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 martensite volume fraction on the mechanical behavior of an UNS S41003 dual-phase stainless steel.(2020) Faria, Geraldo Lúcio de; Godefroid, Leonardo Barbosa; Nunes, Isadora Pereira; Lacerda, José Carlos deUNS S41003 (410D) steel is a relatively low chromium unstabilized ferritic stainless steel. It has superior mechanical and corrosion resistance than ordinary low carbon steels. Therefore, and for its relatively low cost among specialty steels, it is a strong candidate for replacement of low carbon common steels in many applications. In order to enable new applications for this steel, it is important to ensure good performance in relation to its mechanical strength, so the development of hardening mechanisms without significant loss of ductility is desirable. Dual-phase microstructures are an example that fits in this context, because they tend to increase mechanical strength and are favorable to the fracture toughness and fatigue resistance of steels. This research evaluated the influence of quenching heat treatments after intercritical austenitizing on the microstructure, tensile strength, hardness, fracture toughness (J x Δa curves) and fatigue crack growth resistance (da/dN x ΔK curves) of a 410D ferritic stainless steel. The used intercritical austenitization temperatures were defined based on its critical temperatures Ac1 and Ac3 measured by dilatometry. Ten different quenching heat treatments were performed, varying the austenitizing temperature and time, in order to obtain dual-phase microstructures (ferrite and martensite) with different volume fractions of constituents. The obtained results revealed that the increase of the austenitizing temperature and time favor the increase of the martensite volume fraction in the microstructure. Higher martensite volume fractions imply greater hardness and mechanical tensile and fatigue strength of the steel, but with loss of ductility and fracture toughness. The best balance among the studied mechanical properties was presented by steel treated at 825 ◦C for 15min, containing 57% of martensite.Item Microstructure and mechanical properties of two API steels for iron ore pipelines.(2014) Godefroid, Leonardo Barbosa; Cândido, Luiz Cláudio; Toffolo, Rodrigo Vicente Bayão; Barbosa, Luiz Henrique SoaresThis research compares the mechanical behavior of two API steels (X60 and X70) used in the longest pipeline in the world for the conveyance of iron ore. Tensile tests, Charpy impact tests, CTOD tests and fatigue crack growth tests are performed at ambient temperature. Metallographic examination showed a banded microstructure consisting of polygonal ferrite and pearlite in both steels, with smaller grain size and the presence of a small quantity of bainite in the X70 steel. All the mechanical tests revealed a ductile behavior for the two steels. The X70 steel is preferable for the pipeline project, due its better mechanical resistance, with no significant loss of fracture toughness and fatigue resistance. Its performance could be even better, if an appropriate combination of thermomechanical processing parameters were able to produce a microstructure with minor amount of pearlite, where acicular ferrite/bainite are present.