Wobbling laser beam welding of copper

• Autor(a) principal: Franco, Diana Ferreira
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/27684
• topic: Electrolytic Copper welding; Laser beam welding; Laser modulation; Laser Wobbling; Electrical conductivity; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Mecânica

The increase of electrical components in automotive industry and the expansion of renewable energy generation lead to a rising need of a reliable and highly productive welding process for copper. Laser beam welding of copper has been a challenge due to the high thermal conductivity of Cu and its low absorptivity of laser radiation. However, recent developments suggest that these problems can be overcome by power spatial modulation of the beam. This research work was developed at Carrs Welding Technologies, UK, aiming to study the feasibility of fiber laser to weld electrolytic copper components to batteries. The main goal was to determine the parameter combination that allows to obtain a welded seam free of porosity and other weld defects with a penetration of 1.5 mm without losing electrical conductivity which was a mandatory requirement. In a first stage, multiple weld beads with different welding parameter combinations were produced in order to determine the influence of each parameter in the process. In the second stage, single-mode and multimode fiber lasers were compared. The outcome of these two stages were examined using metallography and electrical conductivity tests, namely, Eddy Currents. The results have shown that power spatial modulation can supress porosities, weld shape defects and spatter. A penetration of 1.5 mm can be achieved for a multimode beam power above 4 kW, welding speed between 3.5 and 4 m/min with a circular spatial modulation with a beam rotation of 0.6 to 1 mm diameter at 100 Hz frequency. The hardness measured suggest that there is no significant variation of mechanical resistance of the joins compared to the base material. Electrical conductivity measurements showed there is no variation in the welds. Finally, single-mode fiber laser produced narrow and deeper welds than when multimode fibers were tested, as expected