Behavior of phosphorus enrichment in dephosphorization slag at low temperature and low basicity

Abstract

At low basicity and low temperature, the dephosphorization behavior and phosphorus distribution ratio (L _P) between slag and molten steel in the double slag and remaining slag process were studied with a 180 t basic oxygen furnace industrial experiment. The dephosphorization slags with different basicities were quantitatively analyzed. At the lower basicity range of 0.9–2.59, both L _P and dephosphorization ratio were increased as the basicity of dephosphorization slag increased. Dephosphorization slag consisted of dark gray P-rich, light gray liquid slag, and white Fe-rich phases. With increasing basicity, not only did the morphologies of different phases in the dephosphorization slag change greatly, but the area fractions and P₂O₅ content of the P-rich phase also increased. The transfer route of P during dephosphorization can be deduced as hot metal → liquid slag phase + Fe-rich phase → P-rich phase.

Keywords

dephosphorization / basicity / phosphorus-rich phase / slag / converter steelmaking

References

[1] Ogawa Y, Yano M, Kitamura S-Y, Hirata H. Development of the continuous dephosphorization and decarburization process using BOF. Steel Res. Int., 2003, 74(2): 70.

[2] Sasaki N, Ogawa Y, Mukawa S, Miyamoto K-I. Improvement in hot-metal dephosphorization. Nippon Steel Tech. Rep., 2013, 104, 26.

[3] Kobayashi M, Isobe K, Arai M. Technical progress in steelmaking and casting for special bar and wire steel at muroran works. Nippon Steel Tech. Rep., 2012, 394, 119.

[4] Wang XH, Zhu GS, Li HB, Lü YC. Investigation on “slag-remaining + double-slag” BOF steelmaking technology. China Metall., 2013, 23(4): 40.

[5] Yang X, Sun FM, Yang JL, Liu F, Cheng KS, Wang J H. Optimization of low phosphorus steel production with double slag process in BOF. J. Iron Steel Res. Int., 2013, 20(8): 41.

[6] Tian ZH, Li BH, Zhang XM, Jiang ZH. Double slag operation dephosphorization in BOF for producing low phosphorus steel. J. Iron Steel Res. Int., 2009, 16(3): 6.

[7] Lü JF, Jin ZN, Yang HY, Tong LL, Chen GB, Xiao FX. Effect of the CaO/SiO2 mass ratio and FeO content on the viscosity of CaO-SiO₂-“FeO”-12wt%ZnO-3wt%Al₂O₃ slags. Int. J. Miner. Metall. Mater., 2017, 24(7): 756.

[8] Kitamura S, Shibata H, Shimauchi K, Saito S. The importance of dicalcium-silicate on hot metal dephosphorization reaction. Revue De Métallurgie, 2008, 105(5): 263.

[9] Ito K, Yanagisawa M, Sano N. Phosphorus distribution between solid 2CaO·SiO₂ and molten CaO-SiO₂-FeO-Fe₂O₃ slags. Tetsu-To-Hagané, 1982, 68(2): 342.

[10] Kitamura S, Shibata H, Maruoka N. Kinetic model of hot metal dephosphorization by liquid and solid coexisting slags. Steel Res. Int., 2008, 79(8): 586.

[11] Lin L, Bao YP, Wang M, Zhou HM, Zhang LQ. Influence of SiO₂ modification on phosphorus enrichment in P bearing steelmaking slag. Ironmaking Steelmaking, 2013, 40(7): 521.

[12] Li JY, Zhang M, Guo M, Yang XM. Enrichment mechanism of phosphate in CaO-SiO₂-FeO-Fe₂O₃-P₂O₅ steelmaking slags. Metall. Mater. Trans. B, 2014, 45(5): 1666.

[13] Gao X, Matsuura H, Tsukihashi F. Phase equilibrium for the CaO-SiO₂-FeO-P₂O₅ system at 1673 K for dephosphorization with multi phase flux. J. Iron Steel Res. Int., 2011, 18(Suppl. 2): 84.

[14] Gao X, Matsuura H, Sohn I, Wang WL, Min DJ, Tsukihashi F. Phase relationship for the CaO-SiO₂-FeO-5 mass% P₂O₅ system with oxygen partial pressure of 10^-8 atm at 1673 and 1623 K. Mater. Trans., 2013, 54(4): 544.

[15] Kitamura S, Saito S, Utagawa K, Shibata H, Robertson DGC. Mass transfer of P₂O₅ between liquid slag and solid solution of 2CaO·SiO₂ and 3CaO·P₂O₅. ISIJ Int., 2009, 49(12): 1838.

[16] Xie SL, Wang WL, Luo ZC, Huang DY. Mass transfer behavior of phosphorus from the liquid slag phase to solid 2CaO·SiO₂ in the multiphase dephosphorization slag. Metall. Mater. Trans. B, 2016, 47(3): 1583.

[17] Inoue R, Suito H. Phosphorous partition between 2CaO·SiO₂ particles and CaO-SiO₂-Fe_tO slags. ISIJ Int., 2006, 46(2): 174.

[18] Shimauchi K, Kitamura S, Shibata H. Distribution of P₂O₅ between solid dicalcium silicate and liquid phases in CaO-SiO₂-Fe₂O₃ system. ISIJ Int., 2009, 49(4): 505.

[19] Yang X, Matsuura H, Tsukihashi F. Reaction behavior of P₂O₅ at the interface between solid 2CaO·SiO₂ and liquid CaO-SiO₂-FeO_x-P₂O₅ slags saturated with solid 5CaO·SiO₂·P₂O₅ at 1573 K. ISIJ Int., 2010, 50(5): 702.

[20] Yang X, Matsuura H, Tsukihashi F. Dissolution behavior of solid 5CaO·SiO₂·P₂O₅ in CaO-SiO₂-FeO_x slag. Mater. Trans., 2010, 51(6): 1094.

[21] Yang X, Matsuura H, Tsukihashi F. Condensation of P₂O₅ at the interface between 2CaO·SiO₂ and CaO-SiO₂-FeO_x-P₂O₅ slag. ISIJ Int., 2009, 49(9): 1298.

[22] Du CM, Gao X, Ueda S, Kitamura S. Distribution of P₂O₅ and Na₂O between solid solution and liquid phase in the CaO-SiO₂-Fe₂O₃-P₂O₅-Na₂O slag system with high P₂O₅ content. Metall. Mater. Trans. B, 2018, 49(1): 181.

[23] Lin L, Bao YP, Gu C, Wu W, Zeng JQ. Distribution of P₂O₅ between P-rich phase and matrix phase in P-bearing steel-making slag. High Temp. Mater. Proc., 2018, 37(7): 655.

[24] Pahlevani F, Kitamura S, Shibata H, Maruoka N. Distribution of P₂O₅ between solid solution of 2CaO·SiO₂-3CaO·P₂O₅ and liquid phase. ISIJ Int., 2010, 50(6): 822.

[25] Ito K, Terasawa M. Utilization of multiphase fluxes for the dephosphorization of hot metal. Steel Res. Int., 2009, 80(10): 733.

[26] Hamano T, Fukagai S, Tsukihashi F. Reaction mechanism between solid CaO and FeO_x-CaO-SiO₂-P₂O₅ slag at 1573 K. ISIJ Int., 2006, 46(4): 490.

[27] Gao X, Matsuura H, Sohn I, Wang WL, Min DJ, Tsukihashi F. Phase relationship of CaO-SiO₂-FeO-5 mass pct P₂O₅ system with low oxygen partial pressure at 1673 K (1400°C). Metall. Mater. Trans. B, 2012, 43(4): 694.

[28] Xie SL, Wang WL. Crystallization kinetics study of the (2CaO·SiO₂-3CaO·P₂O₅) solid solution in the multiphase dephosphorization flux. Steel Res. Int., 2016, 87(3): 376.

[29] Healy GW. New look at phosphorus distribution. J. Iron Steel Inst. (London), 1970, 208(7): 664.

[30] Suito H, Inoue R. Phosphorus distribution between MgO-saturated CaO-Fe_tO-SiO₂-P₂O₅-MnO slags and liquid iron. Trans. Iron Steel Inst. Jpn., 1984, 24(1): 40.

[31] Ide K, Fruehan RJ. Evaluation of phosphorus reaction equilibrium in steelmaking. Iron Steelmaker, 2000, 27(12): 65.

[32] Zhang XF, Sommerville ID, Toguri JM. Equation for the equilibrium distribution of phosphorus between basic slags and steel. Trans. Iron Steel Soc. AIME, 1985, 6, 29.

[33] Zhou HM, Bao YP, Lin L. Effect of P₂O₅ on rich phosphorus phase of CaO-SiO₂-Fe_tO-P₂O₅ slag. China Metall., 2013, 23(1): 45.

[34] S.L. Xie, W.L. Wang, D.Y. Huang, H.C. Li, and Y. Du, Clarification of the dissolution of solid CaO and the phosphorus-enrichment capability of calcium silicates in the multiphase slag based on the ion and molecule coexistence theory, Steel Res. Int., 89(2018), No. 2, art. No. 1700317.