Influência da vazão do gás de purga na proteção de soldas em aço inox AISI 304 pelo processo TIG

Abstract

Stainless steels are metal alloys that have mechanical and metallurgical properties, generally different to the most common carbon steel alloys. The most remarkable feature of this alloy is its great corrosion resistance, whether in alkaline or acidic environment. The TIG welding process is the most used process for making metallic joints in these alloys, since the use of an inert gas and a non-consumable electrode can remove problems of oxide development in the weld beads. With the objective of analyzing the importance of using and identifying an appropriate inert gas flow to create a protective atmosphere in the region of the fusion pool and in the surroundings, it has chosen to make this process in different situations. Five AISI 304 stainless steel pipes were chosen to be welded with AISI 309L stainless steel rods, and each with a certain flow of argon gas inside the pipe. Using a gas flow changing of 2.5 l/min for each pipe, starting from zero up to 10 l/min. After the samples welded, they have cut and separated for the surface corrosion experiment. The experiment has done by partial immersion in a saline solution with a concentration of 3,500 ppm of sodium chloride in water and left out of doors. The total immersion time was 120 hours, with solution change of every 24 hours. At the end of the corrosion experiment, it has identified that samples with the flow of 7.5 and 10 l / min have showed less signs of corrosion and a weld bead with the cleanest root.