PSI - Issue 3

M.A. Beltrán et al. / Procedia Structural Integrity 3 (2017) 57–67

66

10

Author name / Structural Integrity Procedia 00 (2017) 000–000

directions was assessed by the coefficient of relative variation "r rv ", which allows to quantitatively relate the influence of the microstructural properties on the mechanical anisotropic behavior of the API -5L. The assessment by the relative variation coefficient (r rv ), shows that the anisotropy on the fracture resistance properties (C v and K IC-CV ) and tensile strength (YS, UTS) of the API-5L steel are mainly influenced by the amount of grains oriented in the planes {101}. As a result, the larger density of grains oriented in the planes {101}, the larger fracture resistance and ductility. This behavior is due to the slip system {101} ˂111˃ is the major source of plastic deformation in materials with bcc crystal structure. The microstructural banding (A i ) of the material, shows an inverse relationship by reducing the pipeline steel fracture resistance (C V , K IC-CV ) and tensile strength properties (YS, UTS). Hence, the higher banding degree (A i ) values the lower C v energy values. This trend shows that a microstructural banding parallel to the crack propagation reduces the fracture resistance of the material, while a perpendicular orientation increases it. On the other hand, with respect to the tensile properties, the higher banding degree (A i ) values the lower tensile strength properties. This trend shows that, if the alignment of the bands is parallel to the direction of the specimen's necking, the ability of the material to strain is reduced by increasing its tensile resistance. The opposite condition occurs when the banding is perpendicular to the direction of necking. Acknowledgements The authors would like to acknowledge the National Polytechnic Institute (IPN), the National Council of Science and Technology (CONACYT) and the Analysis Integrity of Pipelines Group (GAID) for the financial support to carry out this research. References API Specification 5L. Specification for Line Pipe, Forty third edition March 2004. ASTM. Methods for preparation of metallographic specimens. Philadelphia, USA. ASTM E-3. American Society of Testing Materials Standards Handbook. ASTM. Standard practice for assessing de degree of banding or orientation of microstructures. Philadelphia, USA. ASTM E1268-99. American Society of Testing Materials Standards Handbook. ASTM. Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness for Metallic Materials, Philadelphia, USA. ASTM E399-12, American Society of Testing Materials Standards Handbook. ASTM. Standard test methods for Charpy impact test of metallic materials. Philadelphia, USA. ASTM E-23. American Society of Testing Materials Standards Handbook. ASTM. Standard Test Methods for Tension Testing of Metallic Materials Philadelphia, USA. ASTM E-8. American Society of Testing Materials Standards Handbook. González Velázquez, J.L., 2013. Mecánica de fractura 2a edición Limusa editorial. México. González Velázquez, J.L., 2017. Fractografía y análisis de fallas.Author edition. Mexico, CDMX. Hai, Q., Hanamura, T., Torizuka, S., 2014. Influence of grain size on the ductile fracture toughness of ferritic steel. Iron and Steel Institute of Japan International Journal. 54, 1958–1964. Hsun, H., 1974. Texture of metals. Texture, 1, 233-258. Hwang, B., Kim, Y., Lee, S., Kim Young, M., 2005. Effective grain size and charpy impact properties of high-toughness X70 pipeline steels. Metallurgical and materials transactions A. 36A, 2107-2114. Jang-Bog, J., Jung-Suk, L., Jae-il, J., 2007. Fracture toughness anisotropy in API steel line-pipe Materials letters, 61, 5178-5180. Joo, M.S, Suh, D.-W., JBhadeshia, H., 2013. Mechanical anisotropy in steels for pipelines. Iron and Steel Institute of Japan International Journal. 53, 1305–1314. Joo, M.S., Suh, D., Bae, J.,2014. Toughness anisotropy in X70 and X80 line-pipe steels Materials Science and Technology. 30, 439-446. Joo, M.S., Suh, D.-W., Bae, J.H., JBhadeshia, H., 2012. Role of delamination and crystallography on anisotropy of Charpy toughness in API-X80 steel, Materials Science and Engineering A, 546, 314–322. Joo, M.S., Suh, D.-W., Bae, J.H., Mouriño, S. N., 2012. Experiments to separate the effect of texture on anisotropy of pipeline steel Materials Science and Engineering A, 556, 601–606. Kerlins, V., McDonnell, D., 1987. Modes of fracture American Society of Materials Handbook. 12, 12-71. Manh, T., Study of magnetic anisotropy in API 5L steels from crystallographic texture and barkhausen noise measurements. PhD thesis. Mexico city 2016. Okamura, N., 1983. Cleavage fracture of low carbon ferritic steels with fine grain size. Metallurgical Science. 17, 581-589. Oldfield, W., 1975. Fitting impact test data- a statistical procedure American Society of Testing Materials Standardization news, 24. Oxford Instruments HKL, Channel 5 June 2007.