Soldagem em operação de dutos de alta resistência e baixa espessura com ênfase nas trincas a frio

The aim of this study was to evaluate the occurence of cold cracks  associated with in-service welding of pipelines. Two sets of experiments were performed : the first of them was called experiment "F", where the gap between sleeve and pipe was varied and base and weld metal of high carbon equivalent were used, the second set of experiment was denominated "R", when higher restriction was imposed to the welded joint, which was simultaneously more rapid cooled by water flow within the pipe. The welds were made ​​with the following procedures and materials: shielded metal arc welding (SMAW) of tube and pipeline steel ASTM A 335 P5, using AWS E 8018-B8 as weld metal (experiment F). Pulsed MIG / MAG (GMAW-P) and self-shielded cored wire (FCAW-S) welding of tube and pipeline steel API 5L X70, by using respectively AWS ER 80S-G and AWS E 71T-11 filler metals (experiment "R "). To detect cold cracks visual and penetrant liquid inspection were performed. Additionally the welds were evaluated by macrography and microhardness measurements. No cracks were detected, despite the use of basic and filler metals of high carbon equivalent and the higher restraint and therefore more stressed joint. It is assumed that the integrity of the welded joints was due to the use of processes and / consumables with low hydrogen content.