PSI - Issue 72

Nedeljko Vukojević et al. / Procedia Structural Integrity 72 (2025) 157 –163

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Fig. 1. (a) incremental sheet forming; (b) vessel heads final production proces.

After plastic deformation, the dish ends had final dimensions: Ø1250x6 mm; Ø1250x14 mm; Ø2500x6 mm; Ø2500x14 mm. Samples were extracted from the outer cylindrical part of the dish ends, specifically from areas where the plastic deformations were most intense. To evaluate the effect of potentially the weakest part, i.e., the heat-affected zone (HAZ), the test specimens were extracted in a direction transverse to the longitudinal axis of the welded joint.

All results are presented in Tab.1. 3. Test procedure and results 3.1. Metallography

Macrostructure examinations were conducted according to ASTM E 340-00(2015). Metallographic examinations (macrostructure of the welded joint) were performed only on samples from Series I to assess the quality of the welded joint. Macrostructure e xamination was carried out on the transverse section of the sample. After etching in 10% HNO₃, the macrostructure of the fusion-welded joint was revealed. No porosity, cracks, or inclusions were observed in the macrostructure. Representative macrostructure images for steel P460 and for steel S235 are shown in Fig.2. No porosity, cracks or inclusions were observed in the samples, indicating that the welded joints can be considered acceptable for further experimental research.

Fig. 2. (a) macrostructure of the welded platest of P460; (b) macrostructure of the welded platest of S235.

3.2. Hardness test Hardness testing was performed to determine any significant differences and their potential impact on the other mechanical test results. The measurements were conducted on a ZWICK hardness and micro-hardness testing device. The following hardness tests were performed on the transverse section of the welded joint using the Vickers method, with a load of 10 kg (HV1) and a testing temperature of 22°C, BAS EN ISO 6507 (2018). The hardness testing was performed on the transverse section of the sample. The typical appearance of the measuring sample is shown in the Fig.3. Results are presented in Tab.1.