The development of effective technological methods for controlling non-metallic inclusions is a promising direction for improving the complex of properties and quality characteristics of steels. One of the factors regulating the quantity, morphology and distribution of sulfide inclusions over the metal volume is the sulfur content. To organize the production of steel with low sulfur content (up to 0.003 - 0.005%), the desulfurization process is carried out in ladle-furnace installations with the formation of the main slags of the CaO-SiO2-Al2O3 system and deep deoxidation of steel with aluminum. At the same time, one of the main oxide inclusions in steel deoxidized with aluminum is corundum (Al2O3), which deteriorates the properties of steel and leads to “overgrowth” of the inner surface of the immersion nozzle during continuous casting. This negative effect of corundum in steel can be neutralized by removing it into the main liquid slag formed in the ladle-furnace by reducing the activity of Al2O3. However, in practice, an excessive increase in the basicity of refining slag to reduce the activity of Al2O3 is usually accompanied by heterogenization of the slag, an increase in its melting temperature and a decrease in refining properties. One of the promising directions for reducing the activity coefficient of Al2O3 in basic refining slags may be the use of rare earth metal oxides. The use of REM oxides ensures a decrease in their melting point, an increase in fluid mobility, an increase in the coefficient of interphase distribution of sulfur and a decrease in the coefficient of interphase distribution of REM. The paper presents the results of a study of the influence of cerium oxide in the slags of the CaO-SiO2-Al2O3-MgO-CeO2 system on the physicochemical properties. New data were obtained on the influence of temperature, cerium oxide and the basicity of the formed slags on the equilibrium interphase distribution of cerium. 

The research was supported by a grant from the Russian Science Foundation.

Among the priority tasks for the development of the country's metallurgical complex, the problem of improving the quality and reducing the cost of metal products remains relevant. Improving the quality characteristics of structural steels is carried out at all technological stages of steel production. The thermodynamics of the phosphorus oxidation reaction, macrokinetics of oxidation processes, phase composition, structure and physicochemical properties of multicomponent slags of the CaO-SiO2-FeO-MnO-P2O5-MgO and CaO-SiO2-B2O3-Al2O3 system, including viscosity, equilibrium interphase distribution of sulfur and boron during out-of-furnace processing of steel.

The results of fundamental research form the basis for the development of innovative technological solutions that provide:

- smelting of intermediate steel in oxygen converters and modern EAFs under magnesium slag of rational composition with a guaranteed low phosphorus content and high durability of the refractory lining of steel-smelting units;

-deep desulfurization and direct microalloying of structural steel grades with boron in ladle-furnace installations using environmentally friendly boron-containing slag.

The introduction of developed innovative technological solutions ensured the production of low-carbon boron-containing structural steels of a new generation, sparingly alloyed with manganese, with low phosphorus and sulfur content and a complex of increased mechanical properties, incl. for large-diameter pipes of strength category X80 without heat treatment with the prospect of reaching strength category X100-X120.