Influence of Ceramic Foam Filters with Al 2 O 3 Nanocoating on the Aluminum Filtration Behavior Tested With and Without
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aluminum melts using ceramic foam filters is a state-of-the-art technology, with the efficiency of such filtration techniques influenced by a wide range of parameters that may be broadly divided into filter, inclusion, and process parameters.[1] The knowledge on the mode of action of metal melt filters,
CLAUDIA VOIGT, ENRICO STORTI, and CHRISTOS G. ANEZIRIS are with the Institute of Ceramic, Glass and Construction Materials, Technische Universita¨t Bergakademie Freiberg, Agricolastr. 17, 09599 Freiberg, Germany. Contact e-mail: [email protected] BEATE FANKHA¨NEL and MICHAEL STELTER are with the Institute for Nonferrous Metallurgy and Purest Materials, Technische Universita¨t Bergakademie Freiberg, Leipziger Straße 34, 09599 Freiberg, Germany. BJO¨RN DIETRICH and GOTTHARD WOLF are with the Department of Foundry Technology, Technische Universita¨t Bergakademie Freiberg, Bernhard-von-Cotta-Straße 4, 09599 Freiberg, Germany. MARK BADOWSKI and MARGARITA GORSHUNOVA are with the Hydro Aluminium Rolled Products GmbH, Georg-von-Boeselager-Str. 21, 53117 Bonn, Germany. Manuscript submitted October 24, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
particularly the effect of wettability, surface energy, flow behavior of inclusions, grain refiner, etc., is rather limited up to now. Therefore, the Collaborative Research Center 920 Multi-Functional Filters for Metal Melt Filtration—A Contribution towards Zero Defect Materials pursues to research the processes of metal melt filtration from several perspectives on a scientific basis. There are two prevaling divergent opinions concerning the influence of the wetting behavior on the filtration. Bao et al.[2,3] assume that improved wetting (i.e., a lower contact angle) results in enhanced convergence of the aluminum melt with the filter surface, which increases the probability of a collision between inclusions and the filter wall. This theory, however, is limited to the measurement of filtration efficiencies and contact angles of the typical filter materials SiC and Al2O3. Filtration trials carried out using a Liquid Metal Cleanliness Analyzer (LiMCA) with SiC and Al2O3 filters and conducted at SAPA Heat Transfer (Finspa˚ng, Sweden) showed higher filtration efficiencies for SiC filters.[4] The contact angles were evaluated using the sessile drop technique (contact heating) at 1000 C,
1100 C, 1200 C, and 1300 C, and were extrapolated to a temperature of 700 C, with the latter temperature yielding values of 79 deg for SiC and 97 deg for Al2O3.[3] Voigt et al.[5] evaluated the filtration efficiency of the aluminum alloy AlSi7Mg with four filter materials (Al2O3, MgAl2O4, 3Al2O3, 2SiO2, and TiO2) with LiMCA measuring devices at a pilot filtration line at Constellium in France,[6] whereby the contact angles at 730 C were measured with a sessile drop testing apparatus equipped with a capillary purification unit. This temperature was selected due to ongoing reactions between the substrate and the aluminum when using higher temperatures of, e.g., 950 C.[7] Comparison of the filtration efficiencie
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