Observation of melt pool dynamics in pure copper welding with blue-IR hybrid laser

Abstract

A bead on plate welding test of pure copper plate was conducted with a hybrid laser which combined a high-power infrared (IR) laser and a blue laser to achieve a deep penetration and spatter-less welding of pure copper. A 1.5 kW class IR laser which has the wavelength around 1000 nm and a 1.5 kW class blue diode laser which has the wavelength of 450 nm were used as a heat source. The IR laser and the blue diode laser were irradiated perpendicular to the sample at the angles of 0° and 45°, respectively. Each laser was focused onto 2 mm thick pure copper sample and combined on the surface of it as a hybrid laser. The hybrid laser was scanned on the sample at 100 mm/s varying the output power of the IR laser and the blue diode laser. While scanning the lasers, the dynamics of melt pool formation and the spatters were observed with a high-speed video camera. After laser irradiation, the cross-section of the sample was observed and the penetration depth of the bead was measured. As the results, it was found that the penetration depth of pure copper increased and the number of spatters generated per scanning length decreased with the increase of blue laser intensity. Also, it was clarified that the melt pool dynamics affects the amount of spatter generated during welding.