Formation and suppression mechanism of lack of fusion in narrow gap laser-arc hybrid welding

  • Yunfei Meng
  • Geng Li
  • Ming GaoEmail author
  • Chen ZhangEmail author
  • Xiaoyan Zeng


In this study, the main defect, i.e., lack of fusion (LOF), occurring at the sidewalls in narrow gap laser-arc hybrid welding (NGHW) was confirmed to depend on the cross-sectional shape of previous pass, which was classified into four types, namely concave, convex, middle convex, and inclined shapes. Only the concave shape was effective in suppressing the LOF because the sharp corner between the weld and sidewalls could not be completely filled by next pass in the other three types. The effects of the welding parameters on the concave degree of weld cross-sectional shape were obtained from the dimensionless analysis related to the driving forces in the molten pool. It was found that the welding parameters, namely the arc current, welding speed, and groove width had a significant effect on the concave degree, whereas the laser power and laser-arc distance had no direct effect. A semi-quantitative criterion was proposed to predict the occurrence of the LOF. The LOF was suppressed when the ratio of the electromagnetic force to the liquid viscosity force was larger than 3.21 × 105, and the ratio of the surface tension gradient to the liquid viscosity force was larger than 1.28 × 104. The suppression mechanism of the LOF in NGHW was discussed in terms of the forces and melt flow in the molten pool.


Lack of fusion Narrow gap Hybrid welding Dimensionless number 


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Funding information

The study is financially supported by the National Natural Science Foundation of China (nos. 51475183, 51775206, 51605343 and 51429501).


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Copyright information

© Springer-Verlag London Ltd., part of Springer Nature 2018

Authors and Affiliations

  1. 1.Wuhan National Laboratory for OptoelectronicsHuazhong University of Science and TechnologyWuhanChina
  2. 2.The Institute of Technological SciencesWuhan UniversityWuhanChina

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