Investigation into the effect of Ar ratio in He-Ar mixture side assisting gas on plasma properties during CO2 laser welding based on 3D reconstruction

In this paper, a set of synchronous CCD cameras were employed for image taking during CO2 laser welding with He-Ar mixed side assisting gas. The cameras recorded the projection of laser-induced plasma in different directions during welding process. 3D reconstruction based on algebraic reconstruction technology was performed through the projected 2D views of plasma. The volume, height on laser beam axis, and spatial inclination of plasma were extracted from the 3D reconstructed data as plasma characteristics. These characteristics were analyzed to investigate the effect of Ar ratio in He-Ar side assisting gas on plasma properties related to laser energy transfer as well as welding process stability. The experimental results demonstrate that an appropriate Ar ratio in the side assisting gas can help to suppress the plasma height interacting with incident laser and to increase the stability of welding process. (C) 2014 Laser Institute of America.