Estudo da restrição de juntas na soldagem de aço inoxidável duplex e dos efeitos na microestrutura, microdureza e tenacidade

Abstract

The duplex stainless steel present in its microstructure ferrite and austenita, in order to unite good mechanical properties and corrosion resistance. These materials possess are very used in chemical and petrochemical industry, being the DSS UNS S31803 one of the most known commercially. Generally, the manufacture and repair of any industrial equipment involve welding operations. The shielded metal arc welding had been carried for these situacions. There aren´t much works to the study of the influence of the precipitation of Widmanstätten austenite with application of restriction. Soon, this work has as objective to analyze the influence of the restriction of the together one in the phase balances, in the morphology of the precipitated austenite, in the microhardness and the toughness of the HAZ and the FZ. Coated electrode AWS E2209-17 had been carried through welding in V joint in the duplex stainless steel UNS S31803. Weldings in two levels of energy had been carried through: C1 (15 kJ/cm) and C2 (20 kJ/cm), with and without restriction. The energy used for the deposition of the root pass was of 5 kJ/cm. was made a gradual increase of the temperature of interpasse with the deposited passes. In a generalized manner, it had greater amount of ferrite in the finishing passes in relation to the root and wadding passes. Bigger amounts of Widmanstätten austenite in the conditions welded with restriction had been observed. Generally, the HAZ had a coarser microstructure in the finishing passes, in way that did not have significant differences when compared with the conditions with and without restriction. In relation to the microhardness, lesser levels in the conditions had been observed that had presented greater amount of Widmanstätten. Differences in the energy absorbed in HAZ and the FZ had not been observed, comparing the conditions with restriction and without restriction. Soon, the influence of the use of the restriction in the welding was verified, mainly in the phase balances, microstructure and microhardness.