The increasing demand for efficient and powerful lasers causes the market for fiber-and disc lasers to grow. These systems include high brilliance and so the ability of realizing very small foci or long focal length.
This research phenomenological analysis was performed to understand the correlation between small foci and welding depth. Besides, the stability of the laser process and the resulting strength of a double steel sheet joint are investigated.
The power density in the laser beam increases as focusing increases and foci become smaller. But as the flank angle becomes steeper, the Rayleigh length decreases. This can also mean less welding depth. The investigations on bead on plate and beam shape measurements determine a focal diameter threshold below which the welding depth starts decreasing.
Often root fusion occurs at multi sheet joints to maximize the resulting strength. But this can also lead to weld imperfections through holes or burn-ins. This research demonstrates that a controlled reduced welding depth can also provide nearly the same strength and does not impair the underside of the sheet or its coating.