Non-Metallic Inclusions and Acicular Ferrite in Low Carbon Steel

The formation of non-metallic inclusions with variations in various oxygen, nitrogen and titanium contents in low carbon steels has been studied. The relationship between the nature of non-metallic inclusions and the formation of acicular ferrite has been also investigated. It is found that the non-metallic inclusions observed in this study are mainly consist of Ti2O3 and TiN together with a small amount of other complex oxides containing Mn and Si. It has been confirmed that Ti2O3 and TiN play an important role in formation of acicular ferrite as a nucleation site and an austenite grain refiner, respectively. But it is not clear yet whether TiN acts as a nucleation site or not. It is also found that the volume fraction of inclusions is more effective than the type or size distribution of the non-metallic inclusions on the formation of acicular ferrite.