: tundish, annular injection block, nonmetallic inclusions, flotation, physical modeling.
The metallurgical practice of using injection equipment
in tundishes has shown that, under certain conditions, such
injection reduces the number of nonmetallic inclusions in the
molten steel if the injection process is carried out in a certain
regime [1 – 3]. The mechanism by which steel is refined by
injecting it with argon involves the capture of nonmetallic in-
clusions by argon bubbles and transport of the inclusions to
the layer of slag [4, 5].
At the same time, data reported in [6 – 8] indicates that
the practice of injecting inert gas into a tundish requires strict
control over the size of the bubbles and the rate at which they
are formed. Such control is necessary because a high gas
flow rate leads to emulsification of the slag and exposure of
the surface of the metal, which in turn facilitates the metal’s
secondary oxidation. It has been determined that the homog
enizing effect of the injection process is diminished as the
distance between the location of the injection block and the
metering nozzle increases.
Inert gas is fed into the tundish through injection equip
ment located in the bottom of the tundish. The main short
comings of the equipment which is presently used for this
purpose: the low degree of efficiency with which nonmetallic
inclusions are removed from the steel due to the use of injec
tion blocks having pores of different diameters; the fact that
only the volumes of metal in the tundish which are located
just above the injection unit can be injected; a high gas flow
rate, which results in emulsification of the slag and lowers
the temperature of the metal being cast [9 – 11].
The goal of our investigation was to create a porous re-
fractory block that maximizes the removal of nonmetallic in-
clusions, stabilizes gas permeability over its entire service
life (several dozen hours), and allows real-time correction of
gas flow rate during the injection process.
The data in  indicates that the total number of inclu
sions entrained each second by gas bubbles formed by an in
jection system will be:
where H is the height of the metal bath, m; V
is the volume
of the liquid steel displaced by a bubble during its flotation to
the free surface, m
are the temperatures of the
gas at the inlet and inside the tundish, respectively, °C; Q
the rate of flow of the gas, m
is the size of a bubble,
is the density of an inclusion, kg·m
Then the percentage of nonmetallic inclusions removed
from the steel d, %, can be represented as
d = 100[1 – exp(–Kt)], (2)
where t is the time of injection, sec.
Data calculated with Eqs. (1) and (2) shows that inclu
sions are most efficiently removed from steel when the diam
Refractories and Industrial Ceramics Vol. 55, No. 3, September, 2014
1083-4877/14/05503-0173 © 2014 Springer Science+Business Media New York
Donetsk National Technical University, Donetsk, Ukraine.
National Technical University of the Ukraine “Kiev Polytechnic
Institute,” Kiev, Ukraine.