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<p>This study employs high-speed photography and numerical simulation to systematically investigate the heat source coupling, molten pool behavior, and undercut formation mechanism in laser–Tungsten Inert Gas (TIG) hybrid welding of Invar steel. The results show that the arc is stably attracted and deflected by the laser-induced vapor channel, thereby establishing synergistic coupling. When the laser power is increased from 5 to 6&#xa0;kW, the degree of arc deflection increases, the overall flow velocity of the molten pool is enhanced, edge filling improves, and undercut defects are suppressed. When the welding speed is increased from 0.7 to 1&#xa0;m/min, the heat source coupling effect weakens, lateral flow decreases, and the tendency for undercut formation increases. When the welding current is increased from 150 to 170 A, the arc diameter expands, the lateral spreading capability of the molten pool is significantly improved, and undercut defects are suppressed. From the perspective of fluid dynamics, this study elucidates that by adjusting process parameters, the heat source coupling can be optimized to synergistically enhance Marangoni convection, arc shear flow, and keyhole vortex flow. This enhancement increases the lateral mass transport capability of the molten pool, thereby effectively suppressing undercut defects. This study provides a theoretical basis for achieving high-quality welding of Invar steel.</p>

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Study on the molten pool characteristics of 4J36 Invar steel in laser-TIG hybrid welding

  • 期刊论文

  • 发表日期：

    2026年4月24日

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  • Sen Wu,
  • Fei Zhao,
  • Shuili Gong,
  • Lifeng Ma,
  • Haiyan Zhao,
  • Wei Zhang

摘要

This study employs high-speed photography and numerical simulation to systematically investigate the heat source coupling, molten pool behavior, and undercut formation mechanism in laser–Tungsten Inert Gas (TIG) hybrid welding of Invar steel. The results show that the arc is stably attracted and deflected by the laser-induced vapor channel, thereby establishing synergistic coupling. When the laser power is increased from 5 to 6 kW, the degree of arc deflection increases, the overall flow velocity of the molten pool is enhanced, edge filling improves, and undercut defects are suppressed. When the welding speed is increased from 0.7 to 1 m/min, the heat source coupling effect weakens, lateral flow decreases, and the tendency for undercut formation increases. When the welding current is increased from 150 to 170 A, the arc diameter expands, the lateral spreading capability of the molten pool is significantly improved, and undercut defects are suppressed. From the perspective of fluid dynamics, this study elucidates that by adjusting process parameters, the heat source coupling can be optimized to synergistically enhance Marangoni convection, arc shear flow, and keyhole vortex flow. This enhancement increases the lateral mass transport capability of the molten pool, thereby effectively suppressing undercut defects. This study provides a theoretical basis for achieving high-quality welding of Invar steel.