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.
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.
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.
Valve seat insert: air quenching and characterization of components obtained with AISI M3:2 high-speed steel
2018 - GOMES, M.P.; SANTOS, I.P.; REIS, L.A.M.; COUTO, C.P.; BETINI, E.G.; MUCSI, C.S.; COLOSIO, M.A.; ROSSI, J.L.
The development of components ecologically correct is something more and more necessary. The first developement of valve seat inserts (VSI) take in account the use of cobalt and lead in its chemical composition. Such elements are avoided in the current applications due to its high cost and toxicological effects, respectively. In the present work was used VSI developed with a new chemical composition. The aim of this work were to air quench and characterize such components. The studied VSI were obtained with AISI M3:2 high-speed steel admixed with iron powder and another additives such as manganese sulphide, graphite, zinc stearate and carbides. All the air quenched VSI were double tempered, for one hour each, at seven equidistant temperature from 100 °C until 700 °C. The air quenched components had its mechanical and physical properties determined by means of its apparent density, apparent hardness and crush radial strength. The chemical composition was measured through the gases analyses and energy dispersive X-ray fluorescence spectrometry techniques. Microstructural and phase characterizations were performed with the support of optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Regarding the VSI required properties, the best results were obtained with the components air quenched and double tempered at 600 °C.
Experimental study of the weld pool temperature of thin plates of UNS S32304 duplex stainless steel by GTAW process
2018 - BETINI, E.G.; BATLLE, J.; MUCSI, C.S.; LUZ, T.S.; ORLANDO, M.T.; ROSSI, J.L.; SOUZA, A.C.; REIS, L.A.M.
The aim of the experimental arrangement is the measurement of the weld pool temperature during the application of the conventional arc GTA-welding on autogenous thin plates of UNS S32304 duplex stainless steel. Grade UNS S32304 was developed for the most severe applications including off-shore. The stationary arc welding was applied with a DC current for two minutes using pure argon as shielding gas in center of the duplex stainless steel disc. For the temperature into the weld pool were used a S-type (Pt-Rh) and K-type (Ni-Cr) thermocouples connected close to weld pool. The temperatures were measured in top and botton sides of the plates. It was observed an overheating temperature into the weld pool on the top side and as expected the fusion point was verified in corresponding at the bottom side. The microstructure was characterized and an increase of ferrite phase in solidified zone and heat affected zone was observed. The hardness mapping provided information about mechanical properties behaviour. A numerical analysis of temperature distributions were used to simulate welding cycles associated to microstructure evolution.
Heat treatment of sintered valve seat inserts
2018 - GOMES, MAURILIO P.; SANTOS, IGOR P. dos; COUTO, CAMILA P.; BETINI, EVANDRO G.; REIS, LUIS A.M. dos; MUCSI, CRISTIANO S.; COLOSIO, MARCO A.; ROSSI, JESUALDO L.
The characterization of sintered valve seat inserts (VSIs) after being subjected to different heat treatment operations has been carried out. The VSIs were obtained from three different alloys by mixing iron powder with AISI M3:2, AISI M2 high-speed steels, and AISI D2 tool steel. After sintering, the VSI were quenched in air followed by double tempering at seven different temperatures. The cooling rate during air quenching was measured by means of a thermocouple type k attached to a data acquisition system. The characterization of the mechanical and physical properties of the VSIs was achieved by measuring relative density, apparent hardness and crush radial strength. The resulting microstructures for the sintered parts were interpreted using the isothermal and continuous cooling transformation diagrams for similar alloys. The VSI obtained with AISI M3:2 and AISI M2 high-speed steels after air quenching and double tempering at 600 ºC showed the best results in terms of apparent hardness and crush radial strength.
Study on welding thermal cycle and residual stress of UNS S32304 duplex steel selected as external shield for a transport packaging of Mo-99
2017 - BETINI, EVANDRO G.; GOMES, MAURILIO P.; MILAGRE, MARIANA X.; MACHADO, CARULINE S.C.; REIS, LUIS A.M.; MUCSI, CRISTIANO S.; ORLANDO, MARCOS T.D.; LUZ, TEMISTOCLES S.; ROSSI, JESUALDO L.