Evolution mechanism of Ca-containing inclusions in 20Mn23AlV high-manganese non-magnetic steel during the refining process

Abstract

Industrial experiments and thermodynamic calculations were carried out to investigate the evolution mechanism of Ca-containing inclusions in 20Mn23AlV steel with the Al content up to 2 wt-%. After Al deoxidation in AOD, the main inclusions were spherical shape Ca–Al–Si–Mn–O inclusions. Spherical Ca–Al_rich–Si–Mn–O and spherical Ca–Al–Mn–O became the main inclusions after the first Al alloying. After Ca treatment in LF, the typical inclusions were aggregate CaS–CaO inclusions. In tundish, the types of inclusions were CaS and CaS_rich–CaO, and the size and quantity of inclusions were substantially decreased. Thermodynamic analysis indicated that with the Al content increase to about 2 wt-%, the inclusions containing high Al₂O₃ content formed, which were extremely easy to be removed in the steelmaking process. Moreover, after the second Al alloying, the decrease of oxygen content promoted the formation of CaS inclusions, and CaS or CaS–CaO inclusions were formed Lastly, the evolution mechanism of inclusions was summarized in detail.