PSI - Issue 5

Lars Sieber et al. / Procedia Structural Integrity 5 (2017) 1011–1018 Sieber et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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3.3. Radiographic testing of the weld seams

To check the quality of the welded joints, radiographic tests (EN ISO 17636-1:2013) was carried out after a visual inspection of the seams. On the basis of the internal findings, the seams were classified as grades 1 to 3 according to EN 10675-1:2013. Weld seams were produced in high quality (class 1 or 2). The inner weld defects exceeded the normative limit values only for one weld seam. Figure 2 illustrates exemplarily the X-ray film of this welding seam TFT.1.2. The slag inclusions in the region between 10 and 14 cm and at the lower weld edge are particularly clear.

Fig. 2. X-ray film of the weld TFT.1.2

In the evaluation of the X-ray films, it was found that all the weld seams had pores with irregular distribution. In the sample series GDD, MV and TFT, binding defects were also found to a small extent as well as slag inclusions in the samples TFT and TFS. Both welding seam defects are less due to the basic or filler material than to irregularities in the execution of the welding work.

3.4. Test specimen geometry and quantity

Based on the detected weld seam defects, individual cutting plans were developed for the required test specimens (Figure 3). Seam sections with welding defects are shaded. The tensile and the Charpy impact specimens were positioned outside the defective areas in order to avoid influencing the subsequent tests. In contrast, the samples for metallographic investigations were positioned within weld seam defects to analyze them more closely together with the material structure. To analyze the mechanical and metallurgical properties of the welded joints extensive investigations were carried out according to the welding procedure qualification of DIN EN ISO 15614-1:2012. The following test specimens were produced of each weld seam:  2 tension test specimens for transverse tensile tests according to EN ISO 4136:2013  3 Charpy impact specimens (V-notch, standard dimensions) of each weld and 3 subsize Charpy impact specimens of the heat affected zone in the old mild steel for impact tests according to EN ISO 9016:2013  At least 1 specimen for metallographic investigations according to EN ISO 17639:2013 The excess weld metal was removed at all tensile specimens in order to take into account the failure of the weld seam or the heat affected zone. The Charpy impact specimens of the weld seams and the base material were produced in standard dimensions (10 mm width). Due to the small extent of the heat-affected zones, subsize impact specimens up to a width of 5 mm were required (according to EN ISO 148-1:2011). To determine the mechanical characteristics of the unaffected base materials additional tension and Charpy impact specimens were produced and analyzed. As labelled in Figure 3, all test specimens receive unique sample names. The tensile specimens are denoted by "f" and the metallographic specimens by "m". The Charpy impact specimens of the weld are indicated by "w", of the heat affected zone by "h" and of the base material by "g".