The final stage of steelmaking is casting.
Refractory
shrouds are used during casting to prevent atmospheric exposure
and therefore allow reactions to occur between oxygen and
alloying
elements in the molten steel resulting in
inclusions
being formed. Other practices are also used during casting
which actively promote the removal of inclusions from the
steel, thereby improving steel cleanness:
Electromagnetic slag detection in the exit port from the
steelmaking ladle is used to prevent ladle top slag being carried
over into the tundish and entrained in the inclusion population;
as the steel level in the ladle falls during casting, there is a
chance of ladle top slag being entrained in the steel flow through
the exit port. If this happens the magnetic flux measured by
detector coils changes and sends as signal which shuts off the
steel flow from the ladle.
'Tundish Furniture' is used to generate steel flows in the
caster tundish which promote inclusion removal to the tundish
powder layer, with a steel cleaning effect; dams and weirs are
commonly used to set up steel flows across the steel / tundish
powder interface. By doing this, the distance which an inclusion
must travel to float out of the steel and be captured in the
tundish powder is reduced, thereby promoting steel cleaning.
Flow from the tundish to the mould is controlled via a stopper
rod or sliding gate mechanism which is linked to the metal lever
detector in the mould. This stream is also shrouded by a
refractory tube which is carefully designed to optimise flow
conditions in the mould and promote conditions for any further
inclusion flotation.
Select different liquid steel feed rates to the
tundish from the ladle to investigate the effect on the
possibility of generating non-metallic inclusions in the final
steel product.
- The results of sampling at different pouring speeds can be
copied and pasted into spreadsheet applications.
- The micros are generated from the calculated size
distributions - they provide a good visualization of the
importance of pouring speed.
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