PSI - Issue 60

Cyril Reuben Raj et al. / Procedia Structural Integrity 60 (2024) 709–722 Cyril Reuben Raj / Structural Integrity Procedia 00 (2024) 000 – 000

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2.4. Mechanical test

The dimension of the tensile specimen is maintained at length 72 mm, thickness 2.5 mm, guage width 5 mm and gauge length 25 mm as detailed in the figure 2. Figure 3 (a) and (b) shows the photographs of flat dog-bone tensile specimen and its extracted location from the block specimen. The tensile tests were conducted at ambient conditions on a 100 kN Universal Testing Machine in a three step procedure. The test were carried out as per ASTM E8 2016 under quasi-static loading and strain measurement on the gauge length is done through extensometer. The yield strength, ultimate tensile strength and percentage elongation were calculated for the Weld and HAZ zone of SMAW and GTAW section. Red colour box in figure 3 (b) indicates the GTAW region which is 7 mm from the ID of the pipe. Tests were performed to compare and analyze the results of thermally aged specimens with as-welded specimen. All the tests were conducted at room temperature and key observations were recorded at maximum load, maximum stroke travel and failure location.

Fig 2. Dimensions (in mm) of flat tensile specimen.

Fig 3. (a) Actual flat dog-bone tensile specimen, (b) Actual tensile specimen locations with respect to weld region.

3. Results and Discussion 3.1. Effect of thermal aging on ferrite content variation

Table 3. Ferrite content in the weld zone i.e. GTAW and SMAW section.

SI. No.

Specimen ID and Location

Ferrite Content (%)

Ferrite Number (FN) Range

1 2 3 4 5 6

As-welded SMAW As-welded GMAW

4.5, 4.0, 3.8, 3.9 5.1, 4.9, 5.3, 4.4 3.7, 3.6, 4.2, 4.0 8.1, 7.0, 7.1, 7.4 4.4, 4.0, 4.1, 4.8 9.9, 8.4, 10, 10.5

3.8 – 4.5 4.4 – 5.3 3.6 – 4.2 7.0 – 8.1 4.0 – 4.8 8.4 – 10.5

10,000 hrs aged SMAW 10,000 hrs aged GTAW 20,000 hrs aged SMAW 20,000 hrs aged GTAW

Table 3 represents the variation in ferrite content (%) in the weld zone at GTAW and SMAW section of the pipe weldments. The measurements were recorded along and across the welded pipe joint in the as-welded pipe and thermal aged pipes. The result shows that there was a decrease in ferrite content along the thickness of the weld zone and varies with respect to SMAW and GTAW section from 3.3 to 10.5 along the weld center line. The decrement in ferrite content is caused due to lower ferrite in filler (ER308L) metal compared to electrode (E308L). The GTAW section has maximum ferrite content, significantly reduced in the SMAW section. Inclusions in the austenite phase is higher in the SMAW section than in the GTAW section [Kar et al. (2017)]. Along the measurement area of