The influence of different core-ring intensity distributions on the capillary shape and resulting weld in laser welding of steel

Laser welding was carried out using a co-axial core-ring beam, with independent control of the power to the core and the ring. The welding process was observed using high-power X-rays and high-speed imaging equipment. Adjusting the relative powers of the core and the ring beams was found to have profound effects on the shape of both the capillary created and the weld melt pool. Moderate laser power densities in the ring were found to increase the top diameter of the weld pool and reduce fluctuations in the welding process. High laser power densities in the ring led to the creation of a second capillary which largely acted independently of the capillary generated by the laser power in the core. At high power densities and welding speeds the two capillaries were almost completely separated in the direction of travel.