Thermodynamic analysis of the compositional control of inclusions in cutting-wire steel

Abstract

Data from a thermodynamic database and the calculation software FactSage were used to investigate the phase diagrams of the MnO-CaO-SiO₂-Al₂O₃ system in cutting-wire steel and the effects of oxide components on the low-melting-point (LMP) zone in the corresponding phase diagrams. Furthermore, the activities of oxide components in the quaternary system at an Al₂O₃ content of 25wt% were calculated. The contents of dissolved [Al] and [O] in liquid steel in equilibrium with LMP inclusions in the MnO-CaO-SiO₂-Al₂O₃ system were optimized. The results show that the MnO-CaO-SiO₂-Al₂O₃ system possesses the largest LMP zone (below 1400°C) at an Al₂O₃ content of 25wt% and that the CaO content should be simultaneously controlled in the range of 40wt% to 45wt%. The activities of the oxide components CaO, MnO, and SiO₂ should be restricted in the ranges of 0 to 0.05, 0.01 to 0.6, and 0.001 to 0.8, respectively. To obtain LMP inclusions, the [Al] and [O] contents in cutting-wire steel must be controlled within the ranges of 0.5 × 10⁻⁶ to 1.0 × 10⁻⁵ and 3.0 × 10⁻⁶ to 5.0 × 10⁻⁵, respectively.

Keywords

wire steel / cutting / inclusions / thermodynamic calculations / activity / oxides

References

[1] Suito H, Inoue R. Thermodynamics on control of inclusions composition in ultra-clean steels. ISIJ Int., 1996, 36(5): 528.

[2] Liu JH, Wu HJ, Bao YP, Wang M. Inclusion variations and calcium treatment optimization in pipeline steel production. Int. J. Miner. Metall. Mater., 2011, 18(5): 527.

[3] Gagné M, Thibaultt E. Control of inclusion characteristics in direct cast steel billets. Can. Metall. Q., 1999, 38(5): 311.

[4] Wang LF, Zhuo XJ, Zhang JM, Wang XH. Controlling inclusion composition in steelmaking process for tire cord steel. J. Univ. Sci. Technol. Beijing, 2003, 25(4): 308

[5] Kume K, Morita K, Miki T, Sano N. Activity measurement of CaO-SiO₂-AlO_1.5-MgO slags equilibrated with molten silicon alloys. ISIJ Int., 2000, 40(6): 561.

[6] Wang HT, Wang FM, Xu ZB, Jin LL. Composition control of CaO-MgO-Al₂O₃-SiO₂ inclusion in tire cord steel: a thermodynamic analysis. Steel Res. Int., 2008, 79(1): 25

[7] Zheng HG, Chen WQ. Formation of CaO·TiO₂-MgO·DAl₂O₃ dual phase inclusion in Ti stabilized stainless steel. J. Univ. Sci. Technol. Beijing, 2006, 13(1): 16.

[8] Kang YB, Kim HS, Zhang J, Lee HG. Practical application of thermodynamics to inclusions engineer in steel. J. Phys. Chem. Solids, 2005, 66(2–4): 219.

[9] Zhuo XJ, Wang YQ, Wang XH, Lee HG. Thermodynamic calculation and MnS solubility of Mn-Ti oxide formation in Si-Mn-Ti deoxidized steel. J. Iron Steel Res. Int., 2010, 17(2): 10.

[10] Jin LL, Wang HT, Xu ZB, Wang FM. Control on low melting point area in a CaO-SiO₂-Al₂O₃-MnO system. J. Univ. Sci. Technol. Beijing, 2007, 29(6): 574

[11] Kang YB, Jung IH, Decterov SA, Pelton AD, Lee HG. Critical thermodynamic evaluation and optimization of the CaO-MnO-SiO₂ and CaO-MnO-Al₂O₃ systems. ISIJ Int., 2004, 44(6): 965.

[12] Wang SF, Ma H. Effect of deformability of CaO-MgO-SiO₂-Al₂O₃ series inclusion on breakage rate of tire cord steel in processing. Spec. Steel, 2012, 33(3): 32

[13] Zhuo XJ, Wang XH, Wang WJ, Lee HG. Thermodynamic calculations and experiments on inclusions to be nucleation sites for intragranular ferrite in Si-Mn-Ti deoxidized steel. J. Univ. Sci. Technol. Beijing, 2007, 14(1): 14.

[14] Bale CW, Chartrand P, Degterov SA, Eriksson G, Hack K, Mahfoud RB, Melançon J, Pelton AD, Petersen S. FactSage thermochemical software and databases. Calphad, 2002, 26(2): 189.

[15] Kang YB, Lee HG. Inclusions chemistry for Mn/Si deoxidized steels: thermodynamic predictions and experimental confirmations. ISIJ Int., 2004, 44(6): 1006.

[16] Sigworth GK, Elliott JF. The thermodynamics of liquid dilute iron alloys. Met. Sci., 1974, 8(1): 298.