Alumina and zirconia dissolution into molten flux during continuous steel casting

Thesis for the Degree of Doctor of Engineering Alumina and Zirconia Dissolution into Molten Flux during Continuous Steel Casting Anh-Hoa Bui Department of Materials Science and Metallurgy The Graduate School December 2005 The Graduate School Kyungpook National University Alumina and Zirconia Dissolution into Molten Flux during Continuous Steel Casting Anh-Hoa Bui Department of Materials Science and Metallurgy The Graduate School Supervised by Professor In-Sang Chung Approved as a qualified thesis of Anh-Hoa Bui for the degree of Doctor of Engineering by the Evaluation Committee December 2005 Chairman Prof Seong-Hoon Yi Prof Byung-Jun Ye Prof Ho-Sang Sohn Prof In-Sang Chung Prof Hae-Geon Lee The Graduate School Council, Kyungpook National University Alumina and Zirconia Dissolution into Molten Flux during Continuous Steel Casting Anh-Hoa Bui Department of Materials Science and Metallurgy Graduate School, Kyungpook National University Daegu, Korea (Supervised by Professor In-Sang Chung) (Abstract) Alumina and zirconia dissolution into molten flux during the continuous steel casting was investigated by employing the rotating cylinder method at 1550∼1600oC The dissolution rate of alumina and zirconia was determined by measuring weight loss of the rod, initial dipping area, and immersion time Thermodynamic computations (FactSage® software) were done to design the mold fluxes and to ascertain the interaction between the oxides and the molten fluxes Several industrial mold fluxes and zirconia refractory, which are using for the continuous steel casting in POSCO (Pohang Iron and Steel Co., Korea), were employed in the present study It is concluded that alumina dissolution is controlled not only by the mass transfer in the molten flux but also by the formation of intermediate compounds such as CaO⋅6Al2O3, CaO⋅2Al2O3, and 2CaO⋅Al2O3⋅SiO2 on the surface of the rods Alumina concentration driving force, the rod rotation speed, temperature of molten flux, and chemical compositions are important factors which affect the alumina dissolution process The dissolution rate of Al2O3 was found to increase with addition of MgO * A thesis submitted to the Council of the Graduate School of Kyungpook National University in partial fulfillment of the requirements for the degree of Ph.D in December 2005 or CaF2, or up to mass% of Na2O, and then decrease with further increase in the amount of Na2O content The physical erosion of the rod surface by the solid 2CaO⋅SiO2 dispersed in the liquid was attributed to fast alumina dissolution The dissolution rate of alumina into the industrial mold fluxes was determined and compared to the other designed fluxes Under this study, dissolution rate of the zirconia rod was very slow in molten fluxes, but much higher in molten flux/Fe-C alloy or in molten flux/low carbon steel due to a strong dissolution at the flux-metal interface It was found that the dissolution rates increased with increasing rotation speed of the rod, presence of fluoride (F-) or Na2O in the mold fluxes, and higher ZrO2 content in the rod Graphite in the rod dissolves into the liquid metal, while zirconia in the rod dissolves into the molten flux This cyclic process and Marangoni effect that was considered as the dominant factor accelerated the dissolution rate at the flux-metal interface Zirconia dissolution into molten flux was speculated to be the rate-controlling step in the dissolution process of zirconia rod Observation by SEM-EPMA of the rod surface after experiment revealed that the molten flux and the liquid metal, i.e Fe-C alloy or steel, did not penetrate inside the rod It was concluded that flux viscosity, compositions of mold flux, or/and wettability between molten flux and SEN materials, etc are several factors which affect the SEN corrosion during continuous steel casting KEY WORDS: mold flux, dissolution, rotating cylinder method, concentration driving force, intermediate compound, zirconia rod, interfacial dissolution, submerged entry nozzle CONTENTS List of Tables List of Figures Chapter Introduction ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 1.1 Backgrounds of Research ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 1.2 Objectives of This Study ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ Chapter Theory ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 2.1 Selection of Mold Flux Components ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 2.2 Alumina and Zirconia Inclusions in Liquid Steel ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 2.2.1 Source ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 2.2.2 Harmfulness ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 10 2.2.3 Flotation ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 11 2.2.4 Dissolution into molten flux ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 12 2.3 Study on Oxide Dissolution into Molten Slag/Flux ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 13 2.3.1 Study methods ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 13 2.3.2 Review of the literatures ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 15 2.4 Thermodynamic Computation FactSage® Software ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 20 i Chapter Experiments ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 22 3.1 Experimental Method ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 22 3.2 Preparation of Materials ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 25 3.2.1 Mold fluxes ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 25 3.2.2 Oxide rods ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 32 3.2.3 The other materials ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 34 Chapter Results and Discussion ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 35 4.1 Alumina Dissolution into Molten Flux ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 35 4.1.1 Introduction ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 35 4.1.2 Alumina dissolution rate ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 36 4.1.3 Rotation speed of the alumina rod ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 43 4.1.4 Alumina concentration driving force ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 46 4.1.5 Activation energy ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 53 4.1.6 Formation of intermediate phase(s) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 57 4.1.7 Physical erosion in two-phase fluxes ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 64 4.1.8 Alumina dissolution into industrial mold fluxes ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 71 4.2 Zirconia Dissolution into Molten Fluxes ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 73 4.2.1 Introduction ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 73 ii 4.2.2 Dissolution rate of the zirconia rod ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 74 4.3 Zirconia Dissolution into Molten Flux/Metal ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 81 4.3.1 Introduction ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 81 4.3.2 Dissolution behavior in molten flux/Fe-C alloy ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 82 4.3.3 Dissolution behavior in molten flux/low carbon steel ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 94 4.3.4 Dissolution mechanism of the rod at the flux-metal interface ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 102 Chapter Conclusions ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 104 5.1 Alumina Dissolution ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 104 5.2 Zirconia Dissolution ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 105 References ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 107 Appendix ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 114 Abstract (in Korean) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 118 Acknowledgments ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 120 Curriculum Vitae ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 121 iii LIST OF TABLES 2.1 Effect of some components on the flux properties ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 3.1 Chemical compositions of the industrial mold flux (mass%) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 25 3.2 Chemical compositions of the designed mold fluxes (mass%) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 27 3.3 Properties of the ZrO2-Graphite refractory ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 32 4.1 Mass transfer activation energy ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 56 4.2 The flux compositions after the experiment (mass%) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 99 iv LIST OF FIGURES 1.1 The conventional ironmaking and steelmaking stream process ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 1.2 A continuous steel casting mold ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 1.3 An example of the practical SEN corrosion ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 2.1 The rotating cylinder method ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 14 2.2 The particle method ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 14 2.3 Utility of FactSage® software ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 21 3.1 Setup for dissolution experiment ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 24 3.2 Phase diagrams of some mold flux system at 1550oC (by FactSage®) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 31 3.3 Alumina rod (a) and zirconia rod (b) before the experiment ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 33 4.1 Illustration of alumina dissolution experiment ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 36 4.2 Alumina rods after dissolution experiment at 1550oC, 150 rpm ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 37 4.3 Variation of Al2O3 rod weight loss with immersion time ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 38 4.4 Effect of additive components on the dissolution rate ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 40 4.5 Effect of additive content on the dissolution rate ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 41 4.6 Variation of calculated viscosity with (a) basicity (CaO/SiO2) and (b) content of aditives at 1550oC ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 42 v 4.7 Relationship between angular velocity and the dissolution rate ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 45 4.8 Illustration of alumina concentration profile ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 46 4.9 Effect of Al2O3 content in mold flux on the dissolution rate ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 47 4.10 Relationship between the dissolution rate and alumina concentration driving force ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 50 4.11 Dependence of flux viscosity and alumina diffusivity on flux composition ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 51 4.12 Dependence of the dissolution rate on flux composition ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 52 4.13 Effect of temperature on the dissolution rate ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 53 4.14 Determination of activation energy for mass transfer ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 54 4.15 SEM micrograph and EPMA results at the interface of Al2O3 rod after dissolusion in flux F2 at 1550oC, 150 rpm ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 58 4.16 Formation of intermediate compounds at the interface of Al2O3 rods after dissolution in fluxes A1, A2, and A3 ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 60 4.17 Compositional mapping of positive ions for CaO⋅6Al2O3 compounds ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 61 4.18 Difference in intermediate compounds on the interface of Al2O3 rods after dissolution in fluxes D2, F3, and H3 ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 63 4.19 Illustration of two-phase fluxes at 1550oC ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 64 vi 19) X Yu, R J Pompret, and K S Coley: Dissolution of Alumina in Mold Fluxes; Metallurgy and Materials Transactions B, Vol 28, 275-279 (1997) 20) S Sridhar and A W Cramb: Kinetics of Al2O3 Dissolution in CaO-MgOSiO2-Al2O3 Slags: In Situ Observation and Analysis; Metallurgy and Materials Transactions B, Vol 31, 406-410 (2000) 21) J Y Choi, H G Lee, and J S Kim: Dissolution Rate of Al2O3 into Molten CaO-SiO2-Al2O3 Slags; ISIJ International, Vol 42, No 8, 852-860 (2002) 22) M Valdez, K Prapakorn, A W Cramb, and S Sridhar: Dissolution of Alumina Particles in CaO-Al2O3-SiO2-MgO Slags; Ironmaking and Steelmaking, Vol 29, No 1, 47-52 (2002) 23) K W Yi, C Tse, J H Park, M Valdez, A W Cramb, and S Sridhar: Determination of Dissolution Time of Al2O3 and MgO Inclusions in Synthetic Al2O3-CaO-MgO Slags; 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Japan, Tokyo (1988) 44) E M Levin, C R Robbins, and H F McMurdie: Phase Diagrams for Ceramists; The American Ceramic Society, Columbus, Ohio (1964) 45) E D Hondros, M McLean, and K C Mills: Marangoni and Interfacial Phenomena in Materials Processing; The Royal Society of London, Cambridge, UK (1998) 46) Z F Yuan, W L Huang, and K Mukai: Local Corrosion of Magnesia Chrome Refractory Driven by Marangoni Convection at the Slag-Metal Interface, Journal of Colloid and Interface Science, Vol 253, 211-216 (2002) 47) K Fagerlund, S Sun, and S Jahanshahi: Effect of Marangoni-induced Flow on the Rate of Refractory Dissolution in Molten Slags, Scandinavian Journal of Metallurgy, Vol 31, 359-366, (2002) - 113 - Appendix A.1 The Reboud’s Model This model34,35) was developed to estimate the slag viscosity: ⎛B⎞ ⎝T ⎠ η = AT exp⎜ ⎟ where η is dynamic viscosity (1 N⋅s⋅m-2 = 0.1 Poise), T the absolute temperature (K) The parameters A and B are calculated from the mole fractions of the slag components as follows: ln A = - 19.81 - 35.75XAl2O3 + 1.73(XCaO+XMgO) + 5.82XCaF2 + 7.02XNa2O (the unit of A is N⋅s⋅m-2⋅K-1) B = 31140 + 68833 XAl2O3 - 23896(XCaO+XMgO) - 46351XCaF2 - 39519XNa2O (the unit of B is K) - 114 - A.2 Molten Slag Density A method for the estimation of slag density can be obtained as the following equation35): ρ= ∑Mi Xi ∑ Vi X i where Mi is the molecular weight, Xi the mole fraction, and V the partial molar volume Recommended values for V of various slag components at 1500oC: Component V Component V Al2O3 28.31+32XAl2O3-31.45X2Al2O3 MgO 16.1 CaF2 31.3 MnO 15.6 CaO 20.7 Na2O 33.0 FeO 15.8 P2O5 65.7 Fe2O3 34.4 SiO2 19.55+7.966XSiO2 K2O 51.8 TiO2 24.0 - 115 - A.3 Activation energy for Viscous Flow The temperature dependence of slag viscosity is expressed by the Arrhenius relationship34,35): ⎛ EA ⎞ ⎟ ⎝ RT ⎠ η = AA exp⎜ where AA is constant, R the gas constant, T the absolute temperature (K), and EA the activation energy for viscous flow (J⋅mol-1) The activation energy is calculated based on the slope of linear proportion between logarithm of the flux viscosity and the inverse temperature ln(η ) ∝ EA ⎛ ⎞ ⎜ ⎟ R ⎝T ⎠ - 116 - A.4 Liquidus Temperature of Steel Below 0.5% C, where the solidification begins with the formation of delta (δ) iron, the following equation35) would apply: TLiquidus (oC) = 1537 – 73.1[%C] + ∑α[%X] For the carbon content within the range 0.5 to 1.0%, where the solidification begins with the formation of gamma (γ) iron, the following equation35) is recommended: TLiquidus (oC) = 1531 – 61.5[%C] + ∑α[%X] In both equations, X is the alloying element The coefficient (α) is given bellows: α (oC/%X) α (oC/%X) α (oC/%X) Al -2.5 Mo -5.0 Si -14.0 Cr -1.5 Ni -3.5 S -45.0 Mn -4.0 P -30.0 V -4 - 117 - 연속주조용 몰드플럭스로의 알루미나 및 지르코니아의 용해 속도 측정 Anh-Hoa Bui 경북대학교 대학원 금속신소재공학과 (지도교수 정인상) (초 록) 1550~1600℃에서 연속주조용 몰드플럭스로의 알루미나 및 지르코니아의 용해 속도를 원주 회전 측정법과 무게 변화 측정법을 이용하여 측정하였다 또한, 실험에 사용 된 몰드플럭스의 조성을 설계하고 실험에 사용된 알루미나 및 지르코니아와 몰드플럭스와의 반응을 규명하기 위하여 열역학 계산 프로그램인 FACTSAGE 를 사용하였다 실험에 사용된 몰드플럭스 및 지르코니아는 POSCO 에서 직접 공급을 받아 사용하였다 실험 결과 알루미나의 용해 속도는 물질 전달 속도의 영향과 알루미나 표면에 형성되는 CaO ㆍ 6Al2O3, CaO ㆍ 2Al2O3, 2CaO ㆍ Al2O3 ㆍ SiO2 같은 중간 생성물의 영향을 받는 것으로 나타났다 또한, 초기 몰드플럭스의 알루미나의 농도, 원주의 회전 속도, 실험 온도 및 몰드플럭스의 조성이 알루미나의 용해 속도에 큰 영향을 미치는 인자로 나타났다 알루미나의 용해 속도는 MgO, CaF2 의 첨가에 따라 증가하였으나, Na2O 의 경우 5%이상 첨가하였을 경우 오히려 용해 속도가 감소하였으며, 고상의 2CaO ㆍ SiO2 에 의한 물리적인 타격은 알루미나의 용해 속도를 증가 시켰다 이번 논문에서는 다양한 조성의 몰드플럭스로의 알루미나의 용해 속도를 측정, 비교하였다 지르코니아의 몰드플럭스로의 용해 속도는 매우 느린 것으로 나타났다 그러나 Marangoni 효과에 의하여 몰드플럭스와 용강간의 계면에서는 지르코니아의 용해속도가 매우 빠른 것으로 나타났다 지르코니아의 용해 속도는 원주의 회전 속도가 증가할수록 몰드플럭스 속의 F-와 Na2O 의 첨가량이 증가할수록, 지르코니아 원주 속의 ZrO2 의 첨가량이 증가할수록 증가하였다 지르코니아 원주 속의 - 118 - 흑연은 용강 속으로 용해 되었으며, ZrO2 는 몰드플럭스 속으로 용해 되는데, 이러한 ZrO2 의 몰드플럭스 속으로 용해가 지르코니아 원주 용해의 속도 결정 단계로 생각 된다 용해 실험 후 지르코니아 원주 표면의 몰드플럭스와 용강 등을 제거하고 SEM-EPMA 를 이용하여 지르코니아 원주의 단면을 관찰한 결과 몰드플럭스나 용강의 침투 현상은 관찰되지 않았다 이러한 실험 결과로 몰드플럭스의 점도, 조성, 젖음성 등이 SEN 의 용식에 영향을 미치는 것으로 판단 된다 - 119 - ACKNOWLEDGMENTS This thesis has been completed with the encouragements of my family and my wife, Phuong-Lan Nguyen who took care of our son with her patience and diligence during the time I studied in Korea I would like to express my deep appreciation to my academic advisors, Prof In-Sang Chung and Prof Hae-Geon Lee, who supported as well as advised me through all the research works Their experience and advice are very useful for the present study, especially for my career in the future I wish to thank Department of Iron and Steel Engineering, Faculty of Materials Science and Technology, Hanoi University of Technology (Vietnam) and Kyungpook National University (Korea) for providing me with this research opportunity I am thankful to POSCO (Pohang Iron and Steel Co., Korea) who funded this research, and other professors in Department of Materials Science and Metallurgy (KNU) who helped me to finish this study I also acknowledge the professor council for their valuable comments and suggestions during revision of this thesis Finally, a special appreciation goes to all students in the Pyrotechnical Research Laboratory (POSTECH) and Mechanical Metallurgy Laboratory (KNU) for their collaboration and assistance - 120 - CURRICULUM VITAE Full Name: Anh-Hoa Bui Date of Birth: April 25, 1974 Place of Birth: Hanoi, Vietnam Education 2001/09 - 2006/02 Department of Materials Science and Metallurgy (PhD), Kyungpook National University, Daegu, Korea 1998/10 - 2000/10 Department of Iron and Steelmaking Technology (MS), Hanoi University of Technology, Hanoi, Vietnam 1991/09 – 1996/06 Department of Iron and Steelmaking Technology (Eng.), Hanoi University of Technology, Hanoi, Vietnam Experience 2003/11 - 2006/02 Research assistant At Department of Materials Science Engineering, Pohang University of Science and Technology, Pohang, Korea - 121 - 2001/09 - 2003/10 Research assistant At Department of Materials Science and Metallurgy, Kyungpook National University, Daegu, Korea 1997/01 - 2001/08 Teaching assistant At Department of Iron and Steel Engineering, Hanoi University of Technology, Hanoi, Vietnam Publications Anh-Hoa Bui, Hyun-Mo Ha, In-Sang Chung, and Hae-Geon Lee: Dissolution Kinetics of Alumina into Mold Fluxes for Continuous Steel Casting; ISIJ International, Vol 45, No 12, 1856-1863 (2005) Anh-Hoa Bui, Hyun-Mo Ha, In-Sang Chung, and Hae-Geon Lee: Effect of Alumina Content and Solid Phase in Molten Flux on Dissolution of Alumina; Metals and Materials International, Vol 11, No 4, 319-326 (2005) Anh-Hoa Bui, Hyun-Mo Ha, Youn-Bae Kang, In-Sang Chung, and HaeGeon Lee: Dissolution Behavior of Alumina in Mold Fluxes for Steel Continuous Casting; Metals and Materials International, Vol 11, No 3, 183-190 (2005) - 122 - Geon-Young Cha, Anh-Hoa Bui, Won-Woo Baek, Sang-Tae Lee, DukDong Lee, and Jeung-Soo Huh: Effects of Calcining Temperature on SnO2 Sensors for CO and NOx Gases; Metals and Materials International, Vol 10, No 2, 149-152 (2004) Conferences Anh-Hoa Bui, In-Sang Chung, and Hae-Geon Lee: Corrosion Rate of SEN Material during Continuous Steel Casting, Conference of Metals and Materials, Ilsan, Korea (October 2005) Anh-Hoa Bui, Hyun-Mo Ha, Youn-Bae Kang, In-Sang Chung, and HaeGeon Lee: Several Factors Affecting on the Dissolution of Alumina in Mold Flux, Conference of Metals and Materials, Daegu, Korea (April 2005) Anh-Hoa Bui, Hyun-Mo Ha, Youn-Bae Kang, In-Sang Chung, and HaeGeon Lee: A Study on Dissolution of Alumina into Mold Fluxes, Conference of Metals and Materials, Busan, Korea (October 2004) Hyun-Mo Ha, Anh-Hoa Bui, Youn-Bae Kang, and Hae-Geon Lee: Dissolution Rate of Alumina in Mold Flux of CaO-SiO2-Al2O3-MgO-CaF2Na2O System, Conference of Metals and Materials, Kwangju, Korea (April 2004) - 123 - Anh-Hoa Bui, Won-Woo Baek, Sang-Tae Lee, Hee-Kwon Jun, Duk-Dong Lee, and Jeung-Soo Huh: Preparation of SnO2-based Gas Sensor by SolGel Process, Conference of Metals and Materials, Ulsan, Korea (May 2003) Won-Woo Baek, Anh-Hoa Bui, Sang-Tae Lee, Hee-Kwon Jun, Duk-Dong Lee, and Jeung-Soo Huh: Influence of Particle Size on Sensing Characteristics of Hydrothermally treated Nano-sized SnO2, Conference of Metals and Materials, Ulsan, Korea (May 2003) Anh-Hoa Bui, Won-Woo Baek, Sang-Tae Lee, Hee-Kwon Jun, Duk-Dong Lee, and Jeung-Soo Huh: Influence of Cooling Rate on Characteristics of SnO2 Thin Film Fabricated by Thermal Oxidation, Conference of Sensors, Kwangju, Korea (November 2002) - 124 - ... (Abstract) Alumina and zirconia dissolution into molten flux during the continuous steel casting was investigated by employing the rotating cylinder method at 1550∼1600oC The dissolution rate of alumina. .. study on alumina and zirconia dissolution during the continuous steel casting becomes essential The purposes of this study are: 1) Investigate the dissolution behavior of alumina and zirconia into. . .Alumina and Zirconia Dissolution into Molten Flux during Continuous Steel Casting Anh-Hoa Bui Department of Materials Science and Metallurgy The Graduate School