Efeito do alívio de tensões sobre as propriedades mecânicas de uma junta soldada do aço API 5L X60.

Abstract

The purpose of this work was to analyze the influence of the time and temperature of relief stress thermal treatment on the hardness and impact resistance of a welded joint of an API 5L X60 steel pipeline used for petroleum transmission. For this, Vickers hardness and Charpy impact test at 253K (-20 C) were executed in specimens extracted from weld metal, heat affected zone (HAZ) and base metal submitted to thermal treatment at 823K (550 C) and 923K (650 C) for 1 hour and at 923K (650 C) for. lh, 5h, 8h and 11 hours. The results indicated an increase of weld metal and HAZ impact resistance for treatment of 1 hour at both temperatures, with larger efficiency at temperature of 823K (550yC). However, it was observed a great decrease of metal base impact resistance at temperature of 923K (650 C). A decrease of the impact resistance for all the welded joints regions was observed for time higher than 8 hours at 923K (650 C), in spite of the stability of hardness values.