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<p>In the present paper, process parameters of the keyhole TIG welding on the weld morphology of a medium-thickness stainless steel AISI304 are investigated, and the microstructure and mechanical properties of the welds are examined. A three-dimensional (3D) unsteady state numerical model of the weld pool is developed to investigate the keyhole and weld pool formation mechanisms by probing the various forces exerted on the molten pool. It is found that the welding current, arc length, welding speed, electrode tip angle, and gas flow rate all have a prominent influence on the weld formation. The microstructures near the weld top and bottom surfaces present equiaxed morphology, while columnar dendrite grain dominates in the other regions. The weld impact toughness is slightly lower than the base metal and decreases further with the increase in welding current. The primary factors responsible for the keyhole formation are the arc pressure and plasma shear force; the process parameters that affect these forces could give rise to the keyhole dynamics and thus weld pool formation. The Marangoni force, electromagnetic force, and buoyance are negligibly small compared with both arc forces, whereas gravity is the critical factor for the liquid metal to fill the keyhole and sag the molten pool, thus becoming unfavourable for the stabilization of the welding process.</p>

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Keyhole TIG welding of medium-thickness stainless steel and weld formation mechanism

  • 期刊论文

  • 发表日期：

    2025年5月7日

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  • Xinxin Wang,
  • Haochun Xu,
  • Hongyun He,
  • Long Zhou

摘要

In the present paper, process parameters of the keyhole TIG welding on the weld morphology of a medium-thickness stainless steel AISI304 are investigated, and the microstructure and mechanical properties of the welds are examined. A three-dimensional (3D) unsteady state numerical model of the weld pool is developed to investigate the keyhole and weld pool formation mechanisms by probing the various forces exerted on the molten pool. It is found that the welding current, arc length, welding speed, electrode tip angle, and gas flow rate all have a prominent influence on the weld formation. The microstructures near the weld top and bottom surfaces present equiaxed morphology, while columnar dendrite grain dominates in the other regions. The weld impact toughness is slightly lower than the base metal and decreases further with the increase in welding current. The primary factors responsible for the keyhole formation are the arc pressure and plasma shear force; the process parameters that affect these forces could give rise to the keyhole dynamics and thus weld pool formation. The Marangoni force, electromagnetic force, and buoyance are negligibly small compared with both arc forces, whereas gravity is the critical factor for the liquid metal to fill the keyhole and sag the molten pool, thus becoming unfavourable for the stabilization of the welding process.