Inoculation of Primary Austenite in Grey Cast Iron
Tutor / director / evaluatorElmquist, Lennart Diószegi, Attila
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - confidentiality agreement
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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