Numerical modeling on the formation process of keyhole-induced porosity for laser welding steel with T-joint
Numerical modeling on the formation process of keyhole-induced porosity for laser welding steel with T-joint
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DOI：
10.1007/s00170-014-5609-x
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
Xibin Li;F. Lu;H. Cui;Xinhua Tang;Yixiong Wu
中科院分区：
文献类型：
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作者：
Xibin Li;F. Lu;H. Cui;Xinhua Tang;Yixiong Wu
建立了T型接头激光焊接气孔形成的数学模型，研究了小孔气孔的形成过程，有助于理解大截面激光焊接气孔的形成机理。该模型耦合了凝固模型和绝热气泡模型，能更近似地反映气泡的形成及其向孔隙演化的过程。采用VOF方法跟踪小孔和孔隙的自由表面。数值结果表明，激光焊接过程中小孔的不稳定性导致小孔塌陷，导致熔池中产生气泡。这些气泡在熔池中随流体流动而运动，在流动和凝固速度的竞争下，部分气泡会逸出熔池。但在熔池中迁移过程中，一些气泡被凝固壁捕获，会演变成气孔。研究还发现，在熔合线附近形成的气泡更容易被凝固表面捕获，这也解释了熔合线附近出现气孔的原因。模拟结果与实验结果吻合较好，证明了该数学模型的可靠性，同时也较好地阐明了孔隙形成的机理。
A mathematical model of laser welding steel with a T-joint was developed in this paper to investigate the formation process of keyhole-induced porosity, helping to understand the mechanism of porosity formation in laser welding steels with heavy section. Solidification model and adiabatic bubble model were coupled in this model, which could more approximately reflect the formation process of bubble and its evolution into porosity. The volume-of-fluid (VOF) method was taken to track free surfaces of keyhole and porosity. The numerical results showed that the unstable keyhole during the laser welding process induced the collapse of keyhole and then resulted in bubbles in the molten pool. These bubbles moved following with the fluid flow in the molten pool, where some bubbles could escape out of molten pool under the competition of flow and solidification speed. But some bubbles captured by a solidified wall during the migration process in the molten pool would evolve into porosities. It was also found that some bubbles formed adjacent to a fusion line were easier to be captured by a solidification surface, which could give explanation for some porosities occurring close to the fusion line. A good agreement of simulation and experimental results proved the reliability of this mathematical model, while the mechanism of porosity formation was better clarified with this model.