Control of steel cleanliness and non-metallic inclusions in an Al-killed steel through CaO-Al2O3 powder injection during RH refining process

In the current study, an industrial trial of the CaO-Al 2 O 3 powder injection during RH refining process was carried out to investigate the control of steel cleanliness and non-metallic inclusions in an Al-killed steel. At the refining start, main inclusions were Al 2 O 3 . During the refining process, inclusions gradually changed from Al 2 O 3 to calcium aluminate. Meanwhile, the number density and diameter increased first due to the CaO-Al 2 O 3 powder injection and then decreased due to the floating of inclusions. The coagulation coefficient and adhesion work can reflect the aggregation and removal ability of inclusions, respectively. The higher liquid fraction of inclusions lowered their coagulation coefficient, decreasing the aggregation ability of the inclusions. Meanwhile, the adhesion work of inclusions increased with the increased liquid fraction, retarding the removal of inclusions from the steel.