Metall. Res. Technol.
Volume 116, Number 6, 2019
|Number of page(s)||10|
|Published online||23 September 2019|
Inclusions evolution during the LF refining process of 439 ultra-pure ferritic stainless steel
State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing,
10083, PR China
2 Hongxing Iron & Steel Co., Ltd., Jiuquan Iron and Steel Group Corporation, Jiayuguan 735100, PR China
* e-mail: firstname.lastname@example.org
Accepted: 30 August 2019
The morphology, composition, size, and number of inclusions in 439 ultra-pure ferritic stainless steel samples were analyzed using an automatic scanning electron microscope combined with an energy-dispersive X-ray spectrometer. In addition, the appropriate contents of titanium, aluminum, and calcium were analyzed through the coupling of thermodynamics calculation and experimental results. CaO-Al2O3-MgO inclusions existed in the 439 steel before Ti additions in the ladle furnace (LF) refining process. After Ti addition in the LF refining process, the inclusions were transformed into CaO-Al2O3-MgO-TiOx inclusions. The evolution of these inclusions was consistent with thermodynamic calculation, which indicated that when the Al, Ca, and Ti contents were within a reasonable range, Ca treatment could significantly modify the aluminate and spinel to form CaO-Al2O3-MgO liquid inclusions. In addition, the compositions of inclusions after the addition of titanium were mostly located in the Al2O3-TiOx stable phase. The collision of the CaO-Al2O3-MgO liquid inclusions and Al2O3-TiOx inclusions resulted in the modification of the CaO-Al2O3-MgO-TiOx inclusions. The compositions of most inclusions were located in the liquid zone. The control range of the aluminum, calcium, and titanium contents was obtained: logAl% ≥ 1.481logTi% − 0.7166, Ca% ≥ 34.926(Al%)3 − 3.3056(Al%)2 + 0.1112(Al%) − 0.0003.
Key words: 439 ultra-pure ferritic stainless steel / titanium / calcium / aluminum / inclusions evolution / LF refining process
© EDP Sciences, 2019
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