Effect of Silicon on the Desulfurization of Al-Killed Steels: Part II. Experimental Results and Plant Trials
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INTRODUCTION
PART I of this two-part paper presented the background to this work, including the kinetic model used to predict the effect of silicon on ladle desulfurization.[1] In this paper, experimental results are presented which test the effect of silicon on the rate and the extent of desulfurization of aluminum-killed steels in contact with slags of different compositions. Plant trials were conducted in collaboration with an electric arc furnace (EAF) steel producer and the results analyzed to test the silicon effect on desulfurization. II.
EXPERIMENTAL SETUP AND PROCEDURE
A. Experimental Setup Experiments were run using a 10-kW radio frequency induction furnace; a schematic of the experimental setup is shown in Figure 1. The liquid steel was contained in a magnesia crucible (0.049 m ID, 0.062 m OD, 0.15 m high) surrounded by a graphite crucible (0.064 m ID, 0.07 m OD, 0.14 m high). The graphite crucible served as a susceptor to heat and melt the steel and slag and also served as a protective outer crucible. A magnesia crucible
DEBDUTTA ROY, formerly Graduate Student with the Department of Materials Science & Engineering, Center for Iron and Steelmaking Research, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, is now Research Engineer at SaintGobain Abrasives, Worcester, MA. PETRUS CHRISTIAAN PISTORIUS, Professor, and RICHARD J. FRUEHAN, US Steel Professor, are with the Department of Materials Science & Engineering, Center for Iron and Steelmaking Research, Carnegie Mellon University. Contact e-mail: [email protected] Manuscript submitted October 2, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
was chosen to simulate the industrial conditions for desulfurization, where ladles typically have MgO bricks at the slagline. The reaction chamber which contained the magnesia and graphite crucibles was a fused-quartz tube, 0.5 m high, 0.08 m ID, and 0.085 m OD, sealed airtight at the top and bottom using clamped end caps. Argon gas (99.9 pct pure, passed over heated magnesium to getter oxygen) was introduced into the reaction chamber through a gas inlet in the lower end cap; the gas flow rate was maintained at the same value from experiment to experiment with the aid a flow meter. A mullite guide tube (ID 0.0127 m, OD 0.0196 m), attached to a port in the top seal, facilitated additions during the experiment and sampling. The temperature of the melt was measured using two alumina-sheathed type S thermocouples; one was introduced through the lower end cap and with its tip at the bottom of the graphite crucible, and the other was introduced through the upper end cap to measure the temperature at the top surface of the melt (until just before slag addition). The steel used in the experiments was industrial material which was chosen to have low levels of impurities and alloying elements (see the composition in Table I). Slag was prepared by mixing reagent grade powders (CaO, MgO, SiO2, Al2O3) and premelting the slag in a graphite crucible in flowing argon. The liquidus temperatures of the slag composi
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