Study on the effects of Ti micro-addition on the characteristics of MnS inclusions in rail steel

Laboratorial study was carried out to reduce the rates of sulphide inclusions in rail steel. Rail steel was re-melted in an induction furnace with the addition of titanium to 0.0098wt%. The cast ingot was then sampled and inclusions were carefully inspected on the morphology, composition, elastic moduli etc. of sulphide inclusion. The obtained results indicated that sulphides were mostly spherical shapes before/after the addition of Ti. Number density of inclusions with sizes not more than 10µm increased while the larger ones decreased. Compositions of sulphides were converted from MnS to Mn-Ti-S with [Ti] addition. SEM-mapping of the sulphides indicated that Ti distributed in the whole Mn-Ti-S inclusions. Moreover, Ti-enrich regions and Mn-enriched regions were not overlapped but mainly complementary. The measured elastic moduli of MnS and Mn-Ti-S sulphides were 27.3GPa and 34.7GPa, respectively, indicating a rise of about 7GPa against the rise of [Ti] content from 0.0018wt% to 0.0098wt%.