Shape Factor Effect on Inclusion Sedimentation in Aluminum Melts
- PDF / 1,425,074 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 17 Downloads / 176 Views
THE quality requirements of flat aluminum products increase consistently. The quality of the products with low wall thicknesses, such as foils and lithography sheets, strongly depends on the concentration of remaining non-metallic inclusions after the melt treatment steps.[1–3] Non-metallic inclusions are removed mainly by flotation, sedimentation, and filtration. Sedimentation is a removal mechanism benefiting from the density difference between the melt and the inclusions. Particles will tend to settle in case of a higher density than the melt,[4] however, the settling velocity will be also affected by the morphology of the particle. Stokes’s law is typically used for particle settling calculations in fluids.[5] The settling rate equations are derived by assuming that particles are perfect spheres, which is not the case in practice. Leith investigated a dynamic shape factor K, based on Stokes law for
MERTOL GO¨KELMA, KRISTIAN ETIENNE EINARSRUD, and GABRIELLA TRANELL are with the Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim, 7491, Norway. Contact e-mail: [email protected] BERND FRIEDRICH is with the IME Process Metallurgy and Metal Recycling, RWTH Aachen University, Aachen, 52056, Germany. Manuscript submitted August 3, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
non-spherical particles. This extension uses the equivalent spherical diameters ‘‘deq’’ to define the drag force acting on a non-spherical particle.[6] Different analytical and experimental approaches have been introduced for the settling of non-spherical particles in the literature. Dietrich proposed a settling model using Corey’s Shape Factor (CSF), nominal diameter, and roundness.[7] Hartman et al. experimentally measured the settling velocity of lime (W = 0.78) and limestone (W = 0.55) particles over 0.1 mm in dried air as a medium.[8] Tsakalakis et al. measured the settling velocity of irregularly shaped galena and quartz particles over 0.1 mm in water.[9] Tran-Cong et al. measured the settling of agglomerates having six different geometries from smooth glass spheres in water–glycerin solutions. An extension to Schiller and Naumann drag law for irregular shapes and moderate Reynolds numbers is also presented.[10] Simensen analyzed sedimentation of inclusions in aluminum by use of light microscopy after solidification of samples under centrifugation.[11] Razaz studied settling of inclusions along an aluminum billet by applying deep etching on sample surfaces in different heights and subsequent counting of etch pits to determine the concentration of inclusions in different depths.[12] There are few studies which investigated particle settling in-situ in metallic melts. Sztur et al. studied the particle settling in furnaces affected by the liquid aluminum motion experimentally and numerically.[13] Instone et al. developed a model to simulate the behavior of particles having different densities and sizes in the aluminum melting and holding furnaces and
compared the results with experimental dat
Data Loading...
