Experimental and computational investigation of fusion zone geometries during autogenous keyhole mode laser welds

Here we report experimental and numerical modeling efforts targeted at autogenous keyhole mode laser welding of a low-carbon steel (A131 grade EH-36). In order to quantitatively understand the heat transfer and fluid flow processes, a mathematical model involving numerical solution of the equations of conservation of heat, mass and momentum in three dimensions was developed. The model considered formation of a keyhole, liquid steel flow in the weld pool driven by Marangoni convection at the weld pool surface, and heat transfer in the entire weldment. The computed results provide a detailed description of the temperature and velocity fields in the weldment, the shape and size of the keyhole, and the geometry of the fusion zone. There is excellent agreement between the experimental and modelled fusion zones.