PRESEED™ PRECONDITIONER - Elkem
PRESEED™ PRECONDITIONER - Elkem
PRESEED™ PRECONDITIONER - Elkem
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PRESEED <br />
<strong>PRECONDITIONER</strong><br />
ISO 9001 ISO 14001 ISO/TS 16949
PRESEED <strong>PRECONDITIONER</strong><br />
A PRECONDITIONING AGENT FOR ALL CAST IRONS<br />
• Consistency in base irons leading to more uniform casting properties<br />
• Improved graphite morphology<br />
• Reduced shrinkage and carbide formation<br />
• Improved mechanical properties<br />
• Reduction in pig iron usage<br />
Preseed preconditioner has been<br />
proven to be an effective furnace<br />
addition for cast irons.<br />
Small additions of Preseed preconditioner<br />
both increase the levels of<br />
nucleation in the base iron and at the<br />
same time stabilise these crucial particles<br />
to give a long lasting effect that<br />
can be measured right through to the<br />
final properties of the solidified iron.<br />
Increased nucleation levels in the base<br />
iron can reduce the reliance on inoculant<br />
additions which, if the base level of<br />
nuclei is low, may not have the power<br />
to give the desired structures and properties.<br />
This can lead to inconsistencies<br />
which can be equalised through the<br />
use of Preseed preconditioner.<br />
Further, increased nucleation levels and<br />
subsequent improvements in graphite<br />
morphology acts to reduce shrinkage<br />
tendency during the later stages of<br />
solidification and improves mechanical<br />
properties such as tensile strength.<br />
What is Preseed Preconditioner<br />
Preseed preconditioner is a 75% Si<br />
based ferroalloy containing balanced<br />
amounts of the active elements zirconium,<br />
aluminium and calcium. Research<br />
has shown that these elements are<br />
necessary to form stable nuclei in the<br />
melt and, by creating these nuclei early<br />
in the melting process, then consistent<br />
iron is produced for sub sequent treatment<br />
and casting.<br />
The stability of these nuclei can be<br />
demonstrated through measurement of<br />
the graphite activity in the iron, thermal<br />
analysis being an excellent tool to do<br />
this. The positive effects of Preseed <br />
preconditioner can be shown when iron<br />
is held for extended periods of time,<br />
even over a weekend when metal is<br />
contained in a holding furnace.<br />
Typically, in electric induction melting,<br />
a 0.1% addition of Preseed preconditioner<br />
together with the ferrosilicon/recarburiser<br />
additions early in the melting<br />
cycle will show positive effects. This<br />
low addition rate makes Preseed preconditioner<br />
a very cost effective method<br />
of obtaining consistent and well nucleated<br />
cast irons. By creating stable<br />
nuclei at this stage of the process and<br />
stabilising nuclei formed from the<br />
charge materials, then the natural loss<br />
of nucleation is prevented. Normally<br />
nuclei are lost to oxidation, agglomeration<br />
and to the slag, how ever, Preseed <br />
preconditioner created nuclei are<br />
retained within the melt and are thus<br />
available for subsequent initiation of<br />
graphite precipitation in the desired<br />
form.<br />
Preseed preconditioner is produced<br />
at the <strong>Elkem</strong> Bremanger plant in Norway,<br />
a world renowned producer of high<br />
quality inoculants, such as Superseed ® ,<br />
Superseed ® Extra and Ultra seed ®<br />
in oculants. <strong>Elkem</strong> Bremanger has ISO<br />
9001, ISO 14001 and ISO/TS 16949<br />
accreditations.<br />
Preseed preconditioner is produced<br />
in a 0 – 10 mm grading in a variety<br />
of packaging to suit the customer’s<br />
require ments, however most customers<br />
find 25 kg bags very convenient for<br />
storage by the furnace. Preseed preconditioner<br />
is produced to the following<br />
specification:<br />
Chemical Specification<br />
Silicon 62 – 69%<br />
Zirconium 3 – 5%<br />
Aluminium 3 – 5%<br />
Calcium 0.6 – 1.9%<br />
Iron<br />
Balance<br />
Barinoc ® , Foundrisil ® , Reseed ® , SMZ ® , Superseed ® , Ultraseed ® , Vaxon ® and Zircinoc ®<br />
are registered trademarks of <strong>Elkem</strong> AS. Preseed is a trademark of <strong>Elkem</strong> AS.
Traditional Preconditioning<br />
The advantages of preconditioning cast<br />
irons are well known in the industry.<br />
Typically, materials such as silicon carbide,<br />
ferrosilicon, and, more recently,<br />
high barium containing ferrosilicons<br />
have been used at a relatively late<br />
stage in the casting process. Whilst<br />
providing a short-term benefit, all of<br />
these mate rials suffer from fade and the<br />
“preconditioning” effect is lost within<br />
minutes. In many respects, these<br />
materials may be regarded as pre-inoculants<br />
rather than preconditioners.<br />
base metal, if held for 50 minutes, would<br />
be expected to lose nucleation with consequent<br />
reduction in the low eutectic<br />
temperature (LET) and increases in<br />
re calescence (R). This would indicate<br />
a loss of nucleation that may lead to<br />
unsatisfactory and inconsistent castings<br />
being produced. Chill and shrinkage<br />
could be two of the factors found in<br />
these castings.<br />
With a small 0.1% addition of Preseed <br />
preconditioner, the casting properties<br />
have not only been maintained, but the<br />
nucleation level can actually be seen<br />
to be higher, even after 50 minutes,<br />
than in the untreated iron which has<br />
not been held. The LET is higher and<br />
this leads to a reduction in the recaleascence.<br />
Sound castings can be<br />
safely made from this iron.<br />
Preseed preconditioner acts in a<br />
different way. The traditional method<br />
of preconditioning has been to add the<br />
alloy at a fairly late stage, together with<br />
the nodulariser or immediately prior to<br />
tapping from the furnace for example.<br />
Preseed preconditioner is added to<br />
the iron early in the melting cycle, normally<br />
together with the ferro silicon and<br />
recarburiser. Preseed preconditioner<br />
creates stable and long lasting nuclei<br />
which are resistant to the rigours of<br />
melting and subsequent treatments.<br />
Figure 1 shows the long-evity effect of<br />
Preseed preconditioner through the<br />
use of thermal analysis curves.<br />
The curves clearly show the effects of<br />
Preseed preconditioner. The untreated<br />
Figure 1: The effects of Preseed preconditioner: Initial base iron without<br />
Preseed , LET at 1139°C (left). Base iron with 0.1% Preseed , LET at 1145°C<br />
after 50 min holding time in a furnace (right).<br />
Reduction in Pig Iron Usage<br />
In many countries, there is a significant<br />
differential in the prices of steel scrap<br />
and pig iron. Pig iron is a source of<br />
carbon or carbon/silicon units and<br />
makes a contribution to the nucleation<br />
state of the iron through the inherent<br />
nuclei in the pig iron and through the<br />
rust (iron oxide) coating.<br />
The use of Preseed preconditioner to<br />
replace partially or wholly the pig iron<br />
has been shown to be possible, allowing<br />
foundries to increase the amounts of<br />
returns as a replacement for the pig<br />
iron. In cases where the pig iron has<br />
been replaced by Preseed preconditioner<br />
plus steel scrap, then compensation<br />
must be made to balance the<br />
carbon (and silicon) levels in the iron.
Consistency in Base Irons<br />
Many foundries suffer from occasional<br />
structural problems, whether it be a<br />
sudden increase in shrinkage, poor<br />
graphite structures or iron carbides<br />
(chill). The natural tendency is to look<br />
at the inoculating process and to<br />
attempt to cure the problem by adding<br />
more inoculant. Often, the fundamental<br />
cause is further back in the iron preparation<br />
process and can be related to<br />
inconsistencies in the base iron.<br />
Variations in steel scrap, charging<br />
sequences, power inputs, unavoidable<br />
holding times and fluctuating temperatures<br />
can all affect the base iron nucleation.<br />
Many foundries use quantitative<br />
chemical analysis, such as a spectro,<br />
to determine the level of carbon, silicon<br />
etc in the base iron before casting,<br />
although these analyses do not indicate<br />
the level of nucleation, or graphite<br />
activity, in the iron. Two furnaces may<br />
have the same chemical analysis,<br />
however one may have been held for<br />
some time, due to a breakdown, for<br />
example, and have a significantly lower<br />
nucleation than one poured within the<br />
normal time. This can lead to two completely<br />
different sets of castings being<br />
produced, albeit within specification<br />
according to the spectro.<br />
Figure 2 demonstrates the effect of<br />
variations in the base iron nucleation<br />
level. The inoculant addition has a finite<br />
effect and a good base nucleation plus<br />
the inoculant will give the desired structure<br />
and properties. If the base iron<br />
nucleation is low, then the inoculant<br />
may not have the capability to give<br />
sufficient nucleation. Conversely, if the<br />
base nucleation is too high, then an<br />
over-inoculation state can be reached<br />
with the danger of shrinkage.<br />
The use of Preseed preconditioner has<br />
been demonstrated to equalise the base<br />
iron variations to give a much more<br />
consistent iron from the furnace, thus<br />
leading to more consistent casting<br />
properties. As Preseed preconditioner<br />
has been shown to have a long term<br />
effect, any delays in pouring will not<br />
result in sub-standard castings.<br />
Figure 2: Effect of variable base iron<br />
nucleation levels.<br />
Case Studies<br />
Increases in the base nucleation and<br />
nuclei stability through the use of Preseed<br />
preconditioner have led to<br />
foundries reporting improved graphite<br />
morphology, physical and mechanical<br />
properties in grey, ductile and compacted<br />
graphite irons:<br />
Grey iron brake discs are produced by<br />
induction melting of iron in this European<br />
foundry. In competing for a major<br />
<strong>Elkem</strong> AS<br />
Foundry Products<br />
Hoffsveien 65B<br />
P.O. Box 5211<br />
Majorstuen<br />
N-0303, Oslo, Norway<br />
Telephone : +47 22 45 01 00<br />
Telefax : +47 22 45 01 52<br />
www.foundry.elkem.com<br />
automotive manufacturer’s contract<br />
they produced sample discs with the<br />
use of Preseed preconditioner. Compared<br />
to their nor mal process they<br />
achieved virtually 100% type A graphite<br />
and no edge carbides. Their mechanical<br />
properties increased by 10%. They won<br />
the contract and now use Preseed <br />
preconditioner in every melt.<br />
Large, high volume automotive component<br />
producer with Disamatic moulding<br />
lines. Problems with occasional subnodular<br />
structures causing delays to<br />
production. The use of Preseed preconditioner<br />
has virtually eliminated<br />
sub-nodular treatments.<br />
High strength large diesel blocks and<br />
heads are made in this foundry. If the<br />
nucleation is too high, they get shrinkage,<br />
if it is too low, they get carbides.<br />
The use of Preseed preconditioner has<br />
helped them to stabilise their metal and<br />
the occurrence of such defects is now<br />
very rare.<br />
This concast bar producer uses<br />
Preseed preconditioner in every melt<br />
to ensure stability in grey and ductile<br />
bars. Since Preseed preconditioner<br />
was introduced, they have had no failures<br />
due to low mechanical properties<br />
Producer of compacted graphite piston<br />
rings reports that the use of Preseed <br />
preconditioner has considerably improved<br />
the dispersion of compacts<br />
within the structure and led to more<br />
consistent castings and machining<br />
properties.<br />
This medium sized ductile iron jobbing<br />
foundry used to add 25% pig iron to<br />
all melts. They have now replaced half<br />
of the pig iron with cheaper steel scrap<br />
+ 0.1% Preseed preconditioner. Over<br />
a long period, they have seen no<br />
changes to their final iron properties,<br />
but have saved large amounts of money<br />
by reducing the pig iron addition.<br />
Revised April 2012 © Copyright <strong>Elkem</strong> AS