Graphite nucleation sites in commercial grey cast irons

Abstract

Mn and S are present in all of the analysed micro-inclusions: higher Mn content, higher S content. As a compound body, a typical (Mn,X)S system was identified (less than 10 μm size particles), with the presence of sulphide forming elements (X = Mg, Ca, Sr, Al). The analysed areas at the interface between MnS compound and graphite particles show that Mn and S are still present there, but O appears to be the most important characteristic of these regions, in association with Mg, Sr, Al, Ca, Ba. Mg is a new identified active element on the entire section of (Mn,X)S compounds, with possible important role in graphite formation also in grey iron. It is assumed that oxy-sulphide forming elements, included in the interface layer, as MnS enrichment or/and by forming a thin (nano size) superficial layer as oxide or oxy-sulphide, improve the graphite nucleation capacity of the (Mn,X)S micro-inclusions.