PSI - Issue 3

M.A. Beltrán et al. / Procedia Structural Integrity 3 (2017) 57–67 Author name / Structural Integrity Procedia 00 (2017) 000–000

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2.2 Microstructural analysis Specimens for microstructural analysis were set according to the standard procedures contained in ASTM E-3 for specimen preparation including grinding, polishing and etching. The Microstructure was assessed in the longitudinal, circumferential and normal sections by optical microscopy (OM) and electron backscattered diffraction (EBSD). The EBSD samples were taken in the longitudinal and circumferential sections and its results were obtained by Oxford HKL system incorporated on a 7000F JEOL field emission scanning electron microscope. The data was interpreted by CHANNEL5 analysis software provided by Oxford Instruments HKL.

Table 1. Chemical composition API-5L X46 steel.

Experimental chemical composition of API-5L steel Element Fe C Si Mn P S

Cr

Mo

98.0 0.117 0.270 1.05 0.017 0.003 0.156 0.061

w%

Reference chemical composition for API-5L steel Element C (max) Mn (max) S (max)

P (max)

w%

0.24

1.40

0.030

0.030

2.3 Tensile tests Tensile specimens were machined as illustrated in Fig. 1a), according to the ASTM E-8 standard. The specimens were orientated in the longitudinal (L) and circumferential (C) directions. Tests were conducted at room temperature and humidity, using crosshead speed of 5 mm min-1 using a 10t Shimadzu machine.

Fig. 1. Specimens orientation, a) tensile tests samples, b) Charpy impact tests samples.

2.4 Charpy impact tests Charpy impact tests were performed on V-notch (CVN) specimens with a 10 mm x 10 mm x 55 mm size each with a 2 mm-deep V-notch, according to ASTM E-23. Fig. 1b) shows the specified orientations of the specimens in the L and C directions, the fracture planes in this cases are parallel to the crack propagation direction. The tests were conducted at room temperature of 28 °C. To approximate a value of fracture toughness (K IC-CV ) for the API-5L steel used, the equation (1) that relates the K IC-CV and Charpy impact energy (C v ) was used. The K IC-CV was calculated for the L and C directions.