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Welding with fusible electrode and shielding gas (GMAW) using a shielding mixture based on CO2 + O2 is a procedure with high potential for joining low-carbon and low-alloy steels compared with traditional mixtures based on argon. One of the reasons for this is related to the possibility of achieving a high penetration level without the need to increase the heat supply of the electric arc, by employing the shielding mixture of CO2 + O2, and the consequent decrease in the consumption of energy carriers. For that reason, the present paper presents a study on the influence of the shielding atmosphere characteristics (O2/CO2 ratio) and the welding current in the geometry of square groove weld joints on plates. For this purpose, a factorial experimental design was applied to obtaining regression equations, which would map such a behaviour. The equations were obtained using the O2/CO2 ratio and the welding current as independent variables. Nomograms were also plotted in order to make it easier to apply the results of this paper. [ABSTRACT FROM AUTHOR]

Failures in welded joints constitute a challenge that requires a scientific approach due to its phenomenological essence. This work determines the causes of failure in welded joints of a piping system, which were carried out with the SMAW process. Visual inspection, tension tests of the base material, chemical analysis by optical emission spectrometry as well as macrograph and metallography of the welded joint were carried out to a sample extracted from the damaged area using a cooled disc. In conclusion, we can say that the cause of failure has its origin in the poor procedure applied when welding, although other factors such as mechanical fatigue or an inappropriate design could also have been present. [ABSTRACT FROM AUTHOR]

A frequent problem, whose solution requires a scientific approach due to its phenomenological essence, is cracking in aluminum joints. The causes of cracking in 3003 aluminum joints by Gas Metal Arc Welding (GMAW) are defined in this research. The study was carried out on actual joints in a food product container. A refrigerated disk was used for extracting the sample, trying not to alter the material to maintain evidence of possible causes of failure. Macrograph of the welded joints, and visual inspection, chemical analysis by optical emission spectrometry, stress testing of base material analyzes were performed to the joint sample. It is conclude that the lack of fusion and penetration is the cause of cracking, which act as stress concentrations and they were originated by deficiencies when carrying out welding. [ABSTRACT FROM AUTHOR]