Numerical simulations of the multi-kW laser welding of structural carbon steel were conducted to analyze the ef�fects of laser wavelength on fusion zone shape. For the heat and mass transfer analysis, the basic governing equa�tions were utilized in addition to the volume-of-fluid (VOF) conservation equation to calculate the free surface boundary. Laser welding models that considered phenomena such as multiple reflections of the laser beam at the keyhole, absorption, recoil pressure, and shear stress and heat source by metal vapor generated were used as well.
Two models: a general and a simplified model, which were both based on the Fresnel equations, were considered with the wavelengths of CO2, disk, and green lasers for calculating of the laser absorptivity of the material. The dif�ference found in the results of the general model and the simplified model in the range of the wavelengths consid�ered, was negligible. In addition, the results obtained for disk laser welding and green laser welding did not exhibit any considerable difference in terms of their impact on the fusion zone shape.