Influence of weld repair on the residual stresses induced in austenitic stainless steel weld joints

The present paper aims to study the influence of repair welding on the residual stresses induced in austenitic stainless steel weld joints prepared using the gas tungsten arc welding process. Structural components are frequently subjected to weld repair both during fabrication as well as under operating conditions. As the weld metal deposited during repair welding encounters severe structural restraints, there are chances of the development of high localized residual stresses. Hence during the structural integrity assessment of components, it becomes important to study the influence of repair welding on the induced residual stresses. In the present work systematic experimental and numerical studies have been performed to understand the effect of weld repair on weld-induced residual stresses. Initially, two identical weld joints of 12 mm thick SS 304L plates were prepared. Subsequently, one weld joint was left in as-welded condition and weld repair was carried out in the other weld joint by machining out materials from the top and re-depositing material in the same region. Stresses were measured in both the joints using the blind hole drilling technique and they were compared. Finite element analysis of the repair welding process was carried out to study the mechanism of residual stress development during repair welding. The patterns of stresses evaluated using FE analysis are in agreement with the experimental pattern. More than a 100% increase in residual stresses has been observed due to repair welding. The region of tensile residual stresses has increased after weld repair. Partial-length weld repair seems to induce more stress than a full-length repair. Details of the residual stress results obtained from experiment and numerical analysis have been discussed in this paper and the reason behind such stress pattern has been explained.