Tundish Process Performance Parameters and Their Direct Estimation from a New, Plant Measurement-Based Formalism
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Tundish Process Performance Parameters and Their Direct Estimation from a New, Plant MeasurementBased Formalism DIPAK MAZUMDAR A mathematical frame work has been developed to quantitatively investigate inclusion floatation and generation phenomena in a tundish during continuous casting of LCAK (low carbon aluminum killed) steel. Embodying industrial scale measurements of dissolved and total aluminum in VD (vacuum degasser), tundish and bloom in a materials balance frame work, two key dimensionless parameters, viz., inclusion generation (GI) and floatation (FI) indices, have been formulated. To demonstrate their adequacy, as a test case, a 13 metric ton bloom casting tundish has been considered and plant scale data from nearly fifty heats applied. The analysis reveals barely satisfactory inclusion floatation coupled with significant generation, indicating essentially sub-optimal tundish process performance. https://doi.org/10.1007/s11663-020-02033-1 The Minerals, Metals & Materials Society and ASM International 2020
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continuous casting of steel, a tundish offers considerable scope for improvement of cleanliness through enhanced floatation of non-metallic inclusions. This is generally true provided unwarranted chemical reactions between melt and the three phases, i.e., air, slag and refractory are avoided. Indeed, a tundish can perform not only as a refiner but also as a contaminator of molten steel which was elucidated by McLean[1] in great detail, in his 1988 Howe Memorial Lecture. Many intervening studies went on to show[2] that oxygen and nitrogen from ambient are routinely dissolved in steel during ladle to tundish transfer and several chemical reactions among melt–slag–refractory and dissolved oxygen occur frequently in tundish to affect steel cleanliness. Among the chemical reactions, the most significant ones, in the present context are those taking place between dissolved elements such as Al, Ca or Mg (as in low carbon aluminum killed (LCAK) steel) and dissolved oxygen and/or reducible oxides, such as SiO2, present in tundish slag, gunning material and refractory lining. Despite such, in a vast majority of the physical and mathematical model studies of steelmaking tundish systems, rarely a tundish has been treated as a reacting flow system, and inclusion floatation phenomenon, etc., always investigated disregarding inclusion generation
DIPAK MAZUMDAR is with the Department of Materials Science and Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India. Contact e-mail: [email protected]. Manuscript submitted August 1, 2020; accepted November 1, 2020.
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due to such chemical reactions.[3–8] At pilot and industrial scale, however, re-oxidation and accompanied chemical reactions in tundish have been investigated and explored by many investigators,[9–11] although emphasis has been generally on the chemical composition, morphology and types of resultant inclusions. Generation and floatation of inclusions in tundish has been seldom treated in a conjugate fashion
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