Estudo da qualidade micrográfica de juntas soldadas em ligas de alumínio pelo processo MIG

Abstract

The objective of this dissertation is the study of the micrographic quality of joints welded in aluminum alloys by the robotized MIG process. The treatments cycle consisted of solubilization, quenching, and artificial aging. It was also defined as a waiting interval between the last two treatments in order to evaluate the effect of possible natural aging. For the definition of the table of variables, we used the literature and the old works. For solubilization, 3 temperatures were defined: 480, 500 and 520ºC, and times of 30, 60 and 90 minutes. The wait time between quenching and aging was 0, 12 and 24 hours. And finally, the variables defined for the treatment of artificial aging were temperatures of 160, 175 and 190ºC, and times of 6, 14 and 20 hours. Using the Taguchi orthogonal matrix method, it was defined that for the number of selected parameters, 18 different tests would be required. For the study, plates of the AA6082-T6 alloy were soldered through the robotized MIG process, then the samples were cut, and the thermal treatments were carried out. After the heat treatments, the samples were characterized by optical microscopy and microhardness measurement in the welded joint. It was found that the solubilization temperature influences the hardness values, samples solubilized at 520ºC indicated hardnesses about 13% higher when compared to samples that were solubilized at 480ºC. In addition, comparing the sample that reached the highest microhardness value with a sample with no heat treatment, a 43% increase in the average hardness of the part was observed.