Experimental investigation on the weld pool formation process in plasma keyhole arc welding
Experimental investigation on the weld pool formation process in plasma keyhole arc welding
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DOI：
10.1088/1361-6463/aa9902
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发表时间：
2018-01
期刊：
影响因子：
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通讯作者：
Nguyen Van Anh;S. Tashiro;Bui Van Hanh;Manabu Tanaka
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文献类型：
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作者：
Nguyen Van Anh;S. Tashiro;Bui Van Hanh;Manabu Tanaka
本文旨在阐明等离子锁孔弧焊（PKAW）熔池的形成过程。本文首次采用两套x射线透射系统对钨示踪粒子进行立体同步成像，测量了PKAW焊池内的三维对流。利用氧化锆示踪粒子对熔池表面的二维对流进行了测量。通过这些测量，成功地可视化了从锁眼附近到后方的大范围焊接池中的对流。为了探讨熔池内的热传递过程，采用双色热分析法对熔池表面的二维温度分布进行了测量。综合实验测量结果表明，等离子体流动产生的剪切力是PKAW焊池形成过程中的主要驱动力。因此，焊接熔池中的热传递被认为是由靠近锁孔的两个大对流模式控制的：(1)表面上的涡流对（垂直于火炬轴），以及(2)焊接熔池主体上的涡流对（在火炬平面上）。它们以约0.35 m s−1的等速形成，主要由剪切力驱动。此外，由于等离子体流动速度较大，熔池对流的流动速度明显高于其他焊接工艺，如TIG焊和GMA焊。
This paper seeks to clarify the weld pool formation process in plasma keyhole arc welding (PKAW). We adopted, for the first time, the measurement of the 3D convection inside the weld pool in PKAW by stereo synchronous imaging of tungsten tracer particles using two sets of x-ray transmission systems. The 2D convection on the weld pool surface was also measured using zirconia tracer particles. Through these measurements, the convection in a wide range of weld pools from the vicinity of the keyhole to the rear region was successfully visualized. In order to discuss the heat transport process in a weld pool, the 2D temperature distribution on the weld pool surface was also measured by two-color pyrometry. The results of the comprehensive experimental measurement indicate that the shear force due to plasma flow is found to be the dominant driving force in the weld pool formation process in PKAW. Thus, heat transport in a weld pool is considered to be governed by two large convective patterns near the keyhole: (1) eddy pairs on the surface (perpendicular to the torch axis), and (2) eddy pairs on the bulk of the weld pool (on the plane of the torch). They are formed with an equal velocity of approximately 0.35 m s−1 and are mainly driven by shear force. Furthermore, the flow velocity of the weld pool convection becomes considerably higher than that of other welding processes, such as TIG welding and GMA welding, due to larger plasma flow velocity.