Industrial applicability of reflection-assisted laser beam brazing of ZM-coated steel sheets

A major challenge in laser beam brazing of zinc-magnesium-coated (ZM) steel sheets is the uniform pre-heating of the substrate surface for achieving a stable wetting process. A process modification of the con-ventional laser beam brazing that addresses this requirement is the reflection-assisted laser beam brazing in laser leading configuration, which utilizes the laser reflections from the brazing wire onto the substrate material for preheating and wire melting with a single laser beam. In this study the industrial applicability of this process variant is addressed by analyzing the process parameters as well as the required position tolerance limits for continuous and uniform seams.
The results showed the suitability of a laser beam brazing process in laser leading configuration for ZM-coated steel sheets. Process velocities of 6 m/min were possible. Regarding the process tolerances it has been shown that flange joints with a gap width of up to 100 µm and lateral displacements of the TCP of up to 400 µm were joinable. The brazing seams showed a higher tensile shear strength than the substrate ma-terial.