PSI - Issue 20

Ekaterina M. Maksimova / Procedia Structural Integrity 20 (2019) 174–179 Ekaterina M. Maksimova / Structural Integrity Procedia 00 (2019) 000–000

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When welding in the cold (-45° C) with the use of UONI 13/Moroz electrode (plate No. 3) at the area of incomplete melting (fusion line), as well as at a distance of 1.5 mm from it, quenching structures were formed mainly in the form of upper bainite. At a further distance from the FL at the levels of 2 mm and more, a highly dispersed ferritic-carbide mixture was found. The size of ferritic grains averages 8-12 microns (Fig. 3). The structure of the HAZ of sample (plate No. 7), welded at room temperature, is significantly different from the structure of plate No. 3. At the area of incomplete melting and at a distance of 0.5 mm from it, a ferritic-carbide mixture was found with a low content of bainite structure. At a further distance from the FL, the HAZ structure consists of a ferrite-carbide mixture, and the size of ferritic grains at the levels of 2-4 mm is 2-3 times larger than in the structure of plate No. 3. It should be noted here that the average heat input of welding of plate No. 3 6% more than plate No. 7 (Table 3). Figures 5, 6 show the HAZ microstructure of the filling passes of welded joints made by manual arc welding using the UONI 13/Moroz electrode. When welding in the cold (-45° C) using an LB-52TRU electrode (plate No. 6) at the site of incomplete melting (fusion line), as well as at a distance of 1.5 mm from the FL, a ferrite-carbide mixture with quenching bainite structures was formed. At a further distance from the FL at the levels of 2 mm and more, a highly dispersed ferritic carbide mixture was found. The size of ferritic grains averages 8-12 microns.

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Fig. 3. The microstructure of 09G2S in various regions of HAZ of the filling passes of welded joints made by manual arc welding using the UONI 13/Moroz electrode at ambient temperature + 20° С : (a) Fusion line (FL); (b) HAZ, 0,5 mm from the FL; (c) HAZ, 1,0 mm from the FL.

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Fig. 4. The microstructure of 09G2S in various regions of HAZ of the filling passes of welded joints made by manual arc welding using the UONI 13/Moroz electrode at ambient temperature - 45° С : (a) Fusion line (FL); (b) HAZ, 0,5 mm from the FL; (c) HAZ, 1,0 mm from the FL.

The HAZ structure of a sample welded at room temperature (plate No. 8) is significantly different from the structure of plate No. 6. At the site of incomplete melting and at a distance of 0.5 mm from it, a ferritic-carbide mixture with a low content of bainite structure was found. At a further distance from the FL, the HAZ structure