Investigation on Ti-Deoxidized Products Inducing Formation of Intragranular Ferrite

Abstract

Steel samples were prepared using a vacuum carbon deoxidization process combined with a final Ti-deoxidation process. Ti-deoxidized products inducing formation of intragranular ferrite (IGF) was investigated by using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) through various specimens by different methods, as follows: metallographic specimens, electrolyzation, ion thinning technology, RTO method and so on. Mn is found to be more extensively distributed than S in the core of inclusion, which shows that Ti2O3 has character of absorbing Mn. The Mn-depleted zone (MDZ) exists in the peripheral steel of inclusion, the more near the inclusion, the more obvious depletion of Mn. It is also found that outer layer of inclusion exists S-rich and Mn depletion area in specimens prepared using RTO method under TEM. Mn- depleted zone in steel and Mn-depleted but S-rich layer in the periphery of the inclusion indicate that Mn diffuses and diverts is step by step in steel and inclusion, and the extent of S-rich and Mn depletion area should be related with degree of Mn absorbed by Ti2O3 and original precipitation amount of MnS.