Comportamento mecânico e metalúrgico do aço dual phase 1000 galvanizado e não galvanizado em juntas soldadas pelo processo gmaw com transferência por curto-circuito na indústria automotiva

Abstract

With a focus on sustainable growth, automotive industries have been investing in the development of vehicles with materials that reduce mass and provide greater safety for passengers. Dual Phase (DP) steels have stood out among advanced high-strength steels (AHSS), due to their high mechanical resistance, good toughness and ductility. Likewise, GMAW welding by conventional short circuit has shown promise as it is one of the most productive and cheapest processes among existing welding processes. This thesis proposes GMAW welding by conventional short circuit of galvanized and non-galvanized DP 1000 steels with 1.39mm thickness, with variations in welding parameters, preceded by a systematic study of the microstructural and mechanical characteristics of the same, aiming at the production of welded joints with good mechanical and metallurgical characteristics for applications in the automotive industry. The microstructure characterization was carried out using optical microscopy (OM), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and electron backscattered diffraction (EBSD). The mechanical characteristics of the base metal were carried out using Vickers tensile and hardness tests. The most representative welded joints were subjected to uniaxial tensile tests, Charpy, and microhardness mapping. Its microstructural characteristics were analyzed by scanning electron microscopy (SEM), as well as its geometries. As a result, for conventional short circuit welding of coated DP 1000 steels, there was a need for a lower heat input, due to the zinc layer that covers the material. Geometrically, the weld beads of coated and uncoated DP1000 steel met the specifications presented in the German standard SEP 1220-5 (2020). Finally, welding with the GMAW process by conventional short circuit for galvanized and non-galvanized DP 1000 steels constituted a very viable alternative with regard to the mechanical properties presented, as despite reductions in tensile strength limits being observed, and maximum elongation, the reductions occurred within acceptable ranges.