Study of Tensile Deformation and Damage Law in Undermatching X80 Pipeline Steel Welded Joints

This study used a digital imaging technique (DIC) to obtain the strain distribution at various locations in undermatching X80 pipe girth-weld joints under uniaxial tensile loading. In addition, microstructure characteristics and deformation patterns different regions were analyzed by scanning electron microscopy (SEM). The results showed that there was heterogeneity between of welded joint. Strain concentration existed only 12.8 mm base metal heat-affected zone (HAZ) elastic stage. There weld (WM) both sides HAZ close near-fracture stage, maximum WM. When εM = 12.2%, KC 6.27 KF 1.73, 113% 152% KG, respectively. large number slip strips generated indicated serious damage WM near fracture N1 caused softened ferrite. stage grain size non-uniform martensite–austenite (M–A) islands, which may also lead better local toughness cover further affect mechanism