Intense X-Ray Measurement of Transient Hydraulic Phenomena in Molten Pool During Laser Welding Process

Abstract

Spatial temperature distribution during the laser welding process has a huge effect on any residual stress distribution. Therefore, understanding of the transient hydraulic phenomena which affect the temperature distribution in the molten pool is very important. In this work, intense X-ray measurement at the Super Photon ring-8 GeV (SPring-8) facility well carried out to document the transient hydraulic phenomena in the molten pool during the laser welding process. Based on in-situ observation of inside material, the experimental results confirmed that the molten pool shapes, hydraulic condition such as flow velocity, etc.. In the case of laser power is 330W and spot diameter is 1mm, we observed the steady flow which consisted of downward flow and upward flow. The flow velocities were about 19.5 mm/s and 9.0 mm/s, respectively. Moreover, the rate of phase change was obtained from molten pool shape during laser welding. The rate of phase change was not constant during laser welding. Thus the interface shape might change at all time. Therefore, to evaluate the temperature distribution, it is necessary to consider not only convection but also the interface shape. These results indicate that the intense X-ray measurement during laser welding is very effective for the understanding the molten pool phenomena.