Evolução das tensões residuais e sua relação com a “misorientação” microestrutural de um aço astm dh36 após soldagem

Abstract

The residual stress is an important parameter to be studied in order to guarantee reliability and resistance of the structures and to avoid their future failures. A particular phenomenon about residual welding stress changes over time has recently been observed with the residual stress evaluation equipment RAYSTRESS. A study of the grain boundaries misorientation has been carried out with the purpose of explaining this phenomenon by the microstructure alteration. For the analysis of the microstructure, thermomechanical simulation with Gleeble®3800 equipment and scanning electronic microscopy in combination with backscattered electron diffraction (SEM-EBSD) technique were used. One of the relevant experimental procedures for the verification of the thesis involved the simulation of the sample for two hours and its subsequent placement in a vacuum chamber of the SEM, and then the microstructure analyses were carried out for a week with the EBSD technique. The results indicate that during this week there was a change in the misorientation of the microstructure, thus proving the correlation between the variation of the residual stresses and the change in the misorientation of the microstructure. The obtained results confirming the phenomenon associated with the residual stress variation after the completion of the welding procedure, have practical implications for the design and construction of welded structures, especially in the case of ships, in which the studied steel is representative of this type of welded structure.