Investigation of the Effect of Welding Heat Input and Focal Distance of Laser Beam on Penetration Depth and Dynamics of Welding Pool Using a High-Speed Video Camera

The paper presents the investigation results of a metal plate re-melting process by a fiber laser beam using a high-speed video camera. The obtained video materials allow observing the transition process of molten metal to a solid state. The dependence of the molten metal transition to the solid state on the laser welding speed and on the focal distance (in the range of ± 20 mm) is analyzed. A quantitative analysis of the geometric dimensions of the microstructural components of the re-melted metal was carried out. When comparing the processed video material and microstructure elements of the molten pool, the similar trends are observed depending on the re-melting speed by a laser beam in a certain range of speeds from 20 to 45 mm/s. The obtained results can be used to develop a technique for estimating the presence of a key-hole depending on the laser focal distance.