Article ID: ISIJINT-2018-806
The evolution mechanism of oxide inclusions in Cr-Mn-Ni stainless steel was investigated by industrial trials and thermodynamic calculation. The morphology, composition, and size distribution of inclusions in steel specimens were analyzed by scanning electron microscopy and energy dispersive spectroscopy. During the LF refining process, there were mainly liquid Ca–Si–Mg–Al–O inclusions in molten steel deoxidized with FeSi alloy. Combined with the Al–Si–O phase diagram, the specimen compositions were also located in the liquid oxide phase. At the same Al content, increasing Si content could make the steel compositions in the liquid oxide phase to avoid the formation of Al2O3. After continuous casting, the number density of Ca–Si–Mg–Al–O inclusions decreased to 1.81 mm-2. On the contrary, the number density of Mn–(Al–Ti)–O inclusions increased to 4.62 mm-2. The MnO contents of most Mn–(Al–Ti)–O inclusions were higher than 40%. The size of most Mn–(Al–Ti)–O inclusions was smaller than 3 µm. The formation of these inclusions was consistent with thermodynamic calculation, which indicated that Mn–Al–O and Mn–Ti–O inclusions were formed during the solidification of Cr–Mn–Ni stainless steel. The effects of different Al and Ti contents on the formation of oxide inclusions during continuous casting process were discussed.