Inoculation of Primary Austenite in Grey Cast Iron
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Tutor / director / avaluadorElmquist, Lennart
Diószegi, Attila
Tipus de documentProjecte/Treball Final de Carrera
Data2008
Condicions d'accésAccés restringit per acord de confidencialitat
Abstract
Several chemical inoculants were designed and developed to study and control the
primary g-Fe structure and solidification of grey cast iron. The work involved
literature studies of inoculation chemistry, the selection of different chemical
species such as La2O3, MnO2, Fe2O3 and CaC2 which are supposed to act as
effective nucleants according to the mentioned literature, and their blending with
Fe-powders in order to obtain some new inoculants. Four commercial inoculants,
a Fe/Superseed-powder and a SiC-powder were used as well. These inoculants
were tested in a foundry experiment, where the primary structure was obtained
through direct austempering after solidification—DAAS-technique. Finally they
were evaluated according to the primary austenite grain size, the eutectic cell size
and the dendrite arm spacing—DAS—values obtained.
The results show that pure Fe-powders are the most effective inoculants in
promoting the primary austenite nucleation. Fe/La2O3, Fe/MnO2 and Fe/CaC2
powders were found to be effective as well, Fe/Fe2O3-powders were found to have
a medium-low performance, whereas all the commercial inoculants and the SiC
powder were found to have negative effects on primary austenite nucleation.
It was found that the eutectic phase is obviously influenced by the primary
structure. Indeed, three different correlations between the primary structure and
the eutectic phase were found depending on the kind of melt considered:
inoculated with commercial powders, non-inoculated, or inoculated with noncommercial
powders. In the first case, the bigger the DAS the smaller the primary
austenite grains, and as a consequence the smaller the eutectic cells. In the second
case, the bigger the DAS the bigger primary austenite grains, and as a consequence
the bigger the eutectic cells. And in the third case, for a wide range of DAS values
most of primary austenite grains have a diameter around 1100 μm, and as a
consequence the eutectic cell have a wide range of sizes.
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