Impact of the Filter Roughness on the Filtration Efficiency for Aluminum Melt Filtration

Voigt, Claudia; Dietrich, Björn; Badowski, Mark; Gorshunova, Margarita; Wolf, Gotthard; Aneziris, Christos G.

doi:10.1007/978-3-030-05864-7_130

Cited by 14 publications

(7 citation statements)

References 3 publications

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“…Therefore the chance for them to be caught and remain on the wall increases. [22] Nowadays, grain refiners, for example Al-Ti-B and Al-Ti-C master alloys, are often added into aluminum melt to refine the grain structure by increasing the number of nucleation sites during solidification. It is expected that the casting quality can be further improved with the combination of inoculation by grain refiners and CFF filtration.…”

Section: Introductionmentioning

confidence: 99%

Influence of Grain Refiners on the Wettability of Al2O3 Substrate by Aluminum Melt

Yang

Bao

Akhtar

et al. 2020

Metall Mater Trans B

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It is well known that grain refiner additions in aluminum melts significantly reduce the filtration efficiency of ceramic foam filters (CFF). However, the mechanism remains unclear. In this work, the influence of grain refiners on the wettability of alumina substrate by aluminum melt was studied by both conventional sessile drop and improved sessile drop methods at different temperatures and vacuums. Commercial purity aluminum (CP-Al) and grain refiner master alloys Al-3Ti-1B, Al-5Ti-1B, Al-3Ti-0.15C were used. It is found that master alloy melts wet alumina substrate better than CP-Al. Generally, a lower temperature or lower vacuum results in a higher contact angle. The roles of grain refiner particles in improving the wettability were studied by analyzing the solidification structure of post wetting-test droplets using SEM. Strong sedimentation of grain refiner particles at the metal-substrate interface was observed, which is attributed to the higher density of grain refiner particles compared to the Al melt. Meanwhile, a large fraction of grain refiner particles agglomerates at the oxide skin of the aluminum droplets, showing a strong adhesion between the particles and oxide skin. Such adhering of grain refiner particles is proposed to enhance the rupture of the original oxide skin of the droplets and slow down the reoxidation process at the surface layer. Both adherence of grain refiner particles to surface oxide skin and sedimentation of particles at the metal-substrate interface are responsible for the wetting improvement.

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Section: Introductionmentioning

confidence: 99%

Influence of Grain Refiners on the Wettability of Al2O3 Substrate by Aluminum Melt

Yang

Bao

Akhtar

et al. 2020

Metall Mater Trans B

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“…Due to a cold run of the Al 2 O 3 reference filter (blockade of the filter) during filtration trial 2, in the following, the Al 2 O 3 rough filter will be used as a reference filter. The substitution of the Al 2 O 3 reference filter through the Al 2 O 3 rough filter is justifiable given the fact that previous filtration trials demonstrated better filtration efficiencies for the Al 2 O 3 rough filter in comparison with the Al 2 O 3 reference filter [ 18 ].…”

Section: Resultsmentioning

confidence: 99%

“…Table 3 shows that Al 2 O 3 films, carbides, magnesium oxide, spinel, refractory material, iron and manganese oxides, as well as grain refiner were detected in the castings. [18].…”

Section: Filtration Trialsmentioning

confidence: 99%

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Aluminum Melt Filtration with Carbon Bonded Alumina Filters

et al. 2020

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The wetting behavior was measured for Al2O3-C in contact with AlSi7Mg with a conventional sessile drop test (vacuum, 950 °C and 180 min) and a sessile drop test with a capillary purification unit (vacuum, 730 °C and 30 min). The conventional test yielded contact angles of around 92°, whereas the sessile drop measurement with capillary purification showed a strongly non-wetting behavior with a determined apparent contact angle of the rolling drop of 157°. Filtration tests, which were repeated twice, showed that the Al2O3-C filter possessed a better filtration behavior than the Al2O3 reference filter. For both filtration trials, the PoDFA (porous disc filtration analysis) index of the Al2O3-C filter sample was equal to half of the PoDFA index of the Al2O3 reference filter sample, indicating a significantly improved filtration performance when using Al2O3-C filter. Notable is the observation of a newly formed layer between the aluminum and the Al2O3-C coating. The layer possessed a thickness between 10 µm up to 50 µm and consisted of Al, C, and O, however, with different ratios than the original Al2O3-C coating. Thermodynamic calculations based on parameters of the wetting and filtration trials underline the possible formation of an Al4O4C-layer.

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“…Therefore, the knowledge and understanding of the CFF properties, the flow characteristics, and the filtration process with respect to the melt condition is of high importance. Different integral approaches have been adopted in the past for this purpose, for example, dealing with the increase in degree of purity by measuring the amount of oxygen in a filtered metal melt, [1] measuring the inclusion content during filtration, [2] and performing metallographic analysis of the solidified filter cake after a specific filtering process. [3] Furthermore, optical and scanning electron microscopy as well as determination of the mechanical properties, from samples of the cast product have been performed to extrapolate the filtration efficiency from these data.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigations of the Depth Filtration inside Open‐Cell Foam Filters Supported by High‐Resolution Computed Tomography Scanning and Pore‐Scale Numerical Simulations

et al. 2019

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The removal of nonmetallic inclusions from metal melts is a crucial step in producing high‐quality castings that have to meet strict requirements regarding strength, toughness, and machinability. To separate the unwanted impurities, the liquid metal is usually passed through ceramic foam filters (CFF), in which the inclusions adhere to the surface of a complex strut network. The development of improved CFF structures requires a good understanding of the physical phenomena involved in the filtration process. In this respect, an experimental investigation of the real system is challenging, due to the opacity of the melt, high temperature, and the presence of a protective atmosphere. Therefore, the present study relies on water model experiments, which are conducted for different pore counts and flow velocities. To achieve a high degree of similarity to the real system, the wetting properties of the filters and particles are adjusted accordingly. Experimentally evaluated filtration efficiencies are compared with predictions obtained from a detailed numerical model that considers the CFF geometry, which is digitized using 3D X‐Ray micro‐computed tomography, and previously measured particle adhesion forces. The results suggest that a considerable fraction of particles does not remain attached after collision with the CFF struts.

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Impact of the Filter Roughness on the Filtration Efficiency for Aluminum Melt Filtration

Cited by 14 publications

References 3 publications

Influence of Grain Refiners on the Wettability of Al2O3 Substrate by Aluminum Melt

Influence of Grain Refiners on the Wettability of Al2O3 Substrate by Aluminum Melt

Aluminum Melt Filtration with Carbon Bonded Alumina Filters

Experimental Investigations of the Depth Filtration inside Open‐Cell Foam Filters Supported by High‐Resolution Computed Tomography Scanning and Pore‐Scale Numerical Simulations

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