Evaluation of Structural Integrity Following Multiple Weld Repairs in Austenitic Stainless Steel Joints for Cryogenic Service

Abstract The metallurgical and mechanical properties of weldments are typically determined through a procedure qualification record (PQR). This is achieved by welding a test coupon using identical base material groupings and welding consumables classifications as intended for the production weld, then tested rigorously to prove the welding procedure’s effectiveness. Similarly, generating a repair welding PQR shall be required for certain fabrication scenarios involving weld repairs. However, sometimes complete removal of the defective weld and its associated heat affected zone (HAZ) may not be practically achievable to restore the original base metal and joint configuration, which could result in several localized repair efforts within the same weld area. This study presents a structural integrity evaluation of a 304 stainless steel (304SS) circumferential weld subjected to repeated weld repairs within the same region. The weld in question is designed for cryogenic service, operating at temperatures as low as -176 °C (-284 °F). For assessment purposes, a mockup specimen was fabricated by applying the original weld followed by 5 weld repairs, to replicate the conditions of actual production weld. The paper aimed to discuss the impact of these repeated repairs on the mechanical and metallurgical properties of the weldment (i.e., weld metal & HAZ) and the base material. The findings provide insights into the suitability of such muti-repaired welded joints for cryogenic applications.