Kinetics of Ultrasonic Degassing of Aluminum Alloys

Alba-Baena, Noé; Eskin, Dmitry

doi:10.1002/9781118663189.ch162

Cited by 14 publications

(2 citation statements)

References 12 publications

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“…This is obviously not the case as the kinetics of ultrasonic degassing and the level of residual hydrogen clearly show. Cavitation-assisted degassing is very quick (minutes) as compared with the natural degassing (tens of minutes) and the reached level is about 50% lower than the quasi-equilibrium hydrogen solubility [3,8,37]. The latter is evidenced by considerable regassing of ultrasonically degassed melt up to the quasi-equilibrium level [37].…”

Section: Typical Mistakes and Misconceptionsmentioning

confidence: 99%

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Eskin

2017

Materials Science and Technology

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Abstract. Ultrasonic melt processing attracts a lot of interest both from academic researchers and industry. Despite a long history of the subject, with first accounts dating back to the 1930s, the physics, mechanisms and practical applications are still under development. In the second half of the XXth century, pilot-and industrial scale applications of ultrasonic processing of light alloys were demonstrated for melt degassing, filtration, grain refinement, melt atomisation, and zone refining. In the last 10 years the interest to ultrasonic melt processing grew with regard to understanding the underlying mechanisms of previously established effects, developing numerical models of ultrasonic cavitation and the development of nanocomposite technology. This review paper summarises the mechanisms involved in the ultrasonic melt processing, including cavitation, flows, nucleation, activation, fragmentation and their consequences for degassing, structure refinement and particle dispersion. Some typical mistakes made by researchers in performing experiments and in interpretation of the results are discussed. New advanced methods of studying ultrasonic treatment and phenomena are considered. The paper also gives an outlook to future developments and challenges.

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Section: Typical Mistakes and Misconceptionsmentioning

confidence: 99%

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Eskin

2017

Materials Science and Technology

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“…The removal of hydrogen from molten aluminum with vacuum is based on the equilibrium relationship between the dissolved hydrogen and the hydrogen partial pressure in ambient atmosphere [4] [5] [6]. Ultrasonic degassing of aluminum rests on the diffusion of dissolved hydrogen to cavitation bubbles assisted by their pulsation and their evacuation from the molten metal [7] [8] [9]. However, the worldwide most employed process for hydrogen removal from molten aluminum is the inert gas injection by rotating impeller (IGIRI).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen Injection in Molten Aluminum in a Tank Degasser

Maldonado¹,

Barrón²,

Miranda³

2018

WJET

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The injection of nitrogen in molten aluminum through a static impeller in a tank degassing unit is studied. Using basic principles of fluid mechanics, it is analyzed the influence of the nozzle diameter on the bubble diameter and the mean residence time of the bubbles in the molten aluminum. By means of transient isothermal 2D Computational Fluid Dynamics (CFD) simulations, the influence of the nitrogen volumetric flow rate on the phase distributions and the tank degasser dynamics is studied. Finally, an adiabatic CFD simulation is carried out in order to elucidate the changes in the molten aluminum temperature due to the injection of nitrogen at ambient temperature. This simulation shows that molten aluminum does not suffer drastic temperature reductions given that, in spite that the nitrogen is fed at ambient temperature, the mass of nitrogen is relatively small compared with the mass of aluminum.

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A Model of Cavitation for the Treatment of a Moving Liquid Metal Volume

Lebon

Pericleous

Tzanakis³

et al. 2015

Advances in the Science and Engineering of Casting Solidification

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A homogeneous cavitation model, derived from the Keller-Miksis equation, is developed and applied to the two-phase problem of bubble growth, breakup and propagation in the melt. Numerical simulations of the ultrasonic field emanating from an immersed sonotrode are performed and the calculated acoustic pressure is applied to the source term of the bubble transport equation to predict the generation, propagation and collapse of cavitation bubbles in the melt. The use of baffles to modify the flow pattern and amplify sound waves in a launder conduit is examined to determine the optimum configuration that maximizes the residence time of the liquid in high cavitation activity regions. The simulation results demonstrate that dimensions that match integer wavelengths, and are therefore in resonance with the travelling waves, are desirable since they lead to an increase in the concentration of nucleating bubbles in the liquid compared with other dimensions.

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Kinetics of Ultrasonic Degassing of Aluminum Alloys

Cited by 14 publications

References 12 publications

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Nitrogen Injection in Molten Aluminum in a Tank Degasser

A Model of Cavitation for the Treatment of a Moving Liquid Metal Volume

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