Soldagem de manutenção em chapas de baixa espessura de aço carbono via técnica de soldagem em operação.

Abstract

Welding processes are widely used by society, covering small to large components and in various industrial sectors. Among the various possible manufacturing pro-cesses, welding is widely used in the naval industry, which is extremely relevant to the Amazon region. River navigation is the main means of products transporting in the Amazon region and is of great importance for the development of the Amazon economy. During the use of vessels, it is necessary to carry out any ship mainte-nance on the structure due to damage that may lead to a reduction in the thickness of the structural components. This type of maintenance is usually done using weld-ing processes to restore the lost thickness. From this context, what would be the consequence to perform the vessel's hull thickness recovery, where welding in ser-vice takes place on the inner side (dry condition) and what about the vessel is in use, that is, in the water? In this hypothetical case, it is important to evaluate the weldability of carbon steels which compose the ship’s plates because the welding accomplished on these plates suffers an abrupt cooling caused by the water flow on the outside of the ship. Thus, the objective of this work is analyzing the behavior of welded joints in service when they are submitted to air and water cooling conditions. Welding will be carried out using the tubular wire process and it will occur in carbon steel sheets with thicknesses of 2 mm. Three weld beads will be made on each sheet: the first with an extension corresponding to 1/3 of the plate length; the sec-ond with 2/3 and the third along the entire length plate. In this way, it is possible to identify the influence of the second and third weld bead on the first weld bead. The results obtained through the microstructural characterization and hardness tests show that welded joints in water cooling condition have the presence of martensite, a characteristic microstructure of materials whose hardness is high, while in air cool-ing condition was found ferrite and less hardness.