Flow characteristics and element distribution of melten pool in 22MnB5 laser welding with Al-Si coating

The flow behavior of the molten pool plays a decisive role in the distribution of coating elements in the weld seam. By establishing a three-dimensional transient numerical model of the laser welding molten pool, the flow behavior of the molten pool in laser welded of 22MnB5 high-strength steel with Al-Si coating and its influence on the distribution of Al elements in the weld seam were analyzed. In the welding experiment, The reliability of the numerical model was verified based on the scanning data of the welding joint using an energy spectrometer. The flow behavior of the laser welding melten pool and the distribution of Al element in the weld seam were studied by combining simulation and experimental results. The results showed that, according to the different energy and power density thresholds of the laser welding line, the morphology of the melten pool presented three characteristics: keyhole free, partially penetrated keyhole, and fully penetrated keyhole, with significant differences in temperature field, flow field, flow rate and stability. The keyless molten pool has the best stability due to its uniform flow velocity distribution and less vortex generation; The Al element in the coating is prone to segregation in the upper and lower weld toe areas of the welded joint. Compared to the upper surface coating, the Al element segregation phenomenon is more obvious when the lower surface coating enters the molten pool. Therefore, the homogenization distribution of the Al element in the upper part is significantly better than that in the lower part.