In situ Observation of Calcium Oxide Treatment of Inclusions in Molten Steel by Confocal Microscopy

Calcium treatment of aluminum killed steel was observed in situ using high-temperature confocal scanning laser microscope (HT-CSLM). This technique along with a novel experimental design enables continuous observation of clustering behavior of inclusions before and after the calcium treatment. Results show that the increase in average inclusion size in non-calcium-treated condition was much faster compared to calcium-treated condition. Results also show that the magnitude of attractive capillary force between inclusion particles in non-treated condition was about 10 −15 N for larger particles (10 µ m) and 10 −16 N for smaller particles (5 µ m) and acting length of force was about 30 µ m. In the case of calcium-treated condition, the magnitude and acting length of force was reduced to 10 −16 N and 10 µ m, respectively, for particles of all sizes. This change in attractive capillary attractive force is due to change in inclusion morphology from solid alumina disks to liquid lens particles during calcium treatment.