Impact of Residual Stress on the Susceptibility of Corrosion of Longitudinal Welds in API 5L X60 Microalloyed Steel Pipe

IMPACT OF RESIDUAL STRESS ON THE SUSCEPTIBILITY OF CORROSION OF LONGITUDINAL WELDS IN API 5L X60 CARBON STEEL PIPE

This article presents the results obtained from experiments done to measure the impact that residual stress generated during the phase of longitudinal welding and cold expansion has on API 51 X60 carbon steel line pipe during the manufacturing phase.  The electro-chemical potentiodynamic technique was used to determine the behavior of different areas of the joint in filler metal as well and in the area affected by the heat and the adjacent metal base.  We also designed special equipment for this purpose, since we have to measure the entire ring, seeing that if we divide it, the stress relaxes and disappears.  The curves obtained present an increasing relationship as to the velocity of corrosion when the residual stress increases.  Results are analyzed and discussed.