PSI - Issue 35

Kpemou Apou Martial et al. / Procedia Structural Integrity 35 (2022) 254–260 Kpemou A. M. et al. / Structural Integrity Procedia 00 (2019) 000 – 000

256

3

Table 1. Typical chemical composition of API 5L X65 (wt%). C Si Mn P S

Mo

Ni

Al

Cu

V

Nb

Min Max

0.05 0.14

0.15 0.35

1.00 1.50

-

-

-

-

0.01 0.04

-

-

0.020

0.005

0.25

0.25

0.080

0.080

0.040

Table 2. Mechanical proprieties of API 5l X65 at room temperature Yield Stress (MPa) Ultimate Strength (MPa) Elongation at Failure A (%) 465.5 558.6 10.94

Charpy Energy (J)

Fracture Toughness (MPa √ ) 280

Hardness HV

285.2

205

Fig. 1. Microstructure of API 5L X65

3. Instrumented Charpy impact test Charpy impact tests were performed on Standard Charpy specimens (10x10x55) and on ½ Mini – Charpy (5x5x27. 5). The geometry of the specimens ‘thickness B, ligament b, length L and, notch radius r are reported in Table 3. It is significant to notice that both types of specimens tested have the same notch. Tests on air and hydrogenated specimens were carried out. The hydrogen loading has been made by electrolysis, where the specimen acts as the cathode. Electrolysis has been made in NS4 solution for an average of five (05) days. These tests were conducted on two types of machines. The tests on ½ Mini – Charpy Specimens were performed on The CEAST 9350, which is a floor-standing impact system designed to deliver 0.59 -757 J. The CEAST 9350 operates with impact software and a data acquisition system to make analysis simple. A temperature chamber allows performing test at low temperatures in the range [- 196°C to 20°C]. The impact speed is 5.53m/s. Standard Charpy specimens were tested on a pendulum impact tester, the Zwick /Roell RKP 450, with an impact speed of 5.53m/s.

Table 3. Geometries of specimens tested. Specimens B (mm)

b (mm)

L (mm)

r (mm)

10

8 4

55

0.25 0.25

Standard Charpy ½ Mini - Charpy

5

27.5

4. Transition temperature Transition temperature defines the transition from ductile to brittle mode of failure. The transition temperature can be defined at two level of energy on a transition curve (Fracture energy vs temperature): 27 at a conventional level of 27 Joules, and the temperature defines at one-half the jump between the brittle and ductile plateaus: 1/2 = . For this project, this last definition of the transition temperature has been chosen. Plotting the fracture energy K cv (J)