电子束冷床炉熔炼Ti-6Al-4V合金过程中流动、传热和挥发计算

Calculation of flow, heat transfer and evaporation during the electron beam cold hearth melting of Ti-6Al-4V alloy

摘要:

电子束冷床炉熔炼技术是生产航空发动机关键旋转部件用钛合金及钛屑回收利用的一项很有前景的技术。本文研究了Ti-6Al-4V合金在电子束冷床炉熔炼过程中冷床部分熔体的传热、流动和凝固过程。结果表明，冷床部分的熔体被限制在一个非常浅的深度，实验测量约为15mm，熔体速度大约是几厘米每秒。熔体温度随着熔炼功率增加而升高，随着熔炼速率增加而降低。熔池深度随着熔炼功率升高而增加，而熔炼速率对熔池形貌的影响不明显。模拟了不同密度、不同尺寸夹杂物的运动轨迹。结果表明夹杂密度对轨迹影响较大。建立了元素挥发的数学模型，并研究了熔炼工艺参数对铸锭成分的影响。结果表明熔炼温度、熔炼速率和原料配比对铸锭成分均有较大影响。采用工业用电子束冷床炉生产了圆锭，测量了冷床凝壳的形貌并检测了铸锭成分。计算结果与实验结果吻合较好。

Abstract:

Electron beam cold hearth melting (EBCHM) is a promising technique for achieving premium titanium alloys for critical rotating parts of the aero-engine and to recycle the titanium scraps. This article studied the heat transfer, the fluid flow and solidification in the cold hearth during EBCHM process of Ti-6Al-4V alloy. The results show that the melt is constrained to a very shallow depth which is 15mm in our experiment and the melt velocity is about a few centimeters per second. The melt temperature increases with the increase of melting power and decreases with the increase of melting rate. The melt depth increases with the increase of melting power, while the effect of melting rate on the shape of melt pool isn’t obvious. The trajectories of inclusions with different densities and sizes were simulated. The density has great influence on the trajectories of particles. The evaporation model was established to study the influence of melting parameters on the ingot composition. The results indicate that melting temperature, melting rate and composition of row materials have great influence on the ingot composition. Round ingots were produced using the commercial EBCHM furnace in the factory. The morphology of the shell was investigated and the ingot composition was tested. The calculating results are in good agreement with experiment.