真空自耗电弧熔炼过程中搅拌线圈参数对TC17铸锭成分和组织影响的数值模拟与实验验证

Numerical Simulation and Experimental Validation on the Effect of Stirring Coils' Parameters on TC17 Ingot During Vacuum Arc Remelting Process

摘要:

采用MeltFlow VAR软件建立了真空自耗电弧熔炼（VAR）过程中温度、电磁、流动和溶质场的耦合模型，通过数值模拟与实验验证的方法研究了搅拌电流和周期对TC17钛合金铸锭成分和组织的影响规律。结果表明，铸锭中心的Cr元素浓度从底部逐渐升高，在铸锭头部100 mm范围内出现激增，与铸锭边缘和1/2半径处表现出不同的趋势。施加搅拌磁场，有利于铸锭心部Cr元素的降低和1/2直径处等轴晶区域宽度的减小。增加搅拌线圈电流或延长搅拌磁场的周期，可以降低铸锭心部Cr元素含量并减小1/2直径处等轴晶区域宽度。这主要是因为搅拌磁场引起的角速度，加剧了熔池内湍流的速度。采用工程化规格的TC17铸锭实物解剖可知，铸锭下部柱状晶生长方向发生扰动的位置与Cr含量上升的位置相对应，均与该位置搅拌磁场的作用相关。数值模拟结果与实验数据吻合较好。

Abstract:

To reduce the risk of β-flecks, the impact of stirring coils' parameters on ingot composition and grain structure was evaluated in TC17 alloys. A model coupling the temperature, electromagnetic, fluid flow, and the solute field was established using MeltFlow vacuum arc remelting (VAR) software. The results show that Cr concentration at the centre increases gradually from the bottom and then increases sharply within 100 mm to the ingot top, showing unlike tendency compared with locations at the edge and 1/2 diameter of the ingot. The increase in either the stirring coil current or reversal time is beneficial to the decrease in Cr content and the width of equiaxed crystal at the ingot centre, due to the accelerated turbulent velocity, which causes additional mixing within the molten pool. From the macromorphology observations of TC17 ingot, at near half of the lower part of the ingot, the location where the disturbance occurs in the direction of columnar crystal growth is corresponding to the position where Cr content increases, both of which have a relationship with stirring coil parameters. The simulation results fit the experimental data well.