Metall. Res. Technol.
Volume 114, Number 2, 2017
|Number of page(s)||10|
|Published online||17 April 2017|
Formation of MgO-based inclusions during AOD and ladle treatment of Al-killed 2205 duplex stainless steel
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing,
100083, P.R. China
2 Beijing Key Laboratory of Special Melting and Preparation of High-end Metals, Beijing 100083, P.R. China
3 Shandong Taishan Steel Group Co. Ltd., Laiwu 271100, P.R. China
⁎ e-mail: email@example.com
Received in final form: 11 March 2017
Accepted: 27 March 2017
Pilot trials were performed to study the formation mechanism of MgO-cored inclusions in 2205 stainless steel refined using low-Al high-basicity slag. The composition of melts and slags significantly affected the inclusion types, compositions, and shapes. Experimental results showed characteristic CaO and MgO dual-saturation in the slags. The compositions of the inclusions approached those of the slags, viz. the MgO-rich MgO-spinel solid solutions or pure MgO. MgO in the slags provided sufficient Mg to the steel melts that newly generated pure MgO stably approached equilibrium as the Mg–O deoxidization reaction continued. The activity changes of Ca, Mg, and Al during refining were modeled. The activity of Mg exceeded those of Al and Ca, and the Mg–O reaction was always dominant. A kinetics model was established to elucidate the changing mechanisms of inclusions. The transferring kinetics of inclusions was discussed qualitatively to analyze velocity-controlled steps. The concentration of Al was low in molten steel, implying a low potential energy of Al3+ and impeded diffusion into the MgO core to form MA-spinel. Meanwhile, the diffusion of Mg2+ into the MgO core was the rate-limited step.
Key words: duplex stainless steel / MgO-based inclusions / evolution mechanisms / FactSage
© EDP Sciences, 2017
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