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<p>This study employs laser-TIG hybrid welding technology on 4J36 Invar steel to investigate the mechanisms and influence of welding process parameters on the formation of porosity and hot cracking defects in the weld. The results indicate that porosity defects in the weld can be primarily classified into two categories: process-induced and metallurgical; the former are primarily caused by keyhole collapse and insufficient liquid metal refilling, while the latter are closely related to oxidation reactions and gas entrapment within the molten pool. The study found that porosity may act stress concentration sites and influence the initiation and propagation of hot cracks. The segregation of elements such as O, C, P, and S at grain boundaries may reduce grain boundary strength and increase defect susceptibility. Further analysis shows that the effects of process parameters on porosity and cracking exhibit a non-monotonic trend. Within the parameter range of this study, for 12&#xa0;mm thick 4J36 Invar steel, a laser power of 5&#xa0;kW, an arc current of 150&#xa0;A, and a welding speed of 0.68&#xa0;m/min provide a relatively balanced performance in controlling both porosity and cracking. This parameter combination helps improve weld quality to a certain extent. The results provide a reference for understanding defect formation mechanisms and for optimizing process parameters in laser–TIG hybrid welding of Invar steel.</p>

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Mechanisms of porosity and hot cracking in laser–TIG hybrid welding of 4J36 invar steel under varying process parameters

  • 期刊论文

  • 发表日期：

    2026年5月11日

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  • Fei Zhao,
  • Pengfei Wang,
  • Shuili Gong,
  • Haiyan Zhao,
  • Lifeng Ma

摘要

This study employs laser-TIG hybrid welding technology on 4J36 Invar steel to investigate the mechanisms and influence of welding process parameters on the formation of porosity and hot cracking defects in the weld. The results indicate that porosity defects in the weld can be primarily classified into two categories: process-induced and metallurgical; the former are primarily caused by keyhole collapse and insufficient liquid metal refilling, while the latter are closely related to oxidation reactions and gas entrapment within the molten pool. The study found that porosity may act stress concentration sites and influence the initiation and propagation of hot cracks. The segregation of elements such as O, C, P, and S at grain boundaries may reduce grain boundary strength and increase defect susceptibility. Further analysis shows that the effects of process parameters on porosity and cracking exhibit a non-monotonic trend. Within the parameter range of this study, for 12 mm thick 4J36 Invar steel, a laser power of 5 kW, an arc current of 150 A, and a welding speed of 0.68 m/min provide a relatively balanced performance in controlling both porosity and cracking. This parameter combination helps improve weld quality to a certain extent. The results provide a reference for understanding defect formation mechanisms and for optimizing process parameters in laser–TIG hybrid welding of Invar steel.