The stochastic modeling of solidification structures in alloy 718 remelt ingots

Droplet formation and departure from an electrode tip affect the temperature distribution in liquid slag and a molten steel pool, as well as the removal of nonmetallic inclusions in the electroslag remelting process. In this article, magneto-hydrodynamics modules coupled with a volume of fluid (VOF) model (as described in VOF model theory) for tracking phase distribution have been employed to develop the electrode fusion model and to investigate formation and departure of a droplet from the electrode tip. Subsequently, the remelting rate and molten steel pool have been achieved based on the electrode fusion model. Results indicate that a droplet can increase the flow rate of liquid slag, especially the region of droplet fall through the slag pool; yet it has little impact on the flow distribution. Asymmetric flow can take place in a slag pool due to the action of the droplet. The depth of the molten steel pool increases in the presence of droplets, but the width of the mushy zone decreases. In addition, the shape of the electrode tip is not constant but changes with its fusion. The remelting rate is calculated instead of being imposed in this work. The development of the model supports further understanding of the process and the ability to set the appropriate operating parameters, especially for expensive and easy segregation materials.

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“…[14,[27][28][29][30][31][32] Heat flux at the lateral surface of the ingot n can be achieved by the following equation:…”

Section: Molten Steel Pool Model Boundary Conditionsmentioning

confidence: 99%

Comprehensive Mathematical Model for Simulating Electroslag Remelting

Dong

Fan

Cao

et al. 2016

Metall Mater Trans B

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“…This columnar-to-equiaxed transition (CET) well agreed with a mathematical model which predicted the CET by a critical-temperature-gradient criterion (i.e., a temperature-gradient value below which equiaxed nuclei may form). [39] Additionally, as shown in Figure 4(a), the equiaxed grains seldom nucleated in the vicinity of the ingot surface compared with the central area. The reasons were twofold: the rim of the molten pool owned a stepper temperature gradient and was less sensitive to the reduction of heat supply.…”

Section: A Formation Of the Ingot Structurementioning

confidence: 88%

“…[36] Despite the fact that ESR process has been widely used in industrial manufacturing and scientific researching, the details of the remelting conditions are still unclear due to the complexity of the remelting system itself and the difficulties in observing or measuring an ongoing remelting process directly. Enormous mathematical models, therefore, were established to depict and predict the remelting and solidification in terms of the fluid flow, heat transfer, mass transfer, [37] slag/melt interface, [38] columnar-to-equiaxed transition (CET), [39] and so forth.…”

Section: Introductionmentioning

confidence: 99%

Structure, Microsegregation, and Precipitates of an Alloy 690 ESR Ingot in Industrial Scale

Wang

Zha

Gao

et al. 2015

Metall Mater Trans A

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The structure, interdendritic, and intergranular segregation, and precipitates of an Alloy 690 electro-slag remelting (ESR) ingot in commercial scale (3t) were investigated by the optical microscopy, electroprobe microanalysis, scanning electron microscopy, and transmission electron microscopy (TEM) techniques. The results indicate that the central longitudinal section of the ESR ingot comprised the ramp-up, steady-state, and hot-top regions, which could be easily distinguished from each other through the macrostructures of them. In the interdendritic area, Cr and Ti were enriched, while Ni and Fe were depleted, and the nominal segregation indexes (f i = C 0 i /C interdendritic i ) of Ti, Cr, and Ni were 0.40, 0.91, and 1.04, respectively, in the hot-top region where suffered the severest segregation. Nitrides, principally precipitated between dendrites, were identified as TiN by TEM and EDS. The morphology, size distribution, and volume fraction of them were determined as well. In terms of the intergranular area, Cr and C coexisted, while Ni and Fe were depleted. And the dendrite-like carbides continuously distributed on the interface between grains, which were identified as M 23 C 6 by the selected area diffraction pattern.

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“…The detailed physical properties, geometry, and operating conditions are listed in Table I. [24,25,33,34] …”

Section: Fluid Flowmentioning

confidence: 99%

A General Coupled Mathematical Model of Electromagnetic Phenomena, Two-Phase Flow, and Heat Transfer in Electroslag Remelting Process Including Conducting in the Mold

Wang

et al. 2014

Metall Mater Trans B

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A transient three-dimensional finite-volume mathematical model has been developed to investigate the coupled physical fields in the electroslag remelting (ESR) process. Through equations solved by the electrical potential method, the electric current, electromagnetic force (EMF), and Joule heating fields are demonstrated. The mold is assumed to be conductive rather than insulated. The volume of fluid approach is implemented for the two-phase flow. Moreover, the EMF and Joule heating, which are the source terms of the momentum and energy sources, are recalculated at each iteration as a function of the phase distribution. The solidification is modeled by an enthalpy-porosity formulation, in which the mushy zone is treated as a porous medium with porosity equal to the liquid fraction. An innovative marking method of the metal pool profile is proposed in the experiment. The effect of the applied current on the ESR process is understood by the model. Good agreement is obtained between the experiment and calculation. The electric current flows to the mold lateral wall especially in the slag layer. A large amount of Joule heating around the metal droplet varies as it falls. The hottest region appears under the outer radius of the electrode tip, close to the slag/metal interface instead of the electrode tip. The metal pool becomes deeper with more power. The maximal temperature increases from 1951 K to 2015 K (1678°C to 1742°C), and the maximum metal pool depth increases from 34.0 to 59.5 mm with the applied current ranging from 1000 to 2000 A.

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The stochastic modeling of solidification structures in alloy 718 remelt ingots

Cited by 35 publications

References 16 publications

Comprehensive Mathematical Model for Simulating Electroslag Remelting

Comprehensive Mathematical Model for Simulating Electroslag Remelting

Structure, Microsegregation, and Precipitates of an Alloy 690 ESR Ingot in Industrial Scale

A General Coupled Mathematical Model of Electromagnetic Phenomena, Two-Phase Flow, and Heat Transfer in Electroslag Remelting Process Including Conducting in the Mold

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