improving performance in furnace melt treatment process - Pyrotek

Alan Peel,
Managing Director
EMP Division
Page 4
In-Furnace Melt Treatment Process
Purchasing
pure
alloy elements
in a form
that can be
charged
directly
into the
vortex of an
EMP System
also can give
some
financial
benefits.
ALLOYING - A Critical First Step
In Improving Melt Treatment
Performance
Alloying is the modification of melt
chemistry to meet casting specifications. It
is typically done in the melting furnace and
adjusted in the holding furnaces or during
transfer. Alloying elements include, but are
not limited to: silicon, iron, magnesium,
manganese, copper and chromium. Stirring
and melt homogenization are key
components of the alloying process.
Alloying cycle times must allow for
adequate dissolution time as well as for the
time required to complete proper furnace
skimming, refining and settling. For certain
applications, there is a need to select highgrade
alloys (for example, low Fe and Ca
silicon metal for wheel/rim alloys).
To maximize efficiency, operating practices
must measure alloying recoveries, adjust
furnace temperatures and processing
techniques to optimise alloy additions. If
operating in conjunction with a primary
smelter, it is often possible to utilise the hot
metal superheat – a potential source of free
furnace energy. Use powders, flakes and
tablets rather than ingot or waffle to reduce
energy costs and to accelerate dissolution
rates when they can be efficiently stirred
into the metal.
The use of effective techniques to facilitate
forced circulation of the melt during the
melting and alloying phases of the process
demonstrates improvements in cycle times
and more efficient use of expensive alloying
materials.
The EMP and Metaullics division both offer
the LOTUSS vortex system which is a
highly effective method of submergence for
both scrap and alloying materials.
Traditional methods for alloying in the cast
house utilized pre-prepared master alloys.
These are charged directly into the melting
or holding furnace and ‘stirred in’ with the
assistance of the dross rake. The problem
associated with this technique is that it tends
to take longer for the alloy addition to
become fully mixed into the melt as the
mixing is reliant upon the drossing tool to
PYROTEK
SUPPLEMENT
fully mix the bath and master alloys. In an
attempt to overcome this problem of
effective mixing, the master alloys are
usually made with a special flux that
accelerates the mixing of the alloy addition
into the melt.
The EMP and Metaullics pumping systems
for light gauge scrap additions have the
advantage of the unique vortex well as a
medium for the addition of alloys into the
furnace. The furnace door is kept closed
during the entire process, with the following
three operating benefits:
Maintaining the heat transfer efficiency
of the furnace,
Minimising energy losses, and
Minimising environmental emissions to
the casthouse and operators.
The LOTUSS vortex system eliminates the
need to alloy directly through the furnace
doors or by using specially made alloy
tablets. The pure elemental additions Mn
flake, Fe splatter, Cu cuttings/swarf and Mg
bars can now be used in an effective way
by charging directly through the EMP
Vortex.
Fig. 1 Magnesium Ingots Charged Directly Into
the EMP Vortex
Economic Benefits to Alloying Through
The Vortex
With the appropriate feeding equipment,
alloys from lump silicon to magnesium have
been effectively charged into a furnace with
significant reductions in alloy losses and an
improved dissolution time of the alloy into
the melt.
The following graph demonstrates the fast
dissolution of magnesium ingots through a
vortex.