from the conferences organized by TANGER Ltd. provisional website
The paper presents the models of temperature field, phase transformation kinetics, the calculation of thermal and structural strains in a steel element during multi-pass Gas Metal Arc Weld surfacing. The temperature field is described analytically assuming a bimodal volumetric model of heat source and a semi-infinite body model of the surfaced (rebuilt) work-piece. The electric arc is treated physically as one heat source. Part of the heat is transferred by the direct impact of the electric arc, while another part of the heat is transferred to the weld by the melted material of the electrode. The temperature increments caused by overlaying consecutive welding sequences and self-cooling of previously heated areas are considered in the description. Kinetics of phase transformations during heating is limited by temperature values at the beginning and at the end of austenitic transformation, while the progress of phase transformations during cooling is determined on the basis of TTT-welding diagram and Johnson-Mehl-Avrami and Kolomogorov law for diffusive transformations, and Koistinen-Marburger for martensitic transformation. Total strains result from strain history in subsequent cycles of heating and cooling (as the result of the passage of the welding head) and are equal to the sum of thermal and structural strains induced by phase transformations in these cycles.Keywords: mult-ipass welding, temperature field, phase transformation, strains, GMA
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