Adição de elementos gamagênicos na soldagem de chapas de aço superduplex UNS S32750 por laser pulsado Nd:YAG
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2021-06-25
Autores
Seloto, Bruna Berbel
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Universidade Estadual Paulista (Unesp)
Resumo
Os aços inoxidáveis duplex e superduplex apresentam estrutura balanceada de aproximadamente 50% de ferrita e 50% de austenita, porém ao soldá-los, devido à alta velocidade de resfriamento e ao elevado aporte térmico, a zona fundida se revela predominantemente ferrítica. Dessa forma, a soldagem a laser Nd:YAG apresenta boa alternativa para esses materiais visto que oferece energia relativamente baixa e concentrada no cordão , consequentemente, Zona Termicamente Afetada diminuta, porém, mesmo que esse processo apresente boa qualidade na soldagem dos aços inoxidáveis superduplex, ainda há desbalanceamento das fases na Zona Fundida. Alguns elementos de liga contribuem para estabilização da fase austenítica nos aços inoxidáveis, entre eles: zinco (Zn), cobre (Cu), nitrogênio (N), manganês (Mn), níquel (Ni), cobalto (Co) e carbono (C). Dessa maneira, o presente trabalho observou a capacidade de balanceamento de fases na região de solda por meio de adição dos elementos gamagênicos cobre, níquel e cobalto em chapas de aço inoxidável superduplex UNS S32750 por meio da eletrodeposição. As análises se basearam na macroscopia, microscopia e microdureza Vickers. Ao todo foram realizadas treze amostras, três com adição de cobre com banho eletrolítico de 60, 80 e 100 minutos; cinco banhadas por níquel com tempos de 5, 6, 7, 8 e 10 minutos e cinco de cobalto com 15, 30, 31, 32 e 40 minutos. Após a eletrólise as chapas foram soldadas em juntas topo e sem abertura de raiz pelo processo a laser Nd:YAG na condição pulsado com parâmetros fixos velocidade de 1mm/s, tempo de pico 5ms, frequência 9Hz, energia de pulso 10J, potência de pico 2kW e gás argônio com fluxo de 20L/min. O resultados demonstram que as amostras de cobalto e níquel obtiveram bons cordões de solda, sem trincas e com pouca porosidade, destacando-se as amostras de níquel de 7 minutos e cobalto 31 minutos as quais houveram formação próxima de 50% de austenita e 50% de ferrita na Zona Fundida e com durezas semelhantes ao metal base. As amostras de cobre contiveram grande quantidade de trincas e porosidade, além disso, houve pouca formação de austenita para um longo banho eletrolítico. Referente a microdureza, entre as três amostra de cobre, a Cu100 apresentou a microdureza mais próxima em relação ao metal base.
The duplex and superduplex stainless steels have a balanced structure of approximately % 50 ferrite and 50 % of austenite, however, when welding them, due to the high cooling speed and the high thermal input, the molten zone is predominantly ferritic. Thus, Nd: YAG laser welding presents a good alternative for these materials since it offers relatively low and concentrated energy in the bead and, consequently, a small Thermally Affected Zone, however, even though this process shows good quality when welding superduplex stainless steel, there is still an imbalance of the phases in the Fused Zone. Some alloy elements contribute to stabilizing the austenitic phase in stainless steels, including zinc (Zn), copper (Cu), nitrogen (N), manganese (Mn), nickel (Ni), cobalt (Co) and carbon (C ). Thus, the present work observed the ability to balance phases in the weld region by adding the copper, nickel, and cobalt gamma elements in UNS S32750 super-duplex stainless steel sheets through electrodeposition. The analyzes were based on macroscopy, microscopy, and Vickers microhardness. In all, thirteen samples were taken, three with the addition of copper with an electrolytic bath of 60, 80 and 100 minutes; five bathed in nickel with times of 5, 6, 7, 8, and 10 minutes and five cobalt with 15, 30, 31, 32, and 40 minutes. After electrolysis the plates were welded on top joints and without root opening by the Nd: YAG laser process in the pulsed condition with fixed parameters speed of 1mm / s, peak time 5ms, frequency 9Hz, pulse energy 10J, peak power 2kW and argon gas with a flow rate of 20L / min. The results show that the cobalt and nickel samples obtained good weld beads, with no cracks and with little porosity, highlighting the nickel samples of 7 minutes and cobalt 31 minutes which had a formation of near to 50 % of austenite and 50 % ferrite with a hardness similar to the base metal. The copper samples contained several cracks and porosity, also, there was little austenite formation for a long time of electrolytic bath. Regarding microhardness, among the three Cu samples, Cu100 presented the closest microhardness in relation to the base metal.
The duplex and superduplex stainless steels have a balanced structure of approximately % 50 ferrite and 50 % of austenite, however, when welding them, due to the high cooling speed and the high thermal input, the molten zone is predominantly ferritic. Thus, Nd: YAG laser welding presents a good alternative for these materials since it offers relatively low and concentrated energy in the bead and, consequently, a small Thermally Affected Zone, however, even though this process shows good quality when welding superduplex stainless steel, there is still an imbalance of the phases in the Fused Zone. Some alloy elements contribute to stabilizing the austenitic phase in stainless steels, including zinc (Zn), copper (Cu), nitrogen (N), manganese (Mn), nickel (Ni), cobalt (Co) and carbon (C ). Thus, the present work observed the ability to balance phases in the weld region by adding the copper, nickel, and cobalt gamma elements in UNS S32750 super-duplex stainless steel sheets through electrodeposition. The analyzes were based on macroscopy, microscopy, and Vickers microhardness. In all, thirteen samples were taken, three with the addition of copper with an electrolytic bath of 60, 80 and 100 minutes; five bathed in nickel with times of 5, 6, 7, 8, and 10 minutes and five cobalt with 15, 30, 31, 32, and 40 minutes. After electrolysis the plates were welded on top joints and without root opening by the Nd: YAG laser process in the pulsed condition with fixed parameters speed of 1mm / s, peak time 5ms, frequency 9Hz, pulse energy 10J, peak power 2kW and argon gas with a flow rate of 20L / min. The results show that the cobalt and nickel samples obtained good weld beads, with no cracks and with little porosity, highlighting the nickel samples of 7 minutes and cobalt 31 minutes which had a formation of near to 50 % of austenite and 50 % ferrite with a hardness similar to the base metal. The copper samples contained several cracks and porosity, also, there was little austenite formation for a long time of electrolytic bath. Regarding microhardness, among the three Cu samples, Cu100 presented the closest microhardness in relation to the base metal.
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Palavras-chave
Soldagem a laser, Elementos gamagênicos, Eletrólise, Superduplex, Laser welding, Gammagenic elements, Electrolysis, Superduplex