Laser beam welding of brass with combined core and ring beam

Abstract

Brass represents a large part in the production of components within the copper alloy group. Laser beam welding of this alloy offers great potential for many applications in terms of achievable seam quality and productivity. However, there is a very high tendency of the process for irregular seam surfaces and formation of pores as well as spatters. These are due, among other things, to instabilities of the keyhole, which is favored by the evaporation of the alloy component zinc. Furthermore, near-infrared laser beam wavelength can couple poorly into the material due to the low absorption level of brass, whereas absorption jumps during the melt transition. In recent years, high-brilliance near-infrared laser beam sources with adjustable beam profiles have been developed, to contribute to the stabilization of the keyhole. The presented experimental process investigations are on deep penetration welding of different brass alloys (CuZn37 and CuZn39Pb3). A laser beam source with a power of 6000 W and a combined core and ring beam was used for this purpose. It was found that the process parameters, such as energy per unit length, spot size, and process gas supply, have a significant impact on the resulting weld seam. These parameters were systematically varied. The produced seams were analyzed and evaluated using various methods, including micrograph analysis, energy dispersive x-ray spectroscopy, 3D-computed tomography, and 3D-topography imaging. The results were then correlated with the process parameters. Process parameters that produce high-quality bead-on-plate and butt welds for a sheet thicknesses of 2 mm were determined.