Laser brazing of zinc-aluminum-magnesium coated steel – influence of the joint geometry Autorinnen und Autoren
Lasers in Manufacturing (LiM)
Laser brazing of zinc coated steel is a widely spread technique in car body manufacturing. For visible joints at the outer surface a double flanged joint geometry is common. However, the influence of the outer bending radius of the joint geometry is rarely discussed. Furthermore, the influence of zinc aluminum magnesium coatings (ZM) on the laser brazing process has not been reported so far. The properties of laser brazed joints on electrogalvanized (EG) and ZM coatings show deviant properties. In particular, the dimensions of the smallest wetted length, which is a widely used synonymously for the smallest seam thickness in micro-sections, are comparatively lower. Exemplary, the average smallest wetted lengths at a bending radius of 1.6 mm reach values of 0.64 mm on EG coated material and 0.49 mm on ZM coated steel respectively. Depending on the smallest wetted length the tensile strength is reduced as well. In the case described above, values of the tensile strength differ from 228 kN/mm on EG coatings to 187 kN/mm on ZM coatings. Hence, the brazed seam’s thickness is identified as a crucial factor for the strength of a brazed joint. On ZM coatings, the properties of the joints improve to 0.57 mm smallest wetted lengths and 216 kN/mm tensile strength by increasing the outer bending radius. Thus, the connection between the outer bending radius, the smallest seam thickness and the mechanical properties are demonstrated.