Abstract
Mechanical properties of welded joints depend on the way heat flows through the welding passes. In multipass welding the reheating of the heat affected zone (HAZ) can form local brittle zones that need to be delimited for evaluation. The difficulty lies in the choice of a model that can simulate multipass welding. This study evaluated Rosenthal’s Medium Thick Plate (MTP) and the Distributed heat Sources (DHS) of Mhyr and Gröng models. Two assumptions were considered for both models: constant and temperature-dependent physical properties. It was carried out on a multipass welding of an API 5L X80 tube, with 1016 mm (42″) external diameter, 16 mm thick and half V-groove bevel, in the 3G up position. The root pass was welded with Gas Metal Arc Welding (GMAW) process with controlled short-circuit transfer. The Flux Cored Arc Welding (FCAW) process was used in the filling and finishing passes, using filler metal E111T1-K3M-JH4. The evaluation criteria used were overlapping the simulated isotherms on the marks revealed in the macrographs and the comparison between the experimental thermal cycle and those simulated by the proposed models. The DHS model with the temperature-dependent properties presented the best results and simulated with accuracy the HAZ of root and second welding passes. In this way, it was possible to delimit the HAZ heated sub-regions.
Highlights
IntroductionThe addition and the base metals are fused by the heat source and it still imposes phase changes in the solid base metal (BM), i.e., in the heat affected zone (HAZ) [1]
In electric arc welding, the addition and the base metals are fused by the heat source and it still imposes phase changes in the solid base metal (BM), i.e., in the heat affected zone (HAZ) [1].The retention time above certain temperatures reached along the HAZ dissolves precipitates and promotes its redistribution in the austenitic matrix together with grain growth [2,3,4]
This work proposes to evaluate the effectiveness of Medium Thick Plate (MTP) and Distributed heat Sources (DHS) models by overlapping the simulated isotherms on the marks revealed in the macrographs and by means of experimental thermal cycle
Summary
The addition and the base metals are fused by the heat source and it still imposes phase changes in the solid base metal (BM), i.e., in the heat affected zone (HAZ) [1]. A new proposal for the study of welding heat flux was based on the analytical model called discretely distributed point heat sources model (DHS) developed by Myhr and Grong [2], initially intended to predict the convection effects within the weld pool The difficulty of applying these models lies in the definition of the values of the physical properties, since they are temperature-dependent In this way, errors can be made when trying to delimit the HAZ regions, or to simulate thermal cycles with different maximum temperatures. The best option will be used to simulate the HAZ of multipass welding
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