Efeito da soldagem de reparo nas propriedades mecânicas e microestruturais de juntas soldadas do aço ASTM A131 AH36 usado em embarcações navais

Abstract

Recurring repairs with welding are carried out on the hulls of the ships, still in operation, to minimize production losses caused by a possible stoppage for maintenance or replacement of parts. Such welding procedures can increase the hardness of the HAZ and, as a consequence, increase the risks related to the weakening of the structure as a whole, when performed indiscriminately, without taking technical parameters into account. While some standards used in welding procedures limit the number of repairs performed, they also do not provide reliable assessments of the effects caused by these procedures in this region. Furthermore, the limitation of the bibliography regarding the study of the effect of weld repairs, carried out during the maintenance of ASTM A131 steel joints, used in naval vessels, constitutes the main motivation for carrying out this work. Given the relevance of the topic, the study is essential to provide support and precise instruction during the execution of repair welds in naval structures. In this sense, this work aimed to evaluate the effect of multiple repair welding through the gas tungsten arc welding process (GTAW) on the mechanical and microstructural behavior of an ASTM A131 AH36 steel alloy, used in boats. For this purpose, tensile strength, impact and hardness tests were carried out and the results analyzed in terms of microstructural alterations, grain growth and HAZ width. The results showed a trend towards a reduction in tensile strength, hardness and tenacity of welded joints modified by repairs. The dilution and the reintroduction of heat in the HAZ, associated with the microstructural transformations were the main attributed reasons. The reintroduction of sequential heat in this region, with the first, second and third repairs, increased them HAZ width by about 24% and the average grain diameter by 12,6%, 16,7% and 18,1% respectively in relation to as welded condition.