Assessment of castability issues in interstitial-free (IF) steels

Inclusion Characterization of Titanium Stabilized Ultra Low Carbon Steels: Impact of Oxygen Activity before Deoxidation

“…The population of alumina inclusions smaller than 3 µm was higher for heats with late temperature correction than for the heats without late temperature correction, at the RH degasser treatment. In previous studies 2, 18, 19, the late temperature correction practice has shown adverse effect on steel castability and also been correlated to poor Ti recovery at the tundish 2. In this study, it was found that this practice generates a higher population of smaller alumina inclusions in ladle that tends to remain within the liquid steel, do not sufficiently float out and are carried over to the tundish affecting the steel cleanliness.…”

“…Therefore it seems that the effect of oxygen activity before deoxidation at RH degasser is not critical and downgrading criteria for slabs made from heats killed at O greater than 750 ppm was revisited. The population of alumina inclusions smaller than 3 µm was higher for heats with late temperature correction than for the heats without late temperature correction, at the RH degasser treatment. In previous studies 2, 18, 19, the late temperature correction practice has shown adverse effect on steel castability and also been correlated to poor Ti recovery at the tundish 2. In this study, it was found that this practice generates a higher population of smaller alumina inclusions in ladle that tends to remain within the liquid steel, do not sufficiently float out and are carried over to the tundish affecting the steel cleanliness. The overall alumina inclusion content decreased from end‐RH to tundish samples in all heats irrespective of the oxygen activity before deoxidation and these results are verified by both automated SEM analysis and RB‐CLM‐SEM technique.…”

“…Therefore the practice of ‘late temperature correction’ should be minimized at RH‐degasser operation. It is worth noting that higher amounts of coolant addition or oxygen blowing for reheating can significantly alter the steel cleanliness and can cause clogging 18. The Ti‐aluminate inclusion population, on the other hand, did not appear to be affected by the ‘late temperature correction’ practice as shown in Figure 7.…”

“…Two heats that were killed at oxygen activities << 400 ppm were either reheated or cooled following deoxidation at the RH degasser (known as ‘late temperature correction’). This practice has been found to affect the clogging tendency of TiSULC steels 2, 18, 19. The inclusion analysis results of these two heats were compared with those of 10 heats that were killed in similar oxygen activity ranges but produced using standard conditions.…”

Application of Optical Floating Zone Method to Dissolution Kinetics of Inclusions in a Steelmaking Slag

“…Industrial research on Ti containing inclusions has focused on their formation, modification, and distribution in steel refining units . Kaushik et al studied clogging incidents related to industrial operations and found that alumina and aluminum titanates are present in most of the clog mass or the steel collected at the tundish or mold samples analyzed during casting of titanium stabilized ultra‐low carbon (Ti‐SULC) steel.…”