Effect of Mn Content on the Characteristics of Inclusions in Ti-Containing Steel Welds

Steel weld metals containing Ti were prepared with Mn contents of 0.35%–2.98%. The inclusion characteristics in the weld metals were investigated by means of thermodynamic calculations coupled with electron probe microanalyses and transmission electron microscopy. The results show that with an increase in Mn content, the primary constituent phases of the inclusions are changed from pseudobrookite to a combination of pseudobrookite and spinel and eventually to a mixture of (Mn–Si–Al)-oxide, spinel and ilmenite. Ti₃O₅, MnTi₂O₄ and MnTiO₃ are the primary constituents of the pseudobrookite, spinel and ilmenite solid solutions, respectively. Spinel and ilmenite have higher amounts of Mn but lower amounts of Ti compared with that of pseudobrookite. The formation of large amounts of ilmenite and spinel leads to the development of a Mn-depleted zone (MDZ) in the vicinity of the matrix/inclusion interface. Acicular ferrite has a Baker–Nutting orientation relationship with MnTi₂O₄.