Development of simplified active flux tungsten inert gas welding for deep penetration

•A new advanced active flux tungsten inert gas (AA-TIG) welding technique was developed.•Penetration depth was increased by the reversal of the Marangoni convection due to the entrained oxygen.•Penetration depth reached three times deeper than that of the conventional TIG welding.•Only a simple nozzle cap with an air inlet was used for the welding.•Penetration depth could be easily controlled by the nozzle cap design and the welding parameters.

A new advanced active flux tungsten inert gas (AA-TIG) welding technique, named cap active flux tungsten inert gas (CA-TIG) welding using atmospheric oxygen, was proposed to increase the penetration depth of a weld. Only a simple nozzle cap with an air inlet was used for the welding. Flowing inert gas used as a shielding gas through a nozzle center led to the aspiration of oxygen from the atmosphere to the molten pool. The penetration depth was increased by the reversal of the Marangoni convection due to the entrained oxygen, and it reached three times deeper than that of the conventional TIG welding. Additionally, no degradation of the tungsten electrode was observed because it was protected by the inert gas. The penetration depth was changed by the oxygen content in the molten pool and it could be easily controlled by the nozzle cap design and the welding parameters.