Optimization of Laser Keyhole Welding Strategies of Dissimilar Metals by FEM Simulation
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NOWADAYS, joining dissimilar metals is indispensable in manufacturing and constructing advanced equipment and machinery. Different kinds of metals feature different chemical, physical, and metallurgical properties: some are more resistant to corrosion, some are lighter, some are stronger, etc. The aim of joining dissimilar metals is, therefore, to achieve different properties of metals in different parts of a component. This maximizes the performance of the component minimizing material costs. For dissimilar metal welds, it is common practice that mechanical properties of the joint should not be worse than those of the inferior base metal. Different methods of joining metals can be used: fusion welding, pressure welding, explosion welding, friction welding, diffusion welding, brazing, etc. Laser keyhole welding is one of the most promising joining methods because, compared with conventional welding techniques, it provides high productivity (associated to the high welding speeds), narrow joint and heat-affected zone (HAZ), manufacturing flexibility, and ease of automation. Dissimilar metal laser-weld failures occur in many industrial applications, generally attributed to the different VIRGINIA GARCIA NAVAS, JOSU LEUNDA, JON LAMBARRI, and CARMEN SANZ, Researchers, are with the IK4-TEKNIKER, Polo Tecnolo´gico de Eibar, C/In˜aki Goenaga 5, 20600 Eibar, Guipu´zcoa, Spain. Contact e-mails: [email protected]; [email protected] Manuscript submitted September 1, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
metallurgical and physical properties between the two materials, such as laser wavelength absorption, thermal conductivity, reflectivity, melting point, possible formation of brittle phases, and wettability. These different material properties, and as a consequence the different material response to laser, are the origin of the high difficulties of laser-welding dissimilar metals.[1] Consequently, much work should be done to define parameter-operating windows for the different alloys of industrial interest to produce laser-welded joints of dissimilar metals free of defects and with good material properties to guarantee the good performance of the welded component. The effect of laser parameters (laser power, welding speed, defocus distance, laser pulse energy, duration and repetition rates in pulsed lasers, laser beam diameter, etc.) on the final characteristics of dissimilar laser welds can be found in several experimental studies.[2–19] Most of these works are focused on the effect of laser parameters on weld bead geometry although some of them study also other characteristics of the joints such as the mixing behavior of the materials in the fusion zone, the microstructure, the presence of defects, hardness, and mechanical properties. Some authors[20–24] state that a displacement and/or tilting of the laser beam is a good strategy for welding dissimilar materials, able to yield good mechanical properties, high reliability, and repeatability in an industrial application. Panton et al.[5] state also that positioni
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