基于电弧-熔池耦合的小孔型等离子弧焊接简化模型

Simplified Keyhole Plasma Arc Welding Model Based on the Coupling of Arc and Weld Pool

基于电场、磁场、温度场和流场的多物理作用,建立电弧与熔池耦合的等离子弧焊接模型,揭示小孔型模式的焊接熔池形成机制。计算结果表明电弧热流密度和压力均呈现高斯分布形式,并且压力作用范围比热作用范围小一半。发现焊接熔池形成过程具有明显的阶段性,前期增长较快,后期增速变缓,增速下降60%以上。等离子弧受到电磁力压缩作用,能量密度集中,电弧区的电磁力比熔池区高2个数量级。受电弧压力和Marangoni力、曳力等共同作用,熔池底部和顶部边缘分别出现对称分布的环流,熔池横截面逐渐形成"倒喇叭"状的焊缝。进行焊接试验,计算的焊缝熔合线和电弧压力均与试验结果吻合良好。模型能够简便快捷地为等离子弧焊接工程应用提供指导。

Based on the multi-physical interaction of electric field, magnetic field, temperature field and flow field, a plasma arc welding(PAW) model coupling both the arc and weld pool is established to reflect the weld pool formation mechanism in the keyhole mode welding. Calculated results show that arc heat flux and arc pressure both appear in a Gaussian distribution, while the pressure striking area is less than the arc heating area. The former is nearly just half of the latter. Weld pool grows in two different stages where it increases fast in the initial stage, but the growth rate drops by over 60% in the second stage. The plasma arc is compressed by electromagnetic force, and the energy density is concentrated. The electromagnetic force in the arc zone is two orders of magnitude higher than that in the weld pool. With the combined effect of arc pressure, Marangoni force and drag force, two symmetrical circular flows appear at the bottom and on the top edge of the weld pool, respectively. And the weld pool gradually turns into a "reversed bugle-like" shape. Experiment is conducted, and the calculated weld fusion line and arc pressure both agree well with experimental results. It’s simple and convenient to use the model to guide the PAW engineering application.