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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consists of a ferrite-carbide mixture, and the size of ferritic grains at a levels 2-4 mm is 1.5-2 times greater than in the structure of plate No. 6. The average heat input of welding of plate No. 6 is 9% more than plate number 8 (Table 3).

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Fig. 5. The microstructure of 09G2S in various regions of HAZ of the filling passes of welded joints made by manual arc welding using the LB 52TRU 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. 6. The microstructure of 09G2S in various regions of HAZ of the filling passes of welded joints made by manual arc welding using the LB 52TRU 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. Conclusion Welding at low climatic temperatures has its own characteristics associated with an increase in the cooling rate of welded joints. With an increase in the cooling rate, the likelihood of the formation of quenching structures increases. 1. It has been established that the formation of the HAZ structure is significantly influenced by the ambient air temperature at which the welding process is carried out. 2. Investigation of the HAZ structure of 09G2S grade steel welded joints obtained by welding at different ambient temperatures showed that in areas of incomplete melting and overheating, welding at -45° C forms ferritic-carbide mixtures with a higher content of quenching bainite structures more finely dispersed than welding at room temperature. The results of structural studies can be useful for the development of welding technology at low temperatures for solving the problems of increasing the reliability and safety of products of equipment and structures operated under conditions of the North.