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Computational Fluid Dynamics Modeling of Macrosegregation and Shrinkage in Large-Diameter Steel Roll Castings

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Abstract

Minimizing macrosegregation and shrinkage in large cast steel mill rolls challenges the limits of commercial foundry technology. Processing improvements have been achieved by balancing the total heat input of casting with the rate of heat extraction from the surface of the roll in the mold. A submerged entry nozzle (SEN) technique that injects a dilute alloy addition through a nozzle into the partially solidified net-shaped roll ingot can mitigate both centerline segregation and midradius channel segregate conditions. The objective of this study is to optimize the melt chemistry, solidification, and SEN conditions to minimize centerline and midradius segregation, and then to improve the quality of the transition region between the outer shell and the diluted interior region. To accomplish this objective, a multiphase, multicomponent computational fluid dynamics (CFD) code was developed for studying the macrosegregation and shrinkage under various casting conditions for a 65-ton, 1.6-m-diameter steel roll. The developed CFD framework consists of solving for the volume fraction of phases (air and steel mixture), temperature, flow, and solute balance in multicomponent alloy systems. Thermal boundary conditions were determined by measuring the temperature in the mold at several radial depths and height locations. The thermophysical properties including viscosity of steel alloy used in the simulations are functions of temperature. The steel mixture in the species-transfer model consists of the following elements: Fe, Mn, Si, S, P, C, Cr, Mo, and V. Density and liquidus temperature of the steel mixture are locally affected by the segregation of these elements. The model predictions were validated against macrosegregation measured from pieces cut from the 65-ton roll. The effect of key processing parameters such as melt composition and superheat of both the shell and the dilute interior alloy are addressed. The influence of mold type and thickness on macrosegregation and shrinkage also are discussed.

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Acknowledgments

The author would like to acknowledge Whemco, Inc. for sponsoring the research program and Mr. Kevin Marsden for his useful comments in writing this article.

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Authors and Affiliations

  1. Department of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL, 35487-0202, USA

    Laurentiu Nastac (Professor)

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  1. Laurentiu Nastac
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Correspondence to Laurentiu Nastac.

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Manuscript submitted March 24, 2011.

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Nastac, L. Computational Fluid Dynamics Modeling of Macrosegregation and Shrinkage in Large-Diameter Steel Roll Castings. Metall Mater Trans B 42, 1231–1243 (2011). https://doi.org/10.1007/s11663-011-9537-y

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  • DOI: https://doi.org/10.1007/s11663-011-9537-y

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