Abstract
Dramatically variations in GTA weld shape and penetration result from small additions of carbon dioxide (CO2) to the argon shielding gas in welding of a SUS304 stainless steel. The weld depth/width ratio (D/W) increases to 0.5 when the CO2 in the shielding gas in the range of 0.2 vol-% to 0.6 vol-%. A too low or too high CO2 addition content decreases the weld D/W ratio to 0.2. The oxygen from the decomposition of CO2 transfers and becomes an active element solute in the welding pool and further reverses the Marangoni convection model. The heavy oxide layer on the liquid pool surface will inhibit the fluid flow induced by Marangoni convection and also affect the oxygen transfer to the liquid pool.
