Effect of Nano CaO and MgO Addition on the Inclusions Composition in the Cast Microstructure of X80 Pipeline Steel

Nanometer calcium and magnesium oxides were added into molten steel by the carrier method in the experiment. The experiment takes the X80 pipeline steel as the research object and analyses the effect of nanometer calcium and magnesium oxides addition on the inclusions in the cast microstructure of the X80 pipeline steel. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to analyze the composition of the inclusions in the cast microstructure of the X80 pipeline steel. The result reveals that when no addition of nanooxides, the inclusions in the cast microstructure are the C-Fe-Si-Al-Mn-based inclusions. When adding nanoMgO, the inclusions are mainly the composite oxides of Fe-Mg-Si-O, Fe-Mg-Si-Mn-O and Mg-Si-Mn-Al-O. When adding nanoCaO, the inclusions are mainly the composite oxides of Fe-Ca-Al-O, Fe-Ca-Si-O, Fe-Ca-Si-Mn-O and the composite oxides or sulfides of Fe-Ca-Si-Mn-O-S. There is more Fe in some inclusions and Fe is not uniformly dispersed in the molten steel. As the result, some certain segregation phenomenon takes place.