Methodology for Industrial Verification of Flux-Gas Refining Parameters for AK12 Alloy Melt
DOI:
https://doi.org/10.15407/steelcast2026.03.059Keywords:
AK12, Al–Si, flux-gas refining, rotary degassing, argon, hydrogen mass transfer, 22 factorial design, RPT, bifilm index, areal porosity, visible inclusions, industrial verificationAbstract
The aim of this study is to develop a reproducible methodology for industrial verification of flux-gas refining parameters for AK12 cast aluminium alloy melt before pouring into moulds for shaped castings. A 22 factorial design is proposed in which flux treatment F and rotary argon purging G are varied independently, while initial dross removal, final holding, repeated dross removal, and pouring conditions remain identical. The initial screening levels are defined as values to be verified rather than optima: 720-740 ºC, 0.10-0.20% flux, 8-12 L/min Ar, 6-10 min purging, and 8-12 min final holding. The physical basis of de- gassing is represented by the transfer of dissolved hydrogen to dispersed bubbles, specific interfacial area, Sauter diameter d32, and the kLa coefficient. Sampling at points M0-M5 is specified, and direct hydrogen determination CH is distinguished from the indirect RPT/DI and BI indices, areal porosity Vp, apparent areal density of inclusions NA, and specialized melt-cleanliness assessment Cinc. For each heat, chemical composition, return fraction, flux batch, argon purity, rotor geometry, gas flow, and metal temperature before pouring are recorded; process deviations are coded and analysed separately. The statistical model estimates the main effects of F and G, their interaction coefficient βFG, and the blocking effect of charge batch or production day; estimates are reported with 95 % confidence intervals. The method does not equate DI with hydrogen concentration or NA with overall melt cleanliness and requires a uniform RPT protocol, a fixed metallographic field map, and recorded temper- ature-time trajectories. The methodological result is a reproducible protocol for selecting an admissible process window from quality indicators, temperature loss, cycle duration, and signs of excessive turbulence. A final technological decision must be confirmed in independent heats with unchanged charge, equipment, mould, and gating system.
References
Shivkumar, S., Wang, L., & Apelian, D. (1991). Molten metal processing of advanced cast aluminum alloys. JOM, 43, 26-32. https://doi.org/10.1007/BF03220114
Samuel, A. M., & Samuel, F. H. (1992). Various aspects involved in the production of low-hydrogen aluminium castings. Journal of Materials Science, 27, 6533-6563. https://doi.org/10.1007/BF01165936
Czerwinski, F. (2017). Modern Aspects of Liquid Metal Engineering. Metallurgical and Materials Transactions B, 48, 367-393. https://doi.org/10.1007/s11663-016-0807-6
Gyarmati, G., Fegyverneki, G., Tokár, M., & Mende, T. (2021). The Effects of Rotary Degassing Treatments on the Melt Quality of an Al–Si Casting Alloy. International Journal of Metalcasting, 15, 141-151. https://doi.org/10.1007/s40962-020-00428-z
Dispinar, D., & Campbell, J. (2004). Critical assessment of reduced pressure test. Part 1: Porosity phenomena. International Journal of Cast Metals Research, 17(5), 280-286. https://doi.org/10.1179/136404604225020696
Dispinar, D., & Campbell, J. (2004). Critical assessment of reduced pressure test. Part 2: Quantification. International Journal of Cast Metals Research, 17(5), 287-294. https://doi.org/10.1179/136404604225020704
Dispinar, D., & Campbell, J. (2006). Use of bifilm index as an assessment of liquid metal quality. International Journal of Cast Metals Research, 19(1), 5-17. https://doi.org/10.1179/136404606225023300
Dispinar, D., Akhtar, S., Nordmark, A., Di Sabatino, M., & Arnberg, L. (2010). Degassing, hydrogen and porosity phenomena in A356. Materials Science and Engineering: A, 527(16-17), 3719-3725. https://doi.org/10.1016/j.msea.2010.01.088
Dispinar, D., & Campbell, J. (2011). Porosity, hydrogen and bifilm content in Al alloy castings. Materials Science and Engineering: A, 528(10-11), 3860-3865. https://doi.org/10.1016/j.msea.2011.01.084
El-Sayed, M. A., Hassanin, H., & Essa, K. (2016). Bifilm defects and porosity in Al cast alloys. The International Journal of Advanced Manufacturing Technology, 86, 1173-1179. https://doi.org/10.1007/s00170-015-8240-6
El-Sayed, M. A., & Griffiths, W. D. (2014). Hydrogen, bifilms and mechanical properties of Al castings. International Journal of Cast Metals Research, 27(5), 282-287. https://doi.org/10.1179/1743133614Y.0000000113
El-Sayed, M. A. (2016). The Behaviour of Bifilm Defects in Cast Al-7Si-Mg Alloy. PLoS ONE, 11(8), e0160633. https://doi.org/10.1371/journal.pone.0160633
El-Sayed, M. A., Hassanin, H., & Essa, K. (2016). Effect of casting practice on the reliability of Al cast alloys. International Journal of Cast Metals Research, 29(6), 350-354. https://doi.org/10.1080/13640461.2016.1145966
Chen, Q., & Griffiths, W. D. (2021). Modification of Double Oxide Film Defects with the Addition of Mo to an Al-Si-Mg Alloy. Metallurgical and Materials Transactions B, 52, 502-516. https://doi.org/10.1007/s11663-020-02038-w
Griffiths, W. D., Caden, A. J., & Chen, Q. (2017). Effects of transition metal additions on double-oxide film defects in an Al-Si- Mg alloy. Materials Science and Technology, 33(18), 2168-2175. https://doi.org/10.1080/02670836.2017.1346911
Raiszadeh, R., & Griffiths, W. D. (2010). The behaviour of double oxide film defects in liquid Al alloys under atmospheric and reduced pressures. Journal of Alloys and Compounds, 491(1–2), 575-580. https://doi.org/10.1016/j.jallcom.2009.10.271
Raiszadeh, R., & Griffiths, W. D. (2006). A method to study the history of a double oxide film defect in liquid aluminum alloys. Metallurgical and Materials Transactions B, 37, 865-871. https://doi.org/10.1007/BF02735007
El-Sayed, M. A., Salem, H. A., Kandeil, A. Y., & Griffiths, W. D. (2013). A Study of the Behaviour of Double Oxide Films in Al Alloy Melts. Materials Science Forum, 765, 260-265. https://doi.org/10.4028/www.scientific.net/MSF.765.260
El-Sayed, M., Salem, H., Kandeil, A., & Griffiths, W. D. (2011). Effect of Holding Time Before Solidification on Double-Oxide Film Defects and Mechanical Properties of Aluminum Alloys. Metallurgical and Materials Transactions B, 42, 1104-1109. https://doi.org/10.1007/s11663-011-9571-9
Tiryakioğlu, M. (2020). The Effect of Hydrogen on Pore Formation in Aluminum Alloy Castings: Myth Versus Reality. Metals, 10(3), 368. https://doi.org/10.3390/met10030368
Tiryakioğlu, M. (2019). Solubility of hydrogen in liquid aluminium: reanalysis of available data. International Journal of Cast Metals Research, 32(5-6), 315-318. https://doi.org/10.1080/13640461.2020.1718337
Yousefian, P., & Tiryakioğlu, M. (2018). Pore Formation During Solidification of Aluminum: Reconciliation of Experimental Observations, Modeling Assumptions, and Classical Nucleation Theory. Metallurgical and Materials Transactions A, 49, 563-575. https://doi.org/10.1007/s11661-017-4438-6
Campbell, J. (2006). Entrainment Defects. Materials Science and Technology, 22(2), 127-145. https://doi.org/10.1179/174328406X74248
Reilly, C., Green, N. R., Jolly, M. R., & Gebelin, J.-C. (2013). The modelling of oxide film entrainment in casting systems using computational modelling. Applied Mathematical Modelling, 37(18-19), 8451-8466. https://doi.org/10.1016/j.apm.2013.03.061
Cox, M., Wickins, M., Kuang, J. P., Harding, R. A., & Campbell, J. (2000). Effect of top and bottom filling on reliability of investment castings in Al, Fe, and Ni based alloys. Materials Science and Technology, 16(11-12), 1445-1452. https://doi.org/10.1179/026708300101507442
Samuel, A. M., Samuel, E., Songmene, V., & Samuel, F. H. (2023). A Review on Porosity Formation in Aluminum-Based Alloys. Materials, 16(5), 2047. https://doi.org/10.3390/ma16052047
Bogdanoff, T., Tiryakioğlu, M., Liljenfors, T., Jarfors, A. E. W., Seifeddine, S., & Ghassemali, E. (2023). On the Effectiveness of Rotary Degassing of Recycled Al-Si Alloy Melts: The Effect on Melt Quality and Energy Consumption for Melt Preparation. Sustainability, 15(6), 5189. https://doi.org/10.3390/su15065189
Podaril, M., Prášil, T., Majerník, J., Kampf, R., Socha, L., Gryc, K., & Gráf, M. (2022). Aluminum Melt Degassing Process Evaluation Depending on the Design and the Degree of the FDU Unit Graphite Rotor Wear. Materials, 15(14), 4924. https://doi.org/10.3390/ma15144924
Lazaro-Nebreda, J., Patel, J. B., Lordan, E., Zhang, Y., Karakulak, E., Al-Helal, K., Scamans, G. M., & Fan, Z. (2022). Degassing of Aluminum Alloy Melts by High Shear Melt Conditioning Technology: An Overview. Metals, 12(10), 1772. https://doi.org/10.3390/met12101772
Dahle, A. K., Nogita, K., McDonald, S. D., Dinnis, C., & Lu, L. (2005). Eutectic modification and microstructure development in Al-Si alloys. Materials Science and Engineering: A, 413-414, 243-248. https://doi.org/10.1016/j.msea.2005.09.055
Gursoy, O., & Timelli, G. (2020). Lanthanides: a focused review of eutectic modification in hypoeutectic Al-Si alloys. Journal of Materials Research and Technology, 9(4), 8652-8666. https://doi.org/10.1016/j.jmrt.2020.05.105
McDonald, S. D., Nogita, K., & Dahle, A. K. (2004). Eutectic nucleation in Al-Si alloys. Acta Materialia, 52(14), 4273-4280. https://doi.org/10.1016/j.actamat.2004.05.043
Lu, L., Nogita, K., & Dahle, A. K. (2005). Combining Sr and Na additions in hypoeutectic Al-Si foundry alloys. Materials Science and Engineering: A, 399(1-2), 244-253. https://doi.org/10.1016/j.msea.2005.03.091
Emadi, D., Gruzleski, J. E., & Toguri, J. M. (1993). The effect of Na and Sr modification on surface tension and volumetric shrinkage of A356 alloy and their influence on porosity formation. Metallurgical Transactions B, 24, 1055-1063. https://doi.org/10.1007/BF02660997
Fracchia, E., Gobber, F. S., & Rosso, M. (2021). Effect of Alloying Elements on the Sr Modification of Al-Si Cast Alloys. Metals, 11(2), 342. https://doi.org/10.3390/met11020342
Song, H., Zhang, L., Cao, F., Gu, X., & Sun, J. (2021). Oxide bifilm defects in aluminum alloy castings. Materials Letters, 285, 129089. https://doi.org/10.1016/j.matlet.2020.129089
Bogdanoff, T., Tiryakioğlu, M., Jarfors, A. E. W., Seifeddine, S., & Ghassemali, E. (2023). On the combined effects of surface quality and pore size on the fatigue life of Al–7Si–3Cu–Mg alloy castings. Materials Science and Engineering: A, 885, 145618. https://doi.org/10.1016/j.msea.2023.145618
Warke, V. S., Shankar, S., & Makhlouf, M. M. (2005). Mathematical modeling and computer simulation of molten aluminum cleansing by the rotating impeller degasser: Part II. Removal of hydrogen gas and solid particles. Journal of Materials Processing Technology, 168(1), 119-126. https://doi.org/10.1016/j.jmatprotec.2004.10.016
Abreu-López, D., Amaro-Villeda, A., Acosta-González, F. A., González-Rivera, C., & Ramírez-Argáez, M. A. (2017). Effect of the Impeller Design on Degasification Kinetics Using the Impeller Injector Technique Assisted by Mathematical Modeling. Metals, 7(4), 132. https://doi.org/10.3390/met7040132
ASTM International. (2023). Standard Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis (ASTM E1245-03(2023)). https://doi.org/10.1520/E1245-03R23
