Using a hybrid laser plus GMAW process for controlling the bead humping defect

A novel LEW + GMAW hybrid process was investigated, and its ability to suppress weld bead hump formation was characterized. The hybrid process had a relatively low-power-density laser spot focused a short distance in front of the leading edge of the GMA weld pool. The laser power and spot size were varied in tests and it was found that, for given GMAW process settings, bead humping was suppressed by laser heat input of sufficient power density. Comparison of the toe angles of humped and nonhumped weld beads made by the hybrid process and by the GMAW process suggested that capillary instability was likely a factor in weld bead hump formation, but it was not the sole factor in at least some of the tests. Observations made during the experiments suggested that weld pool fluid flows may have been an important factor in weld humping.