L51634 Significance of Changes in Residual Stresses and Mechanical Properties due to SMAW Repair

During pipeline construction, immediate weld repairs are periodically required due to girth weld flaws that exceed specified defect tolerance levels. These defects, often identified through on-site radiographic inspection techniques, include voids, inclusions, and geometric irregularities. Repair welding may be necessary over limited portions of the pipe circumference, with restricted access for execution. Due to the variety of repair types and limited timeframes, weld repair procedures are often less documented than girth weld procedures, lacking thorough qualification.

Weldments typically contain high residual stresses, primarily due to differential contraction during cooling. This contraction is restrained by surrounding cooler material, placing the weld metal in tension and creating balancing compression areas. Additional thermal energy input from repairs in highly restrained regions can alter residual stress patterns, potentially affecting mechanical properties, especially toughness, near the repair.

This research assessed the effects of shielded metal arc welding (SMAW) repair welding on surface residual stress distribution, fracture toughness, and hardness around girth weld joints in line pipe. The study examined part wall repairs, multiple part wall repairs, and full wall repairs, comparing them to non-repaired weld samples.

The findings from this research are crucial for industries involved in pipeline construction and maintenance, where weld integrity is paramount. Understanding the impact of various repair techniques on residual stress and mechanical properties can inform better repair practices, ensuring pipeline safety and longevity.

This report is intended for professionals in the fields of welding engineering, pipeline construction, and maintenance, as well as researchers studying weld integrity and repair techniques.