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.