The paper presents the calculations of temperature field, volume fractions of structural components and strains during multipass GMAW surfacing of a prismatic element made of S235 steel. The bimodal heat source model is used in the description of temperature field. The solution takes into consideration the heating caused by the welding heat source during overlaying subsequent weld beads and self-cooling of already padded areas. The highest temperatures enable to determine characteristic heat-affected zones. The critical temperatures A1 and A3 are used to determine partial and full austenitic transformation zones, while the temperature of solidus is used to determine the fusion line. Kinetics of phase changes during heating is limited by temperature values at the beginning (A1) and at the end (A3) of austenitic transformation. In order to quantitatively describe the dependence of structure and material quality on temperature and transformation time of over-cooled austenite during surfacing, time-temperature-transformation at continuous cooling (TTT) welding diagram is used. The structural and thermal expansion coefficient values are determined on the basis of authors’ own dilatometric research. For calculations are used authors’ programs made in Borland Delphi. The results are presented in the form of temperature and volume phase fraction distributions in the element’s cross section as well as thermal cycles of volume phase fractions and strains at selected points.Keywords: multipass welding, temperature field, phase transformation, strains, GMA
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