Formation of Intragranular Acicular Ferrite Grains in a Ti-containing Low Carbon Steel

On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels

“…Here, the role of N was to increase the volume fraction of V(C, N) inclusions. Working on a Ti-containing low carbon steel, Jin et al 57) found that TiN formed from complex inclusions (Ti 2 O 3 -TiN, TiN-MnS) was an effective nucleant for AF.…”

“…Pure TiN inclusions can also act as potential nucleation sites for AF formation due to its coherency with ferrite, [55][56][57] as was described in Sec. 4.2.…”

“…In the open literature, the following mechanisms have been suggested to cause nucleation of acicular ferrite at inclusions: -a reduction in the interfacial energy for simple heterogeneous nucleation on a surface of inclusions, [49][50][51][52][53][54] -an epitaxial nucleation on the inclusions, which have a good coherency with ferrite, [55][56][57] -a nucleation arising from the thermal strains at the inclusions, which is associated with the different thermal expansion coefficients of the inclusions and steel matrix, 58,59) -a nucleation arising from solute depletion of elements in the matrix near inclusions. 10,12,46,[60][61][62][63][64][65] It should be pointed out that it is, in many cases, difficult to decide which mechanism that is most important for formation of acicular ferrite.…”

Estudo microestrutural de aço carbono soldado com o processo arco submerso e adições de Fe-Ti

“…Os valores encontrados neste trabalho está de acordo com outros resultados encontrados em publicações [1,10,13,20,21]. Desta forma, quanto maior o tamanho das inclusões, maior o potencial de formação de ferrita acicular.…”

Characterization of Inclusions Formed in Ti-containing Steel Weld Metals

“…TiN is a phase having good lattice matching with ferrite and has been believed to be effective for AF nucleation. 19,20) Figure 15 shows the Mn and Ni concentration profiles near the Ti-oxide, demonstrating the presence of an MDZ in this inclusion. Of note in this result is that the Mn content in the Ti-oxides is much lower and the MDZ width is narrower than those of the 3Ti weld.…”