A Reaction Between High Mn-High Al Steel and CaO-SiO 2 -Type Molten Mold Flux: Part II. Reaction Mechanism, Interface Mo
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ING the previous article in the present series on the experimental investigation on the reaction between high Mn-high Al steel and conventional CaOSiO2-type mold flux,[1] the present article describes a kinetic analysis coupled with interfacial morphology observation in order to elucidate the reaction mechanism. The present study aims at elucidating the reaction mechanism between high Mn-high Al TWIP (TWinInduced Plasticity) steel and conventional CaO-SiO2YOUN-BAE KANG, Assistant Professor, MIN-SU KIM, Graduate Student, and HAE-GEON LEE, Professor Emeritus, are with the Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea. Contact e-mail: [email protected] SU-WAN LEE, formerly Graduate Student with the Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, is now Engineer with the Steelmaking Department, Pohang Works, POSCO Ltd, Pohang, Republic of Korea. JUNG-WOOK CHO, formerly Principal Researcher with the Technical Research Laboratories, POSCO Ltd, Gwangyang, Republic of Korea, is now Research Associate Professor with the Graduate Institute of Ferrous Technology, Pohang University of Science and Technology. MIN-SEOK PARK, Senior Researcher, is with the Technical Research Laboratories, POSCO Ltd. Manuscript submitted August 21, 2012. Article published online December 11, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
type molten mold flux in the continuous casting mold. It has been an immediate issue during the casting practice that SiO2 in the molten mold flux is significantly reduced by Al in the steel, and consequently Al2O3 accumulates in the molten mold flux. This affects several physicochemical properties of the flux significantly such that viscosity, melting temperature, crystallization behavior are varied during the casting. This induces unstable heat transfer and lubrication of the mold flux which are responsible for poor casting performance. Although the Al2O3 accumulation in the molten flux containing SiO2 is unlikely to be avoided under the presence of Al in the steel by the following chemical Reaction [1] 4½Al þ 3ðSiO2 Þ ¼ 3½Si þ 2ðAl2 O3 Þ;
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it is thought to be worthwhile to elucidate the exact mechanism of the above reaction. This is because the prediction of the Al2O3 accumulation in the flux coupled with the SiO2 reduction would be utilized in estimation of such physico-chemical properties (viscosity, melting temperature, and crystallization behavior such as primary crystalline phase). Such estimation of the physico-chemical properties would provide with a guide to develop a new mold flux which enhances the current poor casting performance of the TWIP steel. VOLUME 44B, APRIL 2013—309
The SiO2 reduction by Al dissolved in molten iron (Reaction [1]) has been investigated previously.[2–14] The practical purpose of those previous investigations was mainly the observation of interfacial instability[2–4,10] and reoxidation of steel.[5–9] Recently, the same reaction has been revisited in the light of in
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