Method for assembling at least two parts by transparent welding, method for assembling a primary structure of an aircraft pylon by transparent welding, primary structure of an aircraft pylon thus obtained and aircraft comprising said primary structure

A method for assembling at least two parts comprising:

• using an energy input beam for transparent welding, the energy input beam travelling a trajectory so as to generate a weld bead, disposed straddling the two parts and linking them,
• wherein the trajectory follows a closed loop, the trajectory of the energy input beam and/or at least one parameter of the energy input beam configured so that the weld bead has mechanical and/or geometrical characteristics that are substantially constant over all a length of the trajectory, and
• wherein the trajectory comprises at least one overlap portion, travelled at least twice by the energy input beam, the overlap portion having a length greater than or equal to the sum of the lengths of the starting and stopping portions of the energy input beam.