Mechanism and optimization of activating fluxes for process stability and weldability of hybrid laser-arc welded HSLA steel

The effects of activating fluxes on weld bead morphology, arc behavior, electrical signals, and temperature field were investigated. Real-time weld pool dynamics, electrical signal waveforms, and temperature contours were obtained by high speed camera, real-time electric signal acquisition card, and infrared thermal camera. The additions of SiO2, TiO2, ZnO, and Fe2O3 not only improved the weld formation and penetration depth but also reduced the welding voltage and increased welding current. Decomposition and evaporation of activating fluxes produced oxygen caused arc constriction and increased the laser efficiency. The effect of MnO2 was little. CaO and B2O3 dramatically deteriorated process stability since CaO and B2O3 gave rise to droplet transfer mode changing from spray transfer to short-circuit/ large globular repelled transfer.