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金属学报  2016, Vol. 52 Issue (11): 1467-1476    DOI: 10.11900/0412.1961.2016.00008
  本期目录 | 过刊浏览 |
e蒸气对等离子弧焊接熔池行为的影响*
菅晓霞1,2,武传松1()
1 山东大学材料液固结构演变与加工教育部重点实验室, 济南 250061
2 河南工业大学机电工程学院, 郑州 450001
INFLUENCE OF Fe VAPOUR ON WELD POOL BEHAVIOR OF PLASMA ARC WELDING
Xiaoxia JIAN1,2,Chuansong WU1()
1) Key Laboratory for Liquid-Solid Structural Evolution and Materials Processing (Ministry of Education), Shandong University, Jinan 250061, China
2) School of Mechanic & Electrical Engineering, Henan University of Technology, Zhengzhou 450001, China;;
引用本文:

菅晓霞,武传松. e蒸气对等离子弧焊接熔池行为的影响*[J]. 金属学报, 2016, 52(11): 1467-1476.
Xiaoxia JIAN, Chuansong WU. INFLUENCE OF Fe VAPOUR ON WELD POOL BEHAVIOR OF PLASMA ARC WELDING[J]. Acta Metall Sin, 2016, 52(11): 1467-1476.

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摘要: 

建立了包含Fe蒸气影响的等离子弧焊接一体化模型, 其计算区域包含W极、等离子弧、熔池和小孔, 通过在整个区域使用统一的控制方程实现各区域的自适应耦合. 使用黏性近似法处理Fe蒸气的扩散系数. 模拟了焊接电流分别为150, 170和190A时, 3种工艺条件下的穿孔过程中, Fe蒸气在阳极液态金属表面的产生、扩散及其在等离子弧中的聚集过程. 对比分析了Fe蒸气对等离子弧的温度场、电场和熔池形态的实时影响. 结果表明, Fe蒸气的产生决定于液态熔池温度分布. 在等离子流力的作用下, Fe蒸气聚集在等离子弧的边缘区域, 导致该区域的辐射损失增加、电流密度降低. 而弧柱中心区域受Fe蒸气的影响较小. 与不考虑Fe蒸气影响的等离子弧焊接模型相比, 考虑Fe蒸气影响时计算出的焊缝尺寸与实验测试值更接近.

关键词 等离子弧焊接,Fe蒸气,熔池,小孔,等离子弧,数值分析    
Abstract

Plasma arc welding (PAW) is an important joining technology for plates with medium thickness because of the heat source characteristics, however, most models of PAW neglect the vaporization of metal. An axisymmetrical unified PAW model was developed by taking into account the influence of Fe vapor behavior from the molten pool surface as an anode in this work. The simulation region includes tungsten cathode, plasma arc, weld pool, keyhole and their self-consistence coupling using one set conservation equations. A viscosity approximation is used to express the diffusion coefficient in terms of the viscosities of iron vapor. The main physical properties of Ar plasma are set as function of temperature and mass fraction of Fe vapor and are updated every iterate step to reflect the influence of Fe vapor in real time. The process of keyhole formation in stationary plasma arc welding is simulated under welding currents of 150, 170 and 190 A. The transient production, diffusion and concentration in the plasma arc of Fe vapor were presented. The effects of Fe vapor on the plasma arc behavior and formation of weld pool and keyhole are studied. It was shown that the evaporation rate of Fe was greatly dependent on the temperature of the weld pool. Most Fe evaporates from the top part of the keyhole surface and little from the keyhole bottom. The diffusion of Fe vapor is accelerated in the radial direction and is prevented in the axial direction due to the effect of plasma jets flow and at last it tends to be confined to the fringe of the plasma arc closed to the anode. The mixing of Fe vapor in the plasma results in the increase of radiation losses and the decrease of current density of the arc plasma in the fringe, but it had insignificant influence on the arc center. The heat flux from the plasma arc to the anode is also affected by Fe vapor due to its influence on the plasma arc properties. It is found that the calculation result of the width of the molten pool becomes more accurate to consider the effect of Fe vapor.

Key wordsplasma    arc    welding,    Fe    vapor,    weld    pool,    keyhole,    plasma    arc,    numerical    simulation
收稿日期: 2016-01-06     
基金资助:* 国家自然科学基金资助项目50936003
图1  PAW数值模型计算区域示意图
Boundary Vz / (ms-1) Vr / (ms-1) T / K ?/ V Ar / (Tm) Az / (Tm)
ABC ?vz?n=0 ?vr?n=0 ?T?n=0 ???n=0 ?Ar?n=0 ?Az?n=0
CP - - k?T-εαT4 0 ?Ar?n=0 ?Az?n=0
PQ - - k?T-εαT4 ???n=0 ?Ar?n=0 ?Az?n=0
QD - - 1000 ???n=0 0 0
DF Constant 0 1000 ???n=0 ?Ar?n=0 ?Az?n=0
FEGH - - k?T ???n=0 ?Ar?n=0 ?Az?n=0
HI Constant 0 1000 ???n=0 ?Ar?n=0 ?Az?n=0
IK - - 1000 ???n=0 ?Ar?n=0 ?Az?n=0
KA - - 3000 j ?Ar?n=0 ?Az?n=0
表1  等离子弧焊接模型的外部边界条件
Nomenclature Value Unit
Freezing point 1670 K
Melting point 1727 K
Density 7200 kgm-3
Electric conductivity 7.7×105 Sm-1
Surface tension 1.2 Nm-1
coefficient
Surface tension 1×10-4 Nm-1K-1
temperature gradient
Work function 4.65 V
表2  SUS 304主要物性参数
图2  170 A焊接电流下熔池上方最大Fe蒸气质量分数与熔池表面最高温度的关系
图3  熔池上方Fe蒸气最大质量分数随焊接时间的变化
图4  焊接电流为150 A时不同时刻的工件温度、Fe蒸气质量分数和等离子弧的温度场及流场分布
图5  焊接电流为170 A时不同时刻的工件温度、Fe蒸气质量分数和等离子弧的温度场及流场分布
图6  焊接电流为190 A时不同时刻的工件温度、Fe蒸气质量分数和等离子弧的温度场及流场分布
图7  焊接电流为190 A时穿孔时刻Fe蒸气对工件上方1 mm (z=0.005 m) 截面上辐射损失的影响
图8  焊接电流为190 A时Fe蒸气对等离子弧电流密度的影响
图9  穿孔时刻熔池表面温度
Welding Width of topside weld pool / mm Width of backside weld pool / mm
current / A Calculation Calculation Experiment Calculation
without vapor
Calculation
with vapor
Experiment
without vapor with vapor
150 13.1 11.2 9.6 2.1 2.3 3.0
170 14.1 11.9 9.9 2.6 2.5 3.1
190 14.3 11.8 10.3 2.9 2.8 3.2
表3  焊缝熔宽计算与实测结果的对比
图10  焊接电流为190 A时穿孔时刻工件表面电子传热及总热流密度
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