Zhang Hengquan, Jiang Meng, Chen Xi, Wei Lianfeng, Wang Shizhong, Jiang Yumo, Jiang Nan, Wang Zhiyuan, Lei Zhenglong, Chen Yanbin
Nuclear Power Institute of China, Chengdu 610213, China.
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China.
Materials (Basel). 2022 Jan 30;15(3):1095. doi: 10.3390/ma15031095.
The currently available high-power laser shows promising opportunities for the welding of thick plates in a single pass. However, weld-root defect frequently occurs when a high-power laser is used to join thick plates in a full-penetration mode, which has a significantly adverse effect on the serviceability of the weld joint. The purpose of this work is to understand the defect formation mechanism and reduce these defects through controlling welding parameters. In this study, the characteristics of weld root defects were investigated using a 10 kW fiber laser using a program of experiment and theoretical analysis. The corresponding defect formation mechanisms were discussed based on the bottom molten pool behaviors observed by the high-speed camera. The results showed that there were four types of weld-root appearances as follows with an increase of linear heat input from 300 J/mm to 1000 J/mm: weld-root humping (30 mm/s), sound weld (25 mm/s), weld sagging (20 mm/s) and excessive weld sagging. The remedies for reducing weld-root defects were also presented to obtain sound weld bead by optimizing welding parameters. Weld-root humping was formed due to the quasi-full-penetration keyhole. Weld sagging resulted from the imbalance of the hydrostatic pressure and surface tension in the condition of a through keyhole. It was also found that the sound weld was formed when a through keyhole and a proper molten pool size were obtained. Thus, the state of the keyhole and molten pool geometry were the major factors that affect weld-root defects.
目前可用的高功率激光为厚板单道焊接带来了广阔的前景。然而，当使用高功率激光以全熔透模式焊接厚板时，焊缝根部缺陷频繁出现，这对焊接接头的使用性能产生了显著的不利影响。这项工作的目的是了解缺陷形成机制，并通过控制焊接参数来减少这些缺陷。在本研究中，使用10千瓦光纤激光器，通过实验和理论分析程序，研究了焊缝根部缺陷的特征。基于高速摄像机观察到的底部熔池行为，讨论了相应的缺陷形成机制。结果表明，随着线能量从300焦/毫米增加到1000焦/毫米，焊缝根部出现了以下四种类型：焊缝根部隆起（30毫米/秒）、良好焊缝（25毫米/秒）、焊缝下垂（20毫米/秒）和过度焊缝下垂。还提出了减少焊缝根部缺陷的补救措施，通过优化焊接参数来获得良好的焊缝。焊缝根部隆起是由准全熔透小孔形成的。焊缝下垂是由于在贯穿小孔的情况下静水压和表面张力的不平衡导致的。还发现，当获得贯穿小孔和适当的熔池尺寸时，会形成良好的焊缝。因此，小孔状态和熔池几何形状是影响焊缝根部缺陷的主要因素。
