In Situ detection of inclusions in liquid metals: Part II. Metallurgical applications of LiMCA systems
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I. INTRODUCTION
THE previous article (Part I) described the electric sensing zone (ESZ) principle,[1] an Ohmic model,[2] and a mathematical model for studying the electromagnetic fields, fluid flow, and particle behavior within the Liquid Metal Cleanliness Analyzer (LiMCA) system. In the present article, a water-based version of LiMCA system known as the Aqueous Particle Sensor II (APS II) system[3] and a metal-based LiMCA system are first described. The performance of the probes is evaluated based on the predicted electromagnetic and fluid flow fields, as well as pass-through fractions of particles within the ESZ using the mathematical model developed in Part I. The electric circuit of the LiMCA system used at McGill University for particle detection in molten metals is analyzed. Then, the applications of the APS II system in water modeling of inclusion distributions in stirred ladles, inclusion float out in steelmaking tundishes, submerged powder injection in the refining and alloying of melts, and inclusion type discrimination using digital signal processing (DSP) technology[41] are presented. Finally, typical metallurgical applications of LiMCA in molten metals are described, and the knowledge gained as a result of this novel technology is assessed.
RODERICK I.L. GUTHRIE, Macdonald Professor, FRSC, and Director, McGill Metals Processing Center, is with the Department of Mining and Metallurgical Engineering, McGill University, Montreal, PQ, Canada H3A 2B2. MEI LI, formerly Graduate Student, McGill Metals Processing Center, Department of Mining and Metallurgical Engineering, McGill University, is with the Scientific Research Laboratory, Ford Motor Company, Dearborn, MI 48121-2053. Manuscript submitted November 16, 2000.
METALLURGICAL AND MATERIALS TRANSACTIONS B
II. WATER BASED AND METAL BASED LiMCA SYSTEMS A. Water-based LiMCA System—APS II System A schematic experimental setup of the APS II system is shown in Figure 1. The probe of the APS II system used to model the metal-based LiMCA probe is designed on a oneto-one scale to ensure geometrical similarity. The shape of the orifices is parabolic and could be represented as y ⫽ 10⫺3 * x2 ⫹ R
[1]
where R is the radius at the throat of the circular orifice (⬃150 m), and x and y are the axial and radial coordinates, respectively, in micrometer (Figure 2(a) in Part I). The probe head essentially consists of the electrically insulating sampling tube and two concentric electrodes. The inner concentric electrode is press-fixed to the interior of the tube, while the outer concentric electrode surrounds the tube leaving a small gap around the orifice to allow water to pass into it. By alternate use of moderate vacuum and pressure, aqueous samples are aspirated into and, then, exhausted from the sampling tube through the orifice, i.e., the ESZ. To minimize the generation of electrical noise, two venturi tubes are connected in parallel to generate the vacuum needed for air aspiration. The level of vacuum within the probe could be controlled by increasing, or decreasi
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