LUIS AUGUSTO MENDES DOS REIS

LUIS AUGUSTO MENDES DOS REIS

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Processing of zirconium sponge and zirconium alloys in an electric arc furnace
2022 - REIS, L.A.; MORAIS, N.W.; BETINI, E.G.; PEREIRA, L.T.; POLITANO, R.; BARBOSA, L.P.; MARTINEZ, L.G.; MUCSI, C.S.; ROSSI, J.L.
Zirconium and its alloys, as well as titanium and its alloys, are mostly used in the nuclear and aeronautical industries, respectively. A nuclear-grade zirconium sponge is the main component for obtaining nuclear fuel element cladding for nuclear power plants and other components, such as grids and springs. The zirconium sponge is also an important raw material in obtaining various alloys for nuclear fuels from small and medium power reactors, such as U-Zr-Nb. Thus, this project has relevance, since the clean melting of zirconium sponge will provide part of the domain of nuclear fuel technology. In this work, high entropy alloys (Ti-Zr-Nb-Ta-Fe-Cr) were produced in order to evaluate the evolution of the microstructure and modulus of elasticity as a function of temperature and heat treatment. A high entropy alloy with a composition different from those found in the literature is proposed. The materials were separated and melted in an electric arc furnace under a non-consumable electrode vacuum. These alloys were consolidated in the form of bars 220 mm long and thicknesses ranging from 8 to 12 mm. After melting, annealing was carried out at 1100 °C for 24 hours to homogenize the material obtained. The initial microstructural analyzes showed two very distinct phases with defined grain boundaries, the chemical etching to reveal the microstructure was a solution of 100 ml deionized H2O + 10 ml HNO3 + 2 ml HF. The samples are being quenched in oil and X-ray diffraction tests will be carried out in a hot chamber and the results will be presented at this congress.
Effect of shielding gas on thermal properties of thin plates of duplex stainless steel welded by pulsed GTAW process
2022 - BETINI, E.G.; TERUI, C.; REIS, L.A.; MUCSI, C.S.; LUZ, T.d.; ORLANDO, M.T.; ROSSI, J.L.
In this work, UNS32304 duplex stainless steel welds were evaluated by observing the influence of the pulsed GTAW welding process on thermal properties of this material. 1.8 mm duplex stainless steel sheets were welded by the GTAW process varying the shielding gases between pure Ar and Ar + 2%N2 without filler metal. The thermal welding cycles were studied by a type K and S thermocouple system fixed close to the welding line. The temperature distribution along the welding line was determined by reaching values within the phase transformation range of this material. Through a quantitative and semiquantitative evaluation of elements the Creq/Nieq ratio was calculated for the ferrite, austenite and secondary austenite grains of the solidified zone, ZAC and base metal. The addition of 2% N2 in the shielding gas caused an increase of the austenite formation in the solidified zone if compared to welding without N2 addition, being the most suitable atmosphere for welding in duplex stainless steels. The thermophysical properties were studied by laser flash method (MFL) used to determine the thermal diffusivity of the material in the thickness direction. The specific heat and Curie temperature of the solidified zone of welds was obtained by the thermal analysis by differential exploratory calorimetry (DSC). Measurements of porosities and specific mass of the solidified zone were obtained and compared with the base metal and metal as received. With this information it was possible to evaluate the thermal conductivity of the material after welding process. Increased thermal conductivity was found for both welded samples and suggest correlation with increased ferritic phase and decreased porosity also observed for solidified zone.
On the melting of zirconium alloys from scraps using electron beam and induction furnaces
2020 - PEREIRA, LUIZ A.T.; MARTINEZ, LUIS G.; MUCSI, CRISTIANO S.; REIS, LUIS A.M. dos; ROSSI, JESUALDO L.
The pressurized water reactor (PWR) employs UO2pellets as nuclear fuel, which are packedin zirconium alloy tubes called nuclear fuel cladding. In the manufacture of the nuclearfuel, machining scraps are generated which are not easily discarded as scraps because ofits high cost. These zirconium nuclear alloys are very costly and are not produced in Brazil.In this work, novel methods to recycle Zircaloy scraps using vacuum induction melting andelectron beam furnaces were used to obtain ingots. The cast ingots were subjected to ther-mal treatments and then chemically analyzed, followed by microstructural characterization,mechanical properties evaluation, and X-ray diffraction. The results indicated the feasibilityof the processes for obtaining alloys for application in the nuclear area, chemical industryor materials for biological applications such as dental prostheses.
Study of recycling process viability of zirconium alloys chips for melting in VAR furnace
2017 - REIS, L.A.M.; ALENCAR, M.; GOMES, M.P.; PEREIRA, L.A.T.; MUCSI, C.S.; ROSSI, J.L.
Cavacos de ligas de zircônio (M5, Zirlo, Zircaloy) são gerados em elevadas quantidades na confecção de tubos e tampões das varetas que compõem o elemento combustível de reatores de potência refrigerados a água pressurizada (PWR). Essas são ligas importadas e por isso é mostrado interesse pela indústria de reciclagem na sua reutilização. Este trabalho apresenta os estudos de um processo de reciclagem e a obtenção de eletrodos prensados para serem fundidos em um forno VAR (Vacuum Arc Remelting). O processo se inicia com uma separação magnética, lavagem do fluido de corte que é solúvel em água, utilização de um desengraxante industrial, seguido por um enxágue com fluxo contínuo de água em alta pressão e secagem por fluxo de ar quente. Para a obtenção de eletrodos, os cavacos foram prensados em uma matriz de seção quadrada 40x40 mm² com 500 mm de comprimento, resultando num eletrodo com 20% da densidade aparente da liga. A fusão foi feita um forno VAR de laboratório no CCTM-IPEN, gerando um lingote maciço de 0,8 kg. A fusão dos cavacos é possível e viável em um forno VAR o que reduz em até 40 vezes o volume de armazenamento desse material.
Influence of air quenching on apparent hardness of valve seat inserts obtained with AISI M2 high-speed steel powder
2017 - GOMES, M.P.; SANTOS, I.P.; REIS, L.A.M.; CIONE, F.C.; COLOSIO, M.A.; ROSSI, J.L.
The aim of this work consisted of evaluate the influence of heat treatment on sintered valve seat inserts (VSI) obtained with the AISI M2 high-speed steel powder. The AISI M2 high-speed steel powder was mixed with iron powder and additives such as manganese sulphide, zinc stearate, graphite and carbides. The heat treatment of the VSI consisted of air quenching followed by double tempering it in seven different equidistant temperatures, from 100 °C until 700 °C. The mechanical property was measured regarding the VSI apparent hardness. The results indicated that the VSI obtained with the AISI M2 high-speed steel powders mixtures showed the best results regarding its apparent hardness after air quenching and double tempering it at 600 °C.
Effect of the cooling rates on heat-affected zone of UNS S32304 duplex stainless steel welded by pulsed GTAW process
2017 - BETINI, E.G.; GOMES, M.P.; REIS, L.A.; MUCSI, C.S.; ALENCAR, M.C.; ORLANDO, M.T.D.; LUZ, T.S.; AVETTAND-FENOEL, M-N.; ROSSI, J.L.
Two thin plates of UNS 32304 of duplex stainless steel were joined by pulsed gas tungsten arc welding (GTAW) using a mixture 98% of argon plus 2% of nitrogen as shielding gas or pure argon as purging gas at the bottom of the plate without filler metal. The temperature profile close and away from the weld pool was measured using K type (Ni-Cr) thermocouples, connected to a digital data acquisition system. The thermal cycles was recorded in the heat-affected zone (HAZ) at a distance in between 1 and 3 mm from the joint line. The cooling rate and holding time were studied with respect to the used purging gas. Experimental thermal profiles are in good agreement with literature values. The joints welded without any purging gas revealed high peak temperature and cooling rates. The present investigation showed that temperature peaks are comprised in the phase transformation temperature ranges for the welded duplex stainless steel.
Characterization of sintered valve seat inserts obtained with AISI M2 high-speed steel after air quenching
2017 - GOMES, MAURILIO P.; SANTOS, IGOR P. dos; REIS, LUIS A.M. dos; COUTO, CAMILA P.; MUCSI, CRISTIANO S.; COLOSIO, MARCO A.; ROSSI, JESUALDO L.
The aim of this work was to heat treat and characterize sintered valve seat inserts (VSI). The powder metallurgy route was the only way found to substitute cobalt and lead, used in the VSI original alloy, due to their high cost and toxicological effect, respectively. The studied VSI was obtained with AISI M2 high-speed steel powder mixed with iron powder and other additives such as manganese sulphide, graphite, zinc stearate, carbides and copper, which was added by metallic infiltration. All the VSI were air quenched and double tempered, for one hour each, at seven different equidistantly temperatures, ranging from 100 °C up to 700 °C. The physical and mechanical properties were evaluated by means of the VSI apparent density, apparent hardness and crush radial strength. The chemical composition was determined through gas analysis, for the light elements such as carbon and sulfur, and energy dispersive X-ray fluorescence spectrometry for other elements. Microstructural characterization was performed with the support of scanning electron microscopy and energy dispersive spectroscopy. Regarding the VSI final application, the best results were achieved with the inserts air quenched and double tempered at 600 °C.
Study on welding thermal cycle and residual stress of UNS S32304 duplex stainless steel selected as external shield for a transport packaging of Mo-99
2019 - BETINI, E.G.; GOMES, M.P.; MILAGRE, M.X.; MACHADO, C.S.C.; REIS, L.A.M.; MUCSI, C.S.; ORLANDO, M.T.D.; LUZ, T.S.; MARTINEZ, L.G.; ROSSI, J.L.
Thin plates of duplex stainless steel UNS S32304 were welded using the pulsed gas tungsten arc GTAW process (butt joint) without filler addition. The used shielding gas was pure argon and 98% argon plus 2% of nitrogen. The thermal cycles were acquired during welding, in regions near the melting pool. This alloy is candidate for the external clad of a cask for the transport of high activity radiopharmaceuticals substances. For the residual stress measurements in austenite phase an X-ray diffractometer was used in a Bragg-Brentano geometry with CuKα radiation (λ= 0.154 nm) and for ferrite phase was used a pseudo-parallel geometry with CrKα radiation (λ= 0.2291nm). The results of residual stress using sin2 methodology showed that the influence of the high welding temperature leads to compressive stresses for both phases of the duplex steels mainly in the heat-affected zone. It was observed a high temperature peak and an increase of the mean residual stress after addition of ni-trogen to the argon shielding gas.
Investigação do processo para a reciclagem de cavacos de ligas de zircônio através da consolidação por fusão em forno a arco elétrico de refusão de eletrodos consumíveis sob vácuo (VAR)
2019 - REIS, LUIS A.M. dos
Os reatores nucleares de potência refrigerados à água pressurizada (Pressurized Water Reactor - PWR) comumente utilizam pastilhas de dióxido de urânio como o seu combustível nuclear, estas por sua vez são montadas e empilhadas em tubos e tampões de ligas de zircônio (M5, Zirlo, Zircaloy, etc), Na usinagem desses componentes são geradas grandes quantidades de cavacos que estão contaminados com fluido de corte, o armazenamento destes cavacos apresenta riscos de segurança e ambientais por ser um material pirofórico e apresentarem alta área específica. Estas são ligas importadas e por isso é mostrado interesse pela indústria de reciclagem na sua reutilização. Este trabalho apresenta o estudo de um processo de reciclagem e os resultados para buscar, eficiência no processo de limpeza; controle de qualidade; obtenção de eletrodos prensados e a fusão em um forno a arco elétrico sob vácuo (Vacuum Arc Remelting - VAR). O processo de reciclagem se inicia com uma separação magnética de possíveis materiais ferromagnéticos presentes, lavagem do fluido de corte, que é solúvel em água, lavagem com um desengraxante industrial, seguido por um enxágue com fluxo contínuo de água em alta pressão e uma secagem por fluxo de ar quente. A primeira avaliação do processo foi feita por uma análise de fluorescência de raios X por dispersão de energia mostrando impurezas provenientes da mistura com cavacos da usinagem de aços inoxidáveis. Os cavacos foram prensados para a obtenção de eletrodos, para fusão em forno VAR, e para isso foi desenvolvida uma matriz para obtenção de eletrodos. Os eletrodos foram fundidos em um forno VAR de laboratório no Laboratório de Fusão do CECTM IPEN. A fusão dos cavacos é possível e viável em um forno VAR o que reduz em até 40 vezes o volume de armazenamento desse material.
Uma discussão sobre a aeroelasticidade de quadricópteros não tripulados, drones, oferecendo subsídios para projetos
2018 - MUCSI, C.S.; ROSSI, J.L.; ALENCAR, M.C.; REIS, L.A.M.; ROSSI, A.C.
Os veículos aéreos não tripulados vem ganhando grande notoriedade, face à ampla gama de suas aplicações científicas e tecnológicas. Estes apresentam construções tão simples como brinquedos até equipamentos com altíssimo valor técnico científico agregado, destinados à missões relevantes. O presente trabalho visa apresentar uma discussão sobre a aeroelasticidade destes equipamentos na escala métrica, assunto árido e escasso nesta nova aeronáutica. São apresentados resultados de simulações numéricas relacionando o comportamento dos componentes estruturais em função dos esforços mecânicos, mormente os relacionados à mudança de atitude do equipamento, rotações e inclinações. Os resultados obtidos indicam a necessidade de cuidado e atenção no projeto dos braços dos quadcópteros, com especial atenção às suas seções transversais e à raiz do braço, na junção com o corpo; para evitar instabilidades que de outra maneira sobrecarregariam o processador do estabilizador de vôo. Estes dados estão servindo de base para o projeto e construção de um equipamento voltado à detecção e localização de fontes radioativas.