3D FEM Simulation of the Effect of Cooling Rate on SDAS and Macrosegregation of a High Strength Steel

Abstract

Secondary dendrite arm spacing (SDAS) is a macrosegregation parameter directly linked to content of macrosegregation through cooling rates. The aim of this paper is to highlight the effect of cooling rate on the SDAS and macrosegregation patterns in a high strength steel. For this purpose, directionnal solidification in a cylinder was modeled with a plane-front solidification. Two cylinders were modeled with different boundary conditions (Tsurface = 1000°C and 1200°C). Using the FEM software Thercast, 3D macrosegregation maps were generated with thermomechanic algorithm taking into account metal shrinkage. Using Won’s equation, the influence of cooling rates in the mushy zone on SDAS was determined. The results indicated that a 72% lower difference in the area of negative macrosegregation zone (macrosegregation ratio (rseg) < -0.016%) for lower cooling rate (Ts = 1200°C). The difference of the area for positive segregation was 85% lower for higher cooling rates.

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“…That is, they depend both on alloy chemical composition [1] and on its solidifi cation rate [2,3]. Alloy solidifi cation rate changing leads to its dendritic structure dispersion changing, its phase components distribution and morphology [4,5], distance between dendrites secondary axes, quantity of secondary phases [6,7], etc. All these changes, fi nally, have a corresponding infl uence on mechanical, technological and exploitation properties of the cast part.…”