电子束环焊2 mm高纯铌熔池行为的数值模拟

Numerical Simulation of Molten Pool Behavior in Electron Beam Girth Welding of 2 mm Niobium Plate

基于VOF算法建立了2 mm厚的高纯铌电子束环焊过程的三维数学模型,在模型中考虑了金属蒸气反冲压力、表面张力、重力等关键熔池驱动力,计算出了环形熔池的温度场和流场对熔池中关键位置进行分析,并总结了纯铌环焊熔池的特点。模拟结果表明,在纯铌环形结构未熔透时,由于母材对熔池的支撑作用,匙孔波动情况与平焊类似;在环形结构焊透后,在Marangoni效应和重力的作用下,熔池表面液态金属加速扩展。此外,数值模拟与试验结果吻合良好,验证了数学模型的合理性。

Pure niobium girth weld seam is one of the commonest structures in the process of superconducting cavity fabrication.However,the circumferential molten pool behavior in electron beam welding(EBW)is seldom studied.A three-dimensional model,which was based on the VOF model,was established to study the dynamic behavior of circumferential molten pool in electron beam welding of 2 mm niobium plate.The influences of recoil pressure,surface tension and gravity were taken into account during the simulation process.The temperature field and flow field of the circumferential molten pool were calculated,the typical positions in the molten pool were analyzed,and the characteristics of the circumferential molten pool were summarized.During partial penetration EBW,the simulation results show that there is no obvious difference in keyhole evolution between flat welding and girth welding due to the supporting effect of the unfused base metal on the molten pool.After entering the full penetration stage,the tail of the molten pool extends rapidly under the influence of the Marangoni effect and gravity.In addition,the numerical result is in good agreement with the experimental data,which verifies the rationality of the mathematical model.