Effect of TiO₂ on the viscosity and structure of low-fluoride slag used for electroslag remelting of Ti-containing steels

Abstract

The viscosity of CaF₂–CaO–Al₂O₃–MgO–(TiO₂) slag was measured using a rotating crucible viscometer. Raman spectroscopy analysis was performed to correlate the viscosity to slag structure. The viscosity of the slag was found to decrease with increasing TiO₂ content in the slag from 0 to 9.73wt%. The activation energy decreased from 95.16 kJ/mol to 79.40 kJ/mol with increasing TiO₂ content in the slag. The introduction of TiO₂ into the slag played a destructive role in Al–O–Al structural units and Q⁴ units by forming simpler structural units of Q² and Ti₂O₆ ⁴⁻ chain. The amount of Al–O–Al significantly decreased with increasing TiO₂ content. The relative fraction of Q⁴ units in the [AlO₄]⁵⁻-tetrahedral units shows a decreasing trend, whereas the relative fraction of Q² units and Ti₂O₆ ⁴⁻ chain increases with increasing TiO₂ content accordingly. Consequently, the polymerization degree of the slag decreases with increasing TiO₂ content. The variation in slag structure is consistent with the change in measured viscosity.

Keywords

electroslag remelting / slag / titanium dioxide / viscosity / structure

References

[1] Schwerdtfeger K., Wepner W., Pateisky G. Modelling of chemical reactions occurring during electroslag remelting: oxidation of titanium in stainless steel. Ironmaking Steelmaking, 1978, 5(3): 135.

[2] Xue Z.X., Zheng Y.X., Jiang F., Du Y.Q., Guo B.S., Lin P., Shi C.B. Control of the surface quality and as-cast ingot and Ti loss during drawing-ingot-type electroslag rapid remelting of alloy 825. Spec. Steel, 2016, 37(4): 37.

[3] Lu X.C. Effect of titanium on surface formability of ESR super alloy ingot. Foundry, 2002, 51(6): 378.

[4] Shi C.B., Li J., Cho J.W., Jiang F., Jung I.H. Effect of SiO₂ on the crystallization behaviors and in-mold performance of CaF₂−CaO−Al₂O₃ slags for drawing-ingot-type electroslag remelting. Metall. Mater. Trans. B, 2015, 46(5): 2110.

[5] Zheng K., Zhang Z.T., Liu L.L., Wang X.D. Investigation of the viscosity and structural properties of CaO–SiO₂–TiO₂ slags. Metall. Mater. Trans. B, 2014, 45(4): 1389.

[6] Park H., Park J.Y., Kim G.H., Sohn I. Effect of TiO₂ on the viscosity and slag structure in blast furnace type slags. Steel Res. Int., 2012, 83(2): 150.

[7] Zhang S.F., Zhang X., Bai C.G., Wen L.Y., Lv X.W. Effect of TiO₂ content on the structure of CaO–SiO₂–TiO₂ system by molecular dynamics simulation. ISIJ Int., 2013, 53(7): 1131.

[8] Li J.L., Shu Q.F., Chou K.C. Effect of TiO₂ addition on viscosity and structure of CaO–Al₂O₃ based mold fluxes for high Al steel casting. Can. Metall. Q., 2015, 54(1): 85.

[9] Liao J.L., Li J., Wang X.D., Zhang Z.T. Influence of TiO₂ and basicity on viscosity of Ti bearing slag. Ironmaking Steelmaking, 2012, 39(2): 133.

[10] Shin S.H., Cho J.W., Kim S.H. Controlling the shear thinning property of calcium silicate melts by addition of Si3N4. J. Non Cryst. Solids, 2015, 423-424, 45.

[11] Shin S.H., Yoon D.W., Cho J.W., Kim S.H. Controlling shear thinning property of lime silica based mold flux system with borate additive at 1623 K. J. Non Cryst. Solids, 2015, 425, 83.

[12] Shankar A., Görnerup M., Lahiri A.K., Seetharaman S. Experimental investigation of the viscosities in CaO–SiO₂–MgO–Al₂O₃ and CaO–SiO₂–MgO–Al₂O₃–TiO₂ slags. Metall. Mater. Trans. B, 2007, 38(6): 911.

[13] Wang Z., Shu Q.F., Chou K.C. Viscosity of fluoride-free mold fluxes containing B₂O₃ and TiO₂. Steel Res. Int., 2013, 84(8): 766.

[14] Saito N., Hori N., Nakashima K., Mori K. Viscosity of blast furnace type slags. Metall. Mater. Trans. B, 2003, 34(5): 509.

[15] Zhen Y.L., Zhang G.H., Chou K.C. Influence of Al₂O₃/TiO₂ ratio on viscosities and structure of CaO–MgO–Al₂O₃–SiO₂–TiO₂ melts. ISIJ Int., 2014, 54(4): 985.

[16] Sun Y., Zheng K., Liao J., Wang X., Zhang Z. Effect of P₂O₅ addition on the viscosity and structure of titanium bearing blast furnace slags. ISIJ Int., 2014, 54(7): 1491.

[17] Ohno A., Ross H.U. Optimum slag composition for the blast-furnace smelting of titaniferous ores. Can. Metall. Q., 1963, 3, 259.

[18] Gao Y.H., Bian L.T., Liang Z.Y. Influence of B₂O₃ and TiO₂ on viscosity of titanium-bearing blast furnace slag. Steel Res. Int., 2015, 86(4): 386.

[19] Kim H., Sohn I. Effect of CaF₂ and Li₂O additives on the viscosity of CaO–SiO₂–Na₂O slags. ISIJ Int., 2011, 51(1): 1.

[20] Gao Y.M., Wang S.B., Hong C., Ma X.J., Yang F. Effects of basicity and MgO content on the viscosity of the SiO₂–CaO–MgO–9wt%Al₂O₃ slag system. Int. J. Miner. Metall. Mater., 2014, 21(4): 353.

[21] Kim H., Sohn I. Influence of Li₂O on the viscous behavior of CaO–Al₂O₃–12mass%Na₂O–12 mass% CaF₂ based slags. ISIJ Int., 2012, 52(1): 68.

[22] Mysen B., Neuville D. Effect of temperature and TiO₂ content on the structure of Na₂Si₂O₅–Na₂Ti₂O₅ melts and glasses. Geochim. Cosmochim. Acta, 1995, 59(2): 325.

[23] Reynard B., Webb S.L. High-temperature Raman spectroscopy of Na₂TiSi₂O₇ glass and melt: coordination of Ti⁴⁺ and nature of the configurational changes in the liquid. Eur. J. Mineral., 1998, 10(1): 49.

[24] Henderson G.S., Fleet M.E. The structure of Ti silicate glasses by micro-Raman spectroscopy. Can. Mineral., 1995, 33, 399.

[25] Zheng K., Liao J.L., Wang X.D., Zhang Z.T. Raman spectroscopic study of the structural properties of CaO–MgO–SiO₂–TiO₂ slags. J. Non Cryst. Solids, 2013, 376(10): 209.

[26] Kim G.H., Sohn I. Effect of Al₂O₃ on the viscosity and structure of calcium silicate-based melts containing Na₂O and CaF₂. J. Non Cryst. Solids, 2012, 358(12-13): 1530.

[27] Kim H., Matsuura H., Tsukihashi F., Wang W., Min D.J. Effect of Al₂O₃ and CaO/SiO₂ on the viscosity of calcium-silicate based slags containing 10 mass pct MgO. Metall. Mater. Trans. B, 2013, 44(1): 5.

[28] Sun Y., Liao J., Zheng K., Wang X., Zhang Z. Effect of B₂O₃ on the structure and viscous behavior of Ti-bearing blast furnace slags. JOM, 2014, 66(10): 2168.

[29] McMillan P., Piriou B. Raman spectroscopy of calcium aluminate glasses and crystals. J. Non Cryst. Solids, 1983, 55(2): 221.

[30] Licheron M., Montouillout V., Millot F., Neuville D.R. Raman and 27Al NMR structure investigations of aluminate glasses: (1−x) Al₂O₃–xMO, with M = Ca, Sr, Ba and 0.5 < x < 0.75. J. Non Cryst. Solids, 2011, 357(15): 2796.

[31] Higby P.L., Ginther R.J., Aggarwal I.D., Friebele E.J. Glass formation and thermal properties of low-silica calcium aluminosilicate glasses. J. Non Cryst. Solids, 1990, 126(3): 209.

[32] Kim T.S., Park J.H. Structure-viscosity relationship of low-silica calcium aluminosilicate melts. ISIJ Int., 2014, 54(9): 2031.

[33] Kim G.H., Kim C.S., Sohn I. Viscous behavior of alumina rich calcium-silicate based mold fluxes and its correlation to the melt structure. ISIJ Int., 2013, 53(1): 170.

[34] Neuville D.R., Cormier L., Massiot D. Al environment in tectosilicate and peraluminous glasses: a 27Al MQ-MAS NMR, Raman, and XANES investigation. Geochim. Cosmochim. Acta, 2004, 68(24): 5071.

[35] Neuville D.R., Henderson G.S., Cormier L., Massiot D. The structure of crystals, glasses, and melts along the CaO–Al₂O₃ join: results from Raman, Al L- and K-edge X-ray absorption, and 27Al NMR spectroscopy. Am. Mineral., 2015, 95(10): 1580.

[36] Mysen B.O., Ryerson F.J., Virgo D. The influence of TiO₂ on the structure and derivative properties of silicate melts. Am. Mineral., 1980, 65, 1150.