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PRESEED <br />

<strong>PRECONDITIONER</strong><br />

ISO 9001 ISO 14001 ISO/TS 16949

PRESEED <strong>PRECONDITIONER</strong><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

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