Effect of the process parameters on the three-dimensional shape of molten pool during full-penetration laser welding process

The present study designs a low-cost method for determining the three-dimensional (3D) shape of a molten pool formed during a laser full penetration welding process and verifies the feasibility and reproducibility of this method. A dissimilar metal is introduced into the molten pool at the instant when the laser full penetration welding process is about to finish. Under intense stirring, the dissimilar elements are rapidly distributed in the entire molten pool. After the molten pool rapidly solidifies, the 3D shape of the region of the weld seam metal that contains the dissimilar elements can be approximately considered to be the 3D shape of the molten pool. In the present study, 2205 duplex stainless steel is selected as the dissimilar metal, and a test for detecting the 3D shape of a molten pool formed during a fiber laser full penetration welding process is performed on a 5.5-mm-thick low carbon steel plate. The results show that the method designed to detect the 3D shape of molten pool in laser full penetration welding process exhibits good feasibility and reproducibility, and this method can be used to realize the reconstruction of the 3D shape of molten pool in laser full penetration welding process. Welding experiments based on the three-factor and five-level regression orthogonal design are carried out to obtain the ternary quadratic regression equations of the relationships between the welding process parameters (welding power, welding speed, and defocusing distance) and the geometric shape parameters of the molten pool (the lengths and widths of the top, middle, and bottom sections of the molten pool). The significance of the regression equations is then tested. The effect of each process parameter on the 3D shape of the molten pool formed in laser full penetration welding process is discussed based on the regression equation.