Fundamental Studies of Physical-Mechanical Properties of Environmentally Friendly Fluorine-Free Slags and Their Use in Ladle Steel Industry

• Published in: Steel in translation 2022-06, Vol.52 (6), p.568-573
• Main Authors: Babenko, A. A., Smirnov, L. A., Protopopov, E. V., Upolovnikova, A. G., Smetannikov, A. N.
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Basicity; Boron; Boron oxides; Calcium oxide; Carbon; Carbon refractories; Chemical properties; Chemistry and Materials Science; Composition; Deoxidizing; Fluorine; Iron and steel industry; Ladle metallurgy; Ladles; Low carbon steels; Magnesium oxide; Materials Science; Mechanical properties; Periclase; Silicon dioxide; Slag; Steel; Sulfur; Sulfur content; Viscosity
• ISSN: 0967-0912; 1935-0988
• DOI: 10.3103/S096709122206002X

This paper describes theoretical and experimental studies of the dependence of the viscosity, coefficient of sulfur and boron distribution between slag and metal, as well as wear degree of periclase-carbon refractories on the basicity and boron oxide content in the slag. It is shown that the formed slags have the values of basicity from 2.0 to 5.0 and rather a high liquid mobility. These slags are characterized by an equilibrium interfacial distribution coefficient of sulfur increased to 5–20, which provides an equilibrium sulfur content in the metal reduced to 0.001–0.005%. The results of fundamental studies of the physical-chemical properties of refining slags of the CaO–SiO 2 –B 2 O 3 –Al 2 O 3 –MgO system formed the basis for development of the composition of environmentally friendly fluorine-free ladle slags and technological methods for their formation in the ladle-furnace unit. The recommended composition of such low-viscosity slags, which allow deep desulfurization, direct steel microalloying with boron, and a low aggressive effect on the periclase-carbon refractories, ensures formation of slags with a basicity of 3.0–4.0 containing 1–4% B 2 O 3 , 15% Al 2 O 3 , and 8% MgO. The formation of environmentally friendly ladle slags of the recommended composition was carried out in a ladle-furnace by loading lime, boron-containing material—colemanite (Turkey) containing 39–41% B 2 O 3 , 26–29% CaO, not more than 5% SiO 2 , and 3% MgO, and pyramidal aluminum into the steel-teeming ladle for slag deoxidation and boron recovery. Implementation of the developed technology for the formation of ladle slags with the recommended composition ensured production of economically alloyed low-carbon structural boron-containing steels with a low sulfur content, including for production of large-diameter pipes with high strength properties.