Abstract
Keyhole laser welding experiments with 1.5 mm thick aluminum sheets (EN AW-6082) were carried out with transversal beam oscillation and wire feeding. A circular cavity, which was named buttonhole, formed directly behind the laser spot at certain oscillation frequencies. The welding states “no buttonhole”, “unstable buttonhole”, and “stable buttonhole” were distinguished. The melt pool dynamics were experimentally analyzed and correlated with the resulting roughness and waviness of the seam surfaces. Criteria for stable buttonhole welding were derived. On the basis of the cavity radii relations, it is shown that capillary pressure conditions can explain the movement of the buttonhole with the process.
Highlights
The laser has become an indispensable tool for production
Effective methods to increase the wettability by improved pre-heating of the base material include the beam oscillation in brazing direction [7] or the usage of a second laser beam [8]
A simplified model presented in Reference [19] explains the self-sustainability of a cavity in a melt pool by capillary pressure balance
Summary
The laser has become an indispensable tool for production. Through the development of beam sources and system technology, a wide range of applications is available, covering many fields of manufacturing processes such as primary shaping, forming, joining, cutting, coating, and heat treatment. Laser beam welding is one of the largest areas of application It enables precise and reproducible joining of components, and, through innovative approaches, the efficient production of seams with high-surface quality, which can be used in parts of the structure that later become visible to the customer [1]. Thermal laser conduction welding typically enables a higher joint strength in comparison to laser brazing, (see e.g., Reference [9]) In both process techniques, namely laser brazing as well as heat conduction laser welding, the amount of absorbed laser energy is almost completely determined by the one-time Fresnel absorption, which limits the energy efficiency of the process, especially in cases of aluminum alloys and solid-state laser sources with a wavelength of approximately 1 μm. Higher energy coupling is possible by applying deep penetration laser welding
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