Estudo da qualificação de procedimento de soldagem de tubos de aço ASTM 335 P22 utilizados em caldeiras aquatubulares do setor sucroalcooleiro.

Abstract

The objective of this work is to investigate the relationship between the variation in welding parameters using the SMAW and GTAW processes, along with the use of related techniques, and the properties of welded joints in ARBL steel, with a special focus on toughness and hardness. The aim is to ensure greater safety in operations and prevent sudden interruptions for maintenance in boilers in the sugarcane and alcohol sector. In this study, an ASTM 335 P22 steel pipe with an outer diameter of 73 mm and a wall thickness of 9.53 mm was used. Four joints were fabricated, referred to as joints 01, 02, 03, and 04. Joints 01 and 02 were welded using the SMAW process (root pass + hot pass + filler pass), while joints 03 and 04 were welded using the GTAW process for the root pass and the SMAW process for the hot pass and filler pass. In both processes, there was variation in the current and consequently the Welding energy. Metallographic analysis revealed that the base metal of the welded joints had a ferrite-pearlite

microstructure, characteristic of steels in the 2.25Cr-1.0Mo family. The heat- affected zones of joints 01, 02 and 03 exhibited a microstructure composed of

ferrite and tempered bainite. Whereas the heat-affected zone of joints 04 showed a microstructure consisting of ferrite, tempered bainite and regions containing martensite. The weld metal region of joints 01, 02 and 03 is composed of ferrite and tempered bainite, while joint 04 exhibits regions of martensite. Vickers microhardness tests showed that only joint 02 exhibits an average microhardness below 250 HV in the HAZ and the weld metal. The results of Charpy impact tests conducted at -30°C revealed a completely brittle behavior in all joints in the weld metal region.