Globalisation,
starting in early nineties, led
to the thrust on increasing
productivity in steel industry
for better cost competitiveness.
Consequently, reducing
equipments downtime was the
challenge in front of Refractory
makers, particularly for MgO - C
(Magnesia Carbon) grades.
Not so long ago, fused minerals
were considered as the
industry's elite band of
products - premium materials
commanding premium prices, for
use in high-tech applications.
Fused magnesia was no exception
to this select category of the
synthetic minerals. With time,
driven by wider utilisation,
fused magnesia is now
competitively priced.
Fused magnesia based bricks show
very high corrosion resistance,
when used in high wear areas.
Essentially, slag takes magnesia
into solution at temperature
over 1600 degree, using
fused magnesia, particularly
large crystal size (> 800 µ),
the process is slowed down. The
high grades are used in
intensive heat zones, such as
tuyeres and tap holes.
Fused magnesia of chinese origin
is produced by the electric arc
melting of natural magnesite.
The molten material is allowed
to cool naturally to room
temperature. The material at
core is essentially of purer
grade with larger crystal size.
Purity and size of the fused
magnesia crystal gets reduced as
move towards periphery.
The premium grades of the fused
magnesia command higher prices.
There has been considerable
difference between price of 95%
MgO and price of 97.5% MgO.
Along with large crystal size,
the refractory grade fused
magnesia require high magnesia
content in order to have high
refractoriness. A higher lime
and silica ratio restricts the
formation of low melting
silicates, which otherwise leads
to localised corrosion in the
bricks, while in use. The other
factors which helps in
decreasing wear rate in the MgO-C
bricks are: i) use of high
purity graphite; ii) increasing
MgO level in slag by addition
of Dolo flux to the slag.
In MgO-C bricks, it is difficult
to form ceramic bond which l
