PSI - Issue 54

Paulo Mendes et al. / Procedia Structural Integrity 54 (2024) 340–353 Mendes et al. / Structural Integrity Procedia 00 (2023) 000–000

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to weld geometry and microstructure. Parkes et al. (2013) presented a study on the microstructural characteristics and fatigue behavior of welded joints obtained by fiber laser welding on high-strength low alloy and dual-phase steel in both homogeneous and heterogeneous configurations. In this study, high- and low-force Vickers hardness tests were conducted across di ff erent regions of the high strength steel joint to characterize the welded joint and the high-strength steel. Microstructural observations were carried out using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) to identify inclusions or defects from the welding procedure in fractured specimens from di ff erent regions of the welded joints.

2. Materials and experimental details

Test materials consisted of welded joints of S690QL steel with thicknesses of 30-millimeters (J30) and 60 millimeters (J60). This class of steels is a subset of low-alloy steels, and the EN10025-6 standard (European Commit tee for Standardization (2018)) defines and regulates their chemical compositions. The welded joints were produced using the Metal Active Gas (MAG) welding process, as designated by ISO 15609-1:2019 (International Organization for Standardization (2019)) and the filler material used for this process was the Coreweld 69 LT H4 from ESAB, as classified under ISO 18276:2017 (International Organization for Standardization (2017b)). Table 1 presents the chemical compositions for both the steel plates and the filler material, as provided by the steel supplier.

Table 1. Chemical composition (wt. %) of the base material (S690QL) and filler material used to produce the welded joints.

Plates

C Si

Mn P

S

Cr

Mo Ni

Al

V Ti

Nb, Cu, N, B

J30 J60

0.140 0.279 1.203 0.020 0.002 0.299 0.178 0.011 0.035 0.029 0.016 0.047 0.149 0.276 1.253 0.011 0.001 0.621 0.259 0.012 0.030 0.003 0.016 0.050

Filler material

C Si

Mn P

S

Cr

Mo Ni

Al

V Ti

Nb, Cu, N, B

Coreweld 69 LT H4 0.050 0.500 1.700 0.011 0.008 0.060 0.500 2.300 0.010 0.005 0.012 -

The primary mechanical properties of the materials used in this experimental study are shown in Table 2, which includes both base and filler materials.

Table 2. Mechanical properties of the base and filler materials used for the welded joints, provided by the steel and weld consumables supplier. Yield strength, R p 0 . 2 [MPa] Tensile strength, R m [MPa] Elongation, A (%) S690QL (J30) 814 857 17.0 S690QL (J60) 758 835 14.4 Coreweld 69 LT H4 755 790 20.0 Macrohardness tests on the welded joint were performed at two distinct stages of the welding process: with only the root steps and with all the welding steps. The main objective of this test plan was to investigate and compare how the last steps impact the heat input coe ffi cient of the process. This approach enabled observation of when the heat treatment, resulting from the tempering process, drastically changes the mechanical properties of the HAZ. This analysis will also allow for a better understanding of each type of microstructure. The hardness tests were conducted at a macro level according to ISO 9015:2011, parts 1 and 2 (International Organization for Standardization (2011a,b)). Two a ffi liations, A and B, were performed with 10 indentations in each one. The equipment used for this purpose was the EMCOM4U hardness tester. The Vickers test used was the HV10, with an applied force of 10 kgf, corresponding to 98,07 N, with a pressing time of 15 seconds. The minimum distance of each measurement to the end was considered, as well as the distance between indentations. The geometry of the evaluated samples and the indentations distributed for each a ffi liation are illustrated in Figure 1.