Numerical Analysis of Horizontal Twin-Roll Casting for AA3003
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TION
METALLIC sheets can be directly produced from a molten metal by twin-roll casting without repeated heating and rolling processes. This technology is so advantageous in economy as well as quality that it has been developed with various improvements and applied to production of sheets of steel, aluminum, or magnesium alloys.[1–11] They have changed process parameters to control microstructures and productivities for various materials. Recently, wide strips of magnesium alloys with 2000 mm in width and 4 to 8 mm in thickness were successfully manufactured by this technology.[12] Simultaneously, methodologies for essential improvement of quality have become available such as refining microstructure by high rates of shearing and eliminating macro-segregation by static magnetic field with pulse electric current.[13,14] However, the technology has a drawback of low productivity. Recently, new materials such as CuCoBe alloys with high thermal conductivity and tensile strength were developed for rolls and thus the productivity has been improved to some extent by adopting a composite roll, consisting of a steel core and a copper alloy sleeve with internal cooling channels.[15–17]
JONG-JIN PARK is with the Department of Mechanical and System Design Engineering, Hongik University, 94 Wawusanro, Mapo-Gu, Seoul 04066, South Korea. Contact e-mail: [email protected] Manuscript submitted December 30, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
There are two types in twin-roll casting in the aspect of roll arrangement: horizontal twin-roll casting (HTRC) and vertical twin-roll casting (VTRC). One roll is on top of the other so that the melt flows horizontally in the former, while two rolls are aligned side-by-side so that the melt flows vertically in the latter. In general, the equipment cost is less with an easy control of the process in the former while productivity is higher with a better quality of a sheet in the latter.[18] In addition, the latter is advantageous in utilization of the gravitational force as well as easiness in increasing the contact length for enhancing the cooling effect at the interface. Recently, twin-roll casting also has been applied to production of clad sheets of steel, aluminum, or magnesium alloys.[19–22] Along with the experimental studies, numerical studies also have been performed for twin-roll casting. Simple analyses of melt flow and heat transfer were performed,[23] followed by sophisticated analyses, where the development of vortices was found to support the observation of inhomogeneous distributions of microstructure in sheet thickness.[24–27] Recently, comprehensive analyses of VTRC were performed to find that, due to the vortex development, only the melt along the roll surface was solidified and rolled into a sheet, leaving the rest of the melt in rotational motion of vortices.[28] In addition, roll torque, roll-separating force, and contact pressure were predicted by considering plastic deformation after solidification. Assuming no development of vortices, some investigations were carri
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