Abstract
The effect of aluminum content on the penetration behavior in stainless steel tube welded by tungsten inert gas arc welding was investigated from a point of view of the effective oxygen content in molten pool. Girth welding tests were carried out on 18%Cr-9%Ni stainless steel tubes with 0.006-0.030% aluminum and 0.003-0.004% oxygen. The penetration depth, the bead width and the root bead length were measured to evaluate the formability of root bead. Then the aluminum content in weld metal was analyzed. The formability of root bead was deteriorated in proportion to the decrease of penetration depth and the increase of bead width caused by the addition of aluminum to the base metal. The aluminum content in weld metal analyzed was inconsistent with the content estimated from the dilution law but that agree with the content calculated from the solubility of Al2O3. The deterioration of the root bead formability by the increase of aluminum is thought to be caused by the molten metal flow to the molten pool edge induced by the decrease of the soluble oxygen content in molten pool.
