Analysis of phase equilibria in liquid chromium-manganese steels deoxidized by aluminum

This study is devoted to the study of the mechanisms of phase formation during the deoxidation of chromium-manganese steels by aluminum. The control of the composition and morphology of non-metallic inclusions (NMI) is critically important for achieving optimal mechanical properties of steel. The phase equilibria in the Fe–Al–Mn–Cr–O and Fe–Al–Mn–Cr–O–C systems are studied in detail in order to predict the composition of the formed NMI depending on the concentration of key elements: aluminum, manganese, chromium and carbon. For economically alloyed steels, it was found that when aluminum deoxidation (Al > 0.001%) of melts with a manganese content above 1% forms solid solutions of chromium and aluminum oxides. Carbon exhibits deoxidizing properties at low concentrations of aluminum, which can lead to gas porosity and, consequently, to a decrease in the quality of metal products. It is important to note that the formation of pure alumina during deoxidation by aluminum is unlikely, which casts doubt on the widespread model of modification of inclusions by calcium through the formation of calcium aluminates. In high-alloy steels, the behavior of the elements remains similar, with solid solutions dominated by manganese and (or) chromium oxides in the presence of Al2O3. The effect of carbon is less pronounced than in economically alloyed steels, but with its high content (1%) gas porosity is also possible. The results indicate the need to take into account the complex interaction of Al, Mn, Cr, and C in the formation of NMI. To optimize refining processes, especially with the use of calcium, further research is required, focusing on the identified concentration areas of the greatest practical importance. The data obtained make it possible to more accurately predict the composition and properties of NMI, develop more effective strategies for deoxidation and modification, and reduce defects associated with gas porosity.