Simulation of Columnar Crystal Growth in Forced Flow of VAR Based on Phase Field Method

doi:10.20057/j.1003-8620.2024-00078

Abstract

Abstract: A fully coupled flow heat mass model was established based on the phase field method to simulate the growth of columnar crystals in ingots during vacuum arc remelting （VAR） in a forced flow field. The influence mechanism of melt flow on the growth of columnar crystals was analyzed by comparing the growth characteristics of columnar crystals with and without flow field conditions.The simulation results indicated that when the velocity of flow field in the solidification front is 45 μm/s and the direction is perpendicular to the direction of dendrite growth， the secondary dendrites exhibit ‘counter-flow’ growth， and the dendrite trunks tilt downstream due to erosion. A small eddy current is formed between adjacent dendrites， and the solutes and the heat in the upstream of the dendrite trunks are carried into the downstream side with the melt. The boundary layer thickness of the solute and the temperature on the upstream side decreases， from 51 μm in the absence of a flow field to 31.5 μm. The large temperature gradient promotes the development of secondary dendrites. The concentration of solutes and heat in the downstream boundary layer is high， and the boundary layer thickness increases to 78 μm. The decrease in gradient significantly inhibits the development of secondary dendrites. The downstream solute concentration is higher than that in the absence of a flow field， and the slow growth of dendrites increases the risk of micro-segregation.

Key words: Vacuum Arc Remelting, Phase Field, Columnar Crystal Growth, Forced Flow Field, Solute Field, Temperature Field

摘要： 基于相场法建立了流-热-质全耦合模型，模拟了真空自耗电弧重熔（VAR）过程铸锭柱状晶在强制流场中的生长。对比柱状晶在有无流场条件下的生长特征解析熔体流动对柱状晶生长的影响机制。模拟结果表明：凝固前沿流场速度大小为45 μm/s，方向与枝晶生长方向垂直时，二次枝晶表现出“迎流”生长，枝晶干受冲刷作用向下游倾斜；相邻枝晶形成细小涡流，枝晶干上游侧溶质和热量随熔体带入下游侧，上游侧溶质和温度边界层厚度减小，由无流场时的51 μm降至31.5 μm，温度梯度大促进二次枝晶发展；下游侧边界层溶质和热量富集程度大，边界层厚度增至78 μm，梯度减小明显抑制二次枝晶发展。下游溶质浓度高于无流场情况，枝晶生长缓慢增大微观偏析风险。

关键词: 真空自耗重熔, 相场法, 柱状晶生长, 强制流场, 溶质场, 温度场

CLC Number:

TF132

Zhou　Yang, Zhu　Hongchun, Li　Huabing, Jiang　Zhouhua, He　Zhiyu, Ni　Zhuowen. Simulation of Columnar Crystal Growth in Forced Flow of VAR Based on Phase Field Method[J]. Special Steel, 2024, 45(4): 41-46.

周杨, 朱红春, 李花兵, 姜周华, 何志禹, 倪卓文. 基于相场法模拟VAR强迫流场中柱状晶生长[J]. 特殊钢, 2024, 45(4): 41-46.

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