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<p>This study examines the K-TIG welding process for 5&#xa0;mm-thick domestic 4J36 Invar steel, employing a combined approach of simulation analysis and high-speed photographic observation. The low fluidity of 4J36 Invar steel due to its high tensile strength results in a slow ascent rate of gas bubbles, exacerbating the formation of porosity defects. K-TIG welding shortens the molten pool residence time, significantly reducing gas incorporation. Additionally, gas bubbles can escape directly along the keyhole wall, thereby minimizing porosity defects. The study simulates molten pool flow behavior through numerical modeling and employs high-speed photography to observe the welding process in real time. It reveals the dynamics of the molten pool and the bubble escape mechanism during K-TIG welding, providing a theoretical basis for optimizing the K-TIG welding process for 4J36 Invar steel and reducing porosity defects. The results demonstrate that maintaining the welding current at 340–360&#xa0;A, the arc voltage at 18–20&#xa0;V, and the welding speed at 300–350&#xa0;mm/min ensures the stability of the molten pool flow and keyhole formation, thereby facilitating melt flow and enhancing gas escape.</p>

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Study on molten pool dynamics and porosity formation of 4J36 invar steel welded by K-TIG

  • 期刊论文

  • 发表日期：

    2026年4月6日

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  • Yanhong Hou,
  • Fei Zhao,
  • Shuili Gong,
  • Lifeng Ma,
  • Haiyan Zhao,
  • Wei Zhang

摘要

This study examines the K-TIG welding process for 5 mm-thick domestic 4J36 Invar steel, employing a combined approach of simulation analysis and high-speed photographic observation. The low fluidity of 4J36 Invar steel due to its high tensile strength results in a slow ascent rate of gas bubbles, exacerbating the formation of porosity defects. K-TIG welding shortens the molten pool residence time, significantly reducing gas incorporation. Additionally, gas bubbles can escape directly along the keyhole wall, thereby minimizing porosity defects. The study simulates molten pool flow behavior through numerical modeling and employs high-speed photography to observe the welding process in real time. It reveals the dynamics of the molten pool and the bubble escape mechanism during K-TIG welding, providing a theoretical basis for optimizing the K-TIG welding process for 4J36 Invar steel and reducing porosity defects. The results demonstrate that maintaining the welding current at 340–360 A, the arc voltage at 18–20 V, and the welding speed at 300–350 mm/min ensures the stability of the molten pool flow and keyhole formation, thereby facilitating melt flow and enhancing gas escape.