High-strength steels such as DOMEX 700 combine high mechanical strength and great ductility. However, when processed by welding their microstructure could present grain growth and deleterious phase formation. Nevertheless, using highpower GMAW-P the effects of electrode and shielding gas composition on the mechanical and microstructure properties of DOMEX 700 welded joints need to be understood. Thus, wire electrodes such as AWS ER 90S-D2 (A1) and AWS ER 120S-G (A2), and shielding gases such as Ar ? 15% CO 2 (G1) and Ar ? 8% CO 2 (G2) were used and the microstructure of welded joints was analyzed through optical and scanning electron microscope (SEM). Mechanical properties of joints was characterized through joint tensile test, impact test from 20 to-40°C, and microhardness in the joint cross-sectional. It is possible to highlight the increase in strength and elongation values with the use of electrode A2, and reduction in impact energy values for specimens welded by gas mixture G2.
Este trabalho busca avaliar o comportamento dos aços de alta resistência e baixa liga (ARBL) após a soldagem, devido as perdas de propriedades microestruturais do material quando submetido a soldagem. Desta forma os principais objetivos são, avaliar a influência de diferentes eletrodos na resistência a tração e na perda de dureza na zona termicamente afetada, em aços ARBL aplicados na indústria de máquinas agrícolas, soldados pelo processo de soldagem GMAW. Para confecção das amostras foram utilizados três diferentes eletrodos o ER70S-6, ER110S-G e o ER120S-G, ainda se utilizou como material base o aço LNE600 para comparativo com as demais amostras. Na soldagem os parâmetros de tensão e corrente foram mantidos constantes. Para os ensaios de tração, conclui-se que a soldagem que apresentou maior resistência ao escoamento foi realizada com o eletrodo ER120S-G com uma tensão média de escoamento de 680 MPa, seguida do eletrodo ER110S-G com 638 MPa, após LNE600 com 570 MPa e do eletrodo ER70S-6 de 550 MPa. Nos resultados obtidos de microdureza não houve diferença estatística para as regiões de grão grosseiro e grão refinado, apresentando maior dureza apenas no metal de adição para o eletrodo ER120S-G.
Duplex stainless steels are materials with high mechanical strength, toughness, and corrosion resistance, properties that make them rather appealing for the application on chemical and petrochemical industries. However, the exposure of such materials to high temperatures promotes the precipitation of deleterious intermetallic phases that cause significant damage to the mechanical and corrosion properties of these materials. In this study, the UNS S31803 duplex stainless steel received a thermal treatment at a temperature of 830 °C for 30, 90, and 180 minutes. After the treatment, the precipitates were characterized by backscattered electrons (BSE) and chemical composition mapping, and the properties of impact toughness were assessed by Charpy V-notch test for the different treatment conditions. The corrosion resistance properties were assessed by cyclic potentiodynamic polarization study. The thermal treatments at 830 °C resulted in a considerable reduction of impact toughness, and the corrosion resistance was also reduced in longer treatment times along with the loss of the passivation ability of the materials treated.
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