Effect of Zr-oxide Particles on the MnS Precipitation in Low S Steels

Abstract

Combination of deoxidation, Zr addition after Mn-Si deoxidation, was applied for the dispersion of fine Mn-Si oxides which provide sufficient nucleation sites of MnS. It was revealed that Zr addition led to decrease in diameter and increase in specific gravity of oxides by forming MnO-SiO₂-ZrO₂ complex oxides, resulting in the suppression of floatation. Thus, higher number of oxides and MnS is obtained in Mn-Si-Zr deoxidation than in Mn-Si deoxidation. Both model calculation and experiments were conducted to clarify the upper limit of Zr amount for the formation of MnO-SiO₂-ZrO₂ complex oxides, without complete reduction of MnO-SiO₂ by Zr, and calculated results yielded in good agreement with experimental ones. Moreover, both results indicate that Zr addition has wider range of amount than Al addition for obtainig complex oxide: MnO-SiO₂-X.