Evolution Mechanism of Nonmetallic Inclusions in Fe‐1.5Al‐xSi (x = 0.5–3.0 wt%) Alloyed Steels

The effects of Si content of steel melts containing 1.5% Al as well as alloying sequence of Si and Al on the evolution of inclusions are investigated. The SiO 2 inclusion is primarily formed when Si (=0.5–3.0 wt%) is added to the melts at 1873 K, and the area fraction (AF) of the inclusions decreases over time. The subsequent addition of 1.5% Al to the Si‐alloyed steel (i.e., 3.0Si→1.5Al) increases the AF of inclusions due to the formation of Al 2 O 3 . The population density function (PDF) analysis for the preferential Si alloying shows a fractal distribution, indicating that the inclusions grow by a collision mechanism. PDF analysis shows a lognormal distribution because Al 2 O 3 inclusion is formed and grows after subsequent Al alloying. Alternatively, when 1.5% Al is preferentially added to steel, Al 2 O 3 clusters are formed. The AF of Al 2 O 3 cluster decreases over time. When 3.0% Si is subsequently added to the Al‐alloyed steel (i.e., 1.5Al→3.0Si), singular Al 2 O 3 particles are mainly observed. Because the Al alloying results in the formation of Al 2 O 3 regardless of the alloying sequence and Si content, it is important to float up and separate Al 2 O 3 cluster to improve the cleanliness of high‐Si‐Al‐alloyed steels such as electrical steels.