Exploration of morphology evolution of the inclusions in Mg-treated 16MnCrS5 steel

To elucidate the morphology evolution of the inclusions in 16MnCrS5 steel with various masses of Mg addition, the experiments and thermodynamics were carried out with a high-temperature tube electric resistance furnace and FactSage software, respectively. The evolutions of the inclusions after the smelting and hot-processing were described. The experimental results show that with Mg addition of 35–42 ppm, many spindle and spherical inclusions with the size below 20 μm appeared, whereas the long-strip inclusions above 20 μm disappeared; after hot-processing, particularly, the h value was above 50%, beneficial to obtaining more spindle inclusions, and most spherical inclusions at 35 ppm were also obtained. The thermodynamics show that with Mg mass between 0.349 and 6.076 ppm, Al₂O₃ was easily converted to MgO·Al₂O₃, whereas above 6.076 ppm, Mg was directly converted to form MgO; above more, MgS coexisted with MgO.