The study of minor elements and shielding gas on penetration in TIG welding of type 304 stainless steel

The effects of minor elements and shielding gas on the penetration of TIG w elding in type 304 stainless steel have been studied. The bead-on-plate tes t was performed, then the depth and width of the weld were measured using a n optical projection machine. The are voltage was measured with an are data monitor. In addition, the metallurgical characteristics of weld were exami ned using OM and SEM. The results show that oxygen and sulfur are beneficia l in increasing a depth/width ratio because of the increased surface tensio n/temperature gradient. Elements, such as aluminum, that have a deleterious effect on the depth/width ratio will combine with oxygen and reduce the so luble oxygen content in the weld pool. On the other hand, silicon and phosp horus have a minor effect on the depth/width ratio. Shielding gas using Ar + 1% O-2 or Ar + 5% H-2 can significantly promote the depth/width ratio. Th e former contains increased soluble oxygen content in the weld pool, and th e latter produces an are that is hotter than that produced by pure argon.