PRESEED™ PRECONDITIONER - Elkem

PRESEED
PRECONDITIONER
ISO 9001 ISO 14001 ISO/TS 16949

PRESEED PRECONDITIONER
A PRECONDITIONING AGENT FOR ALL CAST IRONS
• Consistency in base irons leading to more uniform casting properties
• Improved graphite morphology
• Reduced shrinkage and carbide formation
• Improved mechanical properties
• Reduction in pig iron usage
Preseed preconditioner has been
proven to be an effective furnace
addition for cast irons.
Small additions of Preseed preconditioner
both increase the levels of
nucleation in the base iron and at the
same time stabilise these crucial particles
to give a long lasting effect that
can be measured right through to the
final properties of the solidified iron.
Increased nucleation levels in the base
iron can reduce the reliance on inoculant
additions which, if the base level of
nuclei is low, may not have the power
to give the desired structures and properties.
This can lead to inconsistencies
which can be equalised through the
use of Preseed preconditioner.
Further, increased nucleation levels and
subsequent improvements in graphite
morphology acts to reduce shrinkage
tendency during the later stages of
solidification and improves mechanical
properties such as tensile strength.
What is Preseed Preconditioner
Preseed preconditioner is a 75% Si
based ferroalloy containing balanced
amounts of the active elements zirconium,
aluminium and calcium. Research
has shown that these elements are
necessary to form stable nuclei in the
melt and, by creating these nuclei early
in the melting process, then consistent
iron is produced for sub sequent treatment
and casting.
The stability of these nuclei can be
demonstrated through measurement of
the graphite activity in the iron, thermal
analysis being an excellent tool to do
this. The positive effects of Preseed
preconditioner can be shown when iron
is held for extended periods of time,
even over a weekend when metal is
contained in a holding furnace.
Typically, in electric induction melting,
a 0.1% addition of Preseed preconditioner
together with the ferrosilicon/recarburiser
additions early in the melting
cycle will show positive effects. This
low addition rate makes Preseed preconditioner
a very cost effective method
of obtaining consistent and well nucleated
cast irons. By creating stable
nuclei at this stage of the process and
stabilising nuclei formed from the
charge materials, then the natural loss
of nucleation is prevented. Normally
nuclei are lost to oxidation, agglomeration
and to the slag, how ever, Preseed
preconditioner created nuclei are
retained within the melt and are thus
available for subsequent initiation of
graphite precipitation in the desired
form.
Preseed preconditioner is produced
at the Elkem Bremanger plant in Norway,
a world renowned producer of high
quality inoculants, such as Superseed ® ,
Superseed ® Extra and Ultra seed ®
in oculants. Elkem Bremanger has ISO
9001, ISO 14001 and ISO/TS 16949
accreditations.
Preseed preconditioner is produced
in a 0 – 10 mm grading in a variety
of packaging to suit the customer’s
require ments, however most customers
find 25 kg bags very convenient for
storage by the furnace. Preseed preconditioner
is produced to the following
specification:
Chemical Specification
Silicon 62 – 69%
Zirconium 3 – 5%
Aluminium 3 – 5%
Calcium 0.6 – 1.9%
Iron
Balance
Barinoc ® , Foundrisil ® , Reseed ® , SMZ ® , Superseed ® , Ultraseed ® , Vaxon ® and Zircinoc ®
are registered trademarks of Elkem AS. Preseed is a trademark of Elkem AS.

Traditional Preconditioning
The advantages of preconditioning cast
irons are well known in the industry.
Typically, materials such as silicon carbide,
ferrosilicon, and, more recently,
high barium containing ferrosilicons
have been used at a relatively late
stage in the casting process. Whilst
providing a short-term benefit, all of
these mate rials suffer from fade and the
“preconditioning” effect is lost within
minutes. In many respects, these
materials may be regarded as pre-inoculants
rather than preconditioners.
base metal, if held for 50 minutes, would
be expected to lose nucleation with consequent
reduction in the low eutectic
temperature (LET) and increases in
re calescence (R). This would indicate
a loss of nucleation that may lead to
unsatisfactory and inconsistent castings
being produced. Chill and shrinkage
could be two of the factors found in
these castings.
With a small 0.1% addition of Preseed
preconditioner, the casting properties
have not only been maintained, but the
nucleation level can actually be seen
to be higher, even after 50 minutes,
than in the untreated iron which has
not been held. The LET is higher and
this leads to a reduction in the recaleascence.
Sound castings can be
safely made from this iron.
Preseed preconditioner acts in a
different way. The traditional method
of preconditioning has been to add the
alloy at a fairly late stage, together with
the nodulariser or immediately prior to
tapping from the furnace for example.
Preseed preconditioner is added to
the iron early in the melting cycle, normally
together with the ferro silicon and
recarburiser. Preseed preconditioner
creates stable and long lasting nuclei
which are resistant to the rigours of
melting and subsequent treatments.
Figure 1 shows the long-evity effect of
Preseed preconditioner through the
use of thermal analysis curves.
The curves clearly show the effects of
Preseed preconditioner. The untreated
Figure 1: The effects of Preseed preconditioner: Initial base iron without
Preseed , LET at 1139°C (left). Base iron with 0.1% Preseed , LET at 1145°C
after 50 min holding time in a furnace (right).
Reduction in Pig Iron Usage
In many countries, there is a significant
differential in the prices of steel scrap
and pig iron. Pig iron is a source of
carbon or carbon/silicon units and
makes a contribution to the nucleation
state of the iron through the inherent
nuclei in the pig iron and through the
rust (iron oxide) coating.
The use of Preseed preconditioner to
replace partially or wholly the pig iron
has been shown to be possible, allowing
foundries to increase the amounts of
returns as a replacement for the pig
iron. In cases where the pig iron has
been replaced by Preseed preconditioner
plus steel scrap, then compensation
must be made to balance the
carbon (and silicon) levels in the iron.

Consistency in Base Irons
Many foundries suffer from occasional
structural problems, whether it be a
sudden increase in shrinkage, poor
graphite structures or iron carbides
(chill). The natural tendency is to look
at the inoculating process and to
attempt to cure the problem by adding
more inoculant. Often, the fundamental
cause is further back in the iron preparation
process and can be related to
inconsistencies in the base iron.
Variations in steel scrap, charging
sequences, power inputs, unavoidable
holding times and fluctuating temperatures
can all affect the base iron nucleation.
Many foundries use quantitative
chemical analysis, such as a spectro,
to determine the level of carbon, silicon
etc in the base iron before casting,
although these analyses do not indicate
the level of nucleation, or graphite
activity, in the iron. Two furnaces may
have the same chemical analysis,
however one may have been held for
some time, due to a breakdown, for
example, and have a significantly lower
nucleation than one poured within the
normal time. This can lead to two completely
different sets of castings being
produced, albeit within specification
according to the spectro.
Figure 2 demonstrates the effect of
variations in the base iron nucleation
level. The inoculant addition has a finite
effect and a good base nucleation plus
the inoculant will give the desired structure
and properties. If the base iron
nucleation is low, then the inoculant
may not have the capability to give
sufficient nucleation. Conversely, if the
base nucleation is too high, then an
over-inoculation state can be reached
with the danger of shrinkage.
The use of Preseed preconditioner has
been demonstrated to equalise the base
iron variations to give a much more
consistent iron from the furnace, thus
leading to more consistent casting
properties. As Preseed preconditioner
has been shown to have a long term
effect, any delays in pouring will not
result in sub-standard castings.
Figure 2: Effect of variable base iron
nucleation levels.
Case Studies
Increases in the base nucleation and
nuclei stability through the use of Preseed
preconditioner have led to
foundries reporting improved graphite
morphology, physical and mechanical
properties in grey, ductile and compacted
graphite irons:
Grey iron brake discs are produced by
induction melting of iron in this European
foundry. In competing for a major
Elkem AS
Foundry Products
Hoffsveien 65B
P.O. Box 5211
Majorstuen
N-0303, Oslo, Norway
Telephone : +47 22 45 01 00
Telefax : +47 22 45 01 52
www.foundry.elkem.com
automotive manufacturer’s contract
they produced sample discs with the
use of Preseed preconditioner. Compared
to their nor mal process they
achieved virtually 100% type A graphite
and no edge carbides. Their mechanical
properties increased by 10%. They won
the contract and now use Preseed
preconditioner in every melt.
Large, high volume automotive component
producer with Disamatic moulding
lines. Problems with occasional subnodular
structures causing delays to
production. The use of Preseed preconditioner
has virtually eliminated
sub-nodular treatments.
High strength large diesel blocks and
heads are made in this foundry. If the
nucleation is too high, they get shrinkage,
if it is too low, they get carbides.
The use of Preseed preconditioner has
helped them to stabilise their metal and
the occurrence of such defects is now
very rare.
This concast bar producer uses
Preseed preconditioner in every melt
to ensure stability in grey and ductile
bars. Since Preseed preconditioner
was introduced, they have had no failures
due to low mechanical properties
Producer of compacted graphite piston
rings reports that the use of Preseed
preconditioner has considerably improved
the dispersion of compacts
within the structure and led to more
consistent castings and machining
properties.
This medium sized ductile iron jobbing
foundry used to add 25% pig iron to
all melts. They have now replaced half
of the pig iron with cheaper steel scrap
+ 0.1% Preseed preconditioner. Over
a long period, they have seen no
changes to their final iron properties,
but have saved large amounts of money
by reducing the pig iron addition.
Revised April 2012 © Copyright Elkem AS