Effect of trace Si on MgO·Al 2 O 3 inclusion in ultra-low-carbon steel

There are four types of Mg–Al–Si–O inclusions observed in the Mg-treated Al-deoxidized ultra-low-carbon steel containing trace Si, including SiO 2 , 2MgO·SiO 2 , 3Al 2 O 3 ·2SiO 2 , and 2MgO·2Al 2 O 3 ·5SiO 2 and their composite inclusions. Using FactSage, the phase relationship of Mg–Al–Si–O system at 1473–2073 K was calculated using FactSage software, and the change in Si content can change the stable region range of different Mg–Al–Si–O-based inclusions. Based on the types of inclusions observed experimentally, the formation pathways of inclusions were predicted and a kinetic model was established to describe the formation process of the x MgO· y Al 2 O 3 –Mg–Al–Si–O and x Al 2 O 3 · y SiO 2 –Mg–Al–Si–O inclusions.