Avaliação das tensões residuais de juntas soldadas do aço API 5L X80 utilizado na indústria de petróleo.

Abstract

This study aimed to evaluate the residual stresses in three welded joints in a steel API 5L X80 , using manual welding processes already established by the API standard . The levels of transverse and longitudinal residual stresses developed in the upper and lower surface thereof , were analyzed. The samples were welded using the multi-pass technique, using the process combination of the GTAW and SMAW and SMAW processes. In welding consumables of different specifications were used. The residual stress measurements were carried out by X-ray diffractometry using a portable diffractometer and its software to analyze the results. With the aid of the graphs of residual stresses is sought to justify the behavior of the residual stresses relating them to the microstructures. In the upper region of the welded joints was observed that the higher was the more compressive heat input levels are transverse residual stresses, and more peaks were shifted from tensile residual stresses. The compressive behavior of weld metal on the top surface could is associated with the formation of acicular microstructures which is tenacious and able to better accommodate the residual stresses. In the lower region of the welded joints was observed that the higher the heat input was more trative were the levels of residual stress in the weld metal region and were lower levels of residual stresses in the heat affected zone (HAZ). For the welding parameters used, the ER1 sample had all passes welded with the SMAW process was that and had the lowest levels of residual stresses.