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 pdf-document (160 kb) |
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| Summary |
Slag carry-over from the furnace to the ladle is known
to result in reduced alloy and aluminium recovery as
well as affecting the level of cleanliness in the final
steel. The SWIMTAP BOS slag retention system is a widely
used and well proven system for the efficient prevention
of slag carry-over into the ladle during tapping. |
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| Description |
SWIMTAP is designed like a fishing ‘float’ and
is used towards the end of tapping of a BOS vessel to
prevent slag carry-over from the vessel into the ladle.
SWIMTAP consists of a refractory cone, possibly with
a discharge runner on the side. The cone is guided in
the tapping hole by a refractory rod which consists of
an inner steel bar and a monolithic refractory coating. |
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| Application |
SWIMTAP is designed such that its density allows it to
sink through the slag but float on top of the steel.
It is added to the furnace above the tap hole towards
the end of tap. The steel is allowed to flow into the
ladle until only the slag remains, when the SWIMTAP closes
the tap hole thus preventing the slag from leaving the
furnace. A mechanical applicator is required to accurately
position the SWIMTAP float above the BOF tap hole. Only
by this means can the units be successfully and consistently
positioned in the taphole, ensuring that slag carry-over
is reduced to a minimum. |
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| Function |
Whilst SWIMTAP alone can prevent up to 90% of slag carry-over,
when used in conjunction with RAMTAP the system can result
in almost slag free tapping. RAMTAP is designed to prevent
the pre-slag carry-over that results when the vessel
is first tilted, helping to eliminate initial slag carry-over. |
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| Benefits |
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Improved recovery of alloying elements such as
manganese, silicon and chromium.
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Reduced aluminium consumption and more consistent
recovery. |
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Improved ladle refractory life due to reduced amount
of oxidising slag carry-over.
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Improved cleanliness of the final steel as measured
by surface defects and non-metallic inclusion levels.
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