Microstructure, Mechanical Properties and SSC Susceptibility of Multiple SMAW Repairs in Line Pipe Girth Welds

Abstract

Girth welds of seamless API X52 steel pipe containing multiple shielded metal arc welding (SMAW) repairs and one as-welded condition were studied. Microstructural characterization, mechanical behavior and sulfide stress corrosion cracking (SSC) susceptibility of the welded joints were evaluated by means of optical and scanning electron microscopy, hardness, tension, Charpy-V impact resistance and slow strain rate tests (SSRT). The results of this work indicate that increasing the number of welding repairs promotes grain growth in the heat affected zone (HAZ). The yield strength (YS) and ultimate tensile strength (UTS) for the different welding repairs satisfy the specified minimum values of the material. Significant reduction in Charpy-V impact resistance with the increases of the number of repairs was found in the coarse grained heat affected zone (CGHAZ). A high susceptibility to SSC was exhibited by the welded joints and the intercritical heat affected zone was the most susceptible area to SSC.