Efeito de diferentes configurações de chanfros nas propriedades mecânicas e microestruturas do aço ASTM 131-A soldado por arco submerso

Abstract

As the Brazilian dockyard in the river boat construction sector are highly competitive with each other, they feel the need to increase their productivity. One option is to use grooves configurations that require few manufacturing steps. Therefore, the purpose of this research is to know the influence of welded joints ASTM A 131 grade A, no-groove and single V-groove, welding by arc submerged, used in the manufacture of hull blocks for butane gas carriers. The chemical composition of the joint was determined by optical emission spectrometry. The mechanical properties of welded joints were determined by tensile strength, Vickers microhardness and Charpy impact tests. The microstructures of each region of the welded joint were verified by optical microscopy while their characteristics were determined by the instrumented indentation test. Optical macroscopy was used to verify the presence of welding defects. The welding flux used supplied Mn and Si to the weld metal of both joints. There is also the presence of slag in both joints. The micrograph showed basically the same microconstituents in each corresponding region between the welded joints, but the CC joint had a more refined structure, indicating that it had undergone a faster cooling. The Vickers microhardness and instrumented indentation tests performed along the welded joint regions showed that the hardness and resistance to deformation gradually increased from the base metal to the weld metal, and the values presented by the CC joint were higher than submitted by the SC. The tensile strength of the CC joint was higher than that of the SC joint, but both joints were influenced by the inclusion of slag, since for most samples the cracks started from the defect ends. The absorbed impact energy values of the CC joint were higher than the SC joint, and for all samples, the fracture occurred through the welding defect, which made the joints more brittle, but both joints presented absorbed impact higher than specified by the standard, as both joints showed large amount of acicular ferrite in the weld metal. In general, the mechanical properties of CC joints were superior to those of SC joints.