Relative Performance of Ca, Ba-FeSi Inoculants to Chill Control in Low-S Grey Cast Irons

Abstract

Low sulphur irons (< 0.05%S) production is more and more promoted in many parts of the world, as small and less efficient cupolas were replaced by the new generation of induction furnaces, while a single low sulphur base iron is very attractive for grey/ductile/compacted irons production. The problem is that at low Slevels, grey irons usually solidify with high eutectic undercooling, favorable for carbides formation, especially in thin wall castings (automotive industry). Relative performance of different Ca, Ba and Al bearing FeSi alloys was calculated to evaluate their efficiency to control chill tendency, in critical base irons [< 0.035%S, (%Mn) x (%S) < 0.02, 0.002%Al]. Relative clear/mottled/total chill measurement criteria were applied, for chill wedges with different cooling modulus (CM = 0.11 – 0.35 cm). The results showed that some inoculants performed better than the other alloys bearing the same base inoculating elements and have different positions for different chill evaluation criteria and wedge size (cooling modulus) parameters reference. An optimum association of Ca, Ba and Al contents at a proper Ba/Ca ratio is more efficient comparing to the increasing of the inoculating elements leveling FeSi-based alloys for inoculation of lower sulphur, electrically melted irons.