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The stationary gas tungsten arc welding(GTA)is carried out on SUS304 stainless steel under Ar-0.1%O_2 and Ar-0.3%O_2 mixed shielding to observe the evolution of the molten pool and investigate the role of Marangoni convection on the weld shape.After welding,the oxygen content in the weld metal was measured by using an oxygen/nitrogen analyzer.Small addition of oxygen to the argon based shielding gas can effectively adjust the weld pool oxygen content.Oxygen plays an important role as an surface active element in determining the pattern of Marangoni convection in the stainless steel weld pool.When the weld metal oxygen content is over the critical value,0.01 wt pct,corresponding to the Ar-0.3%O_2 mixed shielding gas,the Marangoni convection changes from outward to inward direction and the weld shape dramatically changes from wide shallow shape to narrow deep shape.
The stationary gas tungsten arc welding (GTA) is carried out on SUS304 stainless steel under Ar-0.1% O_2 and Ar-0.3% O_2 mixed shielding to observe the evolution of the molten pool and investigate the role of Marangoni convection on the weld shape. After welding, the oxygen content in the weld metal was used by an oxygen / nitrogen analyzer.Small addition of oxygen to the argon based shielding gas can effectively adjust the weld pool oxygen content. Oxygen plays an important role as an active element in surface determine the pattern of Marangoni convection in the stainless steel weld pool. The weld metal oxygen content is over the critical value, 0.01 wt pct, corresponding to the Ar-0.3% O_2 mixed gas shield, the Marangoni convection changes from outward to inward direction and the weld shape dramatic changes from wide shallow shape to narrow deep shape.