Abstract
In the present work macrosegregation during solidification of a 2.45 ton steel ingot is simulated with a pure equiaxed model, which was tested previously via modeling of a benchmark experiment. While the columnar structure is not taken into account, a packed layer formed over inner walls of the mold at an early stage of solidification reproduces to some extent phenomena generally related to zones of columnar dendrites. Furthermore, it is demonstrated that interaction of free-floating equiaxed grains with ascending convective flow in the bulk liquid results in flow instabilities. This defines the irregular form of the negative segregation zone, the formation of which at the ingot bottom corresponds to experimental observation. Vertical channels reported in experimental measurements are reproduced in simulations. It is confirmed that intensification of ingot cooling may decrease segregation in the ingot.
Highlights
Manufacturing of large-size ingots is a fundamental process in industrial production of heavy machinery
We present the numerical simulation for the solidification of a 2.45 ton steel ingot to study the role of equiaxed grain transportation in the formation of global segregation
A three-phase equiaxed solidification model was applied to study the formation of macrosegregation in a 2.45 ton industrial steel ingot
Summary
Manufacturing of large-size ingots is a fundamental process in industrial production of heavy machinery. Similar to previous modeling for steel ingots [11], the initial temperature of the melt was equal to the liquidus temperature of the nominal composition of steel, but this time the growth kinetic was taken into account for the solid phase Due to the latter, the predicted negative segregation at the ingot bottom was more pronounced than in previous results in the case of fixed solid grains [11]. Segregation distribution obtained with free-floating dendrites was quite similar to results with the fixed solid phase but had a more “diffused” character Both cases demonstrated A-type segregation bands, the formation of which was found sensitive to mesh, a zone with positive segregation observed in the real ingot was only partially reproduced with free-floating grains. The effect of surface cooling intensity on grain growth, melt flow, and macrosegregation is investigated
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