Evolution Pathway of Competitive Precipitation of Inclusions in Al–Ti-Deoxidized Steel

Seven types of inclusions are observed in the Al-deoxidized steel followed by Ti-deoxidized steel, while ten types of inclusions are found in Al–Ti simultaneous deoxidized steel. Three special inclusions are only found in Al-deoxidized steel followed by Ti-deoxidized steel as Al₂TiO₅–Ti_xO_y, Al₂TiO₅–Al₂O₃–TiS, and Al₂TiO₅–Al₂O₃–Ti_xO_y–TiS. The precipitation order of inclusions in Al–Ti-deoxidized steel is very dependent on the value of [%Ti]/[%Al] or [%S]/[%O]. The critical value of [%Ti]/[%Al] for the precipitation of inclusions from large to small is Ti_xO_y > Al₂TiO₅ > Al₂O₃, and the critical value of [%S]/[%O] for the precipitation of inclusions from large to small is TiS > Ti_xO_y. The critical value of [%Ti]/[%Al] for the precipitation of Ti_xO_y prior to Al₂TiO₅, and the precipitation of Al₂TiO₅ prior to Al₂O₃ has a close relationship with the content of [%Al]. In addition, the critical value of [%S]/[%O] for the precipitation of TiS prior to Ti_xO_y inclusions increases with an increasing content of [%O] and increased with the decreasing of temperature. The precipitation order of inclusions in the two types of steel is Al₂TiO₅ or Al₂O₃ → Ti₃O₅ → TiO₂ → Ti₂O₃ → TiS.