Welding of the ASTM A106 Gr. B Steel Pipes for High Temperature Service - Part 2-Microstructure and Hardness

摘要

abstract_textpThe objective of this work was to evaluate the welding residual stress in small diameter pipes used in refinering settings. Pipes with a 50.8 mm (2 in) nominal diameter and 3.9 mm thickness were welded using GTAW manual process. The filler metal used was a AWS ER 70 S3. Were used an electronic power supply and data acquisition system to control of welding parameters. Metallographic samples were conventionally prepared and electropolished using a perchloric acid solution. Optical microscopy and scanning electron microscopy were used to evaluate the microstructure. The results show that the welding heat input combination between the root pass and the finishing pass with a low heat input promote a significant grain refinement of the fusion zone and heat affected zone, besides promoting a reduction in the hardness values. The same behavior was not reached for the samples welded with higher welding heat input. None of the welded samples presented hardness values above the maximum established for standard (248 HV)./p/abstract_text