Improved Removal Efficiency of Submicron Inclusions in Non-oriented Silicon Steel during RH Process

Abstract

To improve the removal efficiency of such submicron inclusions, we designed an argon blowing method for an RH facility based on mathematical simulations. The effect of the argon blowing on the liquid steel flow and the movement of submicron inclusions was studied using the k-ε flow model coupled with the DPM model for inclusion movement based on fluid computational dynamics in FLUENT. It was found that a more uniform argon flow can be achieved in the up-leg snorkel with a new nozzle position and inner diameter, which resulted in a favorable up-lifting and mixing movement. The new design also increased the circulation rate of molten steel in the RH chamber. The increased turbulent kinetic energy and turbulent dispersing rate enhanced the collision probability of submicron inclusions, which results in an improved removal for 0.5–1 µm inclusions. The proposed RH facility could increase the removal rate of submicron inclusions from the original 57.1% to 66.4%, which improves the magnetic properties of non-oriented silicon steel.

Keywords

RH treatment / argon blowing method / model optimization / submicron inclusions / numerical simulation

References

[1] Du LY, Zhou GF, Liu J, et al. Fatigue Cracking Characterization of High Grade Non-oriented Electrical Steels[J]. J. Wuhan Univ. Technol.-Mater. Sci. Ed., 2017, 32(6): 1 329-1 335.

[2] Bóc I, Cziráki Á, Gróf T, et al. Analysis of Inclusions in Cold-rolled No Si-Fe Strips[J]. J. Magn. Magn. Mater., 2015, 83(1): 381-383.

[3] Hawezy D. The Influence of Silicon Content on Physical Properties of Non-oriented Silicon Steel[J]. J. Mater. Sci. Technol., 2017, 33(2): 1-10.

[4] Wan Y, Chen W. Effect of Boron Content on the Microstructure and Magnetic Properties of Non-oriented Electrical Steels[J]. J. Wuhan Univ. Technol. -Mater. Sci. Ed., 2015, 30(3): 574-579.

[5] Chen TY, Liu J, Cheng ZY, et al. Study on Inclusion Behavior in RH Refining Process of Non-oriented Silicon Steel[J]. Journal of Wuhan University of Science and Technology, 2019 (1): 1–7 (in Chinese)

[6] Kuwabara T, Umezawa K, Mori K, et al. Investigation of Decarburization Behavior in RH-reactor and Its Operation Improvement[J]. Transactions of the Iron and Steel Institute of Japan, 1988, 28(4): 305-314.

[7] Zhu MY, Huang ZZ. Simulation Study on RH Vacuum Decarburization Refining Process[J]. Acta Metall. Sinica, 2001, 37(1): 91-94. (in Chinese)

[8] Ling HT, Guo C, Conejo AN, et al. Effect of Snorkel Shape and Number of Nozzles on Mixing Phenomena in the RH Process by Physical Modeling[J]. Metall. Res. Technol., 2017, 114(1): 111

[9] Ling HT, Li F, Zhang L, et al. Investigation on the Effect of Nozzle Number on the Recirculation Rate and Mixing Time in the RH Process using VOF+ DPM Model[J]. Metall. Mater. Trans. B, 2016, 47(3): 1 950-1 961.

[10] Yan W. Numerical Study on the Effect of Argon Blowing on the Flow of RH Vacuum Refining Cycle[D]. Northeastern University, 2012 (in Chinese)

[11] Ai XG, Wang CS, Meng FT, et al. Numerical Simulation of the Movement and Removal of Inclusions in Al₂O₃ during RH Refining Process[J]. Journal of Iron and Steel Research, 2016, 28(1): 20-24. (In Chinese)

[12] Wang Y, Li H, Guo LF. Numerical Simulation of Force of Spherical Inclusion Particles in Liquid Steel[J]. Journal of University of Science and Technology Beijing, 2013, 35(11): 1 437-1 442. (in Chinese)

[13] Treadgold CJ. Behaviour of Inclusions in RH Vacuum Degasser[J]. Ironmak. Steelmak., 2003, 30(2): 120-124.

[14] Xu J, Huang F, Wang X, et al. Investigation on the Removal Efficiency of Inclusions in Al-killed Liquid Steel in Different Refining Processes[J]. Ironmak. Steelmak., 2017, 44(6): 455-460.