Evolution of nonmetallic inclusions in 80-t 9CrMoCoB large-scale ingots during electroslag remelting process

Abstract

In combination with theoretical calculations, experiments were conducted to investigate the evolution behavior of nonmetallic inclusions (NMIs) during the manufacture of large-scale heat-resistant steel ingots using 9CrMoCoB heat-resistant steel and CaF₂–CaO–Al₂O₃–SiO₂–B₂O₃ electroslag remelting (ESR)-type slag in an 80-t industrial ESR furnace. The main types of NMI in the consumable electrode comprised pure alumina, a multiphase oxide consisting of an Al₂O₃ core and liquid CaO–Al₂O₃–SiO₂–MnO shell, and M₂₃C₆ carbides with an MnS core. The Al₂O₃ and MnS inclusions had higher precipitation temperatures than the M₂₃C₆-type carbide under equilibrium and nonequilibrium solidification processes. Therefore, inclusions can act as nucleation sites for carbide layer precipitation. The ESR process completely removed the liquid CaO–Al₂O₃–SiO₂–MnO oxide and MnS inclusion with a carbide shell, and only the Al₂O₃ inclusions and Al₂O₃ core with a carbide shell occupied the remelted ingot. The M₂₃C₆-type carbides in steel were determined as Cr₂₃C₆ based on the analysis of transmission electron microscopy results. The substitution of Cr with W, Fe, or/and Mo in the Cr₂₃C₆ lattice caused slight changes in the lattice parameter of the Cr₂₃C₆ carbide. Therefore, Cr_21.34Fe_1.66C₆, (Cr₁₉W₄)C₆, Cr_18.4Mo_4.6C₆, and Cr₁₆Fe₅Mo₂C₆ can match the fraction pattern of Cr₂₃C₆ carbide. The Al₂O₃ inclusions in the remelted ingot formed due to the reduction of CaO, SiO₂, and MnO components in the liquid inclusion. The increased Al content in liquid steel or the higher supersaturation degree of Al₂O₃ precipitation in the remelted ingot than that in the electrode can be attributed to the evaporation of CaF₂ and the increase in CaO content in the ESR-type slag.

Keywords

nonmetallic inclusion / heat-resistant steel / electroslag remelting / M₂₃C₆ carbide / MnS inclusion / supersaturation degree

References

[1] Horiuchi T, Igarashi M, Abe F. Improved utilization of added B in 9Cr heat-resistant steels containing W. ISIJ Int., 2002, 42, S67.

[2] Masuyama F. History of power plants and progress in heat resistant steels. ISIJ Int., 2001, 41(6): 612.

[3] Yan W, Wang W, Shan YY, Yang K, Sha W. 9-12Cr Heat-Resistant Steels, 2015, Cham, Springer International Publishing

[4] F. Abe, Precipitate design for creep strengthening of 9% Cr tempered martensitic steel for ultra-supercritical power plants, Sci. Technol. Adv. Mater., 9(2008), No. 1, art. No. 013002.

[5] Hu XB, Li L, Wu XC, Zhang M. Coarsening behavior of M23C6 carbides after ageing or thermal fatigue in AISI H13 steel with niobium. Int. J. Fatigue, 2006, 28(3): 175.

[6] Zhou XS, Liu CX, Yu LM, Liu YC, Li HJ. Phase transformation behavior and microstructural control of high-Cr martensitic/ferritic heat-resistant steels for power and nuclear plants: A review. J. Mater. Sci. Technol., 2015, 31(3): 235.

[7] Zhou YH, Liu YC, Zhou XS, et al. Precipitation and hot deformation behavior of austenitic heat-resistant steels: A review. J. Mater. Sci. Technol., 2017, 33(12): 1448.

[8] Klueh RL. Elevated temperature ferritic and martensitic steels and their application to future nuclear reactors. Int. Mater. Rev., 2005, 50(5): 287.

[9] Z. Liu, X.T. Wang, and C. Dong, Effect of boron on G115 martensitic heat resistant steel during aging at 650°C, Mater. Sci. Eng. A, 787(2020), art. No. 139529.

[10] M. Sharma, I. Ortlepp, and W. Bleck, Boron in heat-treatable steels: A review, Steel Res. Int., 90(2019), No. 11, art. No. 1900133.

[11] D.S. Kim, G.J. Lee, M.B. Lee, J.I. Hur, and J.W. Lee, Manufacturing of 9CrMoCoB steel of large ingot with homogeneity by ESR process, IOP Conf. Ser. Mater. Sci. Eng., 143(2016), art. No. 012002.

[12] L.Z. Peng, Z.H. Jiang, and X. Geng, Design of ESR slag for remelting 9CrMoCoB steel through experiments and thermodynamic calculations, Calphad, 70(2020), art. No. 101782.

[13] Duan SC, Park JH. Comparison of oxidation behavior of various reactive elements in alloys during electroslag remelting (ESR) process: An overview. ISIJ Int., 2022, 62(8): 1561.

[14] Duan SC, Lee MJ, Kim DS, Park JH. Oxidation behavior of boron in 9CrMoCoB steel by CaF₂–CaO–Al₂O₃–SiO₂–B₂O₃ electroslag remelting (ESR) type slag. J. Mater. Res. Technol., 2022, 17, 574.

[15] J.H. Park and Y. Kang, Inclusions in stainless steels–A review, Steel Res. Int., 88(2017), No. 12, art. No. 1700130.

[16] Park JH, Todoroki H. Control of MgO·Al₂O₃ spinel inclusions in stainless steels. ISIJ Int., 2010, 50(10): 1333.

[17] Park JH, Zhang LF. Kinetic modeling of nonmetallic inclusions behavior in molten steel: A review. Metall. Mater. Trans. B, 2020, 51(6): 2453.

[18] Yang SF, Yang SL, Qu JL, et al. Inclusions in wrought superalloys: A review. J. Iron Steel Res. Int., 2021, 28(8): 921.

[19] Findley KO, Evans JL, Saxena A. A critical assessment of fatigue crack nucleation and growth models for Ni- and Ni, Fe-based superalloys. Int. Mater. Rev., 2011, 56(1): 49.

[20] Holt RT, Wallace W. Impurities and trace elements in nickel-base superalloys. Int. Met. Rev., 1976, 21(1): 1.

[21] Gao XY, Zhang L, Qu XH, Chen XW, Luan YF. Effect of interaction of refractories with Ni-based superalloy on inclusions during vacuum induction melting. Int. J. Miner. Metall. Mater., 2020, 27(11): 1551.

[22] J. Wang, L.Z. Wang, J.Q. Li, C.Y. Chen, S.F. Yang, and X. Li, Effects of aluminum and titanium additions on the formation of nonmetallic inclusions in nickel-based superalloys, J. Alloys Compd., 906(2022), art. No. 164281.

[23] Shi AJ, Wang Z, Shi CB, Guo L, Guo CQ, Guo ZC. Supergravity-induced separation of oxide and nitride inclusions from inconel 718 superalloy melt. ISIJ Int., 2020, 60(2): 205.

[24] Al-Jarba KA, Fuchs GE. Effect of carbon additions on the as-cast microstructure and defect formation of a single crystal Ni-based superalloy. Mater. Sci. Eng. A, 2004, 373(1–2): 255.

[25] He LZ, Zheng Q, Sun XF, et al. Effect of carbides on the creep properties of a Ni-base superalloy M963. Mater. Sci. Eng. A, 2005, 397(1–2): 297.

[26] Liu LR, Jin T, Zhao NR, Sun XF, Guan HR, Hu ZQ. Formation of carbides and their effects on stress rupture of a Ni-base single crystal superalloy. Mater. Sci. Eng. A, 2003, 361(1–2): 191.

[27] Yang SL, Yang SF, Liu W, Li JS, Gao JG, Wang Y. Microstructure, segregation and precipitate evolution in directionally solidified GH4742 superalloy. Int. J. Miner. Metall. Mater., 2023, 30(5): 939.

[28] Ha VT, Jung WS. Niobium carbo-nitride precipitation behavior in a high nitrogen 15Cr-15Ni heat resistant austenitic stainless steel. Met. Mater. Int., 2011, 17(5): 713.

[29] Sun WR, Guo SR, Lu DZ, Hu ZO. Effect of sulfur on the solidification and segregation in Inconel 718 alloy. Mater. Lett., 1997, 31(3–6): 195.

[30] Whelan EP, Grzedzielski MS. H-phase sulphocarbides and sulphur in nickel-base superalloys. Met. Technol., 1974, 1(1): 186.

[31] Chen XC, Shi CB, Guo HJ, Wang F, Ren H, Feng D. Investigation of oxide inclusions and primary carbonitrides in inconel 718 superalloy refined through electroslag remelting process. Metall. Mater. Trans. B, 2012, 43(6): 1596.

[32] Shi X, Duan SC, Yang WS, Mao MT, Guo HJ, Guo J. Effects of remelting current on structure, composition, microsegregation, and inclusions in inconel 718 electroslag remelting ingots. Metall. Mater. Trans. B, 2019, 50(6): 3072.

[33] Duan SC, Shi X, Wang F, et al. Investigation of desulfurization of Inconel 718 superalloys by ESR type slags with different TiO₂ content. J. Mater. Res. Technol., 2019, 8(3): 2508.

[34] Sakuraya K, Okada H, Abe F. BN type inclusions formed in high Cr ferritic heat resistant steel. Energy Mater., 2006, 1(3): 158.

[35] Li Y, Liu C, Zhang T, Jiang M, Peng C. Inclusions modification in heat resistant steel containing rare earth elements. Ironmaking Steelmaking, 2018, 45(1): 76.

[36] Zhang L, Hou YH, Li YC, Xiang ZL, Wang EG. Size and type of inclusions in Fe–Cr–Co Heat–resistant steel and elevated-temperature strength under the effect of electromagnetic stirring. ISIJ Int., 2019, 59(6): 1049.

[37] Li ZB. Electroslag Metallurgy Theory and Practice, 2010, Beijing, Metallurgical Industry Press, 66.

[38] Jiang ZH. Electroslag Metallurgy, 2015, Beijing, Science Press.

[39] A. Kharicha, E. Karimi-Sibaki, M.H. Wu, A. Ludwig, and J. Bohacek, Review on modeling and simulation of electroslag remelting, Steel Res. Int., 89(2018), No. 1, art. No. 1700100.

[40] Fu J, Zhu J. Changes in oxide inclusions during electroslag remelting. Acta Metall. Sin., 1964, 7(3): 250.

[41] Mitchell A, Bell M. On the origin of oxide inclusions in ingots made by the electroslag process. Can. Metall. Q., 1972, 11(2): 363.

[42] Dong YW, Jiang ZH, Cao YL, Yu A, Hou D. Effect of slag on inclusions during electroslag remelting process of die steel. Metall. Mater. Trans. B, 2014, 45(4): 1315.

[43] Wang Q, Wang RT, He Z, Li GQ, Li BK, Li HB. Numerical analysis of inclusion motion behavior in electroslag remelting process. Int. J. Heat Mass Transf., 2018, 125, 1333.

[44] X.C. Huang, B.K. Li, Z.Q. Liu, M.Z. Li, and F.S. Qi, Modeling of fluid flow, heat transfer and inclusion removal in electroslag remelting process with a rotating electrode, Int. J. Heat Mass Transf., 163(2020), art. No. 120473.

[45] Wang SJ, Shi CB, Liang YJ, Wan XX, Zhu X. Evolution and formation of Non-metallic inclusions during electroslag remelting of a heat-resistant steel for ultra-supercritical power plants. Metall. Mater. Trans. B, 2022, 53(5): 3095.

[46] Y. Zhao, C.B. Shi, S.J. Wang, P. Ren, and J. Li, Reoxidation of liquid steel and evolution of inclusions during protective atmosphere electroslag remelting of Ce-containing heat-resistant stainless steel, J. Iron Steel Res. Int., (2023). DOI: https://doi.org/10.1007/s42243-023-01092-3

[47] Park JH, Kim DJ, Min DJ. Characterization of non-metallic inclusions in high-manganese and aluminum-alloyed austenitic steels. Metall. Mater. Trans. A, 2012, 43(7): 2316.

[48] Park JH, Min DJ. Thermodynamics of fluoride vaporisation from slags containing CaF₂ at 1773 K. Steel Res. Int., 2004, 75(12): 807.

[49] Liu Y, Wang Y, Li GQ, Yuan C, Lu R, Li BK. Investigation on the structure, fluoride vaporization and crystallization behavior of CaF₂–CaO–Al₂O₃–(SiO₂) slag for electroslag remelting. J. Therm. Anal. Calorim., 2020, 139(2): 923.

[50] Dai CH, Zhang XP, Shui L. A new method for measuring activities in slags containing a volatile component. Metall. Mater. Trans. B, 1995, 26(3): 651.

[51] Mitchell A, Joshi S. The thermal characteristics of the electroslag process. Metall. Trans., 1973, 4(3): 631.

[52] Schneider R, Wiesinger V, Gelder S, Mitchell A, David D. Effect of different remelting parameters on slag temperature and energy consumption during ESR. ISIJ Int., 2022, 62(6): 1199.

[53] Hou D, Jiang ZH, Dong YW, Gong W, Cao YL, Cao HB. Effect of slag composition on the oxidation kinetics of alloying elements during electroslag remelting of stainless steel: Part-2 control of titanium and aluminum content. ISIJ Int., 2017, 57(8): 1410.

[54] Xuan C, Shibata H, Sukenaga S, Jönsson PG, Nakajima K. Wettability of Al₂O₃, MgO and Ti₂O₃ by liquid iron and steel. ISIJ Int., 2015, 55(9): 1882.

[55] Mukai K, Li ZS, Zeze M. Surface tension and wettability of liquid Fe–16 mass%Cr–O alloy with alumina. Mater. Trans., 2002, 43(7): 1724.

[56] Choi JY, Lee HG. Wetting of solid Al₂O₃ with molten CaO-Al₂O₃-SiO₂. ISIJ Int., 2003, 43(9): 1348.

[57] Monaghan BJ, Abdeyazdan H, Dogan N, Rhamdhani MA, Longbottom RJ, Chapman MW. Effect of slag composition on wettability of oxide inclusions. ISIJ Int., 2015, 55(9): 1834.

[58] Ohta H, Suito H. Dispersion behavior of MgO, ZrO₂, Al₂O₃, CaO–Al₂O₃ and MnO–SiO₂ deoxidation particles during solidification of Fe–10mass%Ni alloy. ISIJ Int., 2006, 46(1): 22.

[59] Furukawa T, Saito N, Nakashima K. Evaluation of interfacial energy between molten Fe and Fe–18% Cr–9% Ni alloy and non-metallic inclusion-type oxides. ISIJ Int., 2021, 61(9): 2381.

[60] X.P. Guo, M. Tan, T. Li, et al., Formation mechanisms and three-dimensional characterization of composite inclusion of MnS–Al₂O₃ in high speed wheel steel, Mater. Charact., 197(2023), art. No. 112669.

[61] Y.F. Qi, J. Li, C.B. Shi, H. Wang, and D.L. Zheng, Precipitation and growth of MnS inclusion in an austenitic hot-work die steel during ESR solidification process, Metall. Res. Technol., 116(2019), No. 3, art. No. 322.

[62] S.C. Duan, J. Kang, J. Cho, M. Lee, W.Z. Mu, and J.H. Park, Manufacturing an ultra-low-sulfur CoCrFeMnNi high-entropy alloy by slagging through induction melting with ferroalloys feedstock, J. Alloys Compd., 928(2022), art. No. 167080.

[63] Zeng J, Zhu CY, Wang WL, Li X. In situ observation of the MnS precipitation behavior in high-sulfur microalloyed steel under different cooling rates. Metall. Mater. Trans. B, 2020, 51(6): 2522.

[64] Xue ZL, Li N, Wang L, Song SQ, Liu DM, Huang A. A coupling model predicting the precipitation and growth of MnS inclusions in U75V high-carbon heavy rail steel. Metall. Mater. Trans. B, 2021, 52(6): 3860.

[65] D.M. Liu, Z.L. Xue, and S.Q. Song, Effect of manganese on the formation mechanism of nonmetallic inclusions in Fe–xMn–7Al–0.7C lightweight steel, Steel Res. Int., 94(2023), No. 1, art. No. 2200551.

[66] Shin JH, Park JH. Modification of inclusions in molten steel by Mg-Ca transfer from top slag: Experimental confirmation of the ‘refractory-slag-metal-inclusion (ReSMI)’ multiphase reaction model. Metall. Mater. Trans. B, 2017, 48(6): 2820.

[67] Shi CB, Wang H, Li J. Effects of reoxidation of liquid steel and slag composition on the chemistry evolution of inclusions during electroslag remelting. Metall. Mater. Trans. B, 2018, 49(4): 1675.

[68] M.G. González-Solórzano, R. Morales, J.R. Ávila, C.R. Muñiz-Valdés, and A.N. Bastida, Alumina nucleation, growth kinetics, and morphology: A review, Steel Res. Int., 94(2023), No. 9, art. No. 2200678.

[69] Shu QF, Visuri VV, Alatarvas T, Fabritius T. Model for inclusion precipitation kinetics during solidification of steel applications in MnS and TiN inclusions. Metall. Mater. Trans. B, 2020, 51(6): 2905.

[70] Zheng DL, Ma GJ, Li J, et al. Effect of cerium on the primary carbides and inclusions in electroslag remelted M35 high speed steel. J. Mater. Res. Technol., 2023, 24, 8252.

[71] Yoshizawa M, Igarashi M, Nishizawa T. Effect of tungsten on the Ostwald ripening of M₂₃C₆ carbides in martensitic heat resistant steel. Tetsu-to-Hagane, 2005, 91(2): 272.

[72] Xiao X, Liu GQ, Hu BF, Wang JS, Ma WB. Coarsening behavior for M23C6 carbide in 12%Cr-reduced activation ferrite/martensite steel: Experimental study combined with DICTRA simulation. J. Mater. Sci., 2013, 48(16): 5410.

[73] J.P. Sanhueza, D. Rojas, J. García, et al., Computational modeling of the effect of B and W in the phase transformation of M23C6 carbides in 9 to 12 pct Cr martensitic/ferritic steels, Mater. Res. Express, 6(2019), No. 11, art. No. 1165d3.

[74] Fraser ME, Mitchell A. Mass transfer in the electroslag process. Part1: Mass-transfer model. Ironmaking Steelmaking, 1976, 3(5): 279.

[75] Valdez M, Shannon GS, Sridhar S. The ability of slags to absorb solid oxide inclusions. ISIJ Int., 2006, 46(3): 450.

[76] Wen Y, Shu Q, Lin Y, Fabritius T. Effect of SiO₂ content and mass ratio of CaO to Al₂O₃ on the viscosity and structure of CaO–Al₂O₃–B₂O₃–SiO₂ slags. ISIJ Int., 2023, 63(1): 1.

[77] Jung IH, Van Ende MA. Computational thermodynamic calculations: FactSage from CALPHAD thermodynamic database to virtual process simulation. Metall. Mater. Trans. B, 2020, 51(5): 1851.

[78] Shi CB, Wang SJ, Li J, Cho JW. Non-metallic inclusions in electroslag remelting: A review. J. Iron Steel Res. Int., 2021, 28(12): 1483.

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

[80] Li GQ, Suito H. Electrochemical measurement of critical supersaturation in F–O–M (M=Al, Si, and Zr) and Fe–O–Al–M (M=C, Mn, Cr, Si, and Ti) melts by solid electrolyte galvanic cell. ISIJ Int., 1997, 37(8): 762.

[81] Kim TS, Lee SB, Park JH. Effect of tundish flux on compositional changes in non-metallic inclusions in stainless steel melts. ISIJ Int., 2021, 61(12): 2998.

[82] Hino M, Ito K. Thermodynamic Data for Steelmaking, 2010, Sendai, Tohoku University Press, 259.

[83] Kishi M, Inoue R, Suito H. Thermodynamics of oxygen and nitrogen in liquid Fe-20mass%Cr alloy equilibrated with titania-based slags. ISIJ Int., 1994, 34(11): 859.

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

[85] T.J. Wen, Q. Ren, L.F. Zhang, et al., Evolution of nonmetallic inclusions during the electroslag remelting process, Steel Res. Int., 92(2021), No. 6, art. No. 2000629.

[86] T.F. Li, G.Q. Li, Z. Zhang, Y. Liu, and X.J. Wang, Fluoride vaporization and crystallization of CaF₂–CaO–Al₂O₃–(La₂O₃) slag for vacuum electroslag remelting, Vacuum, 196(2022), art. No. 110807.

[87] S.C. Duan and H.J. Guo, The methodology development for improving energy utilization and reducing fluoride pollution of the electroslag remelting process: A review, Steel Res. Int., 91(2020), No. 7, art. No. 1900634.

[88] Wagner C. Thermodynamics of Alloys, 1952, Cambridge, MA, Addison-Wesley Press, 47.

[89] Scheil E. Bemerkungen zur schichtkristallbildung. Int. J. Mater. Res., 1942, 34(3): 70.

[90] Choudhary SK, Ghosh A. Mathematical model for prediction of composition of inclusions formed during solidification of liquid steel. ISIJ Int., 2009, 49(12): 1819.

[91] Hou D, Jiang ZH, Dong YW, Li Y, Gong W, Liu FB. Mass transfer model of desulfurization in the electroslag remelting process. Metall. Mater. Trans. B, 2017, 48(3): 1885.

[92] Wang HM, Zhang TW, Zhu H, Li GR, Yan YQ, Wang JH. Effect of B₂O₃ on melting temperature, viscosity and desulfurization capacity of CaO-based refining flux. ISIJ Int., 2011, 51(5): 702.

[93] Zhu QT, Li J, Shi CB, Yu WT. Effect of electroslag remelting on carbides in 8Cr₁₃MoV martensitic stainless steel. Int. J. Miner. Metall. Mater., 2015, 22(11): 1149.