The effect of welding parameters on keyhole and melt pool behavior during laser welding with high power fiber laser

Laser welding has ever growing role in manufacturing technology. Keyhole laser welding is the most important laser welding process for metal industry. This process utilizes efficiently the high energy density of laser beam to vaporize and melt material thus producing a keyhole to material via which the energy is brought to the material. The welding becomes ever more efficient with new generation of lasers having excellent beam quality and good abortion. There are various mathematical models explaining the shape and behavior of keyhole and melt pool during welding. However, the validation of actual keyhole shape, size and behavior against the models is lacking due to the difficulties in performing the measurements of the actual dimensions. The commonly accepted assumptions are that the size of keyhole is according to focal spot size and that the stability of the keyhole plays a major role when considering the ability of the laser welding process to produce high quality welds. Previous studies have shown that the welding process produces good quality in case the focal point in is below the surface of the workpiece. The keyhole size resulting high quality weld is typically 85% of the focal point size.