Influence of Grain Refiners on the Wettability of Al2O3 Substrate by Aluminum Melt (original) (raw)
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Metallurgical and Materials Transactions B
The addition of grain refiner particles in the aluminum melt is known to reduce the filtration efficiency of ceramic foam filter (CFF). In the present work, a systematic study on the influence of the addition level of Al-Ti-B master alloys and the inclusion level on the filtration performance of aluminum melt has been investigated by pilot-scale filtration tests using 50 PPi and 80 PPi filters. The inclusion level of the melt has been measured using both LiMCA and PoDFA. For 80 PPi CFF, the N20 inclusion (diameter larger than 20 μm) value in the post-filtrated melt does not increase when an ultra-high level of inclusions is introduced in the form of chips. For the melts with a low level of grain refiners (~ 0.5 kg/ton), the filtration performance of CFF is not affected by grain refiners, regardless of inclusion load. An addition of 2.0 kg/ton grain refiners reduces the filtration performance for melts with a high inclusion level, where post-filtration inclusions with the size of 15-...
Aluminum Melt Filtration with Carbon Bonded Alumina Filters
Materials
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 thi...
Effect of Inclusion and Filtration on Grain Refinement Efficiency of Aluminum Alloy
Metallurgical and Materials Transactions A, 2022
It is well known that the filtration efficiency of ceramic foam filters (CFF) on aluminum melt can be significantly reduced by the addition of grain refiner particles under a high inclusion load. Also, it is usually considered that the filtration process has little impact on grain refinement efficiency. In this work, the influence of inclusions and filtration on the grain refinement effect of AA 6060 alloy has been studied. This was done through TP-1 type solidification experiments where the aluminum melt prior to and after the filter during a pilot-scale filtration test was investigated. In the experiments, 80 PPi CFFs were used to filtrate aluminum melt with an ultra-high inclusion load and two addition levels of Al–3Ti–1B master alloys. It is found that both inclusions and filtration significantly reduce the grain refinement efficiency of the grain refiner master alloys. A detailed characterization of the used filters shows that the reduction of grain refinement efficiency is due...
Wettability of Aluminum on Alumina
Metallurgical and Materials Transactions B, 2011
The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10 À8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000°C to 1400°C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al 2 O 3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700°C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al 2 O 3 system increases with temperature.
Wetting of pure aluminium on graphite, SiC and Al2O3 in aluminium filtration
Transactions of Nonferrous Metals Society of China, 2012
The wettability of pure aluminium on filter materials and on inclusions is believed to be an important factor affecting the filtration of aluminium. The contact angles of molten aluminium on alumina, SiC and graphite were measured under 10 −8 bar high vacuum in the temperature range of 1000−1300 °C. To describe the wetting behaviour of the Al on ceramic at lower temperatures used in filtration and casting aluminium, a semi-empirical calculation was employed. The calculated contact angles at 700 °C were around 97° for alumina, 92° for vitreous graphite, 126° for single-and poly-crystal graphite, and 79° for single crystal SiC, respectively. This indicates that aluminium does not wet alumina or graphite (or Al 4 C 3 ) around the casting temperature, but wets SiC at this temperature. Thus a priming height is required for aluminium to infiltrate an alumina filter. Increasing temperature can also improve the wettability of Al on ceramic.
Wetting ofAl2O3by Molten Aluminum: The Influence ofBaSO4Additions
Journal of Nanomaterials, 2008
The effects ofBaSO4additions on the wetting of alumina by molten aluminum were studied by the sessile drop technique. To study the effect ofBaSO4decomposition(1100–1150∘C), the additions were treated at two temperatures700∘C(973 K) and1450∘C(1723 K), respectively.BaSO4additions at low and high temperatures did not improve the nonwetting character of these compositions. However, at higher firing temperature, the formation ofBA6 (BaO•6Al2O3)has a nonwetting trend with increasing its content. To address theBA6specifically a pureBaO•6Al2O3was produced and tested. It was more nonwetting than the pure alumina. After the analysis of the contact angles for theBaSO4and theBA6 (BaO•6Al2O3), it was concluded that these additions to alumina do not inhibit wetting by molten aluminum. In fact, at the addition levels common for refractories, the wetting tendency of molten aluminum is enhanced. Alternative explanations for the effectiveness ofBaSO4additions to alumina refractories are discussed.
DEVELOPMENT OF A CERAMIC FOAM FILTER FOR FILTERING MOLTEN ALUMINUM ALLOY IN CASTING PROCESSES
Currently, liquid metal filtration in casting process is a familiar refining technology for casting process. This technique be able to exist removed the inclusions inside the melts and subsequently improves the mechanical properties of the product. Furthermore this will also improved the surface finish and tightness of cast product. This significantly reduced the rework cost. The present research was done to fabricate an improved ceramic foam filter for use in filtering aluminum base alloys. It was an objective of the present work to provide a ceramic foam filter characterized by cost of raw materials. Then experimental tests were carried out to the filters to measure permeability properties before pouring process. After pouring process, thermal shock properties, obtain from pouring liquid aluminum when filter was placed in the gating system to ensure that the filters could withstand temperatures of aluminum alloys. Then filter was cut into several sections to measure the macro and microstructure of the filter and ensure that impurity particles captured by a filter. Further experiments were also done to investigate the efficiency of produced ceramic foam filter on quality of cast products. The result obtained in this investigation, the mechanical properties for aluminum LM6 alloy sand casting increased when ceramic foam filter was inserted into the gating system. A produced filter by using new materials is economical to produce. Further more, the analysis data shows present innovation filter which can be made in any shape and size, has excellent thermal shock resistance, and acceptable permeability properties.
2021
The filtration of molten metal using ceramic foam filters (CFF) is a purification method often used by the aluminum industry to meet the increasing demands the melt quality. CFFs are in most cases produced by the replica method using polyurethane foam templates, which are coated with a ceramic slurry of targeted composition before being sintered into its final structure. Despite the key role of CFFs in view of metal cleanliness, there are only a few quality parameters for their evaluation. In the present study, an overview of the different material properties essential for CFFs, suitable measurement methods, and their limitations are presented. The focuses of this work are the different densities of ceramic foams and the thermal expansion coefficient measured by dilatometry, as well as the filter porosities and microstructure measured through mercury intrusion porosimetry and computer tomography, respectively. Moreover, elastic (Young's Modulus) and mechanical properties (compressive strength) are discussed.
Wetting of Pure Aluminium on Filter Materials Graphite, AlF 3 and Al 2 O 3
The wettability of pure aluminium on filter materials is believed to be an important factor affecting the filtration of aluminium. The contact angle of molten aluminium on graphite, alumina and AlF 3 has been measured in 1 atmosphere of argon with an oxygen partial pressure of about 10 -17 Pa in the temperature range of 1000-1800ºC. Improved techniques to remove the aluminium oxide layer from a molten aluminium drop have been employed in a horizontal graphite tube furnace. The wettability of aluminium on graphite, alumina and AlF 3 has been discussed and compared with the aim to obtain "new" and more effective filter materials.