Effect of Nanometer Calcium and Magnesium Oxides Addition on the Inclusions 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) was used to analyse the morphology and distribution of the inclusions in the cast microstructure of the X80 pipeline steel. The results reveal that there are a small amount of inclusions in the sample of no nanometer oxides addition. With the amount of the nano-MgO oxide addition rising, the number of the inclusions in the sample firstly increases and then decreases gradually. When adding 0.05 wt% nano-MgO or CaO oxides, the size of the inclusions is big and the aggregation phenomenon appears. When adding 0.02 wt% nano-MgO or CaO oxides, the number of the inclusions in the cast microstructure is the most, whose size is smaller, about 2 similar to 4 mu m and the inclusions are the most uniformly distributed.