Regular Article

Study on formation of dual-phase MnO–SiO₂-based inclusions in tire cord steel

¹ Key Laboratory for Ecological Metallurgy of Multimetallic Mineral (Ministry of Education), Northeastern University, Shenyang 110819, China
² School of Metallurgy, Northeastern University, Shenyang 110819, China

^* e-mail: dengzy@smm.neu.edu.cn
^** e-mail: myzhu@mail.neu.edu.cn

Received: 9 March 2022
Accepted: 18 July 2022

Abstract

In order to understand the formation of dual-phase MnO–SiO₂-based inclusions in tire cord steel, laboratory and industrial experiments are carried out to investigate the formation and evolution of inclusions during Si–Mn deoxidation, and thermodynamic calculations are conducted to check the stability of inclusions after deoxidation. The results show that (Fe, Mn)O inclusions and CaO–SiO₂–FeO based inclusions are mainly found in BOF as-tapped crude steel. During Si–Mn deoxidation, the (Fe, Mn)O inclusions will transform into MnO–SiO₂ system inclusions, including liquid MnO–SiO₂ inclusions and SiO₂ + MnO–SiO₂ dual-phase inclusions; while CaO–SiO₂–MnO inclusions will be generated from CaO–SiO₂–FeO based inclusions. In Si–Mn-killed tire cord steel, SiO₂ is proved to be saturated in the MnO–SiO₂ system inclusions, thus the dual-phase inclusions of SiO₂ + MnO–SiO₂ can stably stay in liquid steel after deoxidation, and probably change into dual-phase MnO–SiO₂–Al₂O₃ system inclusions during refining process. The effect of alloy addition sequence on deoxidation is not evident, while the effect of slag is more profound. Proper addition of slag formers should be considered to promote deoxidation result.