The role of residual stress in neutral pH stress corrosion cracking of pipeline steels. Part I: Pitting and cracking occurrence

Stress corrosion cracking behavior of X70 pipe steel in an acidic soil environment

Effect of inclusions on initiation of stress corrosion cracks in X70 pipeline steel in an acidic soil environment

The effect of heat input on microstructural zones, hardness and fracture of T-joints in EN S235JR carbon steel was evaluated using the Vickers hardness, SEM, and fractography on impact fractured specimens. The gas metal arc welding (GMAW) process with pulsed metal arc transfer and different welding speeds was performed by an industrial robot using a teaching pendant. Microstructural observations revealed differences in the size and quantity of phases exhibited in the solidified weld bead and recrystallized heat affected zone (HAZ) as well as a refinement of ferrite with different morphologies when a greater heat input was generated. The hardness results indicated greater hardening with greater heat input for the weld bead than the HAZ, which was associated with fine secondary Widmastätten ferrite sideplates growing from columnar grains separated by a larger amount of fine acicular ferrite. At a speed of 35 cm/min, the greater heat input produced a greater increase in volume fraction and width of HAZ with complex microstructures formed by fine-grained ferrite and acicular ferrite. The weld bead reached a greater hardening and volume fraction compared to the HAZ linked to fine acicular ferrite. The hardening of weld bead was confirmed by fractography that showed the presence of a small microvoid morphology I. Guzman-Flores • J.J. Gasca-Dominguez • J. del Prado • L. Rios-Vargas Manufacturera de cigueñales de México (MACIMEX), Centro de Investigación Innovación y Desarrollo Avanzado, Km. 38.5 Carretera la Marquesa, Tenango del Valle, Estado de México 52300, México e-mail: Isidro.Guzman@macimex.com; JuanJose.Gasca@macimex.com; Joaquin.DelPrado@macimex.com; Leopoldo.Rios@macimex.com B. Vargas-Arista (*) División de Estudios de Posgrado e Investigación, Instituto Tecnológico de Tlalnepantla, Av. Instituto Tecnológico s/n, Col. La Comunidad, Tlalnepantla de Baz, Estado de México 54070, México e-mail: benjaminvar@yahoo.com.mx E. Garfias-Garcia División de CBI, Departamento de Materiales, Área de Ingeniería de Materiales, UAM –Azcapotzalco Av. San Pablo No. 180, Col. Reynosa Tamaulipas, Azcapotzalco 02200, México e-mail: D.F.elgg@correo.azc.uam.mx

Materials Characterization I

Micro-electrochemical characterization of corrosion of welded X70 pipeline steel in near-neutral pH solution

Two patches of near-neutral-pH stress corrosion cracks (SCC), as developed on a pipeline steel during service, have been characterized. The two patches can be characterized as containing e...

E. Vokes

Papers

Characteristics of Near-Neutral-pH Stress Corrosion Cracks in an X-65 Pipeline