A novel measurement method for solidification rate of weld pool surface

Laser spot welding of mild steel was used to reveal the uniform retracting solidification process of the small scale molten pool. A novel method for calculating the solidification rate of laser spot weld pool surface was presented. The surface temperature of weld pool during solidification process was measured by a point infrared sensor. Based on the difference in emissivities of the solid surface and liquid surface, the output data of infrared sensor, which can accurately reveal the liquid-solid transformation, was demonstrated, from which the solidification rates at different locations of the molten pool surface were obtained. Experiment result shows that the solidification rate is related to the bottom weld diameter. This method is also appropriate to measure the solidification rates of various metals in other heat processes.