Influence of slag-changing operation during LF refining on the inclusions in 82B high carbon steel wire

The influence of refining slag-changing operation on the compositions of 82B steel and inclusions were studied on the basis of plant trials combined with thermodynamic analysis. The optimized refining slag system for the refining of 82B steel was obtained through the plant experiments. The slag-changing operation had no effect on the type of oxide inclusions (CaO-SiO2-MnO-Al2O3) compared with the operation without slag-changing, whereas the CaO/SiO2 in inclusions decreased with the decrease of basicity of the top slag. The liquidus temperature of oxide inclusions were decreased with the slag-changing operation. The basicity of the refining slag should be controlled in the range of 2.5 to 3 at the early stage of LF in order to control the oxygen and sulfur in steel. At the later stage of LF refining, the basicity of refining slag should be changed to 1∼1.5, aiming to reduce the activity of [Al] in molten steel and target the good plasticity of oxide inclusions.