The Relationship Between MnS Precipitation and the Induced Nucleation Effect of Ti-Bearing Inclusions

The relationship between MnS precipitation and the induced nucleation effect of Ti-bearing inclusions has been analyzed using SEM and EDS. In comparison with a non-treated sample, it can be seen that the Ti treatment leads to the oxide evolution from Al-Mn-Si-O to Ti-Al-Si-Mn-O. Moreover, it was found that sulfur congregates around both types of oxide, which is attributed to the MnS precipitation. As for pure MnS, its proportion in the total inclusion decreases when a Ti treatment is performed. EDS line analysis suggested that a Mn depletion zone (MDZ) occurs in the Fe matrix surrounding Ti-Al-Si-Mn-O. It does not occur surrounding Al-Mn-Si-O in the comparison sample. This difference leads to different microstructures. The intragranular acicular ferrites (IAFs) are only observed in the Ti-treated sample. Further analysis indicated that this microstructure is induced by Ti-Al-Si-Mn-O inclusions. In the same sample, the similar induced nucleation effect and a MDZ could not be found surrounding pure MnS. This comparison suggests that the formation of the MDZ may be independent of a MnS precipitation.