MAURILIO PEREIRA GOMES

MAURILIO PEREIRA GOMES

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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.
Effect of nitrogen addition to shielding gas on cooling rates and in the microstructure of thin sheets of duplex stainless steel welded by pulsed gas tungsten arc welding process
2019 - BETINI, EVANDRO G.; GOMES, MAURILIO P.; MUCSI, CRISTIANO S.; ORLANDO, MARCOS T.D.; LUZ, TEMISTOCLES de S.; AVETTAND-FENOEL, MARIE-NOELLE; ROSSI, JESUALDO L.
The effect of the nitrogen content in the shielding gas and its effect on temperature distributions at the welded zone of thin sheets of duplex stainless steel have been evaluated. The duplex stainless steels have many features due to unique microstructural combination of austenite and ferrite grains. The phase balance can be easily shifted depending on the welding parameters. Two sheets were welded using pure argon and pure argon plus 2% of nitrogen as shielding gas. The thermal profile had shown that N2-supplemented shielding gas lead to higher peaks of temperature using similar welding parameters. Microstructural examination showed that the austenite phase in the weld increased with the presence of nitrogen in the shielding gas. The added nitrogen promoted primary austenite formation and slightly increases the microhardness at the solidified zone. Microhardness mapping and metallographic imaging presented information about microstructures, confirming the formation of secondary phases during thermal cycle in the temperature range 850 °C and 950 °C. Control of ferrite amounts in the welds is essential mainly to improve mechanical properties and corrosion resistance of welding zones.
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.
Study of the thermal diffusivity variation in thin duplex steel plates welded by GTAW process
2018 - BETINI, EVANDRO G.; GOMES, MAURILIO P.; MUCSI, CRISTIANO S.; LUZ, TEMISTOCLES de S.; ORLANDO, MARCOS T.D.; ROSSI, JESUALDO L.
This study describes the thermal diffusivity of thin duplex steel plates in the thickness direction measured using the laser-flash method after welding. The work reports the experimental efforts in recording temperature profiles of the grade UNS S32304 duplex steel during autogenous welding. The butt weld autogenous joints were carried out by the GTAW (gas tungsten arc welding) process with either argon or argon - 2% nitrogen atmospheres. The amount of nitrogen in the heat affected regions, after welding, was measured and correlated with the variation of the thermal diffusivity of the studied material. The temperature profiles were obtained using k-type thermocouples connected to a digital data acquisition system. Different thermal cycles and thermal diffusivity values were observed in the heat-affected zone (HAZ) for both samples. In the solidified zone (SZ) was observed similar increase of the thermal diffusivity values for the plates welded with pure argon and argon plus nitrogen atmosphere.
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.
Study of the thermal diffusivity variation in thin duplex steel plates welded by GTAW process
2016 - BETINI, E.G.; ROSSI, J.L.; MUCSI, C.S.; GOMES, M.P.; ORLANDO, M.T.; LUZ, T.S.
This study describes the experimental efforts in recording 2-dimensional temperature distribution in thin plates autogenous UNS S32304 steel during welding. The butt-welded autogenous joints were experimentally performed by the GTAW (Gas Tungsten Arc Welding) process with either argon or argon-2%nitrogen atmospheres. The increase of nitrogen mass in the heat affected regions after welding was measured suggesting a correlation with the change in the thermal diffusivity of the material. The laser flash method (LFM) was also used to determine the thermal diffusivity of the material in the thickness direction. The cooling rates of the temperature cycles were recorded by thermocouples embedded by spot welding on surfaces of the plate and connected to an acquisition multichannel data system. The temperature curves suggest a relationship between the microstructures in the solidified and the heat affected zone with the diffusivity variation. These measurements define key parameters regards the residual stress study after welded process.