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Abstract

The article describes the influence of optimization parameters on the efficiency of aluminium melt refining by using physical modelling. The blowing of refining gas, through a rotating impeller into the ladle is a widely used operating technology to reduce the content of impurities in molten aluminium, e.g. hydrogen. The efficiency of this refining process depends on the creation of fine bubbles with a high interphase surface, wide-spread distribution, the residence time of its effect in the melt, and mostly on the wide-spread dispersion of bubbles in the whole volume of the refining ladle and with the long period of their effect in the melt. For physical modelling, a plexiglass model on a scale of 1:1 is used for the operating ladle. Part of the physical model is a hollow shaft used for gas supply equipped with an impeller and also two baffles. The basis of physical modelling consists in the targeted utilization of the similarities of the processes that take place within the actual device and its model. The degassing process of aluminium melt by blowing inert gas is simulated in physical modelling by a decrease of dissolved oxygen in the model liquid (water).
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Bibliography

[1] Michalek, K., Tkadlečková, M., Socha, L., Gryc, K., Saternus, M., Pieprzyca, J. & Merder, T. (2018). Physical modelling of degassing process by blowing of inert gas. Archives of Metallurgy and Materials. 63(2), 987-992. DOI: 10.24425/122432.
[2] Hernández-Hernández, M., Camacho-Martínez, J., González-Rivera, C. & Ramírez-Argáez, M.A. (2016). Impeller design assisted by physical modelling and pilot plant trials. Journal of Materials Processing Technology. 236, 1-8. DOI: 10.1016/j.jmatprotec.2016.04.031.
[3] Mostafei, M., Ghodabi, M., Eisaabadi, G.B., Uludag, M. & Tiryakioglu, M. (2016). Evaluation of the effects rotary degassing process variables on the quality of A357 aluminium alloy castings. Metallurgical and Materials Transactions B. 47(6), 3469-3475. DOI: 10.1017/s11663-016-0786-7.
[4] Merder, T., Saternus, M. & Warzecha, P. (2014). Possibilities of 3D Model application in the process of aluminium refining in the unit with rotary impeller. Archives of Metallurgy and Materials. 59(2), 789-794. DOI: 10.2478/amm-2014-0134.
[5] Saternus, M., Merder, T. & Pieprzyca, J. (2015). The influence of impeller geometry on the gas bubbles dispersion in URO-200 reactor – RTD curves. Archives of Metallurgy and Materials. 60(4), 2887-2893. DOI: 10.1515/amm-2015-0461.
[6] Yamamoto, T., Suzuki, A., Komarov, S.V. & Ishiwata, Y. (2018). Investigation of impeller design and flow structures in mechanical stirring of molten aluminium. Journal of Materials Processing Technology. 261, 164-172. DOI: 10.1016/j.jmatprotec.2018.06.012.
[7] Gao, G., Wang, M., Shi, D. & Kang, Y. (2019). Simulation of bubble behavior in a water physical model of an aluminium degassing ladle unit employing compound technique of rotary blowing and ultrasonic. Metallurgical and Materials Transactions B. 50(4), 1997-2005. DOI: 10.1017/j.s11663-019-01607-y. [8] Yu, S., Zou, Z.-S., Shao, L. & Louhenkilpi, S. (2017). A theoretical scaling equation for designing physical modelling of gas-liquid flow in metallurgical ladles. Steel Research International. 88(1), 1600156. DOI: 10.1002/srin.201600156.
[9] Abreu-López, D., Dutta, A., Camacho-Martínez, J.L., Trápaga-Martínez, G. & Ramírez-Argáez, M. A. (2018). Mass transfer study of a batch aluminium degassing ladle with multiple designs of rotating impellers. JOM. 70, 2958-2967. DOI: 10.1007/s11837-018-3147-y.
[10] Walek, J., Michalek, K., Tkadlečková, M. & Saternus, M. (2021). Modelling of technological parameters of aluminium melt refining in the ladle by blowing of inert gas through the rotating impeller. Metals. 11(2), 284. DOI: 10.3390/met11020284.
[11] Saternus, M. & Merder, T. (2018). Physical modelling of aluminium refining process conducted in batch reactor with rotary impeller. Metals. 8(9), 726. DOI: 10.3390/met8090726.
[12] Lichý, P., Bajerová, M., Kroupová, I. & Obzina, T. (2020). Refining aluminium-alloy melts with graphite rotors. Materiali in Technologije. 54(2), 263-265. DOI: 10.17222/mit.2019.147.
[13] Lichý, P., Kroupová, I., Radkovský, F. & Nguyenová, I. (2016). Possibilities of the controlled gasification of aluminium alloys for eliminating the casting defects. 25th Anniversary International Conference on Metallurgy and Materials, May 25th - 27th 2016 (1474-1479). Hotel Voroněž I, Brno, Czech Republic, EU: Lichý, P.

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Authors and Affiliations

J. Walek
1
ORCID: ORCID
K. Michalek
1
ORCID: ORCID
M. Tkadlečková
1
ORCID: ORCID

  1. VŠB - Technical University of Ostrava, Faculty of Materials Science and Technology, Department of Metallurgical Technologies
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Abstract

This paper deals with the possibilities of using physical modelling to study the degassing of metal melt during its treatment in the refining ladle. The method of inert gas blowing, so-called refining gas, presents the most common operational technology for the elimination of impurities from molten metal, e.g. for decreasing or removing the hydrogen content from liquid aluminium. This refining process presents the system of gas-liquid and its efficiency depends on the creation of fine bubbles with a high interphase surface, uniform distribution, long period of its effect in the melt, and mostly on the uniform arrangement of bubbles into the whole volume of the refining ladle. Physical modelling represents the basic method of modelling and it makes it possible to obtain information about the course of refining processes. On the basis of obtained results, it is possible to predict the behaviour of the real system during different changes in the process. The experimental part focuses on the evaluation of methodical laboratory experiments aimed at the proposal and testing of the developed methods of degassing during physical modelling. The results obtained on the basis of laboratory experiments realized on the specific physical model were discussed.
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Authors and Affiliations

M. Tkadlečková
K. Gryc
K. Michalek
L. Socha
M. Saternus
T. Merder
J. Pieprzyca
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Abstract

The paper evaluates two approaches of numerical modelling of solidification of continuously cast steel billets by finite element method, namely by the numerical modelling under the Steady-State Thermal Conditions, and by the numerical modelling with the Traveling Boundary Conditions. In the paper, the 3D drawing of the geometry, the preparation of computational mesh, the definition of boundary conditions and also the definition of thermo-physical properties of materials in relation to the expected results are discussed. The effect of thermo-physical properties on the computation of central porosity in billet is also mentioned. In conclusion, the advantages and disadvantages of two described approaches are listed and the direction of the next research in the prediction of temperature field in continuously cast billets is also outlined.
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Authors and Affiliations

M. Tkadlečková
K. Michalek
M. Strouhalová
M. Saternus
T. Merder
J. Pieprzyca
J. Sviželová
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Abstract

The paper describes research and development of aluminium melt refining technology in a ladle with rotating impeller and breakwaters using numerical modelling of a finite volume/element method. The theoretical aspects of refining technology are outlined. The design of the numerical model is described and discussed. The differences between real process conditions and numerical model limitations are mentioned. Based on the hypothesis and the results of numerical modelling, the most appropriate setting of the numerical model is recommended. Also, the possibilities of monitoring of degassing are explained. The results of numerical modelling allow to improve the refining technology of metal melts and to control the final quality under different boundary conditions, such as rotating speed, shape and position of rotating impeller, breakwaters and intensity of inert gas blowing through the impeller.

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Authors and Affiliations

J. Sviželová
M. Tkadlečková
K. Michalek
J. Walek
M. Saternus
J. Pieprzyca
T. Merder

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