Evolution Characteristics of Inclusions during Reaction Process between Fe‐Mn‐Al‐C Low‐Density Steel and CaO‐Al₂O₃‐Based Mold Flux

The evolution characteristics of inclusions during reaction process between low‐density steel and CaO‐Al 2 O 3 ‐based mold flux are studied. The results show that the chemical reaction between [Al] and (B 2 O 3 ) mainly occurs, followed by that between [Al] and (SiO 2 ). The mass transfer coefficient of [Al] in steel decreases from 33.86×10 −5 to 9.47×10 −5 m s −1 owning to the reduction in content of [Al] and the increase in interfacial mass transfer resistance caused by the deterioration of mold flux properties. The main inclusion is AlN, followed by AlON. With the increase in reaction time, the number density of inclusions decreases from 281.5 to 176.8 mm −2 , and then, slightly increases to 193 mm −2 . The average diameter of inclusions shows an overall increasing trend from 1.81 to 3.45 μm. Moreover, the number density of inclusions in argon‐cooled steel ingot is 360 mm − 2 , and the average diameter is 2.75 μm. AlN inclusions float up to the steel–slag interface, and there are three removal paths: 1) AlN inclusions self‐decompose to generate [Al] and N 2 ; 2) AlN inclusions react with (B 2 O 3 ) to form BN solid particles; and 3) AlN inclusions react with (SiO 2 ) to form Si 3 N 4 , dissolving in the mold flux.