Application of Alkali Oxides in LF Refining Slag for Enhancing Inclusion Removal in C96V Saw Wire Steel

Abstract

A novel LF refining slag contains K₂O has been developed in order to produce ultraclean saw wire steels. The diameter of ultrafine saw wire is between 50×10⁻⁶ m (50 µm) and 80 ×10⁻⁶ m (80 µm), any hard inclusion which diameter more than 5×10⁻⁶ m (5 µm) should be avoided because it probably will cause wire breaking. In order to enhance inclusion removal in C96V saw wire steel during LF refining process, fundamental work on the effect of alkali oxides (Li₂O, K₂O) on the absorption ability of inclusions in a typical LF refining slag for C96V saw wire steel has been investigated. The results indicated that K₂O additions seems to significantly enhance inclusion removal in steel melts, instead, Li₂O additions hindered inclusion removal. In details, K₂O improve the cleanliness in the as quenched C96V saw wire steel melts compared to preexisting synthetic LF refining slag compositions: (i) The average diameter of nonmetallic inclusions was decreased sharply with the content of K₂O in synthetic LF refining slag increasing. In particular, the diameter of most of inclusions was less than 2.5×10⁻⁶ m (2.5 µm) when the content of K₂O in synthetic LF refining slag more than 10 wt%; (ii) The number of inclusions descend sharply with the content of K₂O in synthetic LF refining slag raising. (iii) Both of the SiO₂–MnO–Al₂O₃, SiO₂–CaO–Al₂O₃ inclusions system mainly concentrated in the low melting zone when the composition of K₂O in synthetic refining slag was less than 10 wt%. While the Li₂O additions has the opposite effect.