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| Ti-Deoxidized Products and Formation Mechanism of Intragranular Ferrite in High Grade Pipeline Steels |
QI Jiang-Hua, XUE Zheng-liang, et al |
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Abstract High grade pipeline steels were prepared using vacuum carbon deoxidization process combined with a final Ti-deoxidation process. The microstructure of the as-cast steels was investigated by using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). SEM observation shows the formation of Intragranular ferrite (IGF) structure was induced by fine inclusions. TEM selected area diffraction patterns (SAD) and elemental distribution analysis indicated that these inclusions are mainly Ti2O3 and MnS. It was also found that Ti2O3 may act as nucleus in the formation of MnS during solidification process. Raman spectroscopic analysis demonstrated the presence of another phase, MnTiO3, which could be formed through entrapment of Mn element by Ti2O3. It is believed that the formation of Mn-depleted region in the inclusions and thus the formation of MnTiO3 phase will lead to increased Mn pickup from matrix and promoted the formation of IGF during solidification of molten steel.
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Received: 02 July 2009
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Corresponding Authors:
Qi Jiang-Hua
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2010, Vol. 17 
