Evaluation of s355nl Steel Welded by Flux Cored Arc Welding Using Different Tubular Wires

High strength low alloy (HSLA) steels are used in several industrial sectors, as they have good mechanical strength and easy weldability. This HSLA is present in several areas, such as naval, petrochemical, piping, and civil construction. S355 NL steel is HSLA grade and has its application in the manufacture of the Brazilian submarine. For the manufacture and finishing of a Brazilian submarine, countless welds are performed during the assembly steps. The welding process currently applied is FCAW (Flux Cored Arc Welding), and the currently applied filler metal is of French origin. However, this import, from France to Brazil, makes manufacturing costs high and the waiting time for the imported product to arrive is long. Thus, in this work, the idea was to characterize a national filler metal (Brazilian) that similarly maintained the microstructure and consequently its mechanical and electrochemical properties concerning the imported filler metal (French). Therefore, the present work aimed at the microstructural, mechanical, and electrochemical characterization of S355NL structural steel welded by the FCAW process with national tubular wire (Brazilian) and imported tubular wire (French). We performed microstructural characterization with the aid of optical microscopy (OM) and scanning electron microscopy (SEM). For the mechanical characterization, we performed the following tests: tensile test, Vickers hardness, and impact at room temperature and -40oC. In the electrochemical characterization, it generated polarization curves where the samples were exposed to a 3.5% NaCl solution to test the behavior in corrosive media. The results showed that the wires, national and imported, behaved homogeneously and uniformly concerning the mechanical properties. In the electrochemical part, the national material presented in the weld metal a corrosion current density interesting. Therefore, the national tubular wire is a promising filler metal for the welding application of this Brazilian submarine.