Visualization technique for quantitative evaluation in laser welding processes

Yamada, Tomonori; Shobu, Takahisa  ; Yamashita, Susumu   ; Nishimura, Akihiko  ; Muramatsu, Toshiharu; Komizo, Yuichi*

Residual stresses caused by welding processes are very important to keep structural health. The stresses depend heavily on the weld thermal history. Thus, we have studied mainly the hydrodynamic which affect the temperature distribution during a welding process. In this present work, we have carried out in-situ X-ray transmission imaging of a few metallic sample during laser welding. Hydrodynamics in a molten aluminum pool was observed using an intense synchrotron radiation source with tracer particles. In the laser intensity of 33 kW/cm, steady flow which consisted of downward flow and upward flow was observed in the molten pool. The Maximum flow velocities were about 19.5 mm/s. The simultaneous observation of molten pool shape and flow velocity enabled the evaluation of convective heat transport. Estimated heat quantity caused by the convective heat transport is almost the same or more than that of heat conduction which is supported by the simulation.