Abstract in Portuguese:

Resumo Nesse trabalho foi proposto avaliar diferentes composições de fluxos para arco submerso factíveis de utilização em suporte de raiz por fluxo, para soldagem de passes de raiz depositados pelo processo de soldagem MIG/MAG. O objetivo foi identificar o efeito dos fluxos sobre a qualidade geométrica do passe de raiz. Para fins de comparação entre fluxos, foi desenvolvido um método para utilização de fluxo como suporte de raiz. Critérios de não aceitabilidade, baseados na geometria do cordão, foram propostos para a análise do desempenho. Cinco diferentes tipos de fluxos foram avaliados sob uma condição de corrente de soldagem (visando alta produção), faixa de folga de raiz e velocidade de soldagem. Análises estatísticas para diferenciar médias e redução de incerteza foram aplicadas como ferramenta. Os efeitos de cada fluxo sobre a geometria da raiz foram analisados. Como conclusão, verificou-se que as características dos fluxos agem de forma concorrente como suporte de raiz. A basicidade parece ser governante na altura de reforço, enquanto a granulometria parece ser governante sobre a convexidade da raiz. Já a regularidade da raiz depende tanto da granulometria como da basicidade. O efeito do ponto de fusão é incerto, não predominando sobre as demais em nenhum dos três critérios.

Abstract in English:

Abstract In this study, it was proposed to evaluate different flux compositions for submerged arc welding that are feasible for use as root backing flux in root pass welding performed by the MIG/MAG welding process. The aim was to identify the effect of these fluxes on the geometric quality of the root pass. For comparison purposes, a method was developed to use the flux as root support. Non-acceptance criteria, based on bead geometry, were proposed to analyze performance. Five different types of fluxes were evaluated under a single welding current condition (aiming at high productivity), root gap range, and welding speed. Statistical analyses to differentiate means and reduce uncertainty were applied as tools. The effects of each flux on the root geometry were analyzed. As a conclusion, it was observed that the characteristics of the fluxes act in a competing manner as root support. Basicity appears to be a determining factor in reinforcement height, while grain size seems to govern root convexity. The regularity of the root depends on both grain size and basicity. The effect of melting point remains uncertain, not prevailing over the others in any of the three criteria.

Abstract in English:

Abstract Resistance spot welding is a widely used welding process for thin plates in industries such as aerospace and automotive. This process involves the combination of heat, force, and electricity, and the development of numerical simulation technology for welding processes has enabled the simulation of complex welding phenomena. Numerical simulation can reduce the need for extensive experimental work and improves welding production efficiency. In this article, the focus is on studying the temperature field and process parameters of resistance spot welding of (0.2+0.2 mm) 304 stainless steel. Initially, a three-dimensional symmetric model was created using Solid Works, and then Abaqus is used to perform a numerical analysis of the thermal-electric three-field coupling. The impact of welding parameters (welding current and welding time) on the temperature field and nugget diameter are analyzed. Next, welding experiments are conducted on the workpiece using different welding times and welding currents. The morphology and diameter changes of the molten material nucleus are observed using a high-magnification digital microscope. The results of the numerical simulation analysis and spot welding experiment analysis for resistance spot welding of 304 stainless steel with an equal thickness of 0.2+0.2 mm show a high level of consistency. Finally, tensile testing is carried out on the solder joints, combining this with the diameter to evaluate their strength and quality for the determination of the optimal welding process parameters.