Bead Morphology of Laser Welded Steel Sheets and Its Correlation to the Joint's Electrical and Mechanical Properties

Nowadays, lasers are routine tools in the widest range of materials processing, including welding of battery packs. The properties of the laser generated weld bead are crucial in determining the electrical and mechanical behavior of the joint. Here, we report on the identification of five morphological bead types, namely, Rosenthal, single wave, elongated, pre-humping, and humping morphologies and their systematic appearance over the laser power versus scanning speed plane. We prove that each type exhibits characteristic electrical and mechanical behavior that differ not only in the magnitude of relevant materials' properties, but also in their variability. We show for nickel-coated steel and uncoated DC01 cold rolled steel that the so-called single wave morphology is best suited for battery welding applications, since this morphology class concomitantly exhibits the lowest electrical resistance and the highest mechanical strength, both with a relatively small margin of error. The results suggest that the bead morphology could be exploited as a simple indicator of joint properties.