Simulation of Solidification Structure During Vacuum Arc Remelting Using Cellular Automaton−Finite Element Method

Abstract

Vacuum arc remelting (VAR) is a secondary melting process for production of metal ingots. [1] In the vacuum condition, the alloy ingot as an electrode was melted by the electric arc and then molten drops fell into the mold. The VAR process was extensively utilized to improve the cleanliness, chemical homogeneity, and mechanical property of metal ingots. [2,3] However, improper melting parameters may result in metallurgical defects, such as macrosegregation, porosities, and beta flecks. [4][5][6] Due to the high temperature of the smelting process, the experimental study was under restriction. The modeling study of the VAR process was used to obtain the optimal parameters for improving the quality of the ingot.Kondrashov et al. [7] developed a simple heat model of the VAR process neglecting the magnetohydrodynamic phenomena in the molten pool. The depth of the molten pool was predicted under different current intensities. Delzant et al. [1] established two models to calculate the thermal radiation of the ingot top during the VAR process. In the crude approach, only the radiative heat transfer between the ingot and the electrode tip was considered. In the detailed approach, all radiative exchanges between the ingot, electrode, and crucible wall were taken into account. Results of the detailed radiation model revealed that the radiative heat transfer of the ingot top was heavily dependent on the arc gap length and the electrode radius. Patel et al. [8] investigated the effect of processing parameters on molten pool profile, flow field, and segregation using a 2D mathematical VAR model. The molten pool profile was significantly affected by the magnetic field. The flow and overall segregation tendency increased with the increase in the magnetic field. Zagrebelnyy et al. [9] established a numerical model to study the segregation of the ingot during the VAR process. The strong flow field was induced by the high arc power resulting in severe macrosegregation. When the arc power was low, the flow was dominated by weaker buoyancy force, and less segregation was formed. Kou et al. [10] calculated the temperature field, fluid flow, and solidification structure of the Ti─6Al─4 V alloy ingot during the VAR process. When the heat radiation was considered, simulated columnar grains on the ingot top agreed well with the experimental results. Chapelle et al. [11] investigated the deformation of the free surface in the VAR process using CFD-based simulations. Two stirring modes were applied in the simulation. In the case of unidirectional stirring, the free surface was a concave dome shape. In the case of alternated stirring, periodic fluctuations of the liquid metal level were generated. Kermanpur et al. [12] established a multiscale

Simulation of Solidification Structure in the Vacuum Arc Remelting Process of Titanium Alloy TC4 Based on 3D CAFE Method

“…As shown in Figure 1, the basic feature of VAR is that the consumable electrode is continuously melted under vacuum conditions, and simultaneously, the ingot is continuously solidified and increased in the mold from the bottom to the top [6,7]. In addition to composition segregation, the ingot produced by vacuum arc remelting also has some defects, such as an uneven solidification structure and shrinkage holes, which are the main factors determining the quality of the ingot [8][9][10][11]. Therefore, in order to obtain ingots with good quality, it is of great significance to study the formation of the solidification structure of ingots by vacuum arc remelting.…”

Numerical simulation of cellular automaton in vacuum arc remelting during the solidification process

“…The results show that the microstructures predicted by the numerical method match the experimental results. Wang et al [13] established a 3D vacuum arc remelting model coupling heat transfer, fluid flow, solidification, nucleation, and grain growth is established. The effect of melting rate and current intensity on the solidification structure, depth of the molten pool, and equiaxed crystal rate is investigated by the simulation.…”

Modeling of the Nonuniform Microstructure and Microsegregation Formation of the Shell in Round Billet Continuous Casting

“…Detailed investigations of microsegragation and microstructure will contribute to the further comprehension and regulation of solidification processes. [10] With the development of the phase field (PF) method [11,12] and cellular automaton (CA) method, [13][14][15][16][17][18][19] the prediction of microstructure and quantitative analysis of microsegregation has become an important research tool in recent years. [7,8,10,20,21] Luo et al established a CA-finite difference (CA-FD) model for the simulation of solute diffusion-controlled solidification in continuous casting, and columnar growth and columnar to equiaxed transition were produced.…”