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Influence mechanism of rare earth (RE) on inclusion modification in non-oriented silicon steel

¹ Anhui Province Key Laboratory of Metallurgical Engineering & Resources Recycling, Anhui University of Technology, Maanshan 243002, China
² School of Metallurgical Engineering, Anhui University of Technology, Ma’anshan, Anhui, Maanshan 243032, China
³ Iron and Steel Research Institute Co., Ltd., Beijing 100081, China
⁴ Silicon Steel & Sheet Business Division, Xinyu Iron and Steel Group Co., Ltd., Xinyu 338001, China

^* e-mail: qiaojialong2015@126.com
^** e-mail: 20130007@ahut.edu.cn

Received: 26 July 2024
Accepted: 24 September 2024

Abstract

Effects of rare earth (La+Ce) on inclusions in hot-rolled band of 3.0∼3.3%Si-0.8∼1.0%Al non-oriented silicon steel was studied using industrial trials, scanning electron microscope (SEM) and thermodynamic analysis. Furthermore, combining Heterogeneous Nucleation Theory with Edge-to-Edge Matching (E2EM) model, the formation mechanism of complex inclusions was also investigated. Rare earth (La+Ce) would promote the spheroidization and coarsening of inclusions, and then transform into regular and near circle morphology composite inclusions of rare earth. The low content of rare earth (21 ppm) mainly deoxidized and modified Al₂O₃ inclusions, and formed (La,Ce)AlO₃ inclusions. Increasing of rare earth (29–45 ppm) would promote the formation of (La,Ce)AlO₃-(La,Ce)₂O₂S and (La,Ce)₂O₂S inclusions, reduce the sulfide precipitation, and promote a gradual transformation of the core of composite inclusions from (La,Ce)AlO₃ to (La,Ce)AlO₃-(La,Ce)₂O₂S and (La,Ce)₂O₂S, which agreed well with the thermodynamic analysis. However, rare earth (29–45 ppm) had a weak metamorphic effect on Al₂O₃ inclusions generated by temperature drop and secondary oxidation. LaAlO₃, CeAlO₃, La₂O₂S and Ce₂O₂S could be the heterogeneous nucleation core of AlN, Al₂O₃, MgO-Al₂O₃, typical composite inclusions with (La,Ce)AlO₃ and (La,Ce)₂O₂S as the core would ultimately form.