Graphite Phase Characteristics in Compacted/Vermicular Graphite Cast Iron Inoculated in the Mould

Abstract

The objective of this research paper is to examine the effects of adding an oxy-sulphide inoculant enhancer alloy [OS-IE = S,O,Al,Mg-CaSi alloy] to a conventional CaBa-FeSi alloy and to examine the graphite phase characteristics in these irons, as affected by different in the mould inoculants, for resin sand mould castings. The surface layer of all the Mg,RE-FeSi treated compacted / vermicular graphite cast iron samples with 0.018 – 0.023% Mgresis influenced by S diffusion from Furan Resin–P-Toluol Sulphonic Acid (PTSA). The graphite phase is strongly influenced in this surface layer. Inoculation has a visible, beneficial effect in both the surface layer and the body of casting. Even with the highest solidification rate, at the surface layer of the 25mm round bar samples, the structure has the lowest graphite nodularity (15-20%), due to the sulphur content in the mould binder, in contrast with 40-50% nodularity in the casting body. Adding two inoculant type alloys Ca,Ba-FeSi + [OS-IE], led to the highest compacted / vermicular graphite formation. Inoculation with [OS-IE] only appears to encourage the formation of a high number of small graphite nodules that also display higher nodularity. This is represented by the second highest levels for circularity and sphericity shape factors at a much smaller inoculant addition, compared with a conventional Ca,Ba-FeSi inoculant addition. Inoculation with oxide-forming elements or pairing oxy-sulphide inoculant enhancer with commercial inoculants appears to be an economical alternative to rare earth (RE) based inoculants in compacted / vermicular graphite iron casting production.