Inoculation of Cast Iron
An inoculant is a material added to the liquid iron just before casting that provides suitable sites for the nucleation of graphite. The most effective inoculants are ferrosilicon alloys containing small amounts of one or more of the elements Ca, Ba, Sr, Zr and/or Ce.
The micrographs and table below show examples of structures and properties obtained in grey and ductile iron with and without the addition of an inoculant. As seen from the micrographs, the uninoculated castings (left) contain large quantities of hard, brittle iron carbides (cementite, Fe3C) and very poor graphite structures. The inoculated castings (right) contain uniform structures of small, random oriented flakes (grey iron) and a large number of small graphite nodules in a ferrite/pearlite matrix (ductile iron).
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