“…In Case 4, segregation is only different near the centreline, where the steep mushy zone causes an almost completely radial shrinkage induced flow, and therefore, severe negative segregation. Although this result is not consistent with experimental studies [2], which observes a reduction in centreline segregation under similar conditions, the disagreement can be explained by the possible change in solidification kinetics not captured by the model. Figure 6 Comparison of the effect of inlet diameter on the copper segregation profiles along z = 0.25 m for Cases 1–4.…”
Section: Resultscontrasting
confidence: 99%
“…The resulting chemical inhomogeneity on the billet scale (macrosegregation) is problematic because it cannot be mitigated by subsequent processing. A recent experimental study showed that material feeding through a narrow vertical jet prevents grain sedimentation at the centreline, leading to a drastic reduction in macrosegregation compared to conventional casting practices [2].…”
The influence of liquid metal feeding on the flow and macrosegregation during direct chill (DC) casting of Al-4.5wt-%Cu billets is investigated. An analytical study for constricted inlets predicts that the inflow only reaches the bottom of the sump for narrow inlets, a result confirmed by steady-state axisymmetric simulations of equiaxed solidification. For wide inlets, and inlets using a combo bag, the inflow is swiftly entrained towards the chill and the final macrosegregation predictions are all similar. For narrow inlets without a combo bag, penetration of the thermal jet to the bottom of the sump locally delays solidification producing an inclination in the packed solid interface and the possible growth of columnar dendrites in this region.
“…In Case 4, segregation is only different near the centreline, where the steep mushy zone causes an almost completely radial shrinkage induced flow, and therefore, severe negative segregation. Although this result is not consistent with experimental studies [2], which observes a reduction in centreline segregation under similar conditions, the disagreement can be explained by the possible change in solidification kinetics not captured by the model. Figure 6 Comparison of the effect of inlet diameter on the copper segregation profiles along z = 0.25 m for Cases 1–4.…”
Section: Resultscontrasting
confidence: 99%
“…The resulting chemical inhomogeneity on the billet scale (macrosegregation) is problematic because it cannot be mitigated by subsequent processing. A recent experimental study showed that material feeding through a narrow vertical jet prevents grain sedimentation at the centreline, leading to a drastic reduction in macrosegregation compared to conventional casting practices [2].…”
The influence of liquid metal feeding on the flow and macrosegregation during direct chill (DC) casting of Al-4.5wt-%Cu billets is investigated. An analytical study for constricted inlets predicts that the inflow only reaches the bottom of the sump for narrow inlets, a result confirmed by steady-state axisymmetric simulations of equiaxed solidification. For wide inlets, and inlets using a combo bag, the inflow is swiftly entrained towards the chill and the final macrosegregation predictions are all similar. For narrow inlets without a combo bag, penetration of the thermal jet to the bottom of the sump locally delays solidification producing an inclination in the packed solid interface and the possible growth of columnar dendrites in this region.
“…The results from the original study 5 examined only cross-sectional samples of the ingots and found a significant reduction of centerline segregation using a properly scaled jet under steady state conditions. A subsequent examination along the length of the entire ingot showed that the region directly underneath the impinging jet exhibited similar centerline segregation to that observed in the standard case 4 . We postulate that the crater formed by the impinging turbulent jet at the bottom of the sump is a proxy for the relative amount of material (grains) re-suspended from the centerline.…”
Section: Introductionmentioning
confidence: 56%
“…In comparison with the uniform removal of loose granular material, a jet of sufficient power could cause the bulk erosion of the coherent network of grains (mushy zone) instead of uniquely suspending mobile grains (slurry region). The periodic removal of large masses of coherent grains could contribute to the random fluctuations in composition found in the most turbulent jet conditions reported in reference (4).…”
Section: Discussionmentioning
confidence: 86%
“…Of particular concern in hypoeutectic alloys is the formation of a severely solute-depleted centerline 1 , which is responsible for mechanical property variations in rolled plate products 2,3 . We have recently postulated the dominant role of the accumulation of solute-lean grains on the formation of this centerline region 4 . In order to prevent the preferential sedimentation of these grains, we have proposed the use of a turbulent jet to re-suspend excess grains 5 thereby mitigating centerline segregation.…”
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