Numerical simulation of TIG arc characteristics of hollow tungsten electrode
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摘要: 建立了内径2 mm的空心钨极TIG焊电弧数值模型,用Fluent软件用户自定义函数(UDF)功能加载了氩气电导率、动量方程和能量方程的源项,计算了稳态下焊接电流为60 A时电弧的温度场、流场以及电弧压力,并与相同条件下实心钨极TIG焊电弧作了对比. 结果表明,空心钨极TIG焊电弧呈钟罩形,空心钨极圆环放电和钨极中心气流的冷却作用使得电弧温度分布云图顶部下凹;电弧等离子体在钨极下方运动速度较快,阳极表面电弧压力呈柱状分布,弧柱区空间压力分布比较均匀;与相同电流条件下TIG焊相比,空心钨极TIG焊电弧峰值温度降低17.3%,钨极下方2 mm位置处峰值温度降低27%,等离子体最大运动速度降低40%,电弧压力峰值降低57%,堆焊焊缝熔宽增加30%,熔深减小27.9%.Abstract: The numerical model of hollow tungsten TIG welding with inner diameter of 2 mm is developed. The source terms of momentum equation and energy equation and the conductivity of argon gas are loaded by the user defined function (UDF) of Fluent software. The temperature field, flow field and arc pressure are calculated when the welding current is 60 A in steady state. The results are compared with those of solid tungsten TIG arc under the same conditions. The results show that the shape of hollow tungsten TIG arc is bell jar shape, and the temperature field is concave at the top middle position due to the air flow and current density. The velocity of plasma below the tungsten pole is faster than other regions. The arc pressure is uniformly distributed, and the anode surface pressure is uniformly distributed in cylindrical shape. Compare with TIG welding under the same current condition, the maximum temperature, maximum plasma flow velocity and peak arc pressure of the hollow tungsten arc are reduced by 17.3%, 40% and 57%, respectively, and the peak temperature of the 2 mm cross section below the tungsten electrode is reduced by 27%. The weld width of surfacing welding increases by 30% but the weld depth decreases by 27.9%.
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表 1 空心钨极TIG焊电弧模型边界条件
Table 1 Boundary condition of hollow tungsten TIG welding arc model
区域 边界类型 氩气流速v1/(m·s−1) 温度T/K 电势φ/V 磁矢量A/Wb AB 轴 — — — — BC 壁面 0 5 000 0 $\partial A{\rm{/}}\partial {\rm{}}z = \partial A{\rm{/}}\partial r{\rm{ = 0}}$ CD 压力出口 — 1 000 $\partial \varphi {\rm{/}}\partial {\rm{}}z = \partial \varphi {\rm{/}}\partial r{\rm{ = 0}}$ 0 DE 速度进口 1.2 1 000 $\partial \varphi {\rm{/}}\partial {\rm{}}z = \partial \varphi {\rm{/}}\partial r{\rm{ = 0}}$ $\partial A{\rm{/}}\partial {\rm{}}z = \partial A{\rm{/}}\partial r{\rm{ = 0}}$ EF 壁面 0 1 000 $\partial \varphi {\rm{/}}\partial {\rm{}}z = \partial \varphi {\rm{/}}\partial r{\rm{ = 0}}$ $\partial A{\rm{/}}\partial {\rm{}}z = \partial A{\rm{/}}\partial r{\rm{ = 0}}$ FG 壁面 0 3 000 $ - \sigma \cdot \partial \varphi {\rm{/}}\partial {\rm{}}z = I/{{{S}}_{\rm{c}}}$ $\partial A{\rm{/}}\partial {\rm{}}z = \partial A{\rm{/}}\partial r{\rm{ = 0}}$ GH 壁面 0 1 000 $\partial \varphi {\rm{/}}\partial {\rm{}}z = \partial \varphi {\rm{/}}\partial r{\rm{ = 0}}$ $\partial A{\rm{/}}\partial {\rm{}}z = \partial A{\rm{/}}\partial r{\rm{ = 0}}$ HA 速度进口 1.2 1 000 $\partial \varphi {\rm{/}}\partial {\rm{}}z = \partial \varphi {\rm{/}}\partial r{\rm{ = 0}}$ $\partial A{\rm{/}}\partial {\rm{}}z = \partial A{\rm{/}}\partial r{\rm{ = 0}}$ 表 2 焊接试验工艺参数
Table 2 Process parameters of welding test
焊接电流
I/A电弧电压
U/V焊接速度
v/(mm·min−1)气体流量
Qo/(L·min−1)弧长
l/mm60 15.9 300 10 4 -
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