Caracterização micro-estrutural e mecânica do aço galvanizado dp1200, soldado pelo processo TIG com metal de adição

Abstract

Dual-phase steels are steels that fall into the new category called AHSS (Advanced High-Strength Steels), and that are being studied, developed and applied in technological advancement in automotive applications. When it comes to advanced steels, certain properties must be achieved and, thus, gaps in the processes are caused in relation to the study of the properties of these materials after processing, such as welding, plastic forming and machining, among others. Welding processes by nature are difficult to be analyzed, so in the processing of these metals, unwanted changes in product properties can occur, especially in the metallurgical zone most influenced by heat, that is, the Thermally Affected Zone (TAZ). The TIG (Tungsten Inert Gas) welding process, also called GTAW (Gas Tungsten Arc Welding), due to its high control of the melt pool, the excellent finish, the greater preservation of properties as a limit of mechanical resistance, as well as the possibility of welding very thin sheets, makes this process an alternative to which its study deserves emphasis to improve the union of these dual-phase steels. The present research aimed at the identification and microstructural characterization of the dual-phase steel DP 1200 submitted to the TIG welding process with the ER70S-3 and ER308L consumables and the relationship with the metallurgical and mechanical aspects. During the work, the steel was subjected to optical microscopy (OM), X-ray diffraction (XRD), X-ray fluorescence (XRF), and tensile and Vickers microhardness tests. As a result, by comparing welds with each consumable, it was obtained one without cracks, with a hardness in the weld region higher than to the base metal and greater than expected joint efficiency.