EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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2 resultados
Resultados da Pesquisa
Item Effect of PWHT on laser-welded duplex stainless steel : the effects of postweld heat treatments on the microstructure, tensile behavior, and corrosion resistance of laser-welded duplex stainless steel were investigated.(2020) Magalhaes, Aparecida Silva; Magalhães, Charles Henrique Xavier Morais; Lima, Milton Sérgio Fernandes de; Alves, Juliane Ribeiro da Cruz; Godefroid, Leonardo Barbosa; Bertazzoli, Rodnei; Faria, Geraldo Lúcio deThe welded joints of duplex stainless steels (DSSs) have been widely used in petrochemical, nuclear, pulp, and paper industries. Welds require a good, superficial finishing and a combination of mechanical and corrosion properties in these types of high-quality, demanding applications. Even though laser welding promotes narrow weld beads and a small heataffected zone, when it is applied to DSSs, it can produce dangerous microstructural discontinuities. In this context, the effects of subsequent heat treatments on the microstructure, corrosion resistance, microhardness, and tensile properties of DSS laser-welded joints are investigated. In this study, samples of UNS S32304 DSS were submitted to two different conditions of laser welding. Subsequently, the plates submitted to the best welding condition were subjected to isothermal heat treatments at different temperatures (850°, 950°, 1050°, and 1150°C) for 10 min. Then they were microstructurally characterized. Phase fraction measurements and microhardness tests were performed. Based on the obtained results, postweld heat-treated samples at 1150°C, which is the best condition, were subjected to corrosion and tensile tests. It was possible to conclude the corrosion properties of the welded joint were significantly improved after the heat treatment. However, the mechanical behavior was strongly influenced by the presence of volumetric discontinuities and intermetallic compounds, which considerably deteriorated the mechanical strength of the material.Item Characterization of the austenite reformation mechanisms as a function of the initial ferritic state in a UNS S32304 duplex stainless steel.(2017) Magalhães, Charles Henrique Xavier Morais; Faria, Geraldo Lúcio de; Lagoeiro, Leonardo Evangelista; Silva, Jéssica DornelasAiming to better understand the effects of heat treatment parameters on Ferrite-Austenite phase transformation in a 2304 duplex stainless steel different thermal cycles were applied to this steel in a quenching dilatometer. The obtained microstructures were characterized by optical microscopy, transmission electron microscopy and electron backscatter diffraction. It was noticed that the austenite formation mechanism is strongly dependent on initial ferritized state. If the initial structure is completely ferritized, the nitrogen supersaturated solid solution leads to chromium nitrides precipitation and the rate of austenite nucleation decreases. For higher cooling rates, the ferrite grain boundaries control the austenite nucleation rate. The higher the ferrite grain size, the lower the final austenite fraction. If the steel is cooled from a partial ferritized state, the ferrite-austenite phase boundaries work as austenite nucleation site and the austenite growth rate is favored due to the high interfacial energy and the austenitic structures becomes coarser.