Thermal behavior and fluid flow during humping formation in high-speed full penetration gas tungsten arc welding
Thermal behavior and fluid flow during humping formation in high-speed full penetration gas tungsten arc welding
复制标题
高速全熔透钨极氩弧焊驼峰形成过程中的热行为和流体流动
DOI：
10.1016/j.ijthermalsci.2018.08.028
复制
发表时间：
2018-12
影响因子：
4.5
通讯作者：
Ran Zong
中科院分区：
文献类型：
--
作者：
Xiangmeng Meng;Guoliang Qin;Ran Zong
高速全熔透GTAW焊缝中可能会出现一种不常见的驼峰缺陷，即周期性驼峰区和穿孔区，严重影响焊缝性能的均匀性。在本文中，通过数值研究揭示了全穿透驼峰（FP-humping）形成过程中的热行为和流体流动，以解释缺陷的物理机制。提出了随瞬态自由表面演化而变化的电弧热通量、电弧压力、电弧剪应力和电磁力的自适应双椭圆分布。首次可以对 GTAW 中 FP 驼峰的实际形态进行数值预测。实验焊缝几何形状和彩色相机捕获的高速熔池图像很好地验证了数值结果。工件在电弧热作用下熔化形成熔池，其自由表面在强电弧力作用下被明显刨削。当气刨区域的深度接近工件厚度时，气刨区域的底部薄液层很容易被破坏，从而开始形成FP驼峰。侧通道成为液态金属倒流的唯一传递通道。侧流道与熔池后部之间的过渡区域将被颈缩，并且在没有电弧热的情况下立即凝固。热传导尺度模型和数值结果都表明颈缩横向通道的过早凝固是影响FP-驼峰形成的主要因素。
An unusual type of humping defect with periodic humped region and perforated region may occur in high-speed full penetration GTAW, which deteriorates the homogeneity of weld property seriously. In this paper, the thermal behavior and fluid flow during full penetration humping (FP-humping) formation is revealed by a numerical investigation to explain the defect's physical mechanism. Self-adaptive double-ellipse distributions of arc heat flux, arc pressure, arc shear stress and electromagnetic force varying with transient free surface evolution are proposed. For the first time, the actual morphology of FP-humping in GTAW can be predicted numerically. The numerical results are well verified by experimental weld geometry and high-speed melt pool images captured by a color camera. The workpiece is melted under arc heat to form the melt pool, and its free surface is gouged significantly under strong arc forces. When the depth of gouging region approaches workpiece thickness, the bottom thin liquid layer in gouging region is easily disrupted to initiate FP-humping formation. The lateral channel becomes the only transfer channel for liquid metal backward flow. The transition region between lateral channel and rear part of melt pool will be necked, and solidified instantly without the arc heat. Both scaling model of thermal conduction and numerical results imply that the premature solidification of necked lateral channel is a predominant factor to influence the FP-humping formation.
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