STEEL + TECHNOLOGY 01/2020 EXTRACT

40 | STEEL TECHNOLOGY
ponent crucible tests. Steel grades with
high manganese content regularly have
lowered opening rates; therefore a 16 wt.-
% Mn steel grade was included in the test
series to study the effect of manganese
content on the reactivity between ladle
well filler and steel. Established conventional
ladle well fillers were compared to
newly developed compositions. Table 1
shows the chemical composition of the
two steel grades in wt.-% as measured
with SEM/EDX.
The evaluation of the crucible tests was
based on the visual appearance of the
bisection surfaces and microstructural
examination via SEM/EDX.
Visual examination of the crucible
tests with ladle well filler and steel
Figure 6. Setup of a crucible test with ladle well filler and steel (Picture: Purmetall)
Table 1. Chemical composition of the steel grades used in crucible tests (wt.-%)
Fe Cr Al Si Mn
Steel 1 (ball bearing steel) 96.1% 1.7% -/- 0.5% 1.7%
Steel 2 (high manganese steel) 78.3% -/- 2.7% 2.2% 16.8%
Figure 7 shows one half of a bisected
crucible with conventional ladle well filler
and steel 1 (ball bearing steel). The refractory
alumina crucible shows a distinct discoloration
and noticeable cavitation inside
of the structure of the crucible bottom.
This indicates corrosion and infiltration of
the crucible material by liquid phases of
the ladle well filler or steel. Furthermore,
the ladle well filler shows pronounced
shrinkage that allowed the steel to flow
along the crucible wall to the bottom of the
crucible after reaching its liquidus temperature.
Figure 8 shows one half of a bisected
crucible with conventional ladle well filler
and the manganese rich steel 2. The original
layer of ladle well filler is completely
dissolved and the crucible in its entirety is
infiltrated with liquid phases from the ladle
well filler or steel. The crucible structure
also shows strong structural decay. This is
caused by intense chemical reactions
between the high manganese steel, the
conventional ladle well filler and the alumina
refractory. This high reactivity is a cause
for the regularly low free opening rates
during the production of high manganese
steel grades.
Microstructural examination via
SEM/EDX of crucible-tests with
ladle well filler and steel
Figure 7. Crucible test 1 with conventional ladle well filler and Steel 1 (Picture: Purmetall)
Samples were taken of the present
halved crucibles to prepare polished sections
for scanning electron microscope
analyses. Figure 10 shows a SEM-picture
of the structure in the contact-area of con-
STEEL + TECHNOLOGY 2 (2020) No. 1