Análise da mudança do perfil geométrico da ferramenta sobre as características simuladas na soldagem FSW do aço inoxidável austenítico AISI 304L.

Abstract

Friction Stir Welding (FSW) is a welding process developed at The Welding Institute (TWI) that consists of joining metal sheets below the melting temperature of the material, using the plastic deformation caused by the rotation of the tool. The geometry of the tool is one of the essential factors for successful welding, since it is the one who, according to the welding parameters used, will perform the mixing of the material in the plastic state. As austenitic stainless steels are widely used in industry, the material chosen for the study was AISI 304L. The numerical simulation of FSW has been studied recently, and more and more authors contribute to the advancement of an increasingly efficient method. This study has as main objective to analyze a new tool profile in the simulation of FSW welding of AISI 304L austenitic stainless steel, comparing it with previous results obtained with a simplified tool configuration. Seven simulations were carried out with different welding parameters, and the results of temperature and viscosity were evaluated and compared with previous simulations and with their macrographs. The present study results showed that changing the tool causes an increase in the peak temperature observed at similar points, and a different profile of heat distribution along the cross section, due to a change in the conditions of heat conduction along with the piece. In addition, the change in the tool profile also caused changes in the viscosity behavior, indicating zones of (low / high) viscosity in regions where defects such as tunnel voids or hook-like recesses have occurred, specifically in the retreating side of the tool. This demonstrates that the simulation of the viscosity behavior can be effective in predicting certain types of defects. Another analysis was an attempt to identify the limits of the different regions of the weld: mixing zone, thermomechanically affected zone and heat affected zone. Some criteria have been proposed for the identification of these zones through numerical simulation.