2015 Volume 55 Issue 8 Pages 1730-1738
The influence of Ti addition on inclusion characteristics and their effects on the nucleation of acicular ferrite has been studied using as-deposited bainitic-type GMA weld metals prepared with oxygen content constant. TEM analysis was carried out to identify the inclusion phases and to investigate the local variation in chemical composition around the inclusions. It was found that the Ti-containing phase changes from (Mn,Ti)-spinel oxide to Ti2O3 at ~0.07 wt.% Ti while Mn-depleted zone (MDZ) starts to form at ~0.02 wt.% Ti. This indicates that MDZs are induced by the formation of Ti2O3 as well as a large amount of (Mn,Ti)-spinel oxide. Due to MDZ formation, acicular ferrite can nucleate to a great extent, even from the amorphous surface of the Mn-silicate phase in the 0.02% Ti weld.