The purpose of this diploma work is to examine the influence of different inoculants, methods of adding inoculants and casting wall thickness on microstructure of spheroidal cast iron type EN-GJS-400-18LT. 6 step shapped castings were made with wall thicknesess of 10, 20, 30, 40, and 50 mm. Four ferosilicon inoculants were used with the additions of aluminium, barium, zirconium and cerium. First three were added to the molten iron during pouring the liquid from one ladle to another. Inoculant with cerium was added to the barium treated iron, once in the mould and once in the stream. One casting was cast without any inoculant treatment. Microstructure examination was performed by light microscopy, while chemical analysis was performed by optical emission spectroscopy.
EN-GJS-400-18LT has a ferritic, perlitic or ferittic-perliric matrix with embeded graphite nodules. Ferrite content gets higher with wall thickness, as we expected. We found out that inoculant with barium has the worst overall results. Nodule count and ferrite content were the lowest and the casting was porrous in the thickest section. Inoculant with added aluminium provided the most constant nodule count but higher pearlite content compared to other inoculants. Inoculant with zirconium provided hight nodule count and low pearlite content in the thinnest section, but failed to have the same effect in the thicker section. In mould inoculation using inoculant with cerium and pouring barium preinoculated iron gave a bit higher nodule count and ferrite content than using only inoculant with barium. The best results were obtained when inoculating barium treated iron in stream with cerium. Nodule count was the highest, nodule shape spherical throughout the whole casting and pealite content the lowest.
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