Fundamental studies of physicochemical properties of environmentally friendly fluorine-free slags and their use in ladle steel industry

The article describes theoretical and experimental studies of dependence of viscosity, coefficients of sulfur and boron distribution between slag and metal, and wear degree of periclase-carbon refractories on basicity and boron oxide content in slag. It is shown that formed slags have basicity of 2.0 – 5.0 and rather high liquid mobility. These slags are characterized by an equilibrium interfacial distribution coefficient of sulfur increased to 5 – 20, which provides equilibrium sulfur content in the metal reduced to 0.001 – 0.005 %. The results of fundamental studies of the physicochemical properties of refining slags of СаО – SiO₂ – В₂O₃ – Al₂O₃ – MgO system formed the basis for development of the composition of environmentally friendly fluorine-free ladle slags and technological methods for their formation in ladle-furnace unit. The recommended composition of such slags of low viscosity, which allows deep metal desulfurization, direct steel microalloying with boron and low aggressive effect on periclase-carbon refractories, provides formation of slags with a basicity of 3.0 – 4.0, containing 1 – 4 % B₂O₃, 15 % Al₂O₃ 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 % B₂O₃, 26 – 28 % CaO, not more than 5 % SiO₂ and 3 % MgO, and pyramidal aluminum into the steel-teeming ladle for slag deoxidation and boron recovery. Introduction of the developed technology for the formation of ladle slags of recommended composition ensured the production of economically alloyed low-carbon structural boron-containing steels with a low sulfur content, incl. for large diameter pipes with high strength properties.

1. Dyudkin D.A., Kisilenko V.V. Steel Production. In 3 vols. Vol. 3. Extra-Furnace Metallurgy of Steel. Moscow: Teplotekhnik, 2010, 544 p. (In Russ.).

2. Chumakov S.M., Lamukhin A.M., Zinchenko S.D., etc. Concept of production of low-sulfur steels at JSC Severstal taking into account technological aspects. In: Proceedings of the VI Congress of Steelma­kers. Moscow: AO “Chermetinformatsiya”, 2001, pp. 63–66. (In Russ.).

3. Takahashi D., Kamo M., Kurose Y., Nomura H. Deep steel desulphurisation technology in ladle furnace at KSC. Ironmaking and Steelmaking. 2003, vol. 30, no. 2, pp. 116–119. https://doi.org/10.1179/030192303225001711

4. Akberdin A.A., Kulikov I.S., Kim V.A., Nadyrbekov A.K., Kim A.S. Physical Properties of the Melts of CaO − SiO2 − Al2O3 − MgO  − CaF2 System. Moscow: Metallurgiya, 1987, 144 p. (In Russ.).

5. Wamg H.-M., Li G.-R., Dai Q.-X., Li B., Zhang X.-J., Shi G.M. САS-OB refining: slag modification with В2О3  –  CaO and СаF2 – CаО. Ironmaking and Steelmaking. 2007, vol. 34, no. 4,

6. pp. 350–353. https://doi.org/10.1179/174328107X155277

7. Ko K.Y., Park J.H. Effect of CaF2 addition on the viscosity and structure of CaO – SiO2 – MnO slags. ISIJ International. 2013, vol.  53, no. 6, pp. 958–965. https://doi.org/10.2355/isijinternational.53.958

8. Demin L.B., Sorokin Yu.V., Smirnov L.A., Shcherbakov E.N. Stabilization of decaying ferroalloy and steelmaking slags. In: Prospects for the Development of Metallurgy and Mechanical Engineering using Completed Fundamental Research and R&D: Proceedings of the Int. Sci. and Pract. Conf. Yekaterinburg, 2018, pp. 342–345. (In Russ.).

9. Babenko A.A., Smirnov L.A., Upolovnikova A.G., Smetannikov  A.N. Development of composition of environmentally friendly fluorine-free slags of ladle steel metallurgy. In: Fundamental Research and Applied Development of Processing and Utilization of Technogenic Formations: Proceedings of the V Int. Congress TECHNOGEN-2021. Yekaterinburg, 2021, pp. 349–350. (In Russ.).

10. Grabeklis A.A., Demin B.L., Kairakbaev S.N., Musabekov Zh.B., Kavanov B.O. New in technology of crystal-chemical stabilization of slags from refined ferrochrome production. Stal’. 2010, no. 5, pp.  78–83. (In Russ.).

11. Demin B.L., Sorokin Yu.V., Sharafutdinov R.Ya., Murzin A.V., Zhilin A.M. Testing the technology of crystal chemical stabilization of self-decaying steelmaking slags. Stal’. 2014, no. 6, pp. 102–106. (In Russ.).

12. Akberdin A.A., Kireeva G.M., Medvedovskaya I.A. Effect of B2O3 on the viscosity of slags CaO − SiO2 −Al2O3 . Izvestiya AN SSSR. Metally. 1986, no. 3, pp. 55–56. (In Russ.).

13. Hongming W., Tingwang Z., Hua Z. Effect of B2O3 on melting temperature, viscosity and desulfurization capacity of CaO – based refining flux. ISIJ International. 2011, vol. 51, no. 5, pp. 702–708. https://doi.org/10.2355/isijinternational.51.702

14. Zhang L., Wang W., Xie S., Zhang K., Sohn I. Effect of basicity and B2O3 on the viscosity and structure of fluorine-free mold flux. Journal of Non-Crystalline Solids. 2017, vol. 460, pp. 113–118. https://doi.org/10.1016/j.jnoncrysol.2017.01.031

15. Benavidez E., Santini L., Valentini M., Brandaleze E. Influence of different oxides on the viscosity of fluorine-free mold fluxes. Procedia Materials Science. 2012, vol. 1, pp. 389–396. https://doi.org/10.1016/j.mspro.2012.06.052

16. Li W., Xue X. Effects of Na2O and B2O3 addition on viscosity and electrical conductivity of CaO – Al2O3 – MgO – SiO2 . ISIJ System International. 2018, vol. 58, no. 10, pp. 1751–1760. https://doi.org/10.2355/isijinternational.ISIJINT-2018-212

17. Liu L.X., Wang G., Wang Sh.J., Dong Y.C., Chai Y.F. Calculation of phase diagram of CaO − SiO2 − Al2O3 − MgO − B2O3 refining slag without CaF2 . Advanced Materials Research. 2012, vol. 512-515, pp. 1558–1563. https://doi.org/10.4028/www.scientific.net/AMR.512-515.1558

18. Babenko A.A., Shartdinov R.R., Upolovnikova A.G., Smetannikov  A.N., Mikhailova L.Yu. Effect of basicity and chromium oxide on the viscosity of boron-containing slags. IOP Conference Series: Materials Science and Engineering. 2020, vol. 966, article 012012. https://doi.org/10.1088/1757-899X/966/1/012012

19. Kim V.A., Nikolai E.N., Akberdin A.A., Kulikov I.S. Planning an Experiment in Research of Physico-Chemical Properties of Metallurgical Slags. Alma-Ata: Nauka, 1989, 116 p. (In Russ.).

20. Babenko A.A., Smirnov L.A., Upolovnikova A.G. Boron distribution between Fe − C − Si − Al melt and boron-bearing slag. Journal of International Scientific Publications: Materials, Methods & Technologies. 2018, no. 12, pp. 202–208.

21. Babenko A.A., Smirnov L.A., Upolovnikova A.G. Theoretical and experimental studies of sulfur and boron distribution between the slag of the CaO − SiO2 − B2O3 − MgO − Al2O3 system and the metal. Defect and Diffusion Forum. 2021, vol. 410, pp. 287–292. https://doi.org/10.4028/www.scientific.net/DDF.410.287

22. Babenko A.A., Smirnov L.A., Upolovnikova A.G. Fundamental research as a basis for the creation of new technologies in steel ladle metallurgy. Materials Science Forum. 2019, vol. 946, pp. 493–499. https://doi.org/10.4028/www.scientific.net/MSF.946.493

23. Arsent’ev P.P., Yakovlev V.V., Krasheninnikov M.G., etc. Physico-Chemical Methods of Metallurgical Processes Research: Textbook for Universities. Moscow: Metallurgiya, 1988, 511 p. (In Russ.).