Efeito dos transientes térmicos na soldagem de aços inoxidáveis duplex.

Abstract

The transient regime is a phenomenon inherent to the welding process, both at the beginning and at the end of each weld bead. However, when analyzing a weld bead or a welded joint, this region is discarded and the analyzed section is called the quasi-stationary regime region. In this region, there is no significant variation in the energy flow via heat; consequently, the bead shape and microstructure are homogeneous. This study aims to analyze the influence of the initial and final transient regime on the physical properties and weld bead morphology of duplex stainless steels UNS S32304 and UNS S31803 using the process GTAW (Gas Tungsten Arc Welding) with the addition of ER2209 and shielding gas Ar + 2%N2.Acquisitions of thermal cycles were performed with thermocouples positioned on the opposite face of the welded plate, and metallographic characterizations were carried out along the weld bead. Thermal cycles and cooling rates were used to identify the transition from transient to quasi-stationary regimes. The results showed that the transition from the initial and final transient regime to the quasi-stationary regime occurred at approximately 18 mm from the beginning of the weld bead. The transition from the quasi-stationary regime to the final transient regime occurred at distances of approximately 68.2 mm to 75.5 mm from the beginning of the weld bead. In addition, weld bead dimensions, such as the length of the fused zone, the extent of the heataffected zone, dilution, width, and bead angles α and β, were also analyzed. Based on the obtained results, it was concluded that the maximum temperature curves were useful to identify the transition from the initial transient regime to the quasi-stationary regime. However, for the final transient regime, only cooling rates were effective.These results provide important information about the effect of the initial and final transient regime during the welding process of duplex stainless steels. This information can be useful for developing more efficient welding strategies and for improving the quality of welded joints for these materials.