Study on effect of melt level on heat transfer characteristics and quality of continuously cast Al-Mg2Si composite sheet

Abstract

Composite sheets fabricated by the Twin roll casting (TRC) process often suffer from quality issues, primarily microporosity resulting from solidification shrinkage. The presence of fabrication defects can be controlled by varying the casting parameters such as casting speed, superheat temperature, rolling force, and the height of the liquid metal in the melt pool. The present study developed a three-dimensional model to analyze the solidification and flow behavior of the melt with increasing melt pool height (4 cm, 6 cm, 8 cm) to see the quality of the fabricated Al-Mg2Si composite sheet. The developed model was validated using the optimized inlet temperature and interlamellar spacing. This model studies the effect of melt pool height on the solidification behavior, optimized inlet temperature, temperature gradient and heat flux. Results show that the increasing melt pool height shifts a solidification temperature above the roll exit and requires a higher inlet temperature for continuous sheet fabrication. Increased melt pool height decreases the heat flux from the roller surface and shows a lesser velocity fluctuation at the top and bottom of the melt pool. Experimental investigation demonstrates that a rise in melt pool height lowers the porosity in the casted sheet from 10.9% to 2.7% due to improved temperature gradient and pressure at the roller exit, enhancing sheet quality within the TRC process.