STEEL + TECHNOLOGY 01/2020 EXTRACT

42 | STEEL TECHNOLOGY
Figure 10. Microstructure of crucible test 1 - conventional ladle
well filler and Steel 1 (SEM 150x) (Picture: Purmetall)
Figure 11. Microstructure of crucible test 2 - conventional ladle
well filler and Steel 2 (SEM 22x) (Picture: Purmetall)
and a manganese steel 2 (crucible test 2).
The ladle well filler is shown in light grey
whereas the corundum crucible is shown
in dark grey. It is obvious that the ladle well
filler infiltrated the structure of the crucible
and destroyed it. According to this a more
intense contact reaction took place
between the conventional ladle well filler
and the corundum crucible.
Steel 2 shows in this crucible test (crucible
test 2) a more intense reaction process
compared to crucible test 1 showing
a less intense reaction, visible by the grade
of infiltration into the crucible.
Conventional ladle well filler and steel 2
do also show redox reactions, as shown by
EDX-analyses (reading points 1 and 2 in
table 3). Reading point 1 shows a MnO-rich
phase which consists of MnO and oxides of
the ladle well filler forming a manganese-chromite
spinel. Reading point 2 of
table 3 furthermore shows that steel 2 lost
manganese and aluminium whereas a
chrome-pickup took place. Figure 12 shows
a SEM-picture of the structure of the contact
zone of a new developed ladle well filler
with manganese steel 2 (crucible test 3).
During crucible test 3 no redox reactions
between the new developed ladle
well filler and the manganese steel (steel
2) took place. EDX analyses therefore give
neither evidence on loss of Mn, Al or Si of
the steel nor a Cr-pickup into the steel.
These observations explain the visual
impression, shown in figure 9, that only a
small reaction potential occurs between
the new ladle well filler, manganese steel
and the crucible.
Conclusion
Figure 12. Microstructure
of crucible
test 3 - new type of
ladle well filler and
Steel 2 (SEM 230x)
(Picture: Purmetall)
Due to field tests it was possible to
demystify the behaviour of ladle well fillers
during real conditions. Ladle well filler do
not act as inert fillings which are heated
through by the temperature of the liquid
steel and therefore sinter as a function of
ladle well filler thickness. In fact, the ladle
well filler can be solved by thermochemical
and erosive processes like tapping the
furnace or rinsing treatments. These processes
are time-depending, explaining
why free opening rates decrease with
increasing retention time of the steel in the
ladle. The alloy composition of the overlaying
steel strongly affects the thermochemical
processes in the ladle well filler. The
conventional ladle well filler completely
dissolved in the presence of steel with
16% manganese content. For the ongoing
development of high-performance steel
grades, a new generation of ladle well fillers
is necessary. Basis for the successful
development of next generation ladle well
fillers is the exact knowledge of the reaction
behaviour of the involved oxides and
elements. Identifying all available reaction
partners and their impact on the reactivity
of ladle well fillers during steelmaking is
subject of ongoing research.
References
[1] Bombeck, M. A.; Janssen, M.; Dannert, C.;
Deinet, T.; Alonso Ona, I.: Grundlegende Untersuchungen
zur Funktionsweise von Schiebersanden.
stahl und eisen 136 (2016) 8, 35-41
[2] Bombeck, M. A.; Janssen, M.; Deinet, T.; El Gammal,
A.: Verhalten von Schiebersanden bei Kontakt
mit flüssigem Stahl“, stahl und eisen 139
(2019) Nr. 4, 46-50
STEEL + TECHNOLOGY 2 (2020) No. 1