Optimization of Robotic Laser Brazing for Electrolytically Galvanized DC06 Steel Under Prototype Production Conditions

Laser brazing is commonly used for joining visible automotive body panels where both mechanical integrity and surface quality are required. The present work addresses optimization of a robotic laser brazing workstation intended for prototype vehicle production. During initial commissioning, irregular braze formation was associated with unstable filler wire feeding. Therefore, the wire feeding system was modified and subsequently evaluated together with the influence of laser power and wire feed speed on joint quality under a constant robot travel speed. Experimental joints were produced from electrolytically galvanized DC06 steel using CuSi3Mn1 filler wire. Joint performance was assessed by tensile testing and metallographic examination. Tensile strengths between 293 and 314 MPa were obtained, while fracture occurred exclusively in the base material outside the brazed region. Metallographic observations revealed regular braze geometry for parameter sets A, B and D, whereas excessive thermal input resulted in blowhole formation, zinc coating degradation and enlargement of the heat-affected zone. Quantitative evaluation showed a nearly linear increase in the HAZ area with increasing delivered energy (R2 = 0.982). The results indicate that stable brazing conditions can be achieved through an appropriate balance between laser power and wire feed speed under constant robot travel speed conditions. The proposed parameter limits may serve as a practical guideline for robotic laser brazing of thin galvanized automotive sheets under prototype production conditions.