Modeling and Experimental Validation of Rapid Cooling and Solidification during High-Speed Twin-Roll Strip Casting of Al
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THE twin-roll strip casting process can eliminate the requirement of hot rolling and produces thin strips with thickness of 0.1 to 6 mm directly from the molten metal by combining casting and rolling into a single step. The process provides better control over the microstructure and mechanical properties of the cast strip, and segregation is almost absent. The materials difficult to hot roll are also manufactured by this technique.[1–3] The process seems simple, but in practice, it is necessary to control many strip casting parameters like the feeding rate of liquid metal, melt level in the pool region, pouring temperature of molten metal, roll diameter, roll speed, roll gap, roll thickness, etc. in a narrow range. It is important to understand the influence of these design and operational parameters on the transport behavior within the liquid metal pool and the structure of the cast strips. The study of these process parameters experimentally is impossible because the process of twin-roll strip casting is dynamic and quick, and it occurs at a high temperature. Thus, comprehensive modeling of fluid flow, heat transfer, and solidification during the twin-roll casting is indispensable. Mehrotra and coworkers[4,5] formulated a mathematical model for the fluid flow, heat transfer, and
SESHADEV SAHOO, Research Scholar, and SUDIPTO GHOSH, Associate Professor, are with the Department of Metallurgical and Materials Engineering, IIT, Kharagpur 721302, India. Contact e-mail: [email protected] AMITESH KUMAR, Assistant Professor, is with the NIFFT, Hatia, Ranchi 834003, India. B.K. DHINDAW, Visiting Professor, is with the School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Pulau Pinang 14300, Malaysia. Manuscript submitted August 17, 2011. Article published online April 10, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
solidification for the single roll strip casting process. They studied the effect of different parameters, i.e., liquid steel head in the tundish, speed of rotation of the caster drum, superheat of melt in the tundish, gap between the caster drum and the tundish, drum geometry, and drum material on process performance using the model. Saitoh et al.[6] developed a two-dimensional numerical model of twin-roll continuous casting. They studied the heat transfer and flow characteristics in both the solid and liquid phases of metal and solved governing equations separately using the finite-difference method. However, they did not focus on the contact phenomenon, contact heat transfer and heat conduction to the roll and adopted constant temperature (290 K [17 °C]) as a boundary condition at the roll surface. The materials properties were also taken as constant in the model. Based on Saitoh et al.,[6] Santos et al.[7] developed a model to simulate the solidification and heat transfer in strip casting with a roll speed 14 rpm, the only main difference being that Santos et al. introduced a heattransfer coefficient between liquid metal and roll instead of constant temperature (290 K [17 °C])
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