PSI - Issue 50

Aleksandr Malikov et al. / Procedia Structural Integrity 50 (2023) 170–177 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Schematic diagram of measuring the phase composition of the weld joint and the base alloy using synchrotron radiation.

Upon completion of the welding process, all samples were sent for cutting. Strength test specimens were made in accordance with GOST R ISO 4136-2009 by milling (see Fig. 2).

Fig.2. Drawing of test specimens.

The mechanical characteristics of welded joints were measured under static tension on a Zwick/Roell Z100 electromechanical testing machine. The relative elongation was measured with an external strain gauge with a measuring base of 12 mm, where a weld was located, the width of which was about 1 mm. For each mode, at least 3 samples were tested. The samples were heat treated in a Carbolite chamber furnace equipped with a temperature controller. Post weld heat treatment obtained with wire was carried out in 2 stages. 1st stage: quenching at 490 °C with holding for 30 min in a muffle furnace; 2nd stage: art ificial aging at 120 °C for 10 hours. For microscopic studies using a scanning electron and optical microscopes, samples of the cross section of the weld were used. 3. Results The optimization of the parameters of the process of laser welding with wire was carried out: welding speed, radiation power, laser beam diameter, depth and location of the focal spot, as well as the consumption of protective neutral gas in order to obtain welded joints without external defects. External defects include cracks, lack of penetration, discontinuities, undercuts, shells, understatements, open porosity of welded joints. The criterion for the quality of the internal microstructure and morphology of the laser weld of butt joints was the minimum porosity, the equality of the width of the upper and root parts, and the production of an X-shaped butt weld with curved bevels (Katayama, 2013). The range of laser radiation power W was 1.6-3.5 kW, the position of the focal spot of laser radiation relative to the workpiece surface was from -3 to 0 mm, the welding speed V was 2-4 m/min (33.3-66.7 mm/sec), gas flow rate in the nozzle was 3-15 l/min. At high speeds of laser scanning, porosity is observed in the weld. At a welding speed equal to the wire feed speed, a high-quality weld was obtained. With a decrease in the depth of the focal spot, the porosity of the welded joint increases, as well as undercuts. At a power of 1.6 kW, there is no X-shape of the weld, and undercuts and sagging of the weld are also observed. Large pores were fixed by reducing the laser radiation power.