Large Steel Ingots: Microstructure Mathematical Modeling

Wołczyński, W.

doi:10.1081/e-eisa-120053685

Cited by 9 publications

(18 citation statements)

References 65 publications

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“…Finally, we would like to notice that although much progress had been made in modeling of ingot solidification [2,17] (nowadays the motion and growth of equiaxed crystals in the presence of columnar solidifying dendrites can even be modeled together with the formation of shrinkage cavities [18][19][20][21][22] ), the presented phenomena is still far too complex for recent simulation models.…”

Section: Discussionmentioning

confidence: 99%

“…Especially during solidification of large steel ingots, the appearing microstructure is partly explained by the so-called ''grain rain'' phenomenon. [2] Hereby, the grains are though to originate by hot-topping compound particle, nonmetallic inclusions, or dendrite fragmentations in such an amount that they form the well-known sedimentary cone at the bottom of the ingot. Furthermore, Kohn [16] reported about an autoradiographic study of solidification on axial sections of killed steel ingots weighing from 1 to 30 tons.…”

Section: Discussionmentioning

confidence: 99%

“…[1,2] The grains of the outer equiaxed zone form in contact with the mold wall by heterogeneous nucleation, and with the columnar dendritic zone by growth competition from the outer equiaxed zone. [3] In the interior of the casting, equiaxed crystals form by either heterogeneous nucleation [4] or fragmentation of dendrites from the columnar zone.…”

Section: Introductionmentioning

confidence: 99%

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Massive Formation of Equiaxed Crystals by Avalanches of Mushy Zone Segments

Ludwig

Stefan-Kharicha

Kharicha

et al. 2017

Metall Mater Trans A

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It is well known that the growth and motion of equiaxed crystals govern important microstructural features, especially in larger castings such as heavy ingots. To determine the origin of the equiaxed crystals, heterogeneous nucleation, and/or fragmentation of dendrite arms from columnar regions are often discussed. In the present study, we demonstrate that under certain conditions relatively large areas of mushy regions slide downward and form spectacular crystal avalanches. These avalanches crumble into thousands of dendritic fragments, whereby the larger fragments immediately sediment and the smaller proceed to behave as equiaxed crystals. Traces of such crystal avalanches can be seen by conspicuous equiaxed layers in the lower part of the casting. From the arguments in the discussion, it is believed that such a phenomenon may occur in alloys which reveal an upward solutal buoyancy in the interdendritic mush. This would include certain steels and other alloys such as Cu-Al, Pb-Sn, or Ni-Al-alloys. Moreover, the occurrence of crystal avalanches contribute to the formation of V-segregations.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Massive Formation of Equiaxed Crystals by Avalanches of Mushy Zone Segments

Ludwig

Stefan-Kharicha

Kharicha

et al. 2017

Metall Mater Trans A

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“…The recently developed method for the ingot structure forecast, [1], is connected with the interpretation of the points of inflection if they are presented by the calculated function. The very informative function in this area is the liquidus isotherm velocity plotted versus time of the static ingot solidification.…”

Section: Forecast Of the Ingot's Structural Zonesmentioning

confidence: 99%

“…A new innovative method for the description of structure formation and especially for the prediction of some structural transformations and resultant situation of structural zones in the steel massive ingot, solidifying as static ingot, has appeared recently, [1]. It is based on the mathematical predictions for the structure appearance in a large steel ingot.…”

Section: Introductionmentioning

confidence: 99%

Some Similarities / Differences between Steel Static and Virtual Brass Static Casting

Kwapisiński

Ivanova

Kania

et al. 2017

Archives of Foundry Engineering

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An innovative method for determining the structural zones in the large static steel ingots has been described. It is based on the mathematical interpretation of some functions obtained due to simulation of temperature field and thermal gradient field for solidifying massive ingot. The method is associated with the extrema of an analyzed function and with its points of inflection. Particularly, the CET transformation is predicted as a time-consuming transition from the columnar-into equiaxed structure. The equations dealing with heat transfer balance for the continuous casting are presented and used for the simulation of temperature field in the solidifying virtual static brass ingot. The developed method for the prediction of structural zones formation is applied to determine these zones in the solidifying brass static ingot. Some differences / similarities between structure formation during solidification of the steel static ingot and virtual brass static ingot are studied. The developed method allows to predict the following structural zones: fine columnar grains zone, (FC), columnar grains zone, (C), equiaxed grains zone, (E). The FCCT-transformation and CET-transformation are forecast as sharp transitions of the analyzed structures. Similarities between steel static ingot morphology and that predicted for the virtual brass static ingot are described.

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On the conditions for the occurrence of crystal avalanches during alloy solidification

Shayesteh,

Ludwig,

Stefan-Kharicha

et al. 2024

J. Phys.: Conf. Ser.

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Experimental studies on the solidification of ammonium-chloride-water alloys in relatively large containments reveal conditions that lead to the formation of numerous crystal avalanches. Columnar segments that occasionally slide downwards along a vertical mushy zone further fragmentate and so crystal multiplication occurs. As a condition for this phenomenon solidification-induced solutal buoyancy that leads to a rising interdendritic flow was identified for the present case. The interaction with sedimentation-induced downward flow ahead of a vertical columnar region results in a redirection of the interdendritic flow and thus, to local conditions that slow down further solidification or even lead to remelting. Gravity is then pulling loose segments downwards. In larger containment, the flow in the bulk melt is generally unsteady and even turbulent. Thus, the outlined flow-solidification/melting interplay happens frequently at numerous positions but in a stochastic manner.

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Large Steel Ingots: Microstructure Mathematical Modeling

Cited by 9 publications

References 65 publications

Massive Formation of Equiaxed Crystals by Avalanches of Mushy Zone Segments

Massive Formation of Equiaxed Crystals by Avalanches of Mushy Zone Segments

Some Similarities / Differences between Steel Static and Virtual Brass Static Casting

On the conditions for the occurrence of crystal avalanches during alloy solidification

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