To understand the alloying process on the cleanliness of Ti-stabilised interstitial-free (IF) steel, two different alloying operation processes were conducted during Ruhrstahl–Heraeus (RH) treatment. It was found that the Ti–Fe alloy contains extremely high oxygen and nitrogen contents. After Al addition, [Al]–[O] deoxidation reaction can quickly get close to equilibrium (within 1 min), and most inclusions are pure Al2O3. After Ti–Fe addition, the TiOx content in the inclusions increases first and then drops. Because the average content of TiOx is lower than 10 mass%, most inclusions should be solid. The addition of Ti–Fe alloy just after Al addition would not evidently weaken the yield of Ti–Fe alloy, or influence the removal efficiency of the inclusions. Due to the longer RH circulation time after Ti–Fe addition, the inclusions and impurities in the alloy can be further removed, resulting in better steel cleanliness.
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