Keyhole welding studies with a moderate-power, high-brightness fiber laser

Bead-on-plate welding tests were performed using a 600 W fiber-delivered fiber laser. Uniform, high-aspect-ratio keyhole welds were observed in 1018 low-carbon steel, 1100 aluminum, and 304 stainless steel. The Rosenthal two-dimensional thermal model for a moving-line heat source was effective in predicting weld width for both partial-penetration and full-penetration welds. By setting the temperature at the perimeter of the keyhole equal to the vaporization temperature, this same model provided a first-order estimate of the weld depth for partial-penetration welds, as well. The two-dimensional model was used to calculate the steady-state temperature field associated with the welding process as well as the temporal thermal history of points in the weld pool and in the heat-affected zone next to the weld pool. A comparison of calculated weld-bead geometries with dimensions scaled from micrographs of bead cross sections showed reasonable agreement.