Influência do pré-aquecimento e do gás de proteção na porosidade em juntas soldadas da liga de alumínio-manganês AA 3003

Abstract

Porosity is one of the most common defects in aluminum welding, the occurrence this type of defect in welds can compromise the integrity of the equipment. At emergency maintenance shutdowns, lost production and environmental impacts are examples of impacts caused by the unexpected failure of a welded component showing a high level of porosity. The main objective of this work is to study the incidence and behavior of pores along a weld bead in an AA 3003 aluminum sheet and correlate this incidence with the parameters of welding like, shielding gas type and preheating. the bodies of evidence were welded by the TIG process in three preheat conditions and gas type of protection. During welding, parameters such as voltage, current, gas, consumables and number of passes were monitored and the values ​​maintained same, regardless of the welding condition. The welding speed was measured, however it was not possible to keep the values ​​uniform because it is a TIG welding manual. The specimens were analyzed through the radiography test to porosity assessment. The porosity was analyzed from the digitized images of radiographic films using visualization software. The pores were quantified and the results showed that, taking into account only the parameters analyzed, it was concluded that the porosity reduction occurs by the increase of the preheating temperature and addition of helium in the shielding gas. But the prolonged exposures of aluminum alloy at elevated temperatures (300°C) cause changes in their properties and metallurgical alterations, discarding the its use in services in corrosive environments. Therefore, the use of parameters of moderate preheating (150 ºC) associated with shielding gas with high thermal potential can be used regardless of the severity of the medium to be exposed to the league.