Aluminum Deoxidation Equilibria in Liquid Iron: Part I. Experimental
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TRODUCTION
ALUMINUM deoxidation equilibria in liquid iron containing Al up to hundreds of ppm have been well investigated for typical Al-killed steels by the various experimental techniques[1–11] and theoretical studies.[12– 16] Recently, the deoxidation limit of some high Alalloyed steels has also received great attention, because new Advanced High Strength Steels (AHSS) containing Al up to 3 mass pct such as Transformation-Induced Plasticity (TRIP) or Twinning-Induced Plasticity (TWIP) steels have been developed for future automotive industry. They provide an excellent combination of high strength, high ductility, and high formability over conventional steels.[17,18] For the production of such steel grades, thermodynamic information on the Al deoxidation equilibria in liquid iron is urgently needed. However, the experimental results of Al-O relation in liquid iron in high Al concentration region have been found inconsistent. The oxygen content in high Al-containing steel has not been well established.[11] MIN-KYU PAEK, formerly Graduate Student, with Department of Materials Engineering, Hanyang University, ERICA, Ansan 426-791, Republic of Korea, is now a post-doctor, with the Department of Mining and Materials Engineering, McGill University, Montreal, QC, H3A 2B2, Canada. JUNG-MOCK JANG, Graduate Student, and JONG-JIN PAK, Professor, are with the Department of Materials Engineering, Hanyang University Contact e-mail: [email protected] YOUN-BAE KANG, Associate Professor, is with the Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang, Kyungbuk, 790-784, Republic of Korea. Manuscript submitted November 19, 2014. Article published online May 20, 2015. 1826—VOLUME 46B, AUGUST 2015
Phases of inclusions in high Mn-high Al steel still need clarification due to accurate deoxidation equilibria.[19] As known, the analytical solution of the deoxidation equilibria, in particular for those of Al in steel, has been described by the interaction parameter formalism,[20] originally proposed by Wagner[21] based on theory proposed by Chipman.[22] Due to its simple concept and equation, it has enjoyed much popularity, and this has shown acceptable results at low Al content in the steel, particularly lower than 0.1 mass pct. However, as the Al concentration increases, the Wagner’s Interaction Parameter Formalism (WIPF) does not show satisfactory result.[4–6,9,10] For the practical application at high Al content, it is now necessary to consider an improved way to account for the Al deoxidation equilibria. The present study is an attempt to measure accurate deoxidation equilibria of Al in liquid iron from almost no Al to pure Al for the first time. In the present study, three different types of experimental techniques were employed depending on the Al content in liquid iron; Al deoxidation by the addition of Al (0.0027 to 17.3 mass pct Al), oxidation of Al by the addition of Fe2O3 (8.04 to 0.0454 mass pct Al), and the addition of CaO flux (>20 mass pct Al). Details of experimental techniques wil
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