Simulação física da soldagem de manutenção em aço de alta resistência e baixa liga utilizado na indústria naval

Abstract

River transport has a great regional economic impact, due to its relationship with the environment, cargo transport capacity and the location of the Amazon basin, to which approximately 85% of the distribution of the vessel fleet is located in the region. During traffic, wear can occur, reducing the thickness of the hull, such as corrosion or impact with rocks. Assuming that the vessel has suffered damage from the outside, reducing the thickness of a steel plate in the vessel's hull, a thickness recovery will be made by maintenance welding on the inner side of the hull and the structure being on the water. This type of maintenance presents a great technical challenge as it abruptly removes heat and consequently alters the metallurgical weldability of the steels used, in this case, EN-10025-2-04-S355-J2-N. Thus, the objective of this work is to analyze the influence of factors: type of cooling (air or water), recovered thickness (25 or 50% of plate thickness), number of solder layers (one or two solder layers) and the welding energy used (low or high energy), on the microstructure and microhardness of the S355 J2N steel, welded with a 7018E coated electrode. A water circulation system at room temperature that sprays water on the face opposite to the weld was used to simulate the maintenance welding in the suggested hypothesis. Among the factors studied, the cooling type is the factor that has the greatest influence, because the abrupt heat removal. Significantly influences the captures thermal cycles (Δt8-5 of the specimen cooled with water are 90 % smaller), extension of the Heat-Affected Zone (área reduction of up to 77 %), in the formed microstructure (microstructures of the water-cooled samples are more refined), increase in hardness (up to 51 %), in the volumetric fraction of the martensite-austenite microconstituent, M-A (samples cooled with water have lower amounts of M-A), in the energy absorbed from the Charpy V impact test and in their respective fractographs.