The effect of beam profile at a focal point on welding deformation. A study of the deformation behaviour by laser welding at micron or submicron level in automobile parts

摘要

Aiming to reduce the influence of welding deformation on the change in circularity in the circumferential welding of cylindrical parts such as electromagnetic actuators, an investigation was carried out by focusing on the beam profile of a laser. The following findings were obtained: By confirming laser energy distributions by way of laser profiles and making clear the relationship between the bead width and the penetration depth, the flattop-profiled laser beam with a narrower base is found to induce greater penetration depth than the convention ally used Gaussian-like profiled beam at the same bead width, hence higher melting efficiency in the plate-thick ness direction. In other words, with the same condensed beam diameter and the same laser output, the flattop-profiled beam enables deeper penetration than the Gaussian-like profiled beam owing to even energy density. High-speed welding with the flattop-profiled laser beam was confirmed to make it possible to improve circularity further than welding with the conventionally used Gaussian-like-profiled beam. The findings obtained in this study suggest that the change of circularity can be reduced to the sub-micron order. These results were obtained from the investigation of beam profiles at the focal point. A further study will aim to understand the mechanism of circularity change in detail by using numerical analysis and examine the phenomena of the whole process so that the technology for controlling deformation at the sub-micr6n level can be established.