Metallurgical investigations and corrosion behavior of failed weld joint in AISI 1518 low carbon steel pipeline

Improvement of Corrosion Resistance of Simulated Weld Heat Affected Zone in High Strength Pipeline Steel Using Electropulsing

“…8) Corrosion and SCC of pipelines are very important issues in oil and gas transportation pipelines, because once the pipeline leaks, ruptures or fails, it usually causes catastrophic accidents to human beings and the environment. 9,10) In order to ensure the safe operation of pipelines, welding, coating and subsequent maintenance need to spend about 20% of the total cost of pipeline construction. 11) Although great efforts have been made to develop alternative welding technology, ring metal arc welding technology is still the main means used to connect large-diameter pipes.…”

“…12) Due to phase transformation and the unevenness of heat, a lot of dislocations and residual stress will be produced in the heat affected zone, which will reduce the corrosion resistance. 3,6,7,9,10) Affected by composition and thermal cycle, ferrite, bainite, martensite and other microstructures will be formed after the phase transformation in the heat affected zone. 5,12) In these microstructures, the martensite microstructures are generated by rapid cooling, and the structures are unbalanced, with high dislocation densities and large residual stress, becoming the areas with the worst corrosion resistance.…”

Pit evolution around the fusion line of a NiCrMoV steel welded joint caused by galvanic and stress-assisted coupling corrosion

“…There are various factors controlling galvanic corrosion of welded joints or dissimilar metals (microstructures), including stress, 1,2 relative size between anode and cathode, [3][4][5] compositions (precipitation), [6][7][8][9][10] microstructures, [10][11][12][13][14][15][16] and temperature. 5,17 In all the scenarios of stress-assisted corrosion, stress and stress-induced defects likely can accelerate local corrosion rates and cause early failure of mechanical structures.…”

Failure investigations of failed valve plug SS410 steel due to cracking

“…The microstructural observation at weld zone was carried out and it showed severe intergranular corrosion, which causes the failure. Shirinzadeh-Dastgiri [8] had carried out the failure investigations of failed weld joint in AISI 1518 low carbon steel pipeline with the help of non-destructive testing, radiographic and metallographic analysis. The identified causes of failure was improper welding since, micro-cracks were noticed on the weld interface and possible corrosion attack due to cracking, this corrosion mechanism was studied by electrochemical techniques.…”